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Sample records for late pleistocene stratigraphy

  1. Revision of the late Pleistocene stratigraphy of Bermuda

    Science.gov (United States)

    Hearty, Paul J.

    2002-10-01

    The Quaternary stratigraphy of Bermuda is one of the world's most complete sedimentary records of interglacial highstands, representing at least the past million years. Yet in terms of the last interglacial (Rocky Bay Formation), marine isotope substage (MIS) 5e, only scanty deposits are preserved. In contrast, MIS 7, generally regarded as a diminutive interglaciation, exposes widespread emergent subtidal deposits of the Belmont Formation indicating a prolonged sea level highstand at ca. +2.5±0.3 m. This "Belmont paradox" has prompted a reexamination of the geology of key sites along the South Shore of Bermuda. This revision of the late Quaternary stratigraphy of Bermuda is based on geological field observations; primarily the questionable origin of red soil-like deposits. It is concluded here that there is no physical evidence of the exposure of the upper Belmont surface for a full glacial cycle (˜70-100 ka), and that interbedded, reddish soil-like, lenticular deposits are the result of colluvial activity during mid-MIS 5e. Reexamination of previously published uranium-series (U/Th) ages indicates that several "+3-m notches" contain a mix of ca. 125 ka and older coral ages. Contrary to previous works, this study favors an early MIS 5e interpretation of the coral ages from the +2.5-m Belmont shoreline, which is further supported by amino acid racemization (AAR) ratios on whole-rock, Poecilozonites, Glycymeris, and Brachiodontes samples from shore and notch deposits. An updated AAR kinetic model demonstrates that the bulk of epimerization occurred during warm interglacial intervals between 130 and 80 ka and the last 10 ka of the Holocene. This revised stratigraphy of Bermuda now falls into accordance with a more general view of middle and late Pleistocene sea level history.

  2. The sedimentary sequence recovered from the Voka outcrops, northeastern Estonia: implications for late Pleistocene stratigraphy

    Directory of Open Access Journals (Sweden)

    Miidel, Avo

    2007-03-01

    Full Text Available New palaeoenvironmental and geological data, which may be integrated with the results from the neighbouring regions, were collected from two well-exposed continuous outcrops in the vicinity of Voka village, northeastern Estonia. These outcrops, situated in a klint depression – klint bay –, show an about 22 m thick stacked sequence of sandy to clayey subaqueous deposits. This succession of water-lain sediments documents the response to climate change during the late Pleistocene. On the basis of grain size characteristics, sedimentological structures, and luminescence chronostratigraphical data, the sequence is subdivided into two main units – A and B. Optical dating of 18 samples from the upper unit A shows that the unit is of middle Järva (= middle Weichselian age (marine isotope stage (MIS 3. Representative pollen spectra derived from 45 samples from the pollen-bearing part of unit A provide convincing evidence of noticeable changes in vegetation and climate in NE Estonia during the time period from 39 to 33 kyr BP, within which two intervals of severe climate and two relatively milder ones have been recognized. Preliminary data from the underlying unit B indicate that deposits of the last interglacial sensu lato and those of early pleniglacial age correlating with MIS 5 and MIS 4, respectively, occur here as well. Thus, the data obtained during the present study show unambiguously that in contrast with the expectations, the greater part of the late Pleistocene sequence is represented in the Voka section. No evidence was found for glacial activity during the late Pleistocene period predating the last glacial maximum. The use of the Voka event stratigraphy as a template facilitates search for correlative horizons in the neighbouring regions.

  3. Glacial stratigraphy of the Bulkley River region: A depositional framework for the late Pleistocene in central British Columbia

    Science.gov (United States)

    Stumpf, A.J.; Broster, B.E.; Levson, V.M.

    2004-01-01

    A depositional framework for late Pleistocene sediments in central British Columbia was developed from the composite stratigraphy of glacial sediments found in the Bulkley River region. Nonglacial deposits correlated to the Olympia Nonglacial Interval, are overlain in succession by sub-till, ice-advance sediments, Late Wisconsinan (Fraser Glaciation) till, and late-glacial sediments. Due to local erosion and depositional variability, some of the units are not continuous throughout the region and differ locally in their thickness and complexity. At the onset of the Fraser Glaciation, ice advance was marked by rising base levels in rivers, lake ponding, and ice marginal sub-aqueous deposition. Physiography and glacier dynamics influenced the position of drainage outlets, direction of water flow, and ponding. The region was completely ice covered during this glaciation and ice-flow directions were variable, being dominantly influenced by the migrating position of ice divides. Deglaciation was marked by the widespread deposition of fine-grained sediments in proglacial lakes and glaciofluvial sands and gravels at locations with unrestricted drainage.

  4. Late Pleistocene Alberca de Guadalupe maar volcano (Zacapu basin, Michoacán): Stratigraphy, tectonic setting, and paleo-hydrogeological environment

    Science.gov (United States)

    Kshirsagar, Pooja; Siebe, Claus; Guilbaud, Marie Noëlle; Salinas, Sergio; Layer, Paul W.

    2015-10-01

    The Late Pleistocene (~ 21,000 yr BP) Alberca de Guadalupe maar is one of the few phreatomagmatic volcanoes occurring within the scoria-cone dominated Plio-Quaternary Michoacán-Guanajuato Volcanic Field. The scarcity of this type of volcano implies that conditions favoring their formation are rarely met in this region. We identify these factors by implementing current methods of investigation with emphasis on hydrogeological conditions. We present the stratigraphy (including a set of 40Ar/39Ar and 14C dates) of the SE margin of the Zacapu intermontane tectonic basin, where the maar just forms a hole (~ 1 km in diameter, ~ 150 m deep, bearing a ~ 9 m deep lake) in the otherwise planar topography of the underlying early Pleistocene lava flows of the Cerro Pelón scoria cone. The maar is composed of typical phreatomagmatic surge deposits that are poorly sorted and rich in accidental lithics (> 60 wt.% of the deposit) with few juveniles (basaltic andesite, SiO2 = 54-58 wt.%). The entire structure is cut by an ENE-WSW trending normal fault and is underlain by andesite lavas and silicic ignimbrites (partly inferred from xenoliths encountered in the maar deposits) that are Miocene to Early Pleistocene in age. The crater is at the center of a N-S elongated drainage basin surrounded by topographic highlands that channel water with high hydraulic pressure from most directions towards the location of the maar. This geometric configuration was already in existence at the time of the maar-forming eruption, but the climate was different. Colder and more humid conditions during the Last Glacial Maximum (Cw2-climate type, annual precipitation of > 1000 mm) favored the saturation of the fractured shallow aquifer system (hydraulic conductivity of 10- 8 to 10- 7 m/s) that supplied sufficient groundwater at a high flow rate directed towards the center of the basin. Upon contact near surface ( 150 m deep crater with steep inner walls and an underlying shallow diatreme (< 300 m). Since then, partial collapse of the walls along listric ring-fractures has reduced crater steepness. The present climate is much drier (Cw1 climate conditions with annual precipitation of 697.5-874.8 mm) and it seems unlikely that a maar would form if these conditions persist. Nonetheless, precipitation is still high enough to sustain a ~ 9-m-deep lake in the crater with insignificant seasonal water table fluctuations. These findings lend further support to the notion that maars can be used as paleoclimate indicators in central Mexico.

  5. A consistent magnetic polarity stratigraphy of late Neogene to Quaternary fluvial sediments from the Heidelberg Basin (Germany): A new time frame for the Plio-Pleistocene palaeoclimatic evolution of the Rhine Basin

    Science.gov (United States)

    Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

    2015-04-01

    This work presents the results of a magnetostratigraphic survey performed on 1150 m of core material from three sites within the Heidelberg Basin. The cores intersect one of the thickest continuous accumulations of Plio-Pleistocene fluvial sediments in western Central Europe. The resultant magnetic polarity stratigraphy includes every Quaternary polarity chron, thereby providing constant age constraint down to the Gauss-Matuyama Boundary (2.58 Ma). Older deposits cannot be unequivocally dated; instead, various age-depth models are discussed. We base our chronostratigraphic interpretation of the successions tentatively on three assumptions. A) The accommodation was almost constant over time. B) Hiatuses in the duration of subchrons (on the order of 0.2 Myr) may occur, and the actual step-like age-depth relationship is best depicted as a smooth curve with almost constant slope. C) Long chrons and subchrons have a higher preservation potential than shorter polarity intervals. The stratigraphic scenarios with the highest probability - based upon our three assumptions - lead to minimum ages of > 5.235 Ma and > 4.187 Ma for the oldest parts of the Viernheim and Heidelberg cores, respectively. Consequently, this study provides the first consistent magnetic polarity stratigraphy for quasi-continuous sequences of late Neogene to Quaternary fluvial sediments in the Rhine Basin and generally in western central Europe. This methodologically independent chronostratigraphy supplies an urgently required temporal model for on-going tectonic and sedimentological studies and the reconstruction of the palaeoclimate since the Pliocene in this part of Europe.

  6. The role of tropical cyclones on landscape dynamics in southern Baja California, Mexico based on Late Pleistocene-Holocene alluvial stratigraphy

    Science.gov (United States)

    McDonald, Eric; Antinao, Jose Luis; Rhodes, Edward J.; Brown, Nathan; Gosse, John

    2015-04-01

    Region-wide alluvial records provide evidence that time-transgressive changes in climate can be a major driver of landscape evolution. Historically, landfall of eastern Pacific tropical cyclones in southwestern North America during the late summer and early fall provide the strongest storms that have demonstrated geomorphic impact on the landscape. The alluvial fan record of the southern portion of Baja California (Mexico) was investigated to determine if linkages exist between region-wide fluvial deposits and tropical cyclones. The regional distribution and Pleistocene to Holocene morphostratigraphy of alluvial fans has been established for the southern portion of Baja California with primary focus on the La Paz and San José del Cabo basins. Six discrete morphopedosedimentary alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development further reinforced with geochronology using radiocarbon, optically stimulated luminescence and cosmogenic depth-profiles. A first phase of regional aggradation began before ~ 100 ka (Qt1) and culminated ~10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units are conformed of multiple 1-3 m thick alluvial packages deposited in upper-flow regime and representing individual storms. Aggradational units (Qt1-Qt4) covered broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are mostly confined to channels of ~0.5-2 km width. Continuous deposition of the thicker sequences is demonstrated by closely spaced luminescence dates in vertical profiles. In a few places disconformities between major units are evident and indicated by partly eroded buried soils. Analysis of historical terraces as part of the younger units incised into older fans show that deposition was accomplished by large tropical cyclone events. Older units feature the same sedimentological traits as these historical deposits. We interpret the whole sequence as indicating discrete periods during the Late Pleistocene and Holocene when climatic conditions allowed large tropical cyclone events that today are not expressed. These discrete periods can be associated with specific periods when (a) insolation at the Equator was at peaks determined by precessional cycles and (b) the Tropical Pacific might have shown a state similar to that currently displayed during El Niño events.

  7. Late Pleistocene and late Holocene lake highstands in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA

    Science.gov (United States)

    Briggs, Richard W.; Wesnousky, Steven G.; Adams, Kenneth D.

    2005-09-01

    Shoreline geomorphology, shoreline stratigraphy, and radiocarbon dates of organic material incorporated in constructional beach ridges record large lakes during the late Pleistocene and late Holocene in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA. During the late Holocene, a transgression began at or after 3595 ± 35 14C yr B.P. and continued, perhaps in pulses, through 2635 ± 40 14C yr B.P., resulting in a lake as high as 1199 m. During the latest Pleistocene and overlapping with the earliest part of the Younger Dryas interval, a lake stood at approximately 1212 m at 10,820 ± 35 14C yr B.P. and a geomorphically and stratigraphically distinct suite of constructional shorelines associated with this lake can be traced to 1230 m. These two lake highstands correspond to periods of elevated regional wetness in the western Basin and Range that are not clearly represented in existing northern Sierra Nevada climate proxy records.

  8. Palynological investigations of late Pleistocene deposits in South Eastern France

    International Nuclear Information System (INIS)

    Palynological investigations were carried out on lignites and other Late Pleistocene deposits in the area north of Grenoble in southeastern France, in order to reconstruct the vegetational and climatic development in this area during the Late Pleistocene. The 14C and ionium content of several lignites were also measured. (Auth.)

  9. Palynological investigations of late pleistocene deosits in southeastern France.

    OpenAIRE

    Gremmen, Wilhelmus Hubertus Emmanuel,

    1982-01-01

    Palynological investigations were carried out of lignites and other Late Pleistocene deposits in the area north of Grenoble in southeastern France, in order to reconstruct the vegetational and climatic development in this area during the Late Pleistocene. The 14C and ionium content of several lignites were also measured.... Zie: Summary

  10. K-Ar age determination of late pleistocene volcanic rocks

    International Nuclear Information System (INIS)

    A newly developed K-Ar age determination system has been tested by comparison of ages derived by this system from Late Pleistocene volcanic rocks, the ages of which have already been estimated by Fission track or Carbon 14 methods, or from historic records. The result indicates that this K-Ar method is applicable to the stratigraphy of volcanoes older than 0.1 m.y. and that the application is more flexible, convenient and accurate than the Fission track method. Potassium analysis was carried out by flame photometry using a 1500 ppm Cs buffer. Argon was analysed on a 30 cm radius sector type mass spectrometer by an isotopic dilution method using an Argon-38 spike. With this new system, it is possible to date to within +-20%, rocks containing atmospheric argon which is up to 97% of the total argon. About six age determinations of calc-alkaline andesites with age near 0.05 m.y. can be carried out per day. (author)

  11. A Late Pleistocene sea level stack

    Science.gov (United States)

    Spratt, R. M.; Lisiecki, L. E.

    2015-08-01

    Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal component analysis (PCA) on seven records from 0-430 ka and five records from 0-798 ka. The first principal component, which we use as the stack, describes ~80 % of the variance in the data and is similar using either five or seven records. After scaling the stack based on Holocene and Last Glacial Maximum (LGM) sea level estimates, the stack agrees to within 5 m with isostatically adjusted coral sea level estimates for Marine Isotope Stages 5e and 11 (125 and 400 ka, respectively). When we compare the sea level stack with the ?18O of benthic foraminifera, we find that sea level change accounts for about ~40 % of the total orbital-band variance in benthic ?18O, compared to a 65 % contribution during the LGM-to-Holocene transition. Additionally, the second and third principal components of our analyses reflect differences between proxy records associated with spatial variations in the ?18O of seawater.

  12. PALEOECOLOGY. Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover.

    Science.gov (United States)

    Cooper, Alan; Turney, Chris; Hughen, Konrad A; Brook, Barry W; McDonald, H Gregory; Bradshaw, Corey J A

    2015-08-01

    The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. We compared ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions and replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement or extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions before the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts. PMID:26250679

  13. Depositional architecture and sequence stratigraphy of Pleistocene coarse-grained deltas along the Ligurian coast (Italy)

    Indian Academy of Sciences (India)

    A Ciampalini; M Firpo

    2015-12-01

    This study aims to develop a better understanding of the stratigraphy of the southern side of the Maritime Alps and of the Ligurian Sea during the Plio-Pleistocene. Five stratigraphic sections were measured and studied in the Segno River valley (Liguria, Italy). These sections are composed of Lower to Middle Pleistocene marine and continental deposits. Based on detailed mapping and sedimentological analysis, 12 marine and deltaic facies were identified. These facies were grouped into facies associations. Two allostratigraphic units were recognized, namely U1 and U2 from oldest to youngest. The lower unit (U1) represents the evolution of a coarse-grained delta developed in a valley or embayment. Within the deltaic sequence, transgressive and highstand systems tracts were recognized. The coarsening/shallowing upward trend observed within the sections suggests that the delta prograded rapidly in the landward portion of the canyon adjacent to the paleo-river outlet. The upper boundary of U1 is represented by a subaerial unconformity overlain by U2, which is composed of sediments deposited by several alluvial fan systems.

  14. A consistent magnetic polarity stratigraphy of Plio-Pleistocene fluvial sediments from the Heidelberg Basin (Germany)

    Science.gov (United States)

    Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

    2014-05-01

    Deep drillings in the Heidelberg Basins provide access to one of the thickest and most complete successions of Quaternary and Upper Pliocene continental sediments in Central-Europe [1]. In absence of any comprehensive chronostratigraphic model, these sediments are so far classified by lithological and hydrogeological criteria. Therefore the age of this sequence is still controversially discussed ([1], [2]). In spite of the fact that fluvial sediments are a fundamental challenge for the application of magnetic polarity stratigraphy we performed a thorough study on four drilling cores (from Heidelberg, Ludwigshafen and nearby Viernheim). Here, we present the results from the analyses of these cores, which yield to a consistent chronostratigraphic framework. The components of natural remanent magnetisation (NRM) were separated by alternating field and thermal demagnetisation techniques and the characteristic remanent magnetisations (ChRM) were isolated by principle component analysis [3]. Due to the coring technique solely inclination data of the ChRM is used for the determination of the magnetic polarity stratigraphy. Rock magnetic proxies were applied to identify the carriers of the remanent magnetisation. The investigations prove the NRM as a stable, largely primary magnetisation acquired shortly after deposition (PDRM). The Matuyama-Gauss boundary is clearly defined by a polarity change in each core, as suggested in previous work [4]. These findings are in good agreement with the biostratigraphic definition of the base of the Quaternary ([5], [6], [7]). The Brunhes-Matuyama boundary could be identified in core Heidelberg UniNord 1 and 2 only. Consequently, the position of the Jaramillo and Olduvai subchron can be inferred from the lithostratigraphy and the development of fluvial facies architecture in the Rhine system. The continuation of the magnetic polarity stratigraphy into the Gilbert chron (Upper Pliocene) allows alternative correlation schemes for the cores Viernheim and Heidelberg. All things considered, the application of magnetic polarity stratigraphy on Pliocene and Pleistocene fluvial sediments from the Heidelberg Basin provides a consistent and independent chronology and opens the perspective for global correlations where other approaches hardly come to results. [1] GABRIEL, G., ELLWANGER, D., HOSELMANN, C. & WEIDENFELLER, M. 2008. Preface: The HeidelbergBasin Drilling Project. E & G (Quaternary Science Journal), 57, 253-260. [2] ELLWANGER, D. & WIELAND-SCHUSTER, U. 2012. Fotodokumentation und Schichtenverzeichnis der Forschungsbohrungen Heidelberg UniNord I und II. LGRB-Informationen, 26, 25-86. [3] KIRSCHVINK, J. L. 1980. The least-squares line and plane and the analysis of palaeomagnetic data. Geophysical Journal, Royal Astronomical Society, 62, 699-718. [4] ROLF, C., HAMBACH, U. & WEIDENFELLER, M. 2008. Rock and palaeomagnetic evidence for the Plio-/Pleistocene palaeoclimatic change recorded in Upper Rhine Graben sediments (Core Ludwigshafen-Parkinsel), Neth. J. Geosci., 87 (1), 41-50. [5] KNIPPING, M. 2008. Early and Middle Pleistocene pollen assemblages of deep core drillings in the northern Upper Rhine Graben, Germany, Neth. J. Geosci., 87(1), 51-65. [6] HEUMANN, G., pers. Comm. [7] HAHNE, J., pers. Comm.

  15. Paleohydrology of Late Pleistocene Superflooding, Altay Mountains, Siberia

    Science.gov (United States)

    Baker, Victor R.; Benito, Gerardo; Rudoy, Alexey N.

    1993-01-01

    Cataclysmic flooding is a geomorphological process of planetary significance. Landforms of flood origin resulted from late Pleistocene ice-dammed lake failures in the Altay Mountains of south-central Siberia. Peak paleoflows, which exceeded 18 × 10^6 cubic meters per second, are comparable to the largest known terrestrial discharges of freshwater and show a hydrological scaling relation to floods generated by catastrophic dam failures. These seem to have been Earth's greatest floods, based on a variety of reconstructed paleohydraulic parameters.

  16. Geochronometric age of late pleistocene terraces on the Lower Yenisei

    International Nuclear Information System (INIS)

    Using the methods of radiocarbon (AMS) and opto-luminescent (OSL) dating the age of deposits of late pleistocene terraces on the Lower Yenisei between Turukhansk and Igarka was determined. It was ascertained that alluvium of terrace II mainly deposited at the beginning of marine isotope stage 3, i.e. approximately 45-60 thousand years ago. Fluvioglacial cover of terrace III was formed as a result of thawing of the Putoransky glaciers 75-60 thousand years ago

  17. Late Pleistocene geomagnetic excursion in Icelandic lavas

    International Nuclear Information System (INIS)

    In 1980 Kristjansson and Gudmundsson reported a late glacial geomagnetic excursion in three hills in the Reykjanes peninsula, Iceland, with shallow negative inclinations and westerly declinations. They named it the Skalamaelifell excursion. More extensive field work has identified the same excursional paleomagnetic direction (declination = 258deg, inclination = -15deg) at four additional outcrops in a 10x10 km area in the Reykjanes peninsula. The excursion lavas are olivine tholeiites with similar petrography and chemical compositions. Paleointensity determinations by the Thellier method average 4.2±0.2 ?T for 8 samples, more than an order of magnitude weaker than the present geomagnetic field in Iceland. Together, these results suggest extrusion of the excursion lavas in a very brief span of time, probably less than a few hundred years. K-Ar dating of the excursion lavas gives a mean age for 19 determinations of 42.9±7.8 ka (2?). Compilation of thirty K-Ar ages of the Laschamp and Olby flows by three laboratories yield a new age for the Laschamp excursion in France of 46.6±2.4 ka (2?). The age of the excursion in southwestern Iceland is statistically indistinguishable from the Laschamp excursion at the 95% confidence level, and both have very low paleointensities. Therefore, we suggest that the Laschamp and Olby flows in France and the Skalamaelifell units of Iceland recorded essentially the same geomagnetic excursion. Differences in the virtual paleomagnetic poles (VGPs) of these excursions may be due to (1) the probable non-dipole character of the geomagnetic field during the excursion, (2) rapid geomagnetic secular variation and possible small age differences of the extrusive rocks in France and Iceland, and/or (3) crustal magnetic anomalies which might dominate the local geomagnetic field during the excursion at either or both locations. (orig.)

  18. Late Quaternary stratigraphy and sea-level history of the northern Delaware Bay margin, southern New Jersey, USA:. a ground penetrating radar analysis of composite Quaternary coastal terraces

    Science.gov (United States)

    O'Neal, Michael L.; McGeary, Susan

    2002-04-01

    Ground penetrating radar (GPR) and lithologic data reveal six Pleistocene sea-level highstand sequences, forming two composite terraces along the northern margin of Delaware Bay in southern New Jersey, USA. The upper terrace (+18 to +9 m MSL) is underlain by four estuarine-marine sequences of middle Pleistocene age, while the lower terrace (+6 m-MSL) contains 2 middle to late Pleistocene sequences. Separating the 2 terraces is a variably sloping escarpment (Cedarville) created by erosion during at least 2 high sea-level events. Intensive radar imaging and boring of these 6 unconformity-bounded units allows for their interpretation in a sequence-stratigraphic context, identifying transgressive, highstand, and regressive phases. Higher than present sea levels of +14, +12, +6, and +16 m during the middle Pleistocene, and +5 m during the middle and/or late Pleistocene are indicated by these sedimentary sequences, suggesting relative stability of this section of the Atlantic Coastal Plain during the past 500 ka. GPR analysis of coastal drainage modification reveals a contrasting lowstand sequence of incised paleovalleys, supporting the interpretation that these bay-margin deposits contain one of the most complete sections of late Quaternary highstand stratigraphy in the Mid-Atlantic region. For appendix see http://www.elsevier.nl/locate/quascirev.

  19. The Pliocene and Pleistocene of Pampean region (Argentina): systematic aspects on taphonomy and bio stratigraphy

    International Nuclear Information System (INIS)

    Canids in South America were first recorded in the Vorohuean (Middle Pliocene) at southeast marine cliff of Pampean region. These records were assigned to Dusicyon cultridens. D. gymnocercus has it oldest record in the Ensenadan (Early to Middle Pleistocene) of the Pampean Region (Argentina) and Tarija (Bolivia). Remains of this species are frequents in the Bonaerian and Lujanian (Middle to Late Pleistocene) of the Buenos Aires and Entre Rios provinces. Outside Argentina D. gymnocercus was recorded in the Lujanian of Brazil and Uruguay. Two new records of Dusicyon from Punta San Andres (Buenos Aires province) are presented here. The first one (MLP 07-V-2-1) comes from Arroyo Seco Formation(Bonaerian, Middle Pleistocene) and is assigned here to D. gymnocercus. MLP 07-V-2-1 constitutes the first record of this species at Arroyo Seco Formation. The other one (MLP 07-V-2-2) was exhumed from a paleocave excavated in San Andres Formationsediments (Sanandresian, Late Pliocene) and filled with sanandresian sediments. Also, rodent remains (Ctenomys chapadmalalensis and cavids) were collected inside of the paleocave. Although, the study carried out prevents the assignation of MLP 07-V-2-2 to any of the Dusicyon species, this remain shows some affinity with D. gymnocercus. If this is confirmed in the future MLP 07-V-2-2 could be the oldest record of D. gymnocercus. In addition we discuss some litoestratigraphic and bioestratigraphic aspects of Punta San Andres and taphonomic implications related with the paleocave were MLP 07-V-2-2 was founded.(author)

  20. Late Pleistocene deglaciation in the upper Gállego Valley, central Pyrenees

    Science.gov (United States)

    Palacios, David; de Andrés, Nuria; López-Moreno, Juan I.; García-Ruiz, José M.

    2015-05-01

    Deglaciation processes in the upper Gállego Valley, central-southern Pyrenees, were studied using geomorphological mapping and 36Cl cosmogenic dating of moraine and rock glacier boulders, as well as polished bedrock. Although the precise position of the Gállego Glacier during the global last glacial maximum is not known, there is evidence that ice tongues retreated to the headwaters, which caused subdivision of the main glacier into a number of individual glaciers prior to 17 ka. A range of ages (16 to 11 ka) was found among three tributary valleys within the general trend of deglaciation. The retreat rate to cirque was estimated to be relatively rapid (approximately 5 km per ka). The mapped glacial sedimentology and geomorphology appears to support the occurrence of multiple minor advances and retreats, or periods of stasis during the late deglaciation. Geomorphological and geological differences among the tributary valleys, and error estimates associated with the results obtained, prevented unambiguous correlations of the advances with the late Pleistocene cold periods. During the latter advances, small glaciers and rock glaciers developed close to the cirque headwalls, and co-occurred under the same climatic conditions. No evidence for Holocene re-advance was found for any of the three tributary valleys.

  1. Seismic stratigraphy of the Bering Trough, Gulf of Alaska: Late Quaternary history of Bering Glacier dynamics

    Science.gov (United States)

    Montelli, A.; Gulick, S. P. S.; Worthington, L. L.; Mix, A. C.; Zellers, S.; Jaeger, J. M.

    2014-12-01

    Sedimentary architecture of the cross-shelf Bering Trough is studied using 5 high resolution seismic profiles integrated with the drilling data acquired during Integrated Ocean Drilling Program (IODP) Expedition 341. The objectives of this work are to constrain the number of advance-retreat cycles that have occurred through the Late Quaternary, examine the impact of the Bering Glacier on the continental shelf and slope, and reconstruct Bering Glacier dynamics. By tying these sequences with ?18O stratigraphy, we can test the Bering Glacier's relation to global ice sheet evolution and better understand the degree to which the glacial advance-retreat cycles were in phase with global events. Our results show that: (1) Identification of erosional surfaces and glacigenic landforms that record positions of stillstand events and diagnose the style of retreat allow us to distinguish nine phases of glacial advances and subsequent retreats. (2) Mapping shows that glacier pathways and flow directions through time are influenced by the occurrence of thick grounding-zone deposits and shifting foci of erosion. (3) Continuous buildup of glacigenic sediment fills tectonically created accommodation space and allows the glacier to advance seaward for the last three advances. Discovery of systematic, prominent deposition of glacial diamict and ice-rafted debris (IRD) during phases of glacial retreat is supported by the drilling data and suggests reconsideration of IRD impact on slope sedimentation. (4) The trough mouth fan started its development during marine isotope stage (MIS) 6, progressively advancing to the position of present shelf edge during the subsequent MIS 4 and MIS 2 and is recognized by evidence of extensive deposition of glacigenic debris flows on the slope. (5) Sedimentation rates in the depocenter are exceptionally high and are estimated to be 1-2 m/k.y. through the middle Pleistocene on the shelf and 4-5 m/k.y. average through MIS 6 on the slope.

  2. Ages of late pleistocene terrace deposits in the Kuromatsunai lowland

    International Nuclear Information System (INIS)

    Kuromatsunai lowland which lies at the neck of Oshima Peninsula extends from Oshamambe to Suttsu, and is considered as a remarkable neo-tectonic zone. In this region, the data for determining the age of terraces and pyroclastic material which is related to the terraces are short. The determination of the age of lower fluvial terraces was attempted using the wood piece specimens collected from three localities in Kuromatsunai town. The determination of the 14C age of three specimens was conducted, and the obtained values were about 26 x 103 yBP, about 30 x 103 yBP and 37 x 103 yBP, respectively. The consideration on the conditions of the existence of specimens and the results of geologival observation of the localities where the specimens were collected, led to the conclusion as follows. 1. The age of the aeolian deposit of volcanic ash is earlier than about 30 x 103 yBP. 2. In Kuromatsunai lowland, the lower fluvial terrace, which is not overlain by the volcanic ash of Pleistocene can be roughly divided into two levels. The age of one level is about 30 x 103 yBP, and another is later than 26 x 103 yBP, which are corresponding to late Pleistocene. The age of the Neppu pyroclastic flow deposit, which is related to the formation of those terraces, was determined as 0.13+-0.03 MaBP by fission track method. Further studies seem to be necessary because some disagreement with the data of other researchers remains. (Ishimitsu, A.)

  3. Seismic Stratigraphy of Pleistocene Deltaic Deposits in Bahía Blanca Estuary, Argentina

    Scientific Electronic Library Online (English)

    SALVADOR, ALIOTTA; SILVIA S., GINSBERG; DARÍO, GIAGANTE; LAURA G., VECCHI; MARTA M., SALVATIERRA.

    2014-06-01

    Full Text Available O estuário da Bahía Blanca (Argentina) tem uma configuração morfológica resultante de processos hidrológicos e sedimentares relacionados a mudanças do nível do mar durante o Quaternário Tardio. Este sistema estuarino ocupa uma ampla planície costeira com uma densa rede de canais de marés, ilhas de b [...] aixa altitude e extensas áreas de intermarés com baixa declividade. Nesta área, pouco se conhece sobre as unidades sedimentares do fundo marinho. Portanto, análise estratigráfica da costa norte do estuário da Bahía Blanca foi realizada usando sísmica de alta resolução (3,5 kHz) com a finalidade de: i) definir sequências quaternárias, ii) descrever estruturas sedimentares, e iii) determinar as condições paleoambientais de sedimentação. Os dados estratigráficos sísmicos obtidos e suas correlações litológicas com dados de perfuração apresentaram cinco sequências sísmicas (S1, S2, S3, S4 e S5), das quais S1-S2 foram correlacionadas com um paleoambiente continental referente ao Mioceno-Pleistoceno. Sequências S3 e S4, de fácies litológicas e sísmicas (estruturas de paleocanais e configurações de reflexão progradantes) foram definidas nestas sequências, evidenciando o desenvolvimento de um ambiente ancestral deltaico que foi parte de um amplo sistema de drenagem do Pleistoceno. A sequência S5 foi formada durante os processos transgressivo-regressivos do Holoceno e preenche a coluna sismo-estratigráfica definida neste estudo. Abstract in english The Bahía Blanca estuary (Argentina) has a morphological configuration resulting from hydrological and sedimentary processes related to Late Quaternary sea level changes. This estuarine system occupies a large coastal plain with a dense net of tidal channels, low-altitude islands and large intertida [...] l flats. Little is known about the sedimentary units of the marine subbottom. Therefore, a stratigraphical analysis of the northern coast of Bahía Blanca estuary was carried out using high resolution seismic (3.5 kHz) in order to: i) define Quaternary sequences, ii) describe sedimentary structures, and iii) determine the paleoenvironmental conditions of sedimentation. The seismic stratigraphic data collected and their correlation with drilling lithological data show five seismic sequences (S1, S2, S3, S4 and S5), of which S1-S2 were found to be associated with a continental paleoenvironment of Miocene-Pleistocene age. Sequences S3 and S4, whose lithology and seismic facies (paleochannel structures and prograding reflection configurations), were defined on these materials, to evidence the development of an ancient deltaic environment which was part of a large Pleistocene drainage system. The S5 sequence was formed during the Holocene transgressive-regressive process and complete the seismostratigraphic column defined in the present study.

  4. Radiocarbon chronology of Late Pleistocene large mammal faunas from the Pannonian basin (Hungary).

    OpenAIRE

    Kovács J

    2012-01-01

    Geochronological data from the mammal fauna of the Pannonian basin during the Late Pleistocene are compiled. Thirty-four megafaunal samples (including both fossil bone and associated materials such as charcoal), previously radiocarbon dated by accelerator mass spectrometry and conventional methods, range from 43 to 10.3 14C ka BP (47-13 ka cal BP). Thus, most samples date within Marine Isotope Stage (MIS) 3 and 2 of the Late Pleistocene, and indicate that the mammoth st...

  5. News from the Late Silurian stratigraphy and global correlation of the strata in the Prague Synform.

    Czech Academy of Sciences Publication Activity Database

    Slavík, Ladislav

    Brno : Mendel Museum MU, 2012 - (Hladilová, Š.; Doláková, N.; Dostál, O.). s. 61-61 ISBN 978-80-210-5978-8. [?esko-slovensko-polský paleontologický seminá? /13./. 18.10.2012-19.10.2012, Brno] Institutional support: RVO:67985831 Keywords : stratigraphy * Late Silurian * Prague Synform Subject RIV: DB - Geology ; Mineralogy

  6. Late Pleistocene raised beaches of coastal Estremadura, central Portugal

    Science.gov (United States)

    Benedetti, Michael M.; Haws, Jonathan A.; Funk, Caroline L.; Daniels, J. Michael; Hesp, Patrick A.; Bicho, Nuno F.; Minckley, Thomas A.; Ellwood, Brooks B.; Forman, Steven L.

    2009-12-01

    We present new stratigraphic, sedimentological, and chronological data for a suite of tectonically raised beaches dating to Marine Isotope Stages 5, 4, and 3 along the Estremadura coast of west-central Portugal. The beach deposits are found in association with ancient tidal channels and coastal dunes, pollen bearing mud and peat, and Middle Paleolithic archaeological sites that confirm occupation of the coastal zone by Neanderthal populations. The significance of these deposits is discussed in terms of the archaeological record, the tectonic and geomorphic evolution of the coast, and correlation with reconstructions of global climate and eustatic sea-level change. Direct correlation between the Estremadura beach sections is complicated by the tectonic complexity of the area and the age of the beach deposits (which are near or beyond the limit of radiocarbon dating). Evidence from multiple sites dated by AMS radiocarbon and optical luminescence methods suggests broad synchroneity in relative sea-level changes along this coast during Marine Isotope Stage 3. Two beach complexes with luminescence and radiocarbon age control date to about 35 ka and 42 ka, recording a rise in relative sea level around the time of Heinrich Event 4 at 39 ka. Depending on assumptions about eustatic sea level at the time they were deposited, we estimate that these beaches have been uplifted at rates of 0.4-4.3 mm yr -1 by the combined effects of tectonic, halokinetic, and isostatic processes. Uplift rates of 1-2 mm yr -1 are likely if the beaches represent sea level stands at roughly 40 m below modern, as suggested by recent eustatic sea level reconstructions. Evidence from coastal bluffs and the interior of the study area indicates extensive colluvial, fluvial, and aeolian sedimentation beginning around 31 ka and continuing into the Holocene. These geomorphic adjustments are related to concomitant changes in climate and sea level, providing context that improves our understanding of Late Pleistocene landscape change and human occupation on the western Iberian margin.

  7. Hominin teeth from the early Late Pleistocene site of Xujiayao, Northern China.

    Science.gov (United States)

    Xing, Song; Martinón-Torres, María; Bermúdez de Castro, Jose María; Wu, Xiujie; Liu, Wu

    2015-02-01

    It is generally accepted that from the late Middle to the early Late Pleistocene (?340-90 ka BP), Neanderthals were occupying Europe and Western Asia, whereas anatomically modern humans were present in the African continent. In contrast, the paucity of hominin fossil evidence from East Asia from this period impedes a complete evolutionary picture of the genus Homo, as well as assessment of the possible contribution of or interaction with Asian hominins in the evolution of Homo sapiens and Homo neanderthalensis. Here we present a comparative study of a hominin dental sample recovered from the Xujiayao site, in Northern China, attributed to the early Late Pleistocene (MIS 5 to 4). Our dental study reveals a mosaic of primitive and derived dental features for the Xujiayao hominins that can be summarized as follows: i) they are different from archaic and recent modern humans, ii) they present some features that are common but not exclusive to the Neanderthal lineage, and iii) they retain some primitive conformations classically found in East Asian Early and Middle Pleistocene hominins despite their young geological age. Thus, our study evinces the existence in China of a population of unclear taxonomic status with regard to other contemporary populations such as H. sapiens and H. neanderthalensis. The morphological and metric studies of the Xujiayao teeth expand the variability known for early Late Pleistocene hominin fossils and suggest the possibility that a primitive hominin lineage may have survived late into the Late Pleistocene in China. PMID:25329008

  8. Testing the correlation of fragmented pollen records of the middle and late Pleistocene temperate stages

    DEFF Research Database (Denmark)

    Kuneš, Petr; Odgaard, Bent Vad

    Quaternary temperate stages have long been described based on changing pollen abundances of various tree taxa in lacustrine sediments. Later, attempts have been made to assign such biostratigraphic units to distinct marine isotope stages (MIS). Existing continuous chronosequences from Southern Europe provide good chronologies and thus enable a biostratigraphic definition of at least younger MIS. In Northern Europe, however, the fragmentary character of the records and the weaknesses of absolute dating prevent good age estimates. Therefore, age-determination of the majority of fragmentary records depends on site-to-site correlations. This comparison has often been performed on a visual basis, lacking clearly defined protocols and statements of underlying assumptions. Here I test the correlation of well and poorly known pollen records of the middle- and late-Pleistocene temperate stages from Northern-Central Europe and evaluate the usefulness of several numerical techniques. TWINSPAN analysis identifies groupsof temperate stages based on presence/absence of their indicative taxa and may be useful for distinguishing between older and younger interglacials. Site-to-site sequence slotting allows the determination of the most similar pairs of records, based on sample dissimilarity following their stratigraphic constraints. Sequence slotting performs well when correlating the Holsteinian interglacial and Cromerian stage II, and also provides tentative correlation of some problematic records. Ordination compares main trends in pollen stratigraphies of all pollen sequences. It finds very similar patterns between Eemian records and Cromerian stage II. Although different methods show sometimes inconsistent results, they can certainly contribute to the discussion of the age of poorly known interglacials. The implications for future directions suggest focusing on better sampling resolution, multi-proxy approaches to climatic reconstruction and obtaining better independent dating.

  9. Late Pleistocene Megafaunal Extinction Consistent With YDB Impact Hypothesis at Younger Dryas Onset

    Science.gov (United States)

    Kennett, J. P.; Kennett, D. J.

    2008-12-01

    At least 35 mammal and 19 bird genera became extinct across North America near the end of the Pleistocene. Modern increases in stratigraphic and dating resolution suggest that this extinction occurred relatively rapidly near 12.9 ka (11 radiocarbon kyrs). Within the context of a long-standing debate about its cause, Firestone et al., (2007) proposed that this extinction resulted from an extraterrestrial (ET) impact over North America at 12.9 ka. This hypothesis predicts that the extinction of most of these animals should have occurred abruptly at 12.9 ka. To test this hypothesis, we have critically examined radiocarbon ages and the extinction stratigraphy of these taxa. From a large data pool, we selected only radiocarbon dates with low error margins with a preference for directly dated biological materials (e.g., bone, dung, etc.) and modern chemical purification techniques. A relatively small number of acceptable dates indicate that at least 16 animal genera and several other species became extinct close to 12.9 ka. These taxa include the most common animals of the late Pleistocene such as horses, camels, and mammoths. Also, the remains of extinct taxa are reportedly found up to, but not above, the base of a widely distributed carbon-rich layer called the black mat. This stratum forms an abrupt, major biostratigraphic boundary at the Younger Dryas onset (12.9 ka), which also contains multiple ET markers comprising the impact layer (the YDB). Surviving animal populations were abruptly reduced at the YDB (e.g., Bison), with major range restrictions and apparent evolutionary bottlenecks. The abruptness of this major extinction is inconsistent with the hypotheses of human overkill and climatic change. We argue that extinction ages older than 12.9 ka for many less common species result from the Signor-Lipps effect, but the impact hypothesis predicts that as new dates are acquired, they will approach ever closer to 12.9 ka. The megafaunal extinction is strongly associated with abrupt and major vegetation changes, abrupt cooling, and widespread biomass burning at the onset of the Younger Dryas over North America. The stratigraphic and chronologic data are consistent with megafaunal extinction being caused by continental-scale ecosystem disruption due to an ET impact.

  10. Soil Stratigraphy from Three Pleistocene Archaeological Sites of the Middle Ter River Valley, Catalonia, Spain

    OpenAIRE

    Sayantani NEOGI

    2010-01-01

    This dissertation summarizes the stratigraphic description of three Pleistocene archaeological sites inthe middle Ter river valley. A long history of archaeological research in this region suggests thepossibility of developing contextual studies. This work is basically an investigation of two soilformation processes from the deep soil horizons of the Mediterranean region: clay illuviation andcarbonatation. This approach has been developed by soil micromorphology, a technique well suitedfor th...

  11. An outline of the Pleistocene stratigraphy of the kleszczów Graben, bec?hatów outcrop, central Poland

    Science.gov (United States)

    Krzyszkowski, Dariusz

    The Pleistocene sequence of the Kleszczów Graben, central Poland, is located in a brown coal quarry 8 km long and 4 km wide. It contains ten separate organic horizons, in part, stacked one above another and, in part, correlated by reference to associated inorganic units using heavy minerals and gravel petrography. Three of the organic horizons represent interglacials: Ferdynandovian, Mazovian (Holsteinian) and Eemian. Others represent interstadial or periglacial deposits. The Tertiary/Quaternary boundary is recorded at the site by Reuverian C and prae-Tiglian biostratigraphy occurring in a single section. A major hiatus exists above the prae-Tiglian and Lower Pleistocene and Cromerian deposits are absent. Glacial deposits are represented by three Elsterian tills, five Saalian tills and glaciofluvial and glaciolacustrine deposits. The Czy?ów Formation lies between the Elsterian and Saalian deposits and contains at least two interglacials, the Ferdynandovian and Mazovian, and several interstadial units without glacial intervening deposits. The Lower Saalian (Odranian = Drenthe) deposits are separated from the Middle Saalian (Wartanian 1) by fluvial sands and organic deposits of the Pilica interstadial. The Middle (Wartanian 1) and Upper Saalian (Wartanian 2) also may be separated by an interstadial palaeosol. The evidence from the Kleszczów Graben, supported by other central European Quaternary sequences, suggest that only four glaciations occurred within the region during the Middle Pleistocene, and that these glaciations were separated by long periods with a complex climate ranging from temperate to periglacial.

  12. Final Pleistocene and Early Holocene at Sitio do Meio, Piauí, Brazil: Stratigraphy and comparison with Pedra Furada

    Directory of Open Access Journals (Sweden)

    Giulia Aimola

    2014-09-01

    Full Text Available English: Sitio do Meio, in southern Piaui, Brazil, is the second rock shelter presenting fully Pleistocene dates and artefacts after Pedra Furada.  Despite the anthropogenic origin of Pedra Furada artefacts has been questioned, SDM has better chances to be accepted by the scientific community because of the absence of the most relevant stone breaking agents in this kind of site, i.e. waterfalls. This paper presents a critical revision of the history of excavations (1980-2000, stratigraphy, chronology, and the archaeological content of the site (sector 2. At least 98 stone tools have been identified and described, all of them being older than 12,500 BP, i.e. belonging to the Upper Pleistocenic phase of Pedra Furada 3, as defined in the close reference site. The lithic industry of Serra Talhada phase (lower Holocene is also presented and compared with paleoindian sites of North-Eastern and Central Brazil.French:Le Sitio do meio, dans le  Piaui méridional (Brésil est le deuxième abri sous roche de la région ayant livré des dates pléistocènes en dehors du site de la Pedra Furada. L'article présente une révision critique des fouilles (1980-2000, la chronostratigraphie et le contenu archéologique du secteur 2. Une centaine d'outils lithiques sont décrits, ils sont plus anciens de 12,5 ka BP  et correspondent à la phase Pléistocène Pedra Furada 3 définie dans le site éponyme de référence. On présente aussi l' industrie lithique de la phase Serra Talhada (Holocène  ancien en la comparant aux industries paléoindiennes du Nord-Est et du centre du Brésil.

  13. Iwo Eleru's place among Late Pleistocene and Early Holocene populations of North and East Africa.

    Science.gov (United States)

    Stojanowski, Christopher M

    2014-10-01

    The Iwo Eleru site in Nigeria preserves the only terminal Pleistocene fossil from tropical West Africa. The peoples of this region contributed to significant population movements throughout the continent during the Holocene. As such, characterizing the phenotype of Late Pleistocene West African populations is critical for disentangling the evolutionary signatures of a highly complex African population history and structure. Previous research approached the calvaria's morphology from a paleoanthropological perspective, noting its mosaic of archaic and modern neurocranial features and distinctiveness from Pleistocene fossil taxa and contemporary modern human samples. In this paper, I compare Iwo Eleru with contemporary Late Pleistocene Africans and also consider the specimen's affinities with Holocene populations of the central and western Sahara, Nile Valley, and East Africa. Craniometric data were recorded for 22 neurocranial dimensions and subjected to principal components analysis and Mahalanobis distance estimation. Multidimensional scaling of distances indicated that Iwo Eleru fell outside the observed range of variation of other terminal Pleistocene supra-equatorial African populations, confirming previous results that documented its divergence from Neanderthals, Upper Paleolithic Europeans, and modern Africans. The calvaria was also distinct from Holocene Saharan, Nile Valley, and East African populations, which suggests limited West African input into the Sahara during the African Humid Period. Results presented here bolster previous research that suggested Iwo Eleru's anatomy reflected either admixture with archaic humans or the long-term survival of populations with more archaic neurocranial anatomy until the end of the Pleistocene. PMID:25065342

  14. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    Science.gov (United States)

    Vazquez, J. A.; Woolford, J. M.

    2015-09-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ˜1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ˜17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ˜17 ka, and produced a lava flow field covering ˜35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  15. Probabilistic sequence alignment of Late Pleistocene benthic ?18O data

    Science.gov (United States)

    Lawrence, C.; Lin, L.; Lisiecki, L. E.; Stern, J.

    2013-12-01

    The stratigraphic alignment of ocean sediment cores plays a vital role in paleoceanographic research because it is used to develop mutually consistent age models for climate proxies measured in these cores. The most common proxy used for alignment is the The stratigraphic alignment of ocean sediment cores plays a vital role in paleoceanographic research because it is used to develop mutually consistent age models for climate proxies measured in these cores. The most common proxy used for alignment is the ?18O of calcite from benthic or planktonic foraminifera because a large fraction of ?18O variance derives from the global signal of ice volume. To date, alignment has been performed either by manual, qualitative comparison or by deterministic algorithms (Martinson, Pisias et al. Quat. Res. 27 1987; Lisiecki and Lisiecki Paleoceanography 17, 2002; Huybers and Wunsch, Paleoceanography 19, 2004). Here we present a probabilistic sequence alignment algorithm which provides 95% confidence bands for the alignment of pairs of benthic ?18O records. The probabilistic algorithm presented here is based on a hidden Markov model (HMM) (Levinson, Rabiner et al. Bell Systems Technical Journal, 62,1983) similar to those that have been used extensively to align DNA and protein sequences (Durbin, Eddy et al. Biological Sequence Analysis, Ch. 4, 1998). However, here the need to the alignment of sequences stems from expansion and/or contraction in the records due to changes in sedimentation rates rather than the insertion or deletion of residues. Transition probabilities that are used in this HMM to model changes in sedimentation rates are based on radiocarbon estimates of sedimentation rates. The probabilistic algorithm considers all possible alignments with these predefined sedimentation rates. Exact calculations are completed using dynamic programming recursions. The algorithm yields the probability distributions of the age at each point in the record, which are probabilistically inferred from the LR04 stack. The complication of the central (1-?)% intervals of these distributions yields the confidence bands. In an extension of this work we are rebuilding the stack using a profile HMM model (Durbin, Eddy et al, Ch. 5). We analyze the confidence bands produced for the alignments of 35 Late Pleistocene benthic ?18O records to the LR04 benthic ?18O stack. We find that the mean width of 95% confidence bands for core alignments varies between 3-23 kyr depending on the resolution and noisiness of the core's ?18O signal. Confidence bands within individual cores also vary greatly, ranging from ~0 to >40 kyr. These alignment confidence bands will allow researchers to examine the robustness of their conclusions with respect to alignment uncertainty at all points in the record. Additionally, they should aid in the identification of possible errors in inferred ages in the input record (e.g., due to core disturbances) because such errors are likely to be associated with large, local uncertainty.

  16. Estratigrafía y geocronología de los dépositos del Pleistoceno tardío/Holoceno de la cuenca del arroyo La Estacada, departamentos de Tunuyán y Tupungato (Valle de Uco), Mendoza / Stratigraphy and geochronology of the Late Pleistocene-Holocene of the Arroyo La Estacada Basin, Departmets of Tunuyán and Tupungato (Uco Valley), Mendoza

    Scientific Electronic Library Online (English)

    Marcelo, Zárate; Adriana, Mehl.

    2008-09-01

    Full Text Available La cuenca del arroyo La Estacada, tributario del río Tunuyán, está situada en el piedemonte andino distal (Departamentos de Tupungato y Tunuyán, Mendoza). En este ámbito se realizaron estudios que abarcaron aspectos estratigráficos, sedimentológicos, geomorfológicos y geocronológicos (dataciones rad [...] iocarbónicas y luminiscencia óptica estimulada) de los depósitos del Pleistoceno tardío-Holoceno. Los resultados señalan que los depósitos componen tres unidades geomorfológicas (planicie de agradación regional, terraza de relleno y planicie de inundación actual) que representan sendos ciclos de agradación. La planicie agradacional está integrada por una sucesión sedimentaria dominantemente areno-limosa, con niveles de tefras y de gravas, cuya edad es mayor a 48.000 años AP y se extiende hasta alrededor de los 3.000 años 14C AP. La terraza de relleno está compuesta por una sucesión granodecreciente, que abarca un intervalo iniciado antes de los 5.500 14C AP hasta los 400-500 años 14C AP. Con posterioridad a estas últimas fechas, comenzaría la formación de la planicie de inundación actual, caracterizada por el apilamiento de bancos horizontales de arena. El levantamiento de perfiles estratigráficos, la litología de los depósitos y su expresión geomorfológica, así como las edades numéricas obtenidas, señalan que los límites estratigráficos, atribuidos originalmente a las Formaciones La Estacada y el Zampal, transgreden lateralmente los paquetes sedimentarios asignados a cada unidad. Considerando la litología y las relaciones estratigráficas observadas se propone agrupar los depósitos de ambas unidades, así como los de la planicie de inundación actual, en una sola unidad litoestratigráfica con rango de formación y de nombre Formación El Zampal. Abstract in english Arroyo La Estacada is a tributary of Rio Tunuyán situated in the distal Andean piedmont of Mendoza, Argentina. Stratigraphic, sedimentological and geomorphological analysis along with numerical dating by 14C and optical stimulated luminescence were performed on the late Pleistocene-Holocene deposits [...] . Three geomorphological units (regional aggradational plain, fill terrace and the present floodplain) have been identified. The regional aggradational plain is made up of a sedimentary succession dominantly composed of sandy-silty deposits; the sediment accumulation started prior to 48,000 years BP and continued until circa 3,000 14C years AP. The fill terrace is composed of a fining upward sequence encompassing a time interval older than 5,500 14C BP and extending until 400-500 14C years BP. The present floodplain, made up of sand beds, was formed after 400-500 14C years BP. Based on the results obtained, the stratigraphic boundaries originally attributed to La Estacada Formation and El Zampal Formation are laterally transgressive in relation to the sedimentary beds included in each of these lithostratigraphic units. Considering both their lithology and stratigraphic relationships we propose to group these deposits into a single lithostratigaphic unit named El Zampal Formation.

  17. Evidences of climatic variations during Late Pleistocene- Holocene in the eastern Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.; Borole, D.V.; Gujar, A.R.; Mascarenhas, A.; Mislankar, P.G.; Rao, Ch.M.

    Based upon the variations of clay minerals, sediment texture, heavy mineral assemblage and sup(230)Th excess in the Late Pleistocene sediments of a hemipelagic core from the eastern Bay of Bengal (2713 m water depth), 35 cm and 73-78 cm levels...

  18. Reconstructing the Last Pleistocene (Late Devensian) Glaciation on the Continental Margin of Northwest Britain

    OpenAIRE

    Davison, Stephen

    2005-01-01

    The continental margin in the area west of Shetland was subjected to repeated and extensive ice sheet advances during the Late Pleistocene. Seabed imagery, seismic survey and borehole core data show the Late Devensian ice sheets expanded across the continental shelf three times, two of these advances reaching the shelf edge. On the inner shelf, where present-day water depths are generally less than 100m, only thin sediments from the last retreat phase and exposed rock surfaces ...

  19. Late Cenozoic structure and stratigraphy of south-central Washington

    International Nuclear Information System (INIS)

    The structural framework of the Columbia Basin began developing before Columbia River Basalt Group (CRBG) volcanism. Prior to 17.5 Ma, the eastern part of the basin was a relatively stable area, with a basement of Paleozoic and older crystalline rock. The western part was an area of subsidence in which large volumes of sediment and volcanic rocks accumulated. Concurrent with eruption of the CRBG, anticlinal ridges of the Yakima Fold Belt (YFB) were growing under north-south compression. Topographic expression of these features was later masked by the large volume of CRBG basalt flowing west from fissures in the eastern Columbia Basin. The folds continued to develop after cessation of volcanism, leading to as much as 1,000 m of structural relief in the past 10 million years. Post-CRBG evolution of the Columbia Basin is recorded principally in folding and faulting in the YFB and sediments deposited in the basins. The accompanying tectonism resulted in lateral migration of major depositional systems into subsiding structural lows. Although known late Cenozoic faults are on anticlinal ridges, earthquake focal mechanisms and contemporary strain measurements indicate most stress release is occurring in the synclinal areas under north-south compression. There is no obvious correlation between focal mechanisms for earthquakes whose foci are in the CRBG and the location of known faults. High in situ stress values help to explain the occurrence of microseismicity in the Columbia Basin but not the pattern. Microseismicity appears to occur in unaltered fresh basalt. Faulted basalt associated with the YFB is highly brecciated and commonly altered to clay. The high stress, abundance of ground water in confined aquifers of the CRBG, and altered basalt in fault zones suggest that the frontal faults on the anticlinal ridges probably have some aseismic deformation. 85 refs

  20. Origin of late pleistocene formation water in Mexican oil reservoirs

    International Nuclear Information System (INIS)

    Brine water invasion into petroleum reservoirs, especially in sedimentary basins, are known from a variety of global oil field, such as the Western Canada sedimentary basin and, the central Mississippi Salt Dome basin (Kharaka et al., 1987). The majority of oil wells, especially in the more mature North American fields, produce more water than they do oil (Peachey et al., 1998). In the case of Mexican oil fields, increasing volumes of invading water into the petroleum wells were detected during the past few years. Major oil reserves in the SE-part of the Gulf of Mexico are economically affected due to decreases in production rate, pipeline corrosion and well closure. The origin of deep formation water in many sedimentary basins is still controversial: Former hypothesis mainly in the 60's, explained the formation of formation water by entrapment of seawater during sediment deposition. Subsequent water-rock interaction processes explain the chemical evolution of hydrostatic connate water. More recent hydrodynamic models, mainly based on isotopic data, suggest the partial migration of connate fluids, whereas the subsequent invasion of surface water causes mixing processes (Carpenter 1978). As part of the presented study, a total of 90 oil production wells were sampled from 1998 to 2004 to obtain chemical (Major and trace elements) and isotopic composition (2H, 13C, 14C, 18O 36Cl, 37Cl, 87Sr, 129I, tritium) of deep formation water at the Mexican Gulf coast. Samples were extracted from carbonate-type reservoirs of the oil fields Luna, Samaria-Sitio Grande, Jujo-Tecominoac (on-shore), and Pol-Chuc (off-shore, including Abkatun, Batab, Caan, and Taratunich) at a depth between 2,900 m b.s.l. and 6,100 m b.s.l. During the field work, the influence of atmospheric contamination e.g. by CO2-atmospheric input was avoided by using an interval sampler to get in-situ samples from the extraction zone of selected bore holes. For wellhead samples, a 20 liter-sampling-reagent was previously filled with N2-gas for the collection and phase separation of the pressurized gas-water-crude oil mixture. No differences in 14C-concentrations were detected applying, both, conventional and AMS-techniques. In contradiction to the expected 'fossil age' of reservoir water as part of a stagnant hydraulic system, measured 14C-concentrations between 0.89 pmC and 31.86 pmC indicate a late Pleistocene-early Holocene, regional event for the infiltration of surface water into the reservoir. The variety in water mineralization from meteoric (TDSmax = 0.5 g/l) to hyper-saline composition (TDSmax = 338 g/l) is not caused by halite dissolution from adjacent salt domes, as shown by elevated Br/Cl ratios. In contrary, the linear correlation between 18O and Cl values reflect varying mixing proportions of two components - meteoric water and evaporated seawater. Instead of water/rock-interaction, evaporation of seawater at the surface prior to infiltration represents the principal process for fluid enrichment in 18O and chlorine, with maximum values of 17.2 %o and 228 g/l, respectively. The young residence time of formation water in Mexican oil reservoirs implies following: - The common assumption of 'hydraulically-frozen' reservoirs is not correct, as main descending fluid migration occurred during glacial period. Probably, major infiltration processes are related to periods with climatic changes and increased humidity - as observed for the adjacent Yucatan region in SE-Mexico during early-mid Holocene (6,000 yr BP) (Metcalfe et al. 2000) - with the probable transgression of Mexican Gulf seawater into the recent Mexican coastal plain. - The common hypothesis of hydrocarbon maturation within Jurassic organic-rich layers, and its subsequent expulsion and migration into Cretaceous/Tertiary sedimentary units must be expanded by a last-step-process: As glacial ground water level is actually located below the hydrocarbon column (due to differences in density), a general mobilization of the entire column of reservoir fluids and the displacement of the organic phase must be pos

  1. The potential use of the TL dating method in chronological studies of Late Pleistocene

    International Nuclear Information System (INIS)

    At present the thermoluminescence method has claimed particular attention because of the wide distribution of its study objects - natural quartz and feldspars in Pleistocene deposits. Since the dating of geological deposits is connected with several specific complications, geological interpretation is of great importance while using the TL technique. The above approach was applied to the study of tens of Late Pleistocene sections on the East European plain and in the Spitsbergen archipelago. In this paper, specific factual material is analysed and on this basis, the criteria of the reliability of dates are presented. (author)

  2. Middle Pleistocene magnetostratigraphy and susceptibility stratigraphy: data from a carbonate aeolian system, Mallorca, Western Mediterranean

    Science.gov (United States)

    Nielsen, K. A.; Clemmensen, L. B.; Fornós, J. J.

    2004-09-01

    This study shows that successions of Pleistocene carbonate aeolian deposits can be placed successfully in a geochronologic framework using magnetostratigraphic and susceptibility stratigraphic analysis supplemented by luminescence dating, studies of wave-cut platforms, and biostratigraphic evidence. The investigated aeolian system covers a significant part of southernmost Mallorca and is exposed in impressive coastal cliff sections. At the study site at Els Bancals the aeolian system has a maximum thickness of 16 m and is composed of alternating dark red colluvial deposits and greyish red aeolian dune and sand-sheet deposits forming seven cyclostratigraphic units. Each cyclostratigraphic unit represents landscape stabilisation, colluviation, and soil formation followed by dunefield development, when marine carbonate sand was transported far inland by westerly or north-westerly winds. The aeolian system is located on top of a wave-cut marine platform 12-14 m a.s.l. This platform probably formed during a sea-level highstand in Marine Isotope Stage (MIS) 11 (427-364 ka), and renewed marine activity probably later in MIS 11 is indicated by the formation of beach deposits. Two sections at Els Bancals were sampled for a paleomagnetic study; additional samples were taken to detect variations in magnetic susceptibility (MS). The characteristic remanent magnetisation has been recovered for the most part of the succession in spite of diagenetic overprinting. There is evidence for two probably three reversal polarity excursions, possible connected to the Levantine, CR1 and CR0/Biwa III episodes. If this correlation is correct, the sampled succession represents a time interval in the Middle Pleistocene between ca 410 and ca 260 ka. This age estimate is supported by the MS study and by luminescence dates of 333±70 ka (aeolianite from lower part of the succession) and 275±23 ka (aeolianite from the top of the succession). The nature of the succession suggests deposition during alternating warm and moist (colluvial deposition; soil formation) and cold, dry and windy conditions (dunefield formation). The susceptibility signal can be correlated with the insolation signal at 65°N suggesting that environmental variation on Mallorca was linked to orbitally forced climate change, and it seems that aeolian activity and dunefield formation were linked to glacial or stadial periods.

  3. Sequence stratigraphy of the Nukumaruan stratotype (Pliocene-Pleistocene, c. 2.08-1.63 Ma), Wanganui Basin, New Zealand

    International Nuclear Information System (INIS)

    Late Pliocene to Early Pleistocene (c. 2.08-1.63 Ma) strata exposed in coastal cliffs along Nukumaru and Ototoka beaches near Wanganui, between the top of the Nukumaru Limestone and the base of the Butlers Shell Conglomerate, comprise 11 depositional sequences of a total thickness of c. 86 m. The sequences consist predominantly of siliciclastic shoreline facies. Non-marine facies (including palaeosols), and a variety of shallow-marine shellbed facies, are also represented. Patterns in facies composition and sequence architecture reveal three sequence motifs (Maxwell, Nukumaru, and Birdgrove) that represent progressively increasing maximum palaeowater depths within a broadly basin-margin palaeogeographic setting. The sequence motif changes systematically up section and records a lower order tectonic influence on accommodation that has modulated the stacking patterns of individual sequences. Correlation of the sequences with oxygen isotope stages 77-57 is achieved using the basin-wide Ototoka tephra, and indicates that the sequences accumulated in response to obliquity driven (41 k.y. duration) glacio-eustatic sea-level oscillations. Correlation of the Nukumaru coast sequences with other sections along basin strike, and the global oxygen isotope record indicates that (i) 500 k.y. (?18O stages MIS 56-34) is missing at the unconformity between the Nukumaruan and overlying Castlecliffian stratotypes on the Wanganui coast, and (ii) the Pliocene-Pleistocene boundary lies within sequence NC7 at the base of the Lower Maxwell Formation. (author). 52 refs., 15 figs., 2 tabs

  4. Late quaternary stratigraphy and sedimentology of the inner part of southwest Joseph Bonaparte Gulf

    International Nuclear Information System (INIS)

    Joseph Bonaparte Gulf is a large embayment on the northwestern continental margin of Australia. It is approximately 300 km east-west and 120 km north-south with a broad continental shelf to seaward. Maximum width from the southernmost shore of Joseph Bonaparte Gulf to the edge of the continental shelf is 560 km. Several large rivers enter the gulf along its shores. The climate is monsoonal. sub-humid, and cyclone-prone during the December-March wet season. A bedrock high (Sahul Rise) rims the shelf margin. The sediments within the gulf are carbonates to seaward, grading into clastics inshore. A seaward-thinning wedge of highstand muds dominates the sediments of the inner shelf of Joseph Bonaparte Gulf. Mud banks up to 15m thick have developed inshore. Coarse-grained sand ridges up to 15m high are found off the mouth of the Ord River. These overlie an Upper Pleistocene transgressive lag of mixed carbonate and gravelly siliciclastic sand. Four drowned strandlines are present on the inner shelf at depths of 20, 25, 28 and 30 m below datum. These are interpreted as having formed during stillstands in the Late Pleistocene transgression. Older strandlines at great depths are inferred as having formed during the fall in sea-level following the last highstand. For the most part the Upper Pleistocene-Holocene marine sediments overlie an erosion surface cut into older Pleistocene sediments. Incised valleys cut into this erosion surface are up to 5 km wide and have a relief of at least 20 m. The largest valley is that cut by the Ord River. Upper Pleistocene sediments deposited in the incised valleys include interpreted lowstand fluvial gravels, early transgressive channel sands and floodplain silts, and late transgressive estuarine sands and gravels. Spot samples were collected and subjected to 14C dating, x-ray diffraction and palynological studies. Older Pleistocene sediments are inferred to have been deposited before and during the 120 ka highstand (isotope stage 5). They consist of sandy calcarenites deposited in high-energy tide-dominated shelf environments. Still older shelf and valley-fill sediments underlie these. The contrast between the Holocene muddy clastic sediments and the sandy carbonates deposited by the 120 ka highstand suggests that either the climate was more arid in the past, with less fluvial transport. or that mud was more effectively trapped in estuaries, allowing development of carbonate depositional environments inshore. Copyright (2000) Geological Society of Australia

  5. Late Pleistocene to Holocene environmental changes from ?13C determinations in soils at Teotihuacan, Mexico

    Directory of Open Access Journals (Sweden)

    E. Vallejo Gómez

    2006-05-01

    Full Text Available Stable carbon isotopic signature (?13C of soil organic matter (SOM is used as a high-spatial resolution tool to infer environmental changes during late Pleistocene to Present in the Teotihuacan valley, Mexico. Interpretation was based on climatic preferences of C3, CAM and C4 plant groups. ?13C values of modern plant types are clearly distinguished. C3 plants display values around –27‰, while C4 and CAM plants have values around––13‰. Data from soil profiles range from -25.7 to -15.5 ‰. Cerro Gordo site ?13C varyies around -20‰, indicating long-term, time-stable co-existence between C3 and C4 or CAM plants. The more depleted signatures (-23 ± 2 ‰ are, dominated by carbon from C3 vegetation of late Pleistocene swamp paleosols in the Tepexpan profile of the Lake Texcoco. Younger paleosols from lower valley sites, have less depleted values (-17 ± 1 ‰, dominated by C4 and CAM carbon. Late Holocene and modern soils present slightly more negative values (1-2 ‰ with respect to ?13C of underlying soils. Our results show 1 an increase of 10-70 % depending on the site, during the transition from the late Pleistocene to early Holocene, and 2 a dominance of C4 vegetation, up to 84%, in valley environment during the middle Holocene. These data support a climatic change from cold and wet conditions in the Last Glacial Maximum and late Pleistocene, to warm and dry conditions in middle Holocene. A slight rise in moisture availability during late Holocene is inferred based on the 4-10% increase in C3 plant carbon in soils from the valley. Conditions remained generally warm and dry, much as they are at present, favouring the development of agriculture in the valley. Our interpretation agrees with results of paleoenvironmental studies at Texcoco Lake based on diatom and pollen analyses in lake.

  6. Radiocarbon age of late pleistocene-holocene paleogeographic events of the Northern Precaspian

    International Nuclear Information System (INIS)

    Results of radiocarbon dating of material of mollusks shells and phyto remnants from holocene sedimentations of the Northern Caspian Sea region are provided. The established age of the carbonate-organogenic material permits quantitative estimation of paleographic events in the Northern Caspian Sea region in the end of late pleistocene-holocene period. It is pointed out that employment in the study of the radiocarbon dating method permits improving essentially the reliability of the results obtained

  7. Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes

    Science.gov (United States)

    Johnson, Thomas C.; Scholz, Christopher A.; Talbot, Michael R.; Kelts, Kerry; Ricketts, R. D.; Ngobi, Gideon; Beuning, Kristina; Ssemmanda, Immacculate; McGill, J. W.

    1996-08-01

    Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid.

  8. Large Late Pleistocene landslides from the marginal slope of the Flysch Carpathians.

    Czech Academy of Sciences Publication Activity Database

    Pánek, T.; Hartvich, Filip; Jankovská, Vlasta; Klimeš, Jan; Tábo?ík, Petr; Bubík, M.; Smolková, V.; Hradecký, J.

    2014-01-01

    Ro?. 11, ?. 6 (2014), s. 981-992. ISSN 1612-510X R&D Projects: GA MŠk LM2010008 Institutional support: RVO:67985891 ; RVO:67985939 Keywords : fossil landslide * radiocarbon dating * electrical resistivity tomography * pollen analysis * Late Pleistocene * Flysch Carpathians * Marine Isotope Stage 3 Subject RIV: DE - Earth Magnetism, Geodesy, Geography; EF - Botanics (BU-J) Impact factor: 2.870, year: 2014

  9. Characterizing the Late Pleistocene MSA Lithic Technology of Sibudu, KwaZulu-Natal, South Africa

    OpenAIRE

    Will, Manuel; Bader, Gregor D.; Nicholas J. Conard

    2014-01-01

    Studies of the African Middle Stone Age (MSA) have become central for defining the cultural adaptations that accompanied the evolution of modern humans. While much of recent research in South Africa has focused on the Still Bay and Howiesons Poort (HP), periods following these technocomplexes were often neglected. Here we examine lithic assemblages from Sibudu that post-date the HP to further the understanding of MSA cultural variability during the Late Pleistocene. Sibudu preserves an except...

  10. Study of cave sediments in Budimirica Cave, Macedonia FYR – Correlation to late pleistocene environmental changes.

    Czech Academy of Sciences Publication Activity Database

    Temovski, M.; Bosák, Pavel; Pruner, Petr; Hercman, H.

    Postojna : Karst Research Institute, Research Centre of the Slovenian Academy of Sciences and Arts,, 2015 - (Zupan Hajna, N.; Mihevc, A.; Gostin?ar, P.). s. 150-151 ISBN 978-961-254-808-7. [International Karstological School Classical Karst /23./. 15.06.2015-19.06.2015, Postojna] Institutional support: RVO:67985831 Keywords : Budimirica Cave * cave sediments * magnetostratigraphy * Late Pleistocene * paleoenvironment Subject RIV: DB - Geology ; Mineralogy http://iks.zrc-sazu.si/datoteke/IKS-23-Guide-book-2015.pdf

  11. Relationship between Late Pleistocene sea-level variations, carbonate platform morphology and aragonite production (Maldives, Indian Ocean)

    DEFF Research Database (Denmark)

    Paul, A.; Reijmer, J.J.G.; Fürstenau, J.; Kinkel, Hanno; Betzler, C.

    2012-01-01

    A piston core from the Maldives carbonate platform was investigated for carbonate mineralogy, grain-size distributions, calcium carbonate content and organic carbon. The sedimentary record was linked to Late Pleistocene sea-level variations, using an age model based on oxygen isotopes obtained from planktonic foramanifera, nannofossil biostratigraphy and C age determinations. The correlation between the sedimentary record and Late Pleistocene sea-level showed that variations in aragonite and mud...

  12. Distribution of late Pleistocene ice-rich syngenetic permafrost of the Yedoma Suite in east and central Siberia, Russia

    Science.gov (United States)

    Grosse, Guido; Robinson, Joel E.; Bryant, Robin; Taylor, Maxwell D.; Harper, William; DeMasi, Amy; Kyker-Snowman, Emily; Veremeeva, Alexandra; Schirrmeister, Lutz; Harden, Jennifer

    2013-01-01

    This digital database is the product of collaboration between the U.S. Geological Survey, the Geophysical Institute at the University of Alaska, Fairbanks; the Los Altos Hills Foothill College GeoSpatial Technology Certificate Program; the Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany; and the Institute of Physical Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences. The primary goal for creating this digital database is to enhance current estimates of soil organic carbon stored in deep permafrost, in particular the late Pleistocene syngenetic ice-rich permafrost deposits of the Yedoma Suite. Previous studies estimated that Yedoma deposits cover about 1 million square kilometers of a large region in central and eastern Siberia, but these estimates generally are based on maps with scales smaller than 1:10,000,000. Taking into account this large area, it was estimated that Yedoma may store as much as 500 petagrams of soil organic carbon, a large part of which is vulnerable to thaw and mobilization from thermokarst and erosion. To refine assessments of the spatial distribution of Yedoma deposits, we digitized 11 Russian Quaternary geologic maps. Our study focused on extracting geologic units interpreted by us as late Pleistocene ice-rich syngenetic Yedoma deposits based on lithology, ground ice conditions, stratigraphy, and geomorphological and spatial association. These Yedoma units then were merged into a single data layer across map tiles. The spatial database provides a useful update of the spatial distribution of this deposit for an approximately 2.32 million square kilometers land area in Siberia that will (1) serve as a core database for future refinements of Yedoma distribution in additional regions, and (2) provide a starting point to revise the size of deep but thaw-vulnerable permafrost carbon pools in the Arctic based on surface geology and the distribution of cryolithofacies types at high spatial resolution. However, we recognize that the extent of Yedoma deposits presented in this database is not complete for a global assessment, because Yedoma deposits also occur in the Taymyr lowlands and Chukotka, and in parts of Alaska and northwestern Canada.

  13. An Arctic perspective on dating Mid-Late Pleistocene environmental history

    DEFF Research Database (Denmark)

    Alexanderson, Helena; Backman, Jan

    2014-01-01

    To better understand Pleistocene climatic changes in the Arctic, integrated palaeoenvironmental and palaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologic age control are required, not least for correlation to extra-Arctic records. In this paper we discuss, from an Arctic perspective, methods and correlation tools that are commonly used to date Arctic Pleistocene marine and terrestrial events. We review the state of the art of Arctic geochronology, with focus on factors that affect the possibility and quality of dating, and support this overview by examples of application of modern dating methods to Arctic terrestrial and marine sequences. Event stratigraphy and numerical ages are important tools used in the Arctic to correlate fragmented terrestrial records and to establish regional stratigraphic schemes. Age control is commonly provided by radiocarbon, luminescence or cosmogenic exposure ages. Arctic Ocean deep-sea sediment successions can be correlated over large distances based on geochemical and physical property proxies for sediment composition, patterns in palaeomagnetic records and, increasingly, biostratigraphic data. Many of these proxies reveal cyclical patterns that provide a basis for astronomical tuning. Recent advances in dating technology, calibration and age modelling allow for measuring smaller quantities of material and to more precisely date previously undatable material (i.e. foraminifera for 14C, and single-grain luminescence). However, for much of the Pleistocene there are still limits to the resolution of most dating methods. Consequently improving the accuracy and precision (analytical and geological uncertainty) of dating methods through technological advances and better understanding of processes are important tasks for the future. Another challenge is to better integrate marine and terrestrial records, which could be aided by targeting continental shelf and lake records, exploring proxies that occur in both settings, and by creating joint research networks that promote collaboration between marine and terrestrial geologists and modellers

  14. Increased late Pleistocene erosion rates during fluvial aggradation in the Garhwal Himalaya, northern India

    Science.gov (United States)

    Scherler, Dirk; Bookhagen, Bodo; Wulf, Hendrik; Preusser, Frank; Strecker, Manfred R.

    2015-10-01

    The response of surface processes to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Himalaya, most large rivers feature prominent fill terraces that record an imbalance between sediment supply and transport capacity, presumably due to past fluctuations in monsoon precipitation and/or effects of glaciation at high elevation. Here, we present volume estimates, chronological constraints, and 10Be-derived paleo-erosion rates from a prominent valley fill in the Yamuna catchment, Garhwal Himalaya, to elucidate the coupled response of rivers and hillslopes to Pleistocene climate change. Although precise age control is complicated due to methodological problems, the new data support formation of the valley fill during the late Pleistocene and its incision during the Holocene. We interpret this timing to indicate that changes in discharge and river-transport capacity were major controls. Compared to the present day, late Pleistocene hillslope erosion rates were higher by a factor of ?2-4, but appear to have decreased during valley aggradation. The higher late Pleistocene erosion rates are largely unrelated to glacial erosion and could be explained by enhanced sediment production on steep hillslopes due to increased periglacial activity that declined as temperatures increased. Alternatively, erosion rates that decrease during valley aggradation are also consistent with reduced landsliding from threshold hillslopes as a result of rising base levels. In that case, the similarity of paleo-erosion rates near the end of the aggradation period with modern erosion rates might imply that channels and hillslopes are not yet fully coupled everywhere and that present-day hillslope erosion rates may underrepresent long-term incision rates.

  15. Late Pleistocene differential uplift inferred from the analysis of fluvial terraces (southern Apennines, Italy)

    Science.gov (United States)

    Giano, Salvatore Ivo; Giannandrea, Paolo

    2014-07-01

    The stratigraphic architecture and morphological assemblage of the Pleistocene fluvial terraces contained in two contiguous fluvial valleys are used to understand the spatial distribution and the timing of the differential uplift that affected two different geological and geomorphological settings of an active orogen. The study areas, both placed in the eastern sector of the southern Apennines of Italy, are the Sant'Arcangelo sedimentary basin and the Valsinni Ridge anticline. Pleistocene uplift rate of 0.7-0.9 mm y- 1 and historical earthquakes affecting those areas suggest active tectonics. Based on the synthem units used to classify the fluvial deposits in the field, several strath, fill, and fill-cut terraces have been mapped in the middle valleys of the Agri and Sinni rivers. Four Middle Pleistocene high terraces (Qes) are found in the Sant'Arcangelo Basin and cut its infill, and three Late Pleistocene low terraces (Qt) are found at both the Agri and Sinni valley flanks. The Agri and Sinni rivers cross-cut the NW-SE-oriented fold-and-thrust belt of the southern Apennines from W to E, producing a transverse drainage. As a result, ten- to hundred-metre deep gorges and wide floodplains were created in the middle reach of the river valleys. Computation of the bedrock incision rates from the Qes1, Qes4, and SQt1 terraces, corresponding to 1.2 ± 0.2 mm y- 1 at 400-240 ka and 0.8 ± 0.2 mm y- 1 in the last 240 ka, together with the terrace profile arrangements in the Agri and Sinni valleys, allow for the documentation of i) the differential uplift of the study area and ii) the age of terrace abandonment corresponding to the beginning age of the vertical incision in the valley floor sediments to form the Qt terraces. The differential uplift is subsequently discussed in a space and time-sequence evolution of the Late Pleistocene to assess the complex morphotectonic development that occurred in the eastern threshold of the basin. The differential uplift of both the Sant'Arcangelo Basin and Valsinni Ridge would appear to indicate that buried fold-and-thrust structures that affect the Mesozoic-Cenozoic sedimentary nappes are still active, and they also controlled the slab retreat processes in the Mediterranean region during the Late Pleistocene.

  16. Denali fault slip rates and Holocene-late Pleistocene kinematics of central Alaska

    Science.gov (United States)

    Matmon, A.; Schwartz, D.P.; Haeussler, P.J.; Finkel, R.; Lienkaemper, J.J.; Stenner, H.D.; Dawson, T.E.

    2006-01-01

    The Denali fault is the principal intracontinental strike-slip fault accommodating deformation of interior Alaska associated with the Yakutat plate convergence. We obtained the first quantitative late Pleistocene-Holocene slip rates on the Denali fault system from dating offset geomorphic features. Analysis of cosmogenic 10Be concentrations in boulders (n = 27) and sediment (n = 13) collected at seven sites, offset 25-170 m by the Denali and Totschunda faults, gives average ages that range from 2.4 ?? 0.3 ka to 17.0 ?? 1.8 ka. These offsets and ages yield late Pleistocene-Holocene average slip rates of 9.4 ?? 1.6, 12.1 ?? 1.7, and 8.4 ?? 2.2 mm/yr-1 along the western, central, and eastern Denali fault, respectively, and 6.0 ?? 1.2 mm/yr-1 along the Totschunda fault. Our results suggest a westward decrease in the mean Pleistocene-Holocene slip rate. This westward decrease likely results from partitioning of slip from the Denali fault system to thrust faults to the north and west. ?? 2006 Geological Society of America.

  17. Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa.

    Science.gov (United States)

    Mackay, Alex; Stewart, Brian A; Chase, Brian M

    2014-07-01

    The later Pleistocene archaeological record of southernmost Africa encompasses several Middle Stone Age industries and the transition to the Later Stone Age. Through this period various signs of complex human behaviour appear episodically, including elaborate lithic technologies, osseous technologies, ornaments, motifs and abstract designs. Here we explore the regional archaeological record using different components of lithic technological systems to track the transmission of cultural information and the extent of population interaction within and between different climatic regions. The data suggest a complex set of coalescent and fragmented relationships between populations in different climate regions through the late Pleistocene, with maximum interaction (coalescence) during MIS 4 and MIS 2, and fragmentation during MIS 5 and MIS 3. Coalescent phases correlate with increases in the frequency of ornaments and other forms of symbolic expression, leading us to suggest that population interaction was a significant driver in their appearance. PMID:24746546

  18. Ancient DNA reveals that bowhead whale lineages survived Late Pleistocene climate change and habitat shifts

    DEFF Research Database (Denmark)

    Foote, Andrew D; Kaschner, Kristin

    2013-01-01

    The climatic changes of the glacial cycles are thought to have been a major driver of population declines and species extinctions. However, studies to date have focused on terrestrial fauna and there is little understanding of how marine species responded to past climate change. Here we show that a true Arctic species, the bowhead whale (Balaena mysticetus), shifted its range and tracked its core suitable habitat northwards during the rapid climate change of the Pleistocene-Holocene transition. Late Pleistocene lineages survived into the Holocene and effective female population size increased rapidly, concurrent with a threefold increase in core suitable habitat. This study highlights that responses to climate change are likely to be species specific and difficult to predict. We estimate that the core suitable habitat of bowhead whales will be almost halved by the end of this century, potentially influencing future population dynamics.

  19. Drainage reversals in Mono Basin during the late pliocene and Pleistocene

    Science.gov (United States)

    Reheis, M.C.; Stine, S.; Sarna-Wojcicki, A. M.

    2002-01-01

    Mono Basin, on the eastern flank of the central Sierra Nevada, is the highest of the large hydrographically closed basins in the Basin and Range province. We use geomorphic features, shoreline deposits, and basalt-filled paleochannels to reconstruct an early to middle Pleistocene record of shorelines and changing spillways of Lake Russell in Mono Basin. During this period of time, Lake Russell repeatedly attained altitudes between 2205 and 2280 m-levels far above the present surface of Mono Lake (~1950 m) and above its last overflow level (2188 m). The spill point of Lake Russell shifted through time owing to late Tertiary and Quaternary faulting and volcanism. During the early Pleistocene, the lake periodically discharged through the Mount Hicks spillway on the northeastern rim of Mono Basin and flowed northward into the Walker Lake drainage basin via the East Walker River. Paleochannels recording such discharge were incised prior to 1.6 Ma, possibly between 1.6 and 1.3 Ma, and again after 1.3 Ma (ages of basaltic flows that plugged the paleochannels). Faulting in the Adobe Hills on the southeastern margin of the basin eventually lowered the rim in this area to below the altitude of the Mount Hicks spillway. Twice after 0.76 Ma, and possibly as late as after 0.1 Ma, Lake Russell discharged southward through the Adobe Hills spillway into the Owens-Death Valley system of lakes. This study supports a pre-Pleistocene aquatic connection through Mono Basin between the hydrologically distinct Lahontan and Owens-Death Valley systems, as long postulated by biologists, and also confirms a probable link during the Pleistocene for species adapted to travel upstream in fast-flowing water.

  20. Late Pleistocene Estuarine Channel-Fill Sediments on the New Jersey Shelf: Response to Glacio-eustatic Sea Level Rise

    Science.gov (United States)

    Stackhouse, S.; Goff, J. A.; Christensen, B. A.; Austin, J. A.

    2008-12-01

    The shallow New Jersey continental shelf has been an area of study for many decades. Evidence for the shelf's response to the Late Pleistocene glacio-eustatic sea level rise, confined principally to interpreted estuarine fill strata within fluvial channel systems, has been imaged extensively with high resolution chirp seismic data. However, little work has been done on sediment samples of these units. This study aids in the ground truthing of previous seismic stratigraphic work done on the New Jersey shelf channel-fill sediments by analyzing cores collected during the summer of 2007. The infilled channels from the study area are characterized as fossil riverine systems that developed on the exposed shelf during the Last Glacial Maximum lowstand ~18 ka. Subsequent sea level rise ~15-10 ka flooded and modified the valleys, forming estuaries. Allen and Posamentier's (1993) stratigraphic model of transgressive estuarine deposition posits the following ordered sequence: (1) a fluvial lag deposit, (2) estuarine mixed sands and muds (3) basin fill mud, and finally (4) estuarine mouth complex sediments. Seismic data over the buried channels on the outer New Jersey shelf (~80 m water depth) exhibit clearly identifiable seismic facies bounded by mostly horizontal boundaries that can be correlated to this interpretation (Nordfjord et al. 2006) We collected one core into these sediments, which likely sampled the estuarine mouth complex and basin fill muds. Previously collected cores supplement our analysis of these sediments. Seismic data over mid-shelf (~30 m water depth) valley channel fill stratigraphy is strikingly different, with finely-laminated U-shaped layering throughout the section, and often with cut-and-fill sequences. We collected 7 cores into these sediments. The cores ranged from 25cm to 5.8m in length. Thus far we have conducted grain size analysis via gross division of the percent of sand, silt, and clay. Initial results indicate that the laminated mid-shelf channel fill units are dominated by fine sands, suggesting a much higher-energy estuarine environment than when the outer-shelf channels were filled. Further grain size analysis will be conducted by sedigraph and settling tube. Radiocarbon analysis of the stratigraphy is being provided by the shell fragments and organic mud within the samples. We obtained one reliable shell fragment 14C date of 9389 ±79 years and eight bulk carbon 14C dates ranging from 10975 to 11445 years, with a strong terrestrial signature. The foraminiferal assemblages found within the sediment samples should eventually aid in determining the depositional environment.

  1. Late Pleistocene Sea level on the New Jersey Margin: Implications to eustasy and deep-sea temperature

    Science.gov (United States)

    Wright, James D.; Sheridan, Robert E.; Miller, Kenneth G.; Uptegrove, Jane; Cramer, Benjamin S.; Browning, James V.

    2009-03-01

    We assembled and dated a late Pleistocene sea-level record based on sequence stratigraphy from the New Jersey margin and compared it with published records from fossil uplifted coral reefs in New Guinea, Barbados, and Araki Island, as well as a composite sea-level estimate from scaling of Red Sea isotopic values. Radiocarbon dates, amino acid racemization data, and superposition constrain the ages of large (20-80 m) sea-level falls from New Jersey that correlate with Marine Isotope Chrons (MIC) 2, 3b, 4, 5b, and 6 (the past 130 kyr). The sea-level records for MIC 1, 2, 4, 5e, and 6 are similar to those reported from New Guinea, Barbados, Araki, and the Red Sea; some differences exist among records for MIC 3. Our record consistently provides the shallowest sea level estimates for MIC3 (˜ 25-60 m below present); it agrees most closely with the New Guinea record of Chappell (2002; ˜ 35-70 m), but contrasts with deeper estimates provided by Araki (˜ 85-95 m) and the Red Sea (50-90 m). Comparison of eustatic estimates with benthic foraminiferal ?18O records shows that the deep sea cooled ˜ 2.5 °C between MIC 5e and 5d (˜ 120-110 ka) and that near freezing conditions persisted until Termination 1a (14-15 ka). Sea-level variations between MIC 5b and 2 (ca. 90-20 ka) follow a well-accepted 0.1‰/10 m linear variation predicted by ice-growth effects on foraminiferal ?18O values. The pattern of deep-sea cooling follows a previously established hysteresis loop between two stable modes of operation. Cold, near freezing deep-water conditions characterize most of the past 130 kyr punctuated only by two warm intervals (the Holocene/MIC 1 and MIC 5e). We link these variations to changes in Northern Component Water (NCW).

  2. Deciphering Late-Pleistocence landscape evolution: linking proxies by combining pedo-stratigraphy and luminescence dating

    Science.gov (United States)

    Kreutzer, Sebastian; Meszner, Sascha; Faust, Dominik; Fuchs, Markus

    2014-05-01

    Interpreting former landscape evolution asks for understanding the processes that sculpt such landforms by means of deciphering complex systems. For reconstructing terrestrial Quaternary environments based on loess archives this might be considered, at least, as a three step process: (1) Identifying valuable records in appropriate morphological positions in a previously defined research area, (2) analysing the profiles by field work and laboratory methods and finally (3) linking the previously considered pseudo-isolated systems to set up a comprehensive picture. Especially the first and the last step might bring some pitfalls, as it is tempting to specify single records as pseudo-isolated, closed systems. They might be, with regard to their preservation in their specific morphological position, but in fact they are part of a complex, open system. Between 2008 and 2013, Late-Pleistocene loess archives in Saxony have been intensively investigated by field and laboratory methods. Linking pedo- and luminescence dating based chronostratigraphies, a composite profile for the entire Saxonian Loess Region has been established. With this, at least, two-fold approach we tried to avoid misinterpretations that might appear when focussing on one standard profile in an open morphological system. Our contribution focuses on this multi-proxy approach to decipher the Late-Pleistocene landscape evolution in the Saxonian Loess Region. Highlighting the challenges and advantages of combining different methods, we believe that (1) this multi-proxy approach is without alternative, (2) the combination of different profiles may simplify the more complex reality, but it may be a useful generalisation to understand and reveal the stratigraphical significance of the landscape evolution in this region.

  3. Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna.

    Science.gov (United States)

    Pushkina, Diana; Raia, Pasquale

    2008-06-01

    Late Pleistocene extinctions are of interest to paleontological and anthropological research. In North America and Australia, human occupation occurred during a short period of time and overexploitation may have led to the extinction of mammalian megafauna. In northern Eurasia megafaunal extinctions are believed to have occurred over a relatively longer period of time, perhaps as a result of changing environmental conditions, but the picture is much less clear. To consider megafaunal extinction in Eurasia, we compare differences in the geographical distribution and commonness of extinct and extant species between paleontological and archaeological localities from the late middle Pleistocene to Holocene. Purely paleontological localities, as well as most extinct species, were distributed north of archaeological sites and of the extant species, suggesting that apart from possible differences in adaptations between humans and other species, humans could also have a detrimental effect on large mammal distribution. However, evidence for human overexploitation applies only to the extinct steppe bison Bison priscus. Other human-preferred species survive into the Holocene, including Rangifer tarandus, Equus ferus, Capreolus capreolus, Cervus elaphus, Equus hemionus, Saiga tatarica, and Sus scrofa. Mammuthus primigenius and Megaloceros giganteus were rare in archaeological sites. Carnivores appear little influenced by human presence, although they become rarer in Holocene archaeological sites. Overall, the data are consistent with the conclusion that humans acted as efficient hunters selecting for the most abundant species. Our study supports the idea that the late Pleistocene extinctions were environmentally driven by climatic changes that triggered habitat fragmentation, species range reduction, and population decrease, after which human interference either by direct hunting or via indirect activities probably became critical. PMID:18199470

  4. Genetic consequences of population expansions and contractions in the common hippopotamus (Hippopotamus amphibius) since the Late Pleistocene

    DEFF Research Database (Denmark)

    Stoffel, Céline; Dufresnes, Christophe; Okello, John B A; Noirard, Christian; Joly, Pierre; Nyakaana, Silvester; Muwanika, Vincent B; Alcala, Nicolas; Vuilleumier, Séverine; Siegismund, Hans Redlef; Fumagalli, Luca

    2015-01-01

    Over the past two decades, an increasing amount of phylogeographic work has substantially improved our understanding of African biogeography, in particular the role played by Pleistocene pluvial-drought cycles on terrestrial vertebrates. However, still little is known on the evolutionary history of semi-aquatic animals, which faced tremendous challenges imposed by unpredictable availability of water resources. In this study, we investigate the Late Pleistocene history of the common hippopotamus ...

  5. Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics

    OpenAIRE

    Campos, Paula F.; Willerslev, Eske; Sher, Andrei; Orlando, Ludovic; Axelsson, Erik; Tikhonov, Alexei; Aaris-Sørensen, Kim; Greenwood, Alex D; Kahlke, Ralf-Dietrich; Kosintsev, Pavel; Krakhmalnaya, Tatiana; Kuznetsova, Tatyana; Lemey, Philippe; MacPhee, Ross DE; Norris, Christopher A.

    2010-01-01

    The causes of the late Pleistocene megafaunal extinctions are poorly understood. Different lines of evidence point to climate change, the arrival of humans, or a combination of these events as the trigger. Although many species went extinct, others, such as caribou and bison, survived to the present. The musk ox has an intermediate story: relatively abundant during the Pleistocene, it is now restricted to Greenland and the Arctic Archipelago. In this study, we use ancient DNA sequences, tempo...

  6. Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics

    DEFF Research Database (Denmark)

    Campos, Paula F; Willerslev, Eske; Sher, Andrei; Orlando, Ludovic; Axelsson, Erik; Tikhonov, Alexei; Aaris-Sørensen, Kim; Greenwood, Alex D; Kahlke, Ralf-Dietrich; Kosintsev, Pavel; Krakhmalnaya, Tatiana; Kuznetsova, Tatyana; Lemey, Philippe; MacPhee, Ross; Norris, Christopher A; Shepherd, Kieran; Suchard, Marc A; Zazula, Grant D; Shapiro, Beth; Gilbert, M Thomas P

    2010-01-01

    The causes of the late Pleistocene megafaunal extinctions are poorly understood. Different lines of evidence point to climate change, the arrival of humans, or a combination of these events as the trigger. Although many species went extinct, others, such as caribou and bison, survived to the present. The musk ox has an intermediate story: relatively abundant during the Pleistocene, it is now restricted to Greenland and the Arctic Archipelago. In this study, we use ancient DNA sequences, temporal...

  7. AMS-dating of Late Pleistocene and Holocene syngenetic ice-wedges

    International Nuclear Information System (INIS)

    We discuss the 14C dating (both conventional and AMS) of Siberian permafrost sediments and ice-wedge ice. Direct dating of Late Pleistocene and Holocene syngenetic ice-wedges was done on organic material included in the ice. The time of ice formation (in 14C years) is 21,000-14,000 BP for Seyaha, and 7100 BP for Shchuch'ya. The AMS dates show that the ice-wedges stratification is normal, i.e., the older ice is located below the younger. The 14C dates yield for the first time a timescale (in 14C years) for paleoclimatic indicators (oxygen and hydrogen isotope ratios from the ice)

  8. U-series component dating for late pleistocene basalt Longgang, Jilin province

    International Nuclear Information System (INIS)

    Longgang volcanic swarm belongs to one of volcanic areas which have been active since modern times. In view of multiple eruptions during histories, it is very important to determine age of every eruption for evaluating volcanic hazards. The alkaline basalt samples taken from Dayizishan and diaoshuihu are analyzed by U-series component method, after magnetic separation. The ages of the two samples are (71 ± 9) ka, (106 ± 13) ka before presence, respectively. These data indicate that there exist intensively eruptive activities during late Pleistocene

  9. A Signal of Ice Loading in Late Pleistocene Activity of the Sudetic Marginal Fault (Central Europe)

    Science.gov (United States)

    Hartvich, F.; Stepancikova, P.; Rockwell, T. K.; Nývlt, D.; Stemberk, J.; Rood, D. H.; Hók, J.; Ortu?o, M.; Myers, M.; Luttrell, K. M.; Wechsler, N.

    2014-12-01

    We combine paleoseismic trench and cosmogenic dating results to study the late Pleistocene-Holocene history of morphologically pronounced NW-SE trending Sudetic Marginal Fault (SMF) situated at the northeastern limit of the Bohemian Massif in central Europe. Eighteen trenches were excavated at the Bila Voda site to study 3D distribution of a beheaded alluvial fan on the NE block of the fault and to find the offset "feeder channel" that sourced the deposits. We interpret a small drainage of about 40-60 m to the SE of the fan apex as the feeder channel. A 2.5 m depth profile was collected for cosmogenic exposure dating from a well-preserved part of the fan. Using a simple model that accounts for pre-depositional exposure (inheritance) and assuming no surface erosion, 10Be concentrations are well-fit with an apparent exposure age of ~12 ka. However, this is a minimum limiting age if the surface was eroded by gelifluction in the late Pleistocene. Assuming a ~25 ka OSL age for the base of the fan apex it gives a left-lateral slip rate of ~2 mm/yr. As the Holocene deposits do not show significant displacement, most of the recorded slip took place during Late Pleistocene with corresponding slip rate of 2.8 to 3.5 mm/yr. Bila Voda site lies ~150 km south from the Late Pleistocene Weichselian maximum (~20 ka) ice-sheet front. Thus, we hypothesize that the slip rate acceleration was due to ice-loading and subsequent unloading during deglaciation. To test this, we calculated the stress induced in the lithosphere from ablation of the Weichselian ice sheet modeled as a flexing elastic plate. Preliminary modeling results indicate that complete deglaciation alters the stress field such that it would inhibit left lateral failure on the SMF, consistent with observations suggesting no slip occurred during the Holocene. Although the SMF is ~150 km from the Weichselian ice sheet front, it is well within the flexural rebound area of the ice sheet, causing normal stress on the SMF to vary by ~1 MPa from deglaciation. Our model is consistent with loading mechanisms reported from other regions due to deglaciation, but is the first documented evidence in central Europe, having a great implication for seismic hazard assessment. Research was supported by Czech Science Foundation (No. P210/12/0573) and Czech Ministry of Education, Youth and Sports (No. LH12078).

  10. Late Pleistocene mammals from Chivacabé, Huehuetenango, Guatemala / Mamíferos del Pleistoceno tardío de Chivacabé, Huehuetenango, Guatemala

    Scientific Electronic Library Online (English)

    Jim I., Mead; Arturo, Baez; Sandra L., Swift; Jon, Lohse; Lorena, Paiz.

    2012-08-01

    Full Text Available Se ha publicado poca información paleontológica detallada de la fauna del Pleistoceno para gran parte de Centroamérica. Probablemente la localidad más rica de vertebrados en Centroamérica es Tomayate, en El Salvador, que data del Pleistoceno temprano a medio. La literatura de especies de vertebrados [...] delPleistoceno tardío de Guatemala es especialmente escasa. El propósito de este trabajo es presentar los restos de mamíferos del Pleistoceno tardío de Chivacabé, en las tierras altas occidentales de Guatemala. La edad de radiocarbono de la fauna de Chivacabé data de entre 15,700 y 12,920 años calendario. Los especímenes recobrados de excavaciones entre 1977 y 1992 son probablemente una pequeña porción de toda la fauna que existe bajo 4 a 5 m de tefra redepositada y aluvión. Los especímenes recobrados incluyen un individuo de Glyptotherium sp., tres de Cuvieronius cf. C. hyodon, uno de Equus sp. y dos de Odocoileus cf. O. virginianus. Un individuo que originalmente se pensaba que representaba una cornamenta de venado es de hecho un hueso flotante de Cuvieronius. Reportes previos de "pecaríes" y de Eremotherium de Chivacabé no son sustentados por fósiles archivados. Ningún espécimen de fauna exhibe las supuestas marcas humanas de modificación dadas a entender por investigadores previos; todas las aberraciones observadas en los huesos y en los dientes pueden ser explicadas por otros procesos tafonómicos. La fauna de Chivacabé representa una de las muy pocas faunas del Pleistoceno tardío de Guatemala descritas hasta ahora. Una lista preliminar de localidades del Pleistoceno tardío de Guatemala sugiere que son necesarios estudios detallados de estas faunas. Abstract in english Few Pleistocene paleontological faunas are published in detail for most of Central America. Probably the richest locality of vertebrates in Central America is at Tomayate, El Salvador, and dates to the early-middle Pleistocene. Literature about late Pleistocene vertebrate species from Guatemala is e [...] specially scarce. The purpose of the present paper is to introduce the late Pleistocene mammalian remains from Chivacabé, in the western highlands of Guatemala. The Chivacabé fauna radiocarbon dates to between 15,700 and 12,920 calendar years ago. The specimens recovered from excavations between 1977 and1992 are probably only a small portion of the entire fauna likely to exist under 4 to 5 m of redeposited tephra and valley alluvium. Recovered specimens include at least one individual of Glyptotherium sp., three individuals of Cuvieronius cf. C. hyodon, one individual of Equus sp., and two individuals of Odocoileus cf. O. virginianus. One specimen that originally was thought to represent a deer antler is in fact a hyoid bone of Cuvieronius. Previous reports of 'peccary ' and Eremotherium from Chivacabé are not supported by archived fossils. No faunal specimens exhibit supposed human modification marks purported by previous investigators; all aberrations observed on the bones and teeth can be explained by other taphonomicprocesses. The Chivacabé fauna represents one of the very few late Pleistocene faunas from Guatemala described thus far. A preliminary list of late Pleistocene localities known in Guatemala suggests that detailed studies of these faunas are warranted.

  11. Phylogeography of the Alcippe morrisonia (Aves: Timaliidae: long population history beyond late Pleistocene glaciations

    Directory of Open Access Journals (Sweden)

    Li Shouhsien

    2009-06-01

    Full Text Available Abstract Background The role of Pleistocene glacial oscillations in current biodiversity and distribution patterns varies with latitude, physical topology and population life history and has long been a topic of discussion. However, there had been little phylogeographical research in south China, where the geophysical complexity is associated with great biodiversity. A bird endemic in Southeast Asia, the Grey-cheeked Fulvetta, Alcippe morrisonia, has been reported to show deep genetic divergences among its seven subspecies. In the present study, we investigated the phylogeography of A. morrisonia to explore its population structure and evolutionary history, in order to gain insight into the effect of geological events on the speciation and diversity of birds endemic in south China. Results Mitochondrial genes cytochrome b (Cytb and cytochrome c oxidase I (COI were represented by 1236 nucleotide sites from 151 individuals from 29 localities. Phylogenetic analysis showed seven monophyletic clades congruent with the geographically separated groups, which were identified as major sources of molecular variance (90.92% by AMOVA. TCS analysis revealed four disconnected networks, and that no haplotype was shared among the geographical groups. The common ancestor of these populations was dated to 11.6 Mya and several divergence events were estimated along the population evolutionary history. Isolation by distance was inferred by NCPA to be responsible for the current intra-population genetic pattern and gene flow among geographical groups was interrupted. A late Pleistocene demographic expansion was detected in the eastern geographical groups, while the expansion time (0.2–0.4 Mya was earlier than the Last Glacial Maximum. Conclusion It is proposed that the complicated topology preserves high genetic diversity and ancient lineages for geographical groups of A. morrisonia in China mainland and its two major islands, and restricts gene exchange during climate oscillations. Isolation by distance seems to be an important factor of genetic structure formation within geographical populations. Although glacial influence to population fluctuation was observed in late Pleistocene, it seems that populations in eastern China were more susceptible to climate change, and all geographical groups were growing stably through the Last Glacial Maximum. Coalescence analysis suggested that the ancestor of A. morrisonia might be traced back to the late Miocene, and the current phylogeographical structure of A. morrisonia is more likely to be attributable to a series geological events than to Pleistocene glacial cycles.

  12. Late Pleistocene and Holocene landscape formation in a gully catchment area in Northern Hesse, Germany

    DEFF Research Database (Denmark)

    Döhler, Susanne; Damm, Bodo

    2015-01-01

    Permanent gully channels under forest are common geomorphological features in Central European low mountain areas. In the Rehgraben/Fuchslöchergraben gully catchment in Northern Hesse, Germany the Late Pleistocene landscape formation is reconstructed based on periglacial cover beds. In addition, the Holocene landscape development and soil erosion history are investigated using anthropogenic soil sediments and alluvial fan sediments. Until now, a combination of these approaches has not been applied to a gully catchment to this extent. The distribution of the different Quaternary sediments enables the differentiation between Pleistocene and Holocene landforms. Radiocarbon and optically stimulated luminescence dating are applied to add numerical data to the relative ages of the sediments and landforms. The gully channels are oriented along Pleistocene depressions that are built up of periglacial cover beds and intercalated reworked loess. As the gully channels cut through the periglacial cover beds, especially the upper layer, the gully system is of Holocene age. At least two phases of gully erosion are identified in the alluvial fan sediments. The initial gully erosion is dated to the time span between the Late Bronze Age and Roman Times. A second gully erosion phase is dated to the 14th century and may be correlated to the severe precipitation events during this time. Gully erosion started during the Younger Holocene and is connected to human settlement and land use activity. The intense human impact hampers the application of the concept of periglacial cover beds to reconstruct landscape formation and limits it to areas where the periglacial upper layer is still preserved. © 2014 Elsevier Ltd and INQUA. All rights reserved.

  13. A chronology of Late-Pleistocene permafrost events in southern New Jersey, eastern USA

    Science.gov (United States)

    French, H.M.; Demitroff, M.; Forman, S.L.; Newell, W.L.

    2007-01-01

    Frost fissures, filled with wind-abraded sand and mineral soil, and numerous small-scale non-diastrophic deformations, occur in the near-surface sediments of the Pine Barrens of southern New Jersey. The fissures are the result of thermal-contraction cracking and indicate the previous existence of either permafrost or seasonally-frozen ground. The deformations reflect thermokarst activity that occurred when permafrost degraded, icy layers melted and density-controlled mass displacements occurred in water-saturated sediments. Slopes and surficial materials of the area reflect these cold-climate conditions. Optically-stimulated luminescence permits construction of a tentative Late-Pleistocene permafrost chronology. This indicates Illinoian, Early-Wisconsinan and Late-Wisconsinan episodes of permafrost and/or deep seasonal frost and a Middle-Wisconsinan thermokarst event. Copyright ?? 2007 John Wiley & Sons, Ltd.

  14. A robust feldspar luminescence dating method for Middle and Late Pleistocene sediments

    DEFF Research Database (Denmark)

    Buylaert, Jan-Pieter; Jain, Mayank

    2012-01-01

    Luminescence dating is used extensively to provide absolute chronologies for Late Pleistocene sediments. Nowadays, most optical dates are based on quartz optically stimulated luminescence (OSL). However, the application of this signal is usually limited to the last ~100 ka because of saturation of the quartz luminescence signal with dose. In contrast, the feldspar infrared stimulated luminescence (IRSL) dose–response curve grows to much higher doses; this has the potential to extend the datable age range by a factor of 4–5 compared with quartz OSL. However, it has been known for several decades that this IRSL signal is unstable, and this instability often gives rise to significant age underestimation. Here we test against independent age control the recently developed feldspar post-IR IRSL approach to the dating of sediments, which appears to avoid signal instability. A physical model explaining our observations is discussed, and the method is shown to be accurate back to 600 ka. The post-IR IRSL signal is reduced by exposure to daylight more slowly than that from quartz and low-temperature IRSL, preventing its general application to young (e.g. Holocene) sediments. Nevertheless, this new approach is widely applicable (feldspar of appropriate luminescence behaviour is even more ubiquitous than quartz). These characteristics make this a method of great importance for the dating of Middle and Late Pleistocene deposits.

  15. The diversity and biogeography of late Pleistocene birds from the lowland Neotropics

    Science.gov (United States)

    Steadman, David W.; Oswald, Jessica A.; Rincón, Ascanio D.

    2015-05-01

    The Neotropical lowlands sustain the world's richest bird communities, yet little that we know about their history is based on paleontology. Fossils afford a way to investigate distributional shifts in individual species, and thus improve our understanding of long-term change in Neotropical bird communities. We report a species-rich avian fossil sample from a late Pleistocene tar seep (Mene de Inciarte) in northwestern Venezuela. A mere 175 identified fossils from Mene de Inciarte represent 73 species of birds, among which six are extinct, and eight others no longer occur within 100 km. These 14 species consist mainly of ducks (Anatidae), snipe (Scolopacidae), vultures/condors (Vulturidae), hawks/eagles (Accipitridae), and blackbirds (Icteridae). Neotropical bird communities were richer in the late Pleistocene than today; their considerable extinction may be related to collapse of the large mammal fauna at that time. The species assemblage at Mene de Inciarte suggests that biogeographic patterns, even at continental scales, have been remarkably labile over short geological time frames. Mene de Inciarte is but one of 300 + tar seeps in Venezuela, only two of which have been explored for fossils. We may be on the cusp of an exciting new era of avian paleontology in the Neotropics.

  16. Paleosoils and pedogenic calcretes formations in Fray Bentos (Oligocene - early miocene) Raigon (late pliocene and middle pleistocene) and Libertad (early - middle pleistocene)

    International Nuclear Information System (INIS)

    The Fray Bentos formation is composed by loessic deposits based on paleosoils and pedogenic calcretes (Oligocene - early miocene). In this deposits are tubular and lamellar formations which would have been formed in arid climates.The fluvial origen of Raigon Formation, (late pliocene and middle pleistocene) presents a paleosoil roof which is generated under a subhumid climate.The Libertad Formation during the glacial intervals consisted of loess deposits

  17. Phylogeography of lions (Panthera leo ssp.) reveals three distinct taxa and a late Pleistocene reduction in genetic diversity.

    Science.gov (United States)

    Barnett, Ross; Shapiro, Beth; Barnes, Ian; Ho, Simon Y W; Burger, Joachim; Yamaguchi, Nobuyuki; Higham, Thomas F G; Wheeler, H Todd; Rosendahl, Wilfried; Sher, Andrei V; Sotnikova, Marina; Kuznetsova, Tatiana; Baryshnikov, Gennady F; Martin, Larry D; Harington, C Richard; Burns, James A; Cooper, Alan

    2009-04-01

    Lions were the most widespread carnivores in the late Pleistocene, ranging from southern Africa to the southern USA, but little is known about the evolutionary relationships among these Pleistocene populations or the dynamics that led to their extinction. Using ancient DNA techniques, we obtained mitochondrial sequences from 52 individuals sampled across the present and former range of lions. Phylogenetic analysis revealed three distinct clusters: (i) modern lions, Panthera leo; (ii) extinct Pleistocene cave lions, which formed a homogeneous population extending from Europe across Beringia (Siberia, Alaska and western Canada); and (iii) extinct American lions, which formed a separate population south of the Pleistocene ice sheets. The American lion appears to have become genetically isolated around 340 000 years ago, despite the apparent lack of significant barriers to gene flow with Beringian populations through much of the late Pleistocene. We found potential evidence of a severe population bottleneck in the cave lion during the previous interstadial, sometime after 48 000 years, adding to evidence from bison, mammoths, horses and brown bears that megafaunal populations underwent major genetic alterations throughout the last interstadial, potentially presaging the processes involved in the subsequent end-Pleistocene mass extinctions. PMID:19302360

  18. Environmental evolutions of the Alzette valley (Grand Duchy of Luxembourg) since Late Pleistocene

    Science.gov (United States)

    Naton, H.-G.; Ruffaldi, P.; Meyrick, R.; Maquil, R.; Colbach, R.; Kausch, B.; Baes, R.; Stead, A.; Le Brun-Ricalens, F.; Brou, L.; Schoellen, A.

    2009-04-01

    The Alzette River rises within France, approximately 4 km south of the French-Luxembourg border, and has a total length of 73 kilometres before joining the Sauer which is a left-bank tributary of the Moselle River. During the construction of the "Nordstrooss" motorway (going north from Luxembourg city towards Ettelbruck) a viaduct was built that crosses the wide alluvial plain (about 1 km) of the Alzette River valley near Lorentzweiler. A lot of drillings were also made for geotechnical purposes by the Geological survey of Luxembourg (SGL). The drillings were able to provide informations about the sediments preserved in the Alzette River valley floor. This information has allowed the construction of a cross-profile through the valley showing the stratigraphy of the quaternary deposits, and illustrating that it was the result of a rather complex evolution (aggradation and incision periods leading to terraces formation, input of slope deposits at the valley margins, possible eolian input, …). A multidisciplinary research project thus started, aiming to reconstruct the paleoenvironment of the Alzette region during the late Pleistocene and Holocene periods. The drilling results make it possible to reconstruct the geometry of the quaternary sedimentary units of the Alzette valley. Three stepped alluvial units are recognized along the cross profile: the lower one (Az0) corresponds with the maximal incision of the Alzette. It is preserved in the western part of the floodplain, with base being located at about 212 m a.s.l.. In the eastern part of the valley the contact between the fluvial deposits and the substratum is located at about 215 m a.s.l.: these deposits may also be allocated to a lower terrace Az1 (relative height : +3 m). A third alluvial unit Az2 was recognized in two drillings, with bedrock located at about 224 m a.s.l. (+12 m). The channel migration in the valley and the assumed meandering dynamics (suggested by the weakness of the longitudinal slope) led to meander downcuttings and to the formation of oxbow lakes. These former oxbow-lakes are subjected either to a mineral or organic filling, the predominance of this latter leading to the formation of peat bogs. Radiocarbon datings were obtained on peaty levels from two drillings, FR-200-364 (Beta-249559:3400±40 BP, Beta-249560:4660±40 BP, Beta-249561:9390±60 BP) and FR-200-365 (Beta-240994:7250±40 BP, Beta-249562:12100±70 BP, Beta-249563:11910±70 BP). Taking account of this dating, sequences of peats found in recent drillings, downstream the viaduct, could belong to the first part of the Holocene. In one of this new drillings (FR-207-353), it is also important to note presence of an organic level within the coarse sediments. It is located at approx. 211 m a.s.l., and contains numerous rests of mollusc shells. Further radiocarbon dating and palynological study are consequently be realised for this level and the new sequence of peats. Two studies in the area are also to considerate: - in the drilling FR-201-055 (located at the western part of the valley), the dating of moss remains (bryophyts) preserved in a clayey level gave an age estimate of about 25280±220 BP (Beta-182249). This result is in good agreement with palynological data, suggesting a dry and cold environment. This age has however to be confirmed due, first to a possible reservoir effect (more study of the bryophyts remains is needed), and secondly to the incoherence and heterogeneity of the drilling samples (mix of alluvial and slope deposits); - in a western tributary called "Seisselbaach stream" a molluscan analysis from a tufaceous holocene deposit has done and a radiocarbon age of 9820±120 BP (Beta-181807) was obtained on charcoal fragments too small for identification. The upstream course of this small river valley offers very convenient conditions to study the end of the glacial period and the beginning of the warmer period in a continental setting. Further results should then lead to improve the global environmental evolution in the Luxembourg area since the last c

  19. Using obsidian transfer distances to explore social network maintenance in late Pleistocene hunter-gatherers.

    Science.gov (United States)

    Pearce, Eiluned; Moutsiou, Theodora

    2014-12-01

    Social behaviour is notoriously difficult to study archaeologically and it is unclear how large the networks of prehistoric humans were, or how they remained connected. Maintaining social cohesion was crucial for early humans because social networks facilitate cooperation and are imperative for survival and reproduction. Recent hunter-gatherer social organisation typically comprises a number of nested layers, ranging from the nuclear family through to the ~1500-strong ethnolinguistic tribe. Here we compare maximum obsidian transfer distances from the late Pleistocene with ethnographic data on the size of the geographic areas associated with each of these social grouping layers in recent hunter-gatherers. The closest match between the two is taken to indicate the maximum social layer within which contact could be sustained by Pleistocene hominins. Within both the (sub)tropical African and Subarctic biomes, the maximum obsidian transfer distances for Pleistocene modern humans (~200km and ~400km respectively) correspond to the geographic ranges of the outermost tribal layer in recent hunter-gatherers. This suggests that modern humans could potentially sustain the cohesion of their entire tribe at all latitudes, even though networks are more dispersed nearer the poles. Neanderthal obsidian transfer distances (300km) indicate that although Neanderthal home ranges are larger than those of low latitude hominins, Neanderthals travelled shorter distances than modern humans living at the same high latitudes. We argue that, like modern humans, Neanderthals could have maintained tribal cohesion, but that their tribes were substantially smaller than those of contemporary modern humans living in similar environments. The greater time taken to traverse the larger modern human tribal ranges may have limited the frequency of their face-to-face interactions and thus necessitated additional mechanisms to ensure network connectivity, such as the exchange of symbolic artefacts including ornaments and figurines. Such cultural supports may not have been required to the same extent by the Neanderthals due to their smaller tribes and home ranges. PMID:25214705

  20. Late Pleistocene biogenic sedimentation in the Gulf of Alaska: A biogeochemical perspective from IODP Expedition 341

    Science.gov (United States)

    Moy, C. M.; Addison, J. A.; Finney, B.; Bahlburg, H.; Childress, L. B.; Cowan, E. A.; Forwick, M.; Ribeiro, F.; Ridgway, K. D.

    2014-12-01

    Reconstructing the timing and nature of past changes in aquatic productivity in the Gulf of Alaska (GoA) can shed light on the primary processes driving biogeochemical cycling over geologic timescales. Here, we present sedimentologic, physical property, stable isotope, and biogenic opal concentration data from IODP Expedition 341 Sites U1417 and U1419 and identify intervals where diatom ooze lithofacies and geochemical evidence for increased algal productivity are prevalent during the Pleistocene. Sites U1417 and U1419 are located in the center and the margin of the Fe-limited GoA, respectively, and they offer the potential to characterize past changes in biogeochemical cycling during different Pleistocene time intervals. Site U1419 cores were collected from a small slope basin at the edge of the continental shelf. Sediment cores reveal two prominent ~6-m-thick intervals of diatomaceous ooze. Between these intervals are numerous 20-cm-thick sections of biogenic-rich sediment, interbedded with gray mud that commonly contains lonestones. Based on preliminary age models, the two diatom ooze intervals likely correspond to the Holocene and MIS 3, while the intervening interbedded glacigenic and biogenic sediment can broadly be ascribed to MIS 2. Diatomaceous ooze and diatom-rich sediments are generally characterized by lower magnetic susceptibility, natural gamma ray, bulk density, and higher b* color reflectance. Initial C & N concentration and stable isotopic data show elevated concentrations and more positive stable isotope values during the Holocene and MIS 3, which approximate the isotopic signature of modern phytoplankton measured in the GoA. Within the glacial period, the biogenic-rich intervals are also characterized by more positive C and N isotopic values. When combined with the shipboard physical property data, the stable isotopic results are indicative of millennial-scale variations in productivity and/or changes in glacial ice extent in the GoA during the last glacial period. We will discuss these results in the context of an improved isotope stratigraphy and ongoing work examining multiple interglacial productivity variations at Site U1417.

  1. Distributional patterns of herbivore megamammals during the Late Pleistocene of South America

    Scientific Electronic Library Online (English)

    VALERIA, GALLO; LEONARDO S., AVILLA; RODRIGO C.L., PEREIRA; BRUNO A., ABSOLON.

    2013-06-01

    Full Text Available A distribuição geográfica de 27 espécies da megafauna de mamíferos herbívoros sul-americanos durante o Pleistoceno Superior foi analisada, visando à identificação de seus padrões de distribuição. A distribuição das espécies foi estudada com o uso do método pan-biogeográfico de análise de traços. Sei [...] s traços generalizados (TGs) e dois nós biogeográficos foram obtidos. Os TGs não superpõem completamente com as áreas de savana aberta presentes no Pleistoceno, nem com os traços bióticos de alguns artrópodes típicos de clima árido, indicando que estes animais evitavam ambiente árido. De um modo geral, os TGs coincidiram com algumas das províncias biogeográficas definidas com base em táxons viventes, indicando que certos padrões de distribuição atuais já existiam no Pleistoceno. Os nós biogeográficos coincidiram com as bordas entre as principais formações vegetais do Pleistoceno, mostrando que o tipo de vegetação teve grande influência na distribuição da megafauna mamaliana. O nó 1 confirmou a existência de zonas de contato entre regiões paleobiogeográficas próximo à borda Argentina-Uruguai. O nó 2 conecta as regiões intertropicais brasileiras. Abstract in english The geographic distribution of 27 species of the South American megafauna of herbivore mammals during the Late Pleistocene was analyzed in order to identify their distributional patterns. The distribution of the species was studied using the panbiogeographical method of track analysis. Six generaliz [...] ed tracks (GTs) and two biogeographic nodes were obtained. The GTs did not completely superpose with the areas of open savanna present in Pleistocene, nor with the biotic tracks of some arthropods typical of arid climate, indicating that these animals avoided arid environment. Overall, the GTs coincided with some biogeographic provinces defined on the basis of living taxa, indicating that certain current distributional patterns already existed in Pleistocene. The biogeographic nodes coincided with the borders between the main vegetal formations of the Pleistocene, showing that the type of vegetation had great influence in the distribution of the mammalian megafauna. The node 1 confirmed the existence of contact zones between paleobiogeographic regions near Argentina-Uruguay border. The node 2 connects the Brazilian Intertropical regions.

  2. Ecosystem Impact of the Campanian Ignimbrite Eruption in Late Pleistocene Europe

    Science.gov (United States)

    Fedele, Francesco G.; Giaccio, Biagio; Isaia, Roberto; Orsi, Giovanni

    2002-05-01

    The dating of the Campanian Ignimbrite (CI) eruption to ˜37,000 cal yr B.P. draws attention to the coincidence of this volcanic catastrophe and the suite of coeval, Late Pleistocene biocultural changes that occurred within and outside the Mediterranean region. These included the Middle to Upper Paleolithic cultural transition and the supposed change from Neanderthal to "modern" Homo sapiens anatomy, a subject of sustained debate. No less than 150 km 3 of magma were extruded in the CI eruption, the signal of which can be detected in Greenland ice cores. As widespread discontinuities in archaeological sequences are observed at or following the CI event, a significant interference with ongoing human processes in Mediterranean Europe is hypothesized.

  3. Environmentally controlled succession in a late Pleistocene coral reef (Sinai, Egypt)

    Science.gov (United States)

    Mewis, H.; Kiessling, W.

    2013-03-01

    The concept of ecological succession has been frequently applied in the study of ancient reefs. Whereas Paleozoic and Mesozoic reefs are commonly thought to reveal an autogenic primary—climax zonation, patterns in Neogene and Quaternary reefs are much more diverse. Here, we describe a well-preserved late Pleistocene coral reef from Dahab on Sinai Peninsula (Egypt), which shows a distinct zonation that resembles an ecological succession. In contrast to classical examples of ecological successions, species composition, paleoenvironmental conditions, and coral biodiversity of the Dahab reef indicate an allogenic, sea-level controlled community change, from marginal marine to reef slope and back reef. A review of the literature confirms that autogenic, short-term successions are virtually absent in Quaternary reefs. We predict that long generation times of corals make it unlikely that classical autogenic successions develop in reefs at all, unless environmental conditions are unusually stable.

  4. Ages and inferred causes of late Pleistocene glaciations on Mauna Kea, Hawai'i

    Science.gov (United States)

    Pigati, J.S.; Zreda, M.; Zweck, C.; Almasi, P.F.; Elmore, D.; Sharp, W.D.

    2008-01-01

    Glacial landforms on Mauna Kea, Hawai'i, show that the summit area of the volcano was covered intermittently by ice caps during the Late Pleistocene. Cosmogen 36Cl dating of terminal moraines and other glacial landforms indicates that the last two ice caps, called Older Makanaka and Younger Makanaka, retreated from their maximum positions approximately 23ka and 13ka, respectively. The margins and equilibrium line altitudes of these ice caps on the remote, tropical Pacific island were nearly identical, which would seem to imply the same mechanism for ice growth. But modelling of glacier mass balance, combined with palaeotemperature proxy data from the subtropical North Pacific, suggests that the causes of the two glacial expansions may have been different. Older Makanaka airatop Mauna Kea was likely wetter than today and cold, whereas Younger Makanaka times were slightly warmer but significantly wetter than the previous glaciation. The modelled increase in precipitation rates atop Mauna Kea during the Late Pleistocene is consistent with that near sea level inferred from pollen data, which suggests that the additional precipitation was due to more frequent and/ or intense tropical storms associated with eastward-moving cold fronts. These conditions were similar to modern La Ni??a (weak ENSO) conditions, but persisted for millennia rather than years. Increased precipitation rates and the resulting steeper temperature lapse rates created glacial conditions atop Mauna Kea in the absence of sufficient cooling at sea level, suggesting that if similar correlations existed elsewhere in the tropics, the precipitation-dependent lapse rates could reconcile the apparent difference between glacial-time cooling of the tropics at low and high altitudes. Copyright ?? 2008 John Wiley & Sons, Ltd.

  5. The age of Late Pleistocene shorelines and tectonic activity of Taranto area, Southern Italy

    Science.gov (United States)

    Belluomini, G.; Caldara, M.; Casini, C.; Cerasoli, M.; Manfra, L.; Mastronuzzi, G.; Palmentola, G.; Sanso, P.; Tuccimei, P.; Vesica, P. L.

    2002-02-01

    The results of isoleucine epimerization ratios in pelecypods ( Glycymeris sp., Arca sp. and Cerastoderma sp.) and U-series dating of bivalves and Cladocora caespitosa sampled from different Late Pleistocene units in the Chéradi Islands and in the coastal areas of Mar Piccolo and Mar Grande near Taranto (Apulia region, Italy) are presented. U-series measurements on pelecypods and on corals directly associated with mollusc samples provide an independent calibration of amino acid data. The D/ L ratios of isoleucine show a strong correlation with age, and thus may be considered as a predictive dating technique. This correlation also supports the reliability of U-series ages obtained for molluscs. These results, including the stratigraphic position, the lithological lateral continuity, the morphological evidence and the palaeontological characteristics of the various units, made it possible to attribute them to different marine trangressive phases referable to oxygen isotope stages (OIS) 5e-c, 5a and 3. No evidence of land emersion between OIS 5e and 5c has been found in the area. Pinkish/red sands deposits located above present sea level (˜1 m) have been referred to OIS 3. The Late Pleistocene morphological evolution and uplift of a complex area between the Apulian foreland and the Bradanic foredeep have been reconstructed. Due to the lack of incontestable indicators of past sea level stands the facies analysis has been performed on U-series dated 89.8 ka, OIS 5c shoreline north of Mar Piccolo and an uplift rate ranging from 0.21-0.27 mm/yr has been calculated.

  6. Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean

    Science.gov (United States)

    Polyak, L.; Bischof, J.; Ortiz, J.D.; Darby, D.A.; Channell, J.E.T.; Xuan, C.; Kaufman, D.S.; Lovlie, R.; Schneider, D.A.; Eberl, D.D.; Adler, R.E.; Council, E.A.

    2009-01-01

    Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.

  7. Relic Late Pleistocene fluvial forms as geomorphic archives indicating periods of high climatic runoff over the East European Plain

    Science.gov (United States)

    Panin, Andrei; Belyaev, Yury; Eremenko, Ekaterina; Sidorchuk, Alexei

    2014-05-01

    In water balance estimations within palaeoenvironmental studies river runoff is estimated as the difference between precipitation and evapotranspiration. The other technique is numerical modeling using general circulation models. Both approaches fail to recognize epochs of extremely high surface runoff characteristic for the Pleistocene cold epochs and recorded in geomorphic outcomes of this runoff. We have studied two kinds of such archives that have wide spatial coverage over the East European Plain (EEP). 1. Post-LGM large palaeochannels (macromeanders) in river valleys with channel width and meander wavelength 5-15 times as great as that of modern rivers. Massive measurements of their parameters and application of specially constructed transfer function provided estimations of palaeo-runoff from large river basins: in the Black Sea and Caspian Sea catchments it carried from 2.2 (Kama River) to 3.1 (Don, Dnieper Rivers) times as great as modern runoff. High runoff lasted long enough to provide formation of 2-3 generations of macromeanders characteristic for many valleys. Macromeanders were radiocarbon dated at 6 sites over EEP in the range 13-19 cal ka BP, but it is not clear whether high runoff was characteristic for the entire period or it performed during short isolated epochs within this interval. Therefore, it is not clear to what exact time palaeohydrological estimations should be attributed. 2. Dendritic and parallel systems of gentle hollows clearly designated in vegetation-free areas south from 55-57ºN. Distinctive spatial patterns and full integration into water transportation through modern fluvial landscapes provides interpretation of these hollow systems as partially or totally buried networks of small dry valleys (balkas). It is supported by revelation of buried incisions up to 10 m deep by coring and trenching across hollows. Ancient erosion network demonstrates erosion density much higher and Horton's "belt of no erosion" much narrower and therefore exhibits much abundant surface runoff than those at present. Dating of buried balkas has until recent times been based either on pollen spectra from peat deposits (in central EEP), or on stratigraphy of paleosoils found in the bottom of paleoforms (in southern EEP). Both markers point at Eemian (MIS 5e) age of their stabilization and therefore pre-Eemian (late MIS 6?) age of incision. However first attempt of OSL dating gave the contradictory result of filling of a 6-m deep balka by slopewash sediments during 80-70 ka BP. Questionable is the >30-ka delay between the soil formation in the balka bottom and start of its filling. It may mean either post-Eemian age of the soil, which would be unfortunate for the regional soil stratigraphy, or insufficient sensitivity of local quartz at ages close to Eemian. The conclusion is that geomorphic evidences make unique palaeohydrological archives that document changes not recorded in other types of palaeoenvironmental data, but they suffer from uncertainties and low resolution of dating. This presentation contributes to RFBR Projects 14-05-00119 and 14-05-00146.

  8. 3D seismic interpretations of the Pliocene-Pleistocene stratigraphy and tunnel valleys of the North Sea Plateau-Fladen area, northern North Sea

    Science.gov (United States)

    Reinardy, Benedict; Hjelstuen, Berit; Petter Sejrup, Hans; Stoddart, Daniel

    2014-05-01

    The increasing coverage of 3D seismic data across the North Sea has allowed the detailed investigation of depositional environments extending beyond the most recent glacial advance into the basin. There are several generations of channels and incisions interpreted as tunnel valleys of varying size at varying stratigraphic depths throughout the Pliocene-Pleistocene units in the North Sea. Many of these features appear to have been reactivated on more than one occasion. The acoustic character of sediments infilling these features is also variable even within the same channel and their significance in relation to palaeo-ice sheet dynamics is still debated. We suggest that some of the observed incisions/valleys, particularly those formed around the Pliocene-Pleistocene boundary, may in fact be fluvial features rather than subglacially formed (based on size and flow path). Many of the smaller, straighter more recent generations of channels probably formed subglacially. If some of the older channels are fluvial, this has significant implications for the marine limit during this late Pliocene early Pleistocene period in the northern North Sea. Palaeo-iceberg scours are also found at certain stratigraphic horizons and these can be compared to those horizons with valleys/channels. Interpretations of the acoustic units/features will also be based on information from well and shallow core data allowing their depositional history and chronology to be investigated. Several physical properties have been measured on a number of cores from the investigated area. To be able to refine the chronology of the Pleistocene sediments for this part of the North Sea we plan to carry out new analyses and dating (strontium, radiocarbon and amino acid) on shallow cores/well material from the region. This will allow us to better constrain the times at which channels were being formed in this area and relate this to known glacial cycles in the North Sea.

  9. Tanque Loma, a new late-Pleistocene megafaunal tar seep locality from southwest Ecuador

    Science.gov (United States)

    Lindsey, Emily L.; Lopez R., Eric X.

    2015-01-01

    Fossil deposits in the petroleum-rich sediments of the Santa Elena Peninsula in southwestern Ecuador contain some of the largest and best-preserved assemblages of Pleistocene megafaunal remains known from the neotropics, and thus represent an opportunity to greatly expand our knowledge of Pleistocene paleoecology and the extinction of Quaternary megafauna in this region. This paper reports data from excavations at Tanque Loma, a late-Pleistocene locality on the Santa Elena Peninsula that preserves a dense assemblage of megafaunal remains in hydrocarbon-saturated sediments along with microfaunal and paleobotanical material. The megafauna bones are concentrated in and just above a ?0.5 m thick asphaltic layer, but occur sparsely and with poorer preservation up to 1 m above this deposit. Several meters of presumed-Holocene sediments overlying the megafauna-bearing strata are rich in bones of microvertebrates including birds, squamates, and rodents. These are interpreted as raptor assemblages. While over 1000 megafaunal bones have been identified from the Pleistocene strata at Tanque Loma, more than 85% of these remains pertain to a single species, the giant ground sloth Eremotherium laurillardi. Only five other megafauna taxa have been identified from this site, including Glossotherium cf. tropicorum, Holmesina occidentalis, cf. Notiomastodon platensis, Equus (Amerhippus) c.f. santaeelenae, and a cervid tentatively assigned to cf. Odocoileus salinae based on body size and geography. No carnivores have yet been identified from Tanque Loma, and microvertebrate remains are extremely rare in the Pleistocene deposits, although terrestrial snail shells and fragmented remains of marine invertebrates are occasionally encountered. Accelerator Mass Spectrometry radiocarbon dates on Eremotherium and cf. Notiomaston bones from within and just above the asphaltic layer yielded dates of ?17,000 - 23,500 radiocarbon years BP. Taken together, the taxonomic composition, taphonomy, geologic context, and sedimentology of Tanque Loma suggest that this site represents a bone bed assemblage in a heavily vegetated, low-energy riparian environment with secondary infiltration of asphalt that helped to preserve the bones. The predominance of Eremotherium fossils at this site indicate that it may have been an area where these animals congregated, suggesting possible gregarious behavior in this taxon. The radiocarbon dates so far obtained on extinct taxa at Tanque Loma are consistent with a model positing earlier extinctions of megafauna in tropical South America than of related taxa further south on the continent, although this pattern may be an artifact of low sampling in the region. xml:lang="es" Aunque más de 1.000 huesos de megafauna han sido identificados en los estratos del Pleistoceno en Tanque Loma, más del 85% de esos mismos pertenecen a una sola especie, el perezoso gigante Eremotherium laurillardi. Sin embargo, otros cinco taxones de megafauna han sido recuperados de este sitio, los cuales son: Glossotherium cf. G. tropicorum, Holmesina occidentalis, cf. Notiomastodon platensis, Equus (Amerhippus) c.f. santaelenae y un cérvido identificado tentativamente en base a tamaño y geografía como cf. Odocoileus salinae. Ningún carnívoro ha sido identificado aún en Tanque Loma, y los restos de microvertebrados son muy raros en los estratos del Pleistoceno, aunque las conchas de caracol terrestre y los restos fragmentados de invertebrados marinos son encontrados ocasionalmente dentro de esas capas. Los fechados de radiocarbono por espectrómetro de acelerador de masas (AMS) en huesos de Eremotherium y cf. Notiomastodon de la capa de asfalto y por encima de esta resultaron en ?17,000-23,500 años radiocarbónicos AP. En conjunto, la tafonomía, la composición taxonómica, el contexto geológico, y la sedimentolgía del sitio Tanque Loma surgieren que esta localidad representa un yacimiento depositado en un ambiente ribereño con bajo flujo y vegetación densa, con infiltraciones secundarias de asfalto lo que ayudó a preserv

  10. Lineage-specific late pleistocene expansion of an endemic subtropical gossamer-wing damselfly, Euphaea formosa, in Taiwan

    Directory of Open Access Journals (Sweden)

    Huang Jen-Pan

    2011-04-01

    Full Text Available Abstract Background Pleistocene glacial oscillations have significantly affected the historical population dynamics of temperate taxa. However, the general effects of recent climatic changes on the evolutionary history and genetic structure of extant subtropical species remain poorly understood. In the present study, phylogeographic and historical demographic analyses based on mitochondrial and nuclear DNA sequences were used. The aim was to investigate whether Pleistocene climatic cycles, paleo-drainages or mountain vicariance of Taiwan shaped the evolutionary diversification of a subtropical gossamer-wing damselfly, Euphaea formosa. Results E. formosa populations originated in the middle Pleistocene period (0.3 Mya and consisted of two evolutionarily independent lineages. It is likely that they derived from the Pleistocene paleo-drainages of northern and southern Minjiang, or alternatively by divergence within Taiwan. The ancestral North-central lineage colonized northwestern Taiwan first and maintained a slowly growing population throughout much of the early to middle Pleistocene period. The ancestral widespread lineage reached central-southern Taiwan and experienced a spatial and demographic expansion into eastern Taiwan. This expansion began approximately 30,000 years ago in the Holocene interglacial period. The ancestral southern expansion into eastern Taiwan indicates that the central mountain range (CMR formed a barrier to east-west expansion. However, E. formosa populations in the three major biogeographic regions (East, South, and North-Central exhibit no significant genetic partitions, suggesting that river drainages and mountains did not form strong geographical barriers against gene flow among extant populations. Conclusions The present study implies that the antiquity of E. formosa's colonization is associated with its high dispersal ability and larval tolerance to the late Pleistocene dry grasslands. The effect of late Pleistocene climatic changes on the subtropical damselfly's historical demography is lineage-specific, depending predominantly on its colonization history and geography. It is proposed that the Riss and Würm glaciations in the late Pleistocene period had a greater impact on the evolutionary diversification of subtropical insular species than the last glacial maximum (LGM.

  11. Late Pliocene to Pleistocene sensitivity of the Greenland Ice Sheet in response to external forcing and internal feedbacks

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Sebastian J.; DeConto, Robert M. [University of Massachusetts, Department of Geosciences, Amherst, MA (United States); Pollard, David [Pennsylvania State University, Earth and Environmental Systems Institute, College of Earth and Mineral Sciences, University Park, PA (United States)

    2011-09-15

    The timing and nature of ice sheet variations on Greenland over the last {proportional_to}5 million years remain largely uncertain. Here, we use a coupled climate-vegetation-ice sheet model to determine the climatic sensitivity of Greenland to combined sets of external forcings and internal feedbacks operating on glacial-interglacial timescales. In particular, we assess the role of atmospheric pCO{sub 2}, orbital forcing, and vegetation dynamics in modifying thresholds for the onset of glaciation in late Pliocene and Pleistocene. The response of circum-Arctic vegetation to declining levels of pCO{sub 2} (from 400 to 200 ppmv) and decreasing summer insolation includes a shift from boreal forest to tundra biomes, with implications for the surface energy balance. The expansion of tundra amplifies summer surface cooling and heat loss from the ground, leading to an expanded summer snow cover over Greenland. Atmospheric and land surface fields respond to forcing most prominently in late spring-summer and are more sensitive at lower Pleistocene-like levels of pCO{sub 2}. We find cold boreal summer orbits produce favorable conditions for ice sheet growth, however simulated ice sheet extents are highly dependent on both background pCO{sub 2} levels and land-surface characteristics. As a result, late Pliocene ice sheet configurations on Greenland differ considerably from late Pleistocene, with smaller ice caps on high elevations of southern and eastern Greenland, even when orbital forcing is favorable for ice sheet growth. (orig.)

  12. Late Pleistocene and Holocene Glacial Evolution and Isotasy in the Antarctic Peninsula

    Science.gov (United States)

    Ivins, E. R.; Raymond, Carol A.; Heflin, M. B.; James, T. S.

    1989-01-01

    Employing a numerical model of Payne et al. that simulates the late-Pleistocene evolution of the former Antarctic Peninsula Ice Sheet (APIS) as a basis, we compute the present-day postglacial vertical isostasy of this region. The region may also experience significant mid-to late-Holocene glacial mass changes. Climate and oceanographic studies indicate that the ice mass imbalance of this region may be of larger magnitude that elsewhere in Antarctica. We compute the crustal response to these more recent ice mass changes and Holocene fluctuations with a simple gravitating Earth model consisting of an elastic lithosphere and a viscoelastic mantle (half-space). The calculations demonstrate that the present-day response could be significant, possibly at the level of about 4 - 11 mm/yr. Such significant crustal motion could be driven by glacial mass changes integrated over the last 1000 years if the regional mantle viscosity is below about 2 x 10(exp 20) Pa sec. In this lower viscosity range, present-day crustal motion has a significant phase-lagged character and the composite lithosphere/mantle viscoelastic response to late-Holocene events dominates over purely elastic (instantaneous) responses to present-day ice mass changes. For a higher mantle viscosity, greater than about 5 x 10(exp 20) Pa sec, the predicted present-day vertical isostasy is dominated by gravitational response to glacial unloading during the 18 - 6 kyr BP collapse of the APIS, and is analogous to that known to be occurring in the Gulf of Bothnia and Hudson Bay.

  13. Late Miocene-Pleistocene Stability of upper Ferrar Glacier, Dry Valleys, Antarctica

    Science.gov (United States)

    Staiger, J. W.; Marchant, D. R.; Schaefer, J. M.; Johnson, J. V.; Oberholzer, P.

    2005-12-01

    Vernier Valley (78o S, 161o E) opens onto a peripheral lobe of upper Ferrar glacier in the Dry Valleys of southern Victoria Land, Antarctica. The areal distribution of Ferrar drifts, along with a relative and numerical chronology afforded by surface-weathering characteristics and 3He - 21Ne exposure-age data, are used to reconstruct the Late Miocene-to-Pleistocene history of upper Ferrar Glacier. Applying a modest erosion rate correction of 10 cm Ma-1, our results show that the glacial record provided by Ferrar (1, 2, 3, and 4) drifts in Vernier Valley extends back into late Miocene time. Cosmogenic ages for clasts on the modern, ice-cored Ferrar 1 moraine suggest that nuclide inheritance is negligible. The development of weathering pits and desert varnish on surface cobbles varies linearly with cosmogenic age. Ice-surface profiles reconstructed from the moraine distribution and exposure-ages of boulders atop the moraines indicate that the ice-surface elevation of upper Ferrar Glacier has lowered roughly 50 m throughout the Quaternary Period and roughly 125 m since late Miocene time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no higher than today and may have been below modern levels. The moraine now forming through ice sublimation and debris accumulation at the modern, cold-based Ferrar Glacier margin is texturally similar to older drifts up-valley. The slow recession of cold-based glacier ice (and without surface melting ablation zones) in lower Vernier Valley implies enduring cold-desert conditions, much like those of today, for at least the last ~6.5 Ma. Results from a 2-D glacier flow-band model also demonstrate that upper Ferrar Glacier lacked basal-melting zones even during the Pliocene optimum. The overall stability of this glacial system has implications for the response of ice in this sector of Antarctica to future polar warming.

  14. The Late Pleistocene Duoi U'Oi cave in northern Vietnam: palaeontology, sedimentology, taphonomy and palaeoenvironments

    Science.gov (United States)

    Bacon, Anne-Marie; Demeter, F.; Duringer, P.; Helm, C.; Bano, M.; Vu, The Long; Kim Thuy, Nguyen Thi; Antoine, P.-O.; Thi Mai, Bui; Huong, Nguyen Thi Mai; Dodo, Y.; Chabaux, F.; Rihs, S.

    2008-08-01

    This paper describes new fossil materials recovered at the Duoi U'Oi site, in December 2003, by a Vietnamese-French-Japanese team. The Duoi U'Oi cave is located in Man Duc village, 25 km of Hoà Binh city in northern Vietnam. It belongs to a karstic network developed in a dark grey micritic marine limestone dated from the Lower to the Middle Triassic. The sedimentary fill produced a rich mammalian fauna, essentially composed of isolated teeth of middle- to large-sized mammals (Artiodactyla, Perissodactyla, Proboscidea, Carnivora, Rodentia, Primates), and characteristic of Late Pleistocene. The results of the Duoi U'Oi fieldwork are of great interest for the following reasons: (1) the biochronological age of the fauna is consistent with 230Th/ 234U/ 238U dating from the calcitic floors (66±3 ka). The Duoi U'Oi fauna is thus the oldest well-dated modern fauna known for the Southeast Asian mainland; (2) in terms of sedimentology, the analysis of the formation of the fossiliferous breccia and that of the processes of deposits shows a close relation between the karstic deposits inside the cave and the deposits in the alluvial terraces. The observation of three levels of alluvial terraces associated with three caves situated at 62, 10 and 3 m above the present alluvial plain suggests that exokarstic and endokarstic sediments evolved together; (3) in terms of palaeobiogeography, Duoi U'Oi is the continental fauna showing the strongest resemblance with the Late Pleistocene faunas from Indonesian islands (Punung, Gunung Dawung, Lida Ajer, Sibrambang and Djambu caves); this implies that, at the time of Duoi U'Oi, ca 70 ka, the Sundaland was mainly characterised by faunas of modern aspect; (4) the analysis of major taphonomic factors that led to the mammal assemblage reveals a combination of selective agents (selective role of predators and porcupines, selective destruction of age classes for some species, selective preservation of fossils due to the deposition processes in the karstic network), which contribute to the poor representation of the diversity of the fauna; no arguments show that humans, present at Duoi U'Oi, might have a possible role in the taphonomic process; (5) the palaeoenvironmental reconstruction based on the composition of the faunal assemblage suggests a forested area and some open habitats, under warm and humid conditions.

  15. Reconstructing the climate states of the Late Pleistocene with the MIROC climate model

    Science.gov (United States)

    Chan, Wing-Le; Abe-Ouchi, Ayako; O'ishi, Ryouta; Takahashi, Kunio

    2014-05-01

    The Late Pleistocene was a period which lasted from the Eemian interglacial period to the start of the warm Holocene and was characterized mostly by widespread glacial ice. It was also a period which saw modern humans spread throughout the world and other species of the same genus, like the Neanderthals, become extinct. Various hypotheses have been put forward to explain the extinction of Neanderthals, about 30,000 years ago. Among these is one which involves changes in past climate and the inability of Neanderthals to adapt to such changes. The last traces of Neanderthals coincide with the end of Marine Isotope Stage 3 (MIS3) which was marked by large fluctuations in temperature and so-called Heinrich events, as suggested by geochemical records from ice cores. It is thought that melting sea ice or icebergs originating from the Laurentide ice sheet led to a large discharge of freshwater into the North Atlantic Ocean during the Heinrich events and severely weakened the Atlantic meridional overturning circulation, with important environmental ramifications across parts of Europe such as sharp decreases in temperature and reduction in forest cover. In order to assess the effects of past climate change on past hominin migration and on the extinction of certain species, it is first important to have a good understanding of the past climate itself. In this study, we have used three variants of MIROC (The Model for Interdisciplinary Research on Climate), a global climate model, for a time slice experiment within the Late Pleistocene: two mid-resolution models (an atmosphere model and a coupled atmosphere-ocean model) and a high-resolution atmosphere model. To obtain a fuller picture, we also look at a cool stadial state as obtained from a 'freshwater hosing' coupled-model experiment, designed to mimic the effects of freshwater discharge in the North Atlantic. We next use the sea surface temperature response from this experiment to drive the atmosphere models. We discuss the general features of the model-simulated climates and how model resolution can affect these results. We also compare our results with some available proxy data to elucidate where model simulations show good agreement.

  16. Late Silurian and Early Devonian conodont stratigraphy in the Prague Synform and correlation of bioevents.

    Czech Academy of Sciences Publication Activity Database

    Slavík, Ladislav

    Buenos Aires : Asociacio?n Paleontolo?gica Argentina, 2013 - (Albanesi, G.; Ortega, G.). s. 149-149 [Conodonts from the And es : International Conodont Symposium /3./. 15.07.2013-19.07.2013, Mendoza] Institutional support: RVO:67985831 Keywords : conodonts * stratigraphy * Silurian * Devonian Subject RIV: DB - Geology ; Mineralogy

  17. Late Pleistocene-Holocene volcanic activity in northern Victoria Land recorded in Ross Sea (Antarctica) marine sediments

    Science.gov (United States)

    Del Carlo, P.; Di Roberto, A.; Di Vincenzo, G.; Bertagnini, A.; Landi, P.; Pompilio, M.; Colizza, E.; Giordano, G.

    2015-05-01

    Eight pyroclastic fall deposits have been identified in cores of Late Pleistocene-Holocene marine sediments from the Ross Sea (Antarctica), and their components, granulometry and clast morphologies were analysed. Sedimentological, petrographic and geochemical analysis of clasts, with 40Ar-39Ar dating of alkali feldspar grains, indicate that during this period at least five explosive eruptions of mid to high intensity (plinian to subplinian) occurred, and that three of these eruptions took place from Mount Melbourne volcanic complex, between 137.1 ± 3.4 and 12 ka. Geochemical comparison of the studied tephra with micro- and crypto-tephra recovered from deep Antarctic ice cores and from nearby englacial tephra at Frontier Mountain indicates that eruptive activity in the Melbourne Volcanic Province of northern Victoria Land was intense during the Late Pleistocene-Holocene, but only a general area of provenance for the majority of the identified tephra can be identified.

  18. Late Pliocene/Early Pleistocene environments inferred from the Lake El'gygytgyn pollen record

    Science.gov (United States)

    Andreev, Andrei; Wennrich, Volker; Tarasov, Pavel; Raschke (Morozova), Elena; Brigham-Grette, Julie; Nowaczyk, Norbert; Melles, Martin

    2014-05-01

    The Arctic is known to play a crucial role within the global climate system. The mid-Pliocene (3-3.5 Ma) is considered to be the most probable scenario of the future climate changes. However, reliable climate projections are hampered by the complexity of the underlying natural variability and feedback mechanisms. An important prerequisite for the validation and improvement of the future projections is a better understanding of the long-term environmental history of the Arctic. Unfortunately, formation of continuous paleoenvironmental records in the Arctic was widely restricted due to repeated glaciations. Continuous sequences that penetrate the entire Quaternary and further into the Pliocene are highly desired and would enable to validate the temperature rise during the mid-Pliocene that was proposed by former studies. Such a record has now become available from Lake El'gygytgyn (67º30'N, 172º05E') located in a meteorite impact crater in north-eastern Siberia. The impact nearly 3.6 Ma ago formed an 18 km wide hole in the ground that then filled with water. The retrieved lake sediments have trapped pollen from a several thousand square-kilometer source area providing reliable insights into regional and over-regional millennial-scale vegetation and climate changes of the Arctic since the Pliocene. The ''El'gygytgyn Drilling Project" of ICDP has completed three holes in the center of the lake, penetrating about 318 m thick lake sediments and about 200 m of the impact rocks below. Because of its unusual origin and high-latitude setting in western Beringia, scientific drilling at Lake El'gygytgyn offered unique opportunities for paleoclimate research, allowing time-continuous climatic and environmental reconstructions back into the Pliocene. Late Pliocene and Early Pleistocene pollen assemblages can be subdivided into 55 pollen zones, which reflect the main environmental fluctuations in the region 3.55-2.15 Ma BP. Pollen-based climate reconstructions show that conditions in the study area were the warmest about 3.55-3.4 Ma BP when spruce-pine-fir-hemlock-larch-Pseudotsuga forests dominated in nowadays tundra area. After ca 3.4 Ma BP dark coniferous taxa gradually disappeared from the vegetation. Very pronounced environmental changes are revealed about ca 3.35-3.275 Ma BP when treeless tundra and steppe habitats dominated. Treeless and shrubby environments are also indicative after ca 2.6 Ma. Dry and cold climate conditions were similar to those during the Late Pleistocene. The Early Pleistocene sediments contain pollen assemblages reflecting alternation of treeless intervals with cold and dry climate and warmer intervals when larch forests with stone pines, shrub alders and birches were also common in the region. Very dry environments are revealed after ca 2.175 Ma BP. High amounts of green algae colonies (Botryococcus) in the studied sediments point to shallow-water conditions ca 2.55, 2.45, and ca 2.175 Ma BP. Thus, pollen studies show that sediments accumulated in Lake El'gygytgyn are an excellent archive of environmental changes since 3.55 Myr BP. The record well reflects main regional paleoenvironmental fluctuations. The further high-resolution palynological study of the core will reveal climate fluctuations inside the main glacial/interglacial intervals and will give the first continuous and detailed scheme of environmental changes for a whole Arctic.

  19. Late Pleistocene deglaciation chronology in the NW of the Iberian Peninsula using cosmic-ray produced 21Ne in quartz

    International Nuclear Information System (INIS)

    Late Pleistocene glaciations in the NW Iberian Peninsula over Serra de Queixa and Serra de Xures, all with granite substrata, were studied by mass spectrometry using cosmogenic 21Ne. Rock cores were drilled in glacial polished surfaces and push-moraine boulders, and were analyzed to determine their integral exposure time to cosmic rays. First results, which are consistent with the relative geomorphologic model estimates, allow the identification of at least three different glacial stages, with the latest terminating about 15 ka BP

  20. A Phylogeographic Study of the Tiger (Panthera tigris): Using Holocene Distribution Models to Assess Late Pleistocene Range Shifts

    OpenAIRE

    Cooper, David Matthew

    2013-01-01

    Assessing tiger distributions through the Late Pleistocene can provide insight to the evolutionary histories of currently recognized tiger subspecies. If global tiger ranges have been continuous, and not sufficiently isolated through glacial or interglacial periods, then there should be fewer subspecies than those currently recognized. This paper uses a phylogeographic approach, by modelling tiger distributions for the present day and the Last Glacial Maximum using a maximum entropy framework...

  1. Late Pliocene and Early Pleistocene vegetation history of northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    OpenAIRE

    Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M.

    2014-01-01

    The 318 m thick lacustrine sediment record from Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities for the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments demonstrate their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. ...

  2. Mamíferos del pleistoceno terminal de la localidad de El Hatillo, Panamá / Late pleistocene mammals from El Hatillo, Panama

    Scientific Electronic Library Online (English)

    Spencer G., Lucas.

    2014-06-01

    Full Text Available Documentamos aquí por primera vez los mamíferos del Pleistoceno tardío de la localidad de El Hatillo en la península de Azuero en Panamá, originalmente reportado por C. L. Gazin en 1957. Los siguientes taxa están presente: Hoplophorinae?, Glyptotherium floridanum, Eremotherium laurillardi, Paramylod [...] on harlani, Equus conversidens, Platygonus sp., Odocoileus sp., Mixotoxodon larensis y Cuvieronius hyodon. Este es un conjunto característico de mamíferos del Pleistoceno Tardío de Centroamérica destacado por fósiles de Eremotherium en asociación con fósiles de Mixotoxodon y Equus. Me refiero a este tipo de asociación como montaje EME y postulo que la mayoría de estos montajes de Centroamérica son de edad del Pleistoceno Tardío. Los montajes EME representan una fauna mixta de pasteadores y ramoneadores que eran muy común en toda Centroamérica durante uno o más de los fines interestadiales del Pleistoceno. Abstract in english Late Pleistocene mammals from the El Hatillo locality on the Azuero Peninsula in Panama, originally reported by C. L. Gazin in 1957, are documented here for the first time. The following taxa are present: Hoplophorinae?, Glyptotherium floridanum, Eremotherium laurillardi, Paramylodon harlani, Equus [...] conversidens, Platygonus sp., Odocoileus sp., Mixotoxodon larensis and Cuvieronius hyodon. This is a characteristic assemblage of late Pleistocene mammals from Central America that is dominated by fossils of Eremotherium in association with fossils of Mixotoxodon and Equus. I refer to such associations as EME assemblages and posit that most of these assemblages from Central America are of Late Pleistocene age. EME assemblages represent a mixed fauna of grazers and browsers that was common across Central America during one or more of the Late Pleistocene interstadials.

  3. Paleoecological and climatic implications of stable isotope results from late Pleistocene bone collagen, Ziegeleigrube Coenen, Germany

    Science.gov (United States)

    Wißing, Christoph; Matzerath, Simon; Turner, Elaine; Bocherens, Hervé

    2015-07-01

    Climatic and ecological conditions during Marine Oxygen Isotope Stage (MIS) 3 are complex and the impact of cold spells on the ecosystems in Central Europe still needs to be investigated thoroughly. Ziegeleigrube Coenen (ZC) is a late Pleistocene MIS 3 locality in the Lower Rhine Embayment of Germany, radiocarbon-dated to > 34 14C ka BP. The site yielded a broad spectrum of mammal species. We investigated the carbon (?13C), nitrogen (?15N) and sulfur (?34S) isotope signatures of bone collagen, since these are valuable tools in characterizing ecological niches, environmental conditions and aspects of climate and mobility. By comparison with pre- and post-Last Glacial Maximum (LGM) sites in Central Europe we show that ZC belongs in a cold event of MIS 3 and was climatically more similar to post-LGM sites than to pre-LGM sites. However, the trophic structure resembled that of typical pre-LGM sites in Belgium. This cold event in MIS 3 changed the bottom of the foodweb, but do not seem to have had a direct impact on the occurrence of the mammalian species and their ecological distribution. Apparently the (mega-) faunal community could adapt also to harsher environmental conditions during MIS 3.

  4. A late Pliocene to middle Pleistocene pluvial lake in Fish Lake Valley, Nevada and California

    Science.gov (United States)

    Reheis, M.C.; Slate, J.L.; Sarna-Wojcicki, A. M.; Meyer, C.E.

    1993-01-01

    The question of whether a pluvial lake existed in Fish Lake Valley, Nevada and California, has been debated for more than 100 yr. New stratigraphic evidence indicates that a lake did exist in this valley at intervals during late Pliocene to middle Pleistocene time. This lake may have drained northward, or it may have been periodically contiguous with a pluvial lake to the north in Columbus Salt Marsh. Proof of the existence of this lake, informally named Pluvial Lake Rennie, is derived from three principal outcrops of shallow-water deposits, two outcrops of deep-water deposits, and several drilling logs. The deposits contain beds of silicic tephra, which provide age control. Pluvial Lake Rennie fluctuated in size and depth beginning prior to 2 Ma and continuing until sometime after 0.77 Ma. At about 0.77 Ma, the lake had a highstand at an elevation of ~1460 m, covered an area of 400-500 km2, and had a maximum depth of ~250 m. The lake level dropped just after the eruption of the Bishop ash, but the lake may have persisted at a lower level until ~0.5 Ma. -from Authors

  5. Characteristics of the active Luoshan Fault since Late Pleistocene, North Central China

    Directory of Open Access Journals (Sweden)

    M. Fengying

    2003-06-01

    Full Text Available The Luoshan Fault located at the northeastern margin of Tibet plateau strikes roughly N-S, and is composed of six left-stepping sections with a total length of 60 km. Much evidence suggests that the Luoshan Fault is a reverse right-lateral strike-slip fault. The largest right-lateral strike-slip displacement and the most abundant dextral offset phenomena are located along the central section. Based on the right-lateral strike-slip offsets of the oldest alluvial fan, and of a gully and on the average displacement of the same order of gullies, the minimum slip-rate has been 2.15 ± 0.2 mm/yr since Late Pleistocene. Many surface rupture phenomena, such as fault scarps with fresh free-face, ground fissures, displacements of very young gullies, imply that a recent earthquake occurred along this fault. Combining the historical catalogue and our results, we believe that the 1561 A.D. earthquake was produced by the Luoshan Fault. Three paleoearthquakes were determined by means of paleoseismic studies along the Luoshan Fault: they occurred after 8200 ± 600 years BP, between 3130 ± 240 years BP and 4150 ± ± 120 years C.BP, and before 2230 ± 170 years BP, respectively.

  6. Late Pleistocene Interstadial Environment on Faddeyevskiy Island, East-Siberian Sea, Russia

    Science.gov (United States)

    Andreev, Andrei A.; Peteet, Dorothy M.; Romanenko, Fedor A.; Filimonova, Ludmila V.; Sulerzhitsky, Leopold D.; Tarasov, Pavel E.

    1999-01-01

    Pollen, plant macrofossil, LOI and radiocarbon analyses of a 1.4-m section from Faddeyevskiy Island, Novosibirskie Ostrova archipelago (75 deg 20 min N, 143 deg 50 min E, 30m elevation) provide new information on the Late Pleistocene interstadial environmental history of this high Arctic region. Bulk radiocarbon dates of 25,700 +/- 1000, 32,780 +/- 500, 35,200 +/- 650 and two AMS dates of 29,950 +/- 660 and 42,990 +/- 1280 indicate that the deposits accumulated during the Kargian (Boutellier) interval. Numerous mammoth (Mammuthus primigenius) remains collected in the vicinity of the site were radiocarbon dated to 36,700-18,500 yr. BP. Rare bison (Bison priscus) bones were dated to 32,200 +/- 600 and 33,100 +/- 320. Poaceae, Cyperaceae, and Artemisia pollen dominate the pollen spectra with some Ranunculaceae, Caryophyllaceae, Rosaceae, and Compositae. These pollen spectra reflect a tundra-steppe vegetation which probably was dominant on the exposed shelf of the Arctic Ocean. The presence of Carex macrofossils infer a summer climate two degrees warmer than today. The productivity of this local vegetation during the Kargian interstadial was apparently high enough to feed the grass-eater herds.

  7. Major controls on architecture, sequence stratigraphy and paleosols of middle Pleistocene continental sediments ("Qc Unit"), eastern central Italy

    Science.gov (United States)

    Di Celma, Claudio; Pieruccini, Pierluigi; Farabollini, Piero

    2015-05-01

    Middle Pleistocene continental sediments in central Italy ("Qc Unit") record the oldest fluvial accumulation along the uplifting margin of the Peri-Adriatic basin. The architecture of the sediment body can be divided into two unconformity-bounded, fining-upward cycles interpreted as genetically related depositional sequences. These sequences highlight the systematic adjustment of the fluvial system to changes in the ratio between accommodation space and sediment supply (A/S ratio) and, from base to top, comprise the following surfaces and stratal components: (i) a regionally correlative sequence boundary resulting from an A/S ratio ? 0; (ii) a low-accommodation systems tract characterized by conglomerate-rich, amalgamated channel fills and recording an A/S ratio 1; and (v) a mature red argillic paleosol. To constrain the climatic signal for paleosols formation, the two sequence-capping mature paleosols have been investigated. The results of these studies suggest that they were developed under humid and warm climatic conditions associated with interglacial phases, which have been correlatively attributed to Marine Oxygen Isotope Stages 11 and 9.

  8. Stable isotopes composition of water recharged in Late Pleistocene and Halocene in Central Poland

    International Nuclear Information System (INIS)

    Changes of isotope composition of the Pleistocene and Halocene infiltrating waters in Poland are presented. They have been reconstructed on the basis of air-temperature changes in the Pleistocene and Halocene periods and linear relationships between ?18O in meteoric water and average air-temperature in Poland. (author)

  9. Late Pleistocene to Holocene environmental changes from ?13C determinations in soils at Teotihuacan, Mexico

    Scientific Electronic Library Online (English)

    E, Lounejeva Baturina; P, Morales Puente; H. V, Cabadas Báez; E, Cienfuegos Alvarado; S, Sedov; E, Vallejo Gómez; E, Solleiro Rebolledo.

    2006-06-01

    Full Text Available Utilizamos la firma de isótopos estables de carbono, medida como ?13C, en la materia orgánica de suelo (SOM) como un método de alta resolución espacial para inferir algunos cambios ambientales durante el Pleistoceno tardío y el Holoceno en el valle de Teotihuacan. La interpretación se basa en la dif [...] erencia de ?13Cy preferencias climáticas correspondientes de las plantas referidas como C3, C4 y CAM. Los valores de ?13Cobtenidos de plantas que crecen en el valle hoy en día difieren claramente entre dos grupos: los de las plantas C3 con un promedio de -27%o, y los de C4 y CAM con un promedio cerca de -13%o. Los datos obtenidos para los suelos se encuentran en el intervalo de -25.72 a -15.54 %o. Las secuencias de suelos Pleistoceno tardío- Reciente del valle alto (posición geomorfológica alta), localizadas en el perfil de Cerro Gordo, se caracterizan por una ?13Ccon poca variabilidad alrededor de -20%o, indicando una coexistencia duradera entre las plantas C3 y C4 (y CAM). Las firmas más empobrecidas (-23 ± 2) %o, dominadas por carbono derivado de la vegetación tipo C3, corresponden a los suelos de pantano del Pleistoceno tardío en el perfil retrógrado de transición Tepexpan del antiguo lago de Texcoco-Xaltocan. Los paleosuelos en el valle bajo (Pleistoceno tardío - Holoceno medio), incluyendo los de la Pirámide de la Luna, están menos empobrecidos (-17 ± 1) %o, o bien, dominados por carbono de plantas C4 y CAM. Los suelos del Holoceno tardío y modernos presentan una disminución (1-2 %o) respecto a las ?13Cde los suelos subyacentes. A partir de las ?13Cde suelos se estimó la porción relativa de la contribución de las plantas C4 a la materia orgánica del mismo. Nuestros resultados implican un incremento, dependiendo del lugar, de entre 10 y 70%, durante el período de transición entre el Pleistoceno tardío y Holoceno temprano, y un dominio de la vegetación tipo C4 en el ambiente del valle, hasta en un 84%, durante Holoceno medio. Nuestros datos apoyan la idea de un cambio natural de un clima más frío y húmedo durante el último Máximo Glacial y el Pleistoceno tardío a uno más seco y caluroso en el Holoceno medio. Un ligero incremento de humedad y establecimiento de un clima semejante al actual, aún cálido y seco, se infiere del incremento en todo el valle, dependiendo del lugar, de 4 a 10%, de la población de plantas C3. Sugerimos que este último cambio climático pudo favorecer el desarrollo de la antigua agricultura. Nuestra interpretación general de los primeros datos de isótopos estables del carbono concuerda con interpretaciones paleoambientales para el área basadas en registros palinológicos y paleolimnológicos en sedimentos lacustres. Abstract in english Stable carbon isotopic signature (?13C) of soil organic matter (SOM) is used as a high-spatial resolution tool to infer environmental changes during late Pleistocene to Present in the Teotihuacan valley, Mexico. Interpretation was based on climatic preferences of C3, CAM and C4 plant groups. ?13Cval [...] ues of modern plant types are clearly distinguished. C3 plants display values around -27%o, while C4 and CAM plants have values around-13%o. Data from soil profiles range from -25.7 to -15.5 %o. Cerro Gordo site ?13Cvaryies around -20%o, indicating long-term, time-stable co-existence between C3 and C4 or CAM plants. The more depleted signatures (-23 ± 2 %o) are, dominated by carbon from C3 vegetation of late Pleistocene swamp paleosols in the Tepexpan profile of the Lake Texcoco. Younger paleosols from lower valley sites, have less depleted values (-17 ± 1) %o, dominated by C4 and CAM carbon. Late Holocene and modern soils present slightly more negative values (1-2 %o) with respect to ?13Cof underlying soils. Our results show 1) an increase of 10-70 % depending on the site, during the transition from the late Pleistocene to early Holocene, and 2) a dominance of C4 vegetation, up to 84%, in valley environment during the middle Holocene. These data support a climatic change from cold and

  10. Relationship between Late Pleistocene sea-level variations, carbonate platform morphology and aragonite production (Maldives, Indian Ocean)

    DEFF Research Database (Denmark)

    Paul, A.; Reijmer, J.J.G.

    2012-01-01

    A piston core from the Maldives carbonate platform was investigated for carbonate mineralogy, grain-size distributions, calcium carbonate content and organic carbon. The sedimentary record was linked to Late Pleistocene sea-level variations, using an age model based on oxygen isotopes obtained from planktonic foramanifera, nannofossil biostratigraphy and C age determinations. The correlation between the sedimentary record and Late Pleistocene sea-level showed that variations in aragonite and mud during the past 150000years were clearly related to flooding and sea floor exposure of the main lagoons of the atolls of the Maldives carbonate platform. Platform flooding events were characterized by strongly increased deposition of aragonite and mud within the Inner Sea of the Maldives. Exposure events, in contrast, can be recognized by rapid decreases in the values of both proxy records. The results show that sediments on the Maldives carbonate platform contain a continuous record of Pleistocene sea-level variations. These sediments may, therefore, contribute to a better understanding of regional and even global sea-level changes, and yield new insights into the interplay between ocean currents and carbonate platform morphology. © 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists.

  11. Sedimentary architecture and chronostratigraphy of a late Quaternary incised-valley fill: A case study of the late Middle and Late Pleistocene Rhine system in the Netherlands

    Science.gov (United States)

    Peeters, J.; Busschers, F. S.; Stouthamer, E.; Bosch, J. H. A.; Van den Berg, M. W.; Wallinga, J.; Versendaal, A. J.; Bunnik, F. P. M.; Middelkoop, H.

    2016-01-01

    This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage/MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a 3D geological model. The incised-valley fill consists of a ca. 50 m thick and 10-20 km wide sand-dominated succession and includes a well-developed sequence dating from the Last Interglacial: known as the Eemian in northwest Europe. The lower part of the valley fill contains coarse-grained fluvio-glacial and fluvial Rhine sediments that were deposited under Late Saalian (MIS 6) cold-climatic periglacial conditions and during the transition into the warm Eemian interglacial (MIS 5e-d). This unit is overlain by fine-grained fresh-water flood-basin deposits, which are transgressed by a fine-grained estuarine unit that formed during marine high-stand. This ca. 10 m thick sequence reflects gradual drowning of the Eemian interglacial fluvial Rhine system and transformation into an estuary due to relative sea-level rise. The chronological data suggests a delay in timing of regional Eemian interglacial transgression and sea-level high-stand of several thousand years, when compared to eustatic sea-level. As a result of this glacio-isostatic controlled delay, formation of the interglacial lower deltaic system took only place for a relative short period of time: progradation was therefore limited. During the cooler Weichselian Early Glacial period (MIS 5d-a) deposition of deltaic sediments continued and extensive westward progradation of the Rhine system occurred. Major parts of the Eemian and Weichselian Early Glacial deposits were eroded and buried as a result of sea-level lowering and climate cooling during the early Middle Weichselian (MIS 4-3). Near complete sedimentary preservation occurred along the margins of the incised valley allowing the detailed reconstruction presented here.

  12. A lacustrine record from Lop Nur, Xinjiang, China: Implications for paleoclimate change during Late Pleistocene

    Science.gov (United States)

    Chao, L.; Zicheng, P.; Dong, Y.; Weiguo, L.; Zhaofeng, Z.; Jianfeng, H.; Chenlin, C.

    2009-01-01

    Climate variability during the Late Pleistocene is studied from the proxies in core CK-2 drilled from the Luobei Depression (91??03???E, 40??47???N), Lop Nur in the eastern Tarim Basin, Xinjiang, China. Geophysical and geochemical properties, including magnetic susceptibility, granularity, chroma, carbonate content, loss on ignition and trace elements, have been determined to reconstruct the environmental evolution of the area during 32-9 ka BP. The chronology is established by uranium-thorium disequilibrium dating techniques. Our data suggest four paleoclimate stages, indicating glacial variations between cold-humid and warm-arid environments. A period of extreme humidity occurred during 31,900-19,200 yr BP is attributed the last glacial maximum (LGM). The period was followed by a warm-arid episode during 19,200-13,500 yr BP. Then a cold-humid interval during 13,500-12,700 yr BP may correspond to another cooling phases at high latitudes of the Northern Hemisphere. The last stage from 12,700 to 9000 yr BP has a trend that the climate turned warm and arid. The Lop Nur region is characterized by particularly humid stadials and arid interstadials. The climate variability in Lop Nur was constrained by global climate change because it is correlated with Dansgaard-Oeschger and Heinrich events, which were observed at the northern high latitudes. The synchroneity of the palaeoclimatic events suggested that cold air activity at the northern high latitudes was the most important factor that influenced the climate evolution in the Lop Nur region. A probable mechanism that involves the migration of westerly winds is proposed to interpret this synchroneity. ?? 2008 Elsevier Ltd.

  13. Late-Pleistocene avifaunas from Cape Wanbrow, Otago, South Island, New Zealand

    International Nuclear Information System (INIS)

    Fossil avifaunas from the Hillgrove Formation at Boatmans Harbour, Ruby Gully, and Old Rifle Butts, all on Cape Wanbrow, Oamaru, north-east Otago, are listed. The marine beach sands and gravels at Old Rifle Butts that form the lowest part of the Hillgrove Formation and overlie the palaeo-wave platform were deposited during the last interglacial ? 130-110 kyr BP (Oxygen Isotope Stage 5). There are a few small avifaunas (totalling 11 spp.) from these beach sediments (J41/f8710, f8214, f8227). The colluvial, valley-fill deposits in Ruby Gully and at its mouth are the youngest in the sequence. Radiocarbon dating indicates their emplacement between 27 and 34 kyr BP, or the later part of Oxygen Isotope Stage 3. If these ages are representative of the true age of the samples and not the limitations of radiocarbon technology, they indicate that these deposits in Ruby Gully are much younger than the beach deposits. Radiocarbon ages on a pitfall fauna from a small cave 3-4 m above the base of the Hillgrove Formation indicate that the cave fauna has a similar age as that in Ruby Gully. The dune and interdune waterlaid deposits at Old Rifle Butts (>2 m above the wave platform) may date from an unknown time between 100 and 35 kyr BP or be coeval with those in Ruby Gully. Fifty-three species of bird (32 land and freshwater taxa) are represented in the combined avifaunas making this the richest Pleistocene avifauna known from New Zealand. All bird taxa are known from Late Holocene avifaunas in the eastern South Island. Key taxa (Pachyornis elephantopus, Emeus crassus, Euryapteryx geranoides, Coturnix, Chenonetta, Cnemiornis, Harpagornis, Fulica, Porphyrio, Gallinula) indicate that the habitat was mainly grassland and shrubland. Tuatara, indeterminate skinks, and seals are also present. (author). 57 refs., 10 figs., 2 tabs

  14. Stable isotope paleoecology of Late Pleistocene Middle Stone Age humans from the Lake Victoria basin, Kenya.

    Science.gov (United States)

    Garrett, Nicole D; Fox, David L; McNulty, Kieran P; Faith, J Tyler; Peppe, Daniel J; Van Plantinga, Alex; Tryon, Christian A

    2015-05-01

    Paleoanthropologists have long argued that environmental pressures played a key role in human evolution. However, our understanding of how these pressures mediated the behavioral and biological diversity of early modern humans and their migration patterns within and out of Africa is limited by a lack of archaeological evidence associated with detailed paleoenvironmental data. Here, we present the first stable isotopic data from paleosols and fauna associated with Middle Stone Age (MSA) sites in East Africa. Late Pleistocene (?100-45 ka, thousands of years ago) sediments on Rusinga and Mfangano Islands in eastern Lake Victoria (Kenya) preserve a taxonomically diverse, non-analog faunal community associated with MSA artifacts. We analyzed the stable carbon and oxygen isotope composition of paleosol carbonate and organic matter and fossil mammalian tooth enamel, including the first analyses for several extinct bovids such as Rusingoryx atopocranion, Damaliscus hypsodon, and an unnamed impala species. Both paleosol carbonate and organic matter data suggest that local habitats associated with human activities were primarily riverine woodland ecosystems. However, mammalian tooth enamel data indicate that most large-bodied mammals consumed a predominantly C4 diet, suggesting an extensive C4 grassland surrounding these riverine woodlands in the region at the time. These data are consistent with other lines of paleoenvironmental evidence that imply a substantially reduced Lake Victoria at this time, and demonstrate that C4 grasslands were significantly expanded into equatorial Africa compared with their present distribution, which could have facilitated dispersal of human populations and other biotic communities. Our results indicate that early populations of Homo sapiens from the Lake Victoria region exploited locally wooded and well-watered habitats within a larger grassland ecosystem. PMID:25805041

  15. The Balitx landslide (Mallorca, Spain) and its possible seismic origin: active spreading since the Late Pleistocene

    International Nuclear Information System (INIS)

    The Balitx landslide, located on the steep coastal side of the Tramuntana range on the island of Mallorca, is a large translational rock landslide in which the failure surface coincides with the reactivation of an earlier normal fault. The dating of calcite striae on the fault plane with U/Th techniques reveals that the last movement was over 400 kyr ago, which falls outside of the range of this method. The volume of the landslide is estimated to be over 700 million cubic metres, with a north-westward displacement of 300 m. Active extensional cracks as well as block spreads have been identified along the main scarp, together with displacement and toppling of blocks, the beginning of which coincides with oxygen isotope stage OIS 5a (Late Pleistocene = 83 kyr), a wetter and warmer period than the present. Currently active decametre-long cracks up to 50 m wide can be seen to affect the displaced materials. They reveal the rupture of the displaced block into several units at different speeds. A retrospective analysis of slope stability has been carried out, taking into account different scenarios according to three critical sea stands. All the scenarios are stable, with a safety factor of over 1.35. These results support the thesis that the Balitx landslide could have been triggered by seismicity. A study of the Balitx landslide under dynamic conditions reveals that the landslide could have been triggered by a moderate-to-high-magnitude earthquake (Mw=6.0) located close to the landslide (10-30 km) and probably related to some of the active faults identified in Majorca, such as the Palma Fault. (Author) 58 refs.

  16. Morphological Chronoclines among Late Pleistocene Muskrats ( Ondatra zibethicus: Muridae, Rodentia) from Northern Florida

    Science.gov (United States)

    Mihlbachler, Matthew C.; Hemmings, C. Andrew; Webb, S. David

    2002-11-01

    The muskrat ( Ondatra zibethicus) is presumed to have undergone a rapid phyletic size decrease near the end of the Pleistocene. Evolutionary changes in the size of middle to late Wisconsinan (ca. 32,000-12,300 14C yr B.P.) muskrats from the Aucilla River, Jefferson County, Florida, were reconstructed by examining length and width of the lower first molar (m1). Body mass, estimated from m1 length, was relatively stable from 32,000 to 16,000 14C yr B.P. and decreased only slightly by 12,300 14C yr B.P. If the size trend found in the Aucilla River material is characteristic of the southeastern United States, a body size decrease after 12,300 14C yr B.P. is needed to explain the smaller size of modern populations. It was previously thought that the length/width (l/w) ratio of the muskrat m1 was a paleoenvironmental indicator based on its presumed correlation with latitude in modern populations. We examined the length and width of modern muskrats from several geographic regions and found only a very weak trend in the size of the m1 between northern and southern populations; however, highly significant differences were found between regions of similar latitude. Our data indicate that chronoclines in the m1 of the Aucilla muskrat material and other such documented trends among fossil muskrats have paleoenvironmental significance, but it is not yet clear which environmental variables can best be predicted from them.

  17. Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics.

    Science.gov (United States)

    Campos, Paula F; Willerslev, Eske; Sher, Andrei; Orlando, Ludovic; Axelsson, Erik; Tikhonov, Alexei; Aaris-Sørensen, Kim; Greenwood, Alex D; Kahlke, Ralf-Dietrich; Kosintsev, Pavel; Krakhmalnaya, Tatiana; Kuznetsova, Tatyana; Lemey, Philippe; MacPhee, Ross; Norris, Christopher A; Shepherd, Kieran; Suchard, Marc A; Zazula, Grant D; Shapiro, Beth; Gilbert, M Thomas P

    2010-03-23

    The causes of the late Pleistocene megafaunal extinctions are poorly understood. Different lines of evidence point to climate change, the arrival of humans, or a combination of these events as the trigger. Although many species went extinct, others, such as caribou and bison, survived to the present. The musk ox has an intermediate story: relatively abundant during the Pleistocene, it is now restricted to Greenland and the Arctic Archipelago. In this study, we use ancient DNA sequences, temporally unbiased summary statistics, and Bayesian analytical techniques to infer musk ox population dynamics throughout the late Pleistocene and Holocene. Our results reveal that musk ox genetic diversity was much higher during the Pleistocene than at present, and has undergone several expansions and contractions over the past 60,000 years. Northeast Siberia was of key importance, as it was the geographic origin of all samples studied and held a large diverse population until local extinction at approximately 45,000 radiocarbon years before present ((14)C YBP). Subsequently, musk ox genetic diversity reincreased at ca. 30,000 (14)C YBP, recontracted at ca. 18,000 (14)C YBP, and finally recovered in the middle Holocene. The arrival of humans into relevant areas of the musk ox range did not affect their mitochondrial diversity, and both musk ox and humans expanded into Greenland concomitantly. Thus, their population dynamics are better explained by a nonanthropogenic cause (for example, environmental change), a hypothesis supported by historic observations on the sensitivity of the species to both climatic warming and fluctuations. PMID:20212118

  18. New Proxies from Loess-Paleosols on Mount Kilimanjaro document Late Pleistocene Megadroughts in East Africa

    Science.gov (United States)

    Zech, R.; Huang, Y.; Russell, J. M.; Tarozo, R.; Gao, L.; Hemp, A.; Zech, W.

    2009-12-01

    Innovative, new proxies from loess and paleosol sediments hold great potential to obtain more quantitative information about paleoclimate changes in terrestrial environments. Here we present results from lipid biomarkers (GDGTs) and hydrogen isotopic measurements on long-chain fatty acids and alkanes that we extracted from 69 paleosol samples from Mt Kilimanjaro, Tanzania (~3°S). The respective soil pit and sediment core at ~2700 m above sea level is radiocarbon-dated to 38.4 ka BP, and probably covers most of the Late Pleistocene, making it one of the longest, continuous, terrestrial archives in the East African tropics. Our compound-specific deuterium measurements show lowest ?D values from ~9 to 5 ka in the Early/Middle Holocene, consistent with regional evidence for an “African Humid Period,” followed by a shift towards more arid conditions during the Late Holocene (~5‰ shift). The Younger Dryas is characterized by a ?D enrichment (=aridity) of ~15‰ compared to the Early/Middle Holocene, almost reaching LGM values (~20‰ shift). The enrichment during the LGM is, however, significantly smaller than the 50‰ change as observed in Lake Tanganyika further southwest. At present it is not possible to determine whether these differences result from geographic variations in precipitation and humidity, or isotopic distillation processes along the vapor transport trajectories across East Africa. Much more arid conditions (~40‰ enrichment) can be inferred for the paleosols older than ~60 ka. Although further dating efforts are required to determine the exact timing, this corroborates earlier findings from African lakes that suggested ‘megadroughts’ occurred during Marine Isotope Stages 5 and 4. Acknowledging the general perception that precipitation in East Africa is strongly controlled by ITCZ positioning, we highlight the role of (strong) eccentricity in modulating the precessional forcing, which - in combination with high-latitude glacial boundary conditions - may have caused extreme amplitudes of seasonal ITCZ migration and corresponding variability of climate conditions in the tropics on orbital timescales. Counter-intuitively, our GDGT temperature reconstruction based on MBT and CBT indices shows temperatures ~5°C warmer throughout the LGM and MIS3 than during the Holocene. Although local soil temperature may be affected by vegetation and/or cloud cover, such results advice caution and highlight the necessity to further validate and develop these new biomarker proxies.

  19. An Arctic perspective on dating Mid-Late Pleistocene environmental history

    DEFF Research Database (Denmark)

    Alexanderson, Helena; Backman, Jan; Cronin, T.M.; Funder, Svend Visby; Ingólfsson, Ó; Jakobsson, Martin; Landvik, Jon Ytterbø; Löwemark, Ludwig; Mangerud, Jan; März, Christian; Möller, Per; O'Regan, Matt; Spielhagen, R.F.

    2014-01-01

    To better understand Pleistocene climatic changes in the Arctic, integrated palaeoenvironmental and palaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologic age control are required, not least for correlation to extra-Arctic records. In this paper we discuss, from an Arctic perspective, methods and correlation tools that are commonly used to date Arctic Pleistocene marine and terrestrial events. We review the state of the art of Arctic geochron...

  20. Late Pleistocene and Holocene Hydroclimate Variability in the Tropical Andes from Alpine Lake Sediments, Cordillera de Mérida, Venezuela

    Science.gov (United States)

    Larsen, D. J.; Abbott, M. B.; Polissar, P. J.

    2014-12-01

    The tropics play a major role in the global hydrologic cycle and changes to tropical rainfall patterns have critical implications for water resources and ecosystem dynamics over large geographic scales. In tropical South America, late Pleistocene and Holocene precipitation variability has been documented in geologic records and associated with numerous external and internal variables, including changes in summer insolation, South American summer monsoon strength, Pacific Ocean sea surface temperatures, continental moisture recycling, and other climate processes. However, there are few records from the northern hemisphere tropical Americas, a key region for understanding interhemispheric linkages and the drivers of tropical hydroclimate variability. Here, we present a ~13 ka record of coupled hydroclimate and environmental changes from Laguna Brava, a small (~0.07 km2), hydrologically closed lake basin situated at 2400 m asl in the Cordillera de Mérida, Venezuela. Sediment cores collected from varying water depths and proximity to shore are placed in a chronologic framework using radiocarbon ages from terrestrial macrofossils, and analyzed for a suite of physical, bulk geochemical, and stable isotopic parameters. Compound specific hydrogen isotope (D/H) measurements of terrestrial plant waxes (long-chain n-alkanes) show a sharp increase in the late Pleistocene, followed by a long-term trend toward more negative values that suggest a ~20‰ decrease in the D/H ratios of South American tropical precipitation during the Holocene. This pattern is consistent in sign and magnitude to other South American precipitation reconstructions from both hemispheres, indicating interhemispheric similarities in tropical hydroclimate variability. Superimposed on this continent-scale trend are changes in moisture balance and environmental conditions in the Venezuelan Andes. We reconstruct these parameters at Laguna Brava at multidecadal and centennial resolution and evaluate this record within the context of late Pleistocene and Holocene South American tropical hydroclimate variability and global climate changes.

  1. The application of regional-scale geochemical data in defining the extent of aeolian sediments : the Late Pleistocene loess and coversand deposits of East Anglia, UK

    OpenAIRE

    Scheib, Andreas; Lee, Jonathan R.

    2010-01-01

    The ‘European Coversand Sheet’ is a discontinuous ‘sheet’ of aeolian (windblown) loess and coversand that extends through eastern and southern England, across the English Channel into northern France, Belgium and the Netherlands (Kasse, 1997; Antoine et al., 2003). Whilst some of the earlier aeolian sediments date from the Middle Pleistocene, most correspond to the Late Pleistocene Weichselian / Devensian and earliest Holocene stages. East Anglia contains considerable acc...

  2. Late Pleistocene glacial chronology of the Retezat Mts, Southern Carpathians, using 10Be exposure ages

    Science.gov (United States)

    Ruszkiczay-Rüdiger, Zsófia; Kern, Zoltán; Urdea, Petru; Braucher, Régis; Madarász, Balázs; Schimmelpfennig, Irene

    2015-04-01

    Our knowledge on the timing of glacial advances in the Southern Carpathians is limited. Recently, some attempts have been made to develop an improved temporal framework for the glaciations of the region using cosmogenic 10Be exposure dating. However, glacial chronology of the Romanian Carpathians remains contradictory. E.g. the timing of the maximum ice advance appears to be asynchronous within the area and also with other dated glacial events in Europe. Main objective of our study is to utilize cosmogenic in situ produced 10Be dating to disentangle the contradictions of the Southern Carpathian Late Pleistocene glacial chronology. Firstly, previously published 10Be data are recalculated in accordance with the new half-life, standardization and production rate of 10Be. The recalculated 10Be exposure ages of the second largest (M2) moraines in the Retezat Mts. appear to be ca. 19-24% older than exposure ages calculated by Reuther et al. (2007, Quat. Int. 164-165, 151-169). This contradicts the earlier conclusions suggesting post LGM age of M2 glacial advance and suggests that M2 moraines can be connected to the end of the LGM with final stabilization possibly at the beginning of the Late Glacial. We emphasize that it is ambiguous to correlate directly the exposure-dated glacier chronologies with millennial scale climate changes due to uncertainties in sample collection and in computation of exposure ages from measured nuclide concentrations. New 10Be samples were collected in order to determine the 10Be exposure age of moraines outside the most prominent generation (M2) including the largest and oldest moraine (M1) and the landforms connected to the smallest ice advances (M4), which remained undated so far. The new exposure ages of M2 moraines are well in harmony with the recalculated ages of Reuther at al. (2007). 10Be exposure age of boulders on the smallest moraine suggest that the last glaciers disappeared in the area during the Late Glacial, indicating no glaciation during the Younger Dryas and Holocene. Previous works, based on geomorphologic analogies and pedological properties suggested that the M1 ice advance was older than LGM, and possibly occurred during the MIS4. Our 10Be exposure dating provided LGM ages for boulders on the M1 side moraine. It is question of further research whether these ages show the time when the glacier abandoned the moraine or they only indicate an LGM erosional event affecting an older moraine. If we accept the LGM age of maximum ice extent (M1), our 10Be exposure age data enables the calculation of a mean glacier retreat rate of 1.3 m/a for the period between M1 and M4 (21.4 to 13.6ka). Alternatively, considering only the oldest 10Be exposure age of the M2 moraine, the M2 to M4 (20.2-13.6ka) glacier retreat rate was slightly lower: 1.1 m/a. Our research was supported by the OTKA PD83610, by the MTA-CNRS cooperation (NKM-96/2014), by the Bolyai Scholarship, and by the 'Lendület' program of the HAS (LP2012-27/2012). The 10Be measurements were performed at the ASTER AMS national facility (CEREGE, Aix en Provence, France).

  3. Comaparison of late pleistocene glacier extensions along a meridian Himalaya transect by geomorphological and pedological methods

    Science.gov (United States)

    Wagner, M.

    2009-04-01

    There is still a controverse discussion on Late Pleistocene glacier extensions for many parts of the Himalaya. Besides differing geomorphological results, more recent pedological relative datings of moraines delivered further inconsistent findings. For a meridian Himalaya transect along the Kali Gandaki a detailed field review of these different glaciogeomorphological reconstructions has been carried out, supplemented by new equilibrium line altitude (ELA) calculations. In a second step these findings have been used as benchmark to explore the options and limits of pedological relative dating of glacigene accumulations in the Higher Himalaya. A review of the already existing glaciogeomorphological results clearly appoved the more extended glaciation and the detailed relative chronology found in Kuhle (1982), while the more restricted glaciation view advanded by Fort (2000) is the result of foulty and missing geomorphological interpretations. To reconstruct former ELA depressions within the very steep and highly dynamic landforms of the Himalaya, „Toe-To-Summit-Altitude-Methods" (TSAM) are most adequate. Only the upper and lower glacier margin need to be known, which can be identified quite certain even for pre-existing glacier extensions. The method Kuhle is proved to provide the most suitable results, because the strong influence of the valley topography and the degree of debris cover on the position of the ELA within the vertical extension of the glacier can be simulated by the „factor of snowline deviation" (FSD). Maximum ELA depressions of 1300 to 1500 m can be observed for the south-face of the Higher Himalaya as well as for the arid north-face and the Inner Himalaya. The extreme topographical changeover arising from the inflow of the former glaciers from the tributary valleys into the wide and flat valley bottoms lead to little uncertainness, but the relative chronology of the glacier stages can certainly be derived. Most of the granulometric weathering indices are inapplicable as relative dating methods because of the typically high textural variability within till deposits. On the other hand around the central mountain range crossing section of the Kali Gandaki most of the pedochemical weathering indices mirror the relative chronology of deglaciation correctly, since comparable soil development conditions can be found. Thereby not only a differentiation between the High-, Late-, and Neoglacial is possible, but also within the Late Glacial. North of the Himalaya main range, only a few very certain pedochemical relative dating methods are applicable as a consequence of the drier climatic conditions. South of the Higher Himalaya variations of the parent material and the for the southern slope typical characteristics, e.g., a high degree of relief energy, precipitation, and anthropogenic use, preclude a reliable deduction of the relative age of the glacigenic accumulations from the soil age, since a required undisturbed soil development and primary form conservation of the accumulations, is nearly impossible.

  4. Rapid changes in Late Pleistocene precipitation and stream discharge determined from medium- and coarse-grained sediment in saline lakes

    Science.gov (United States)

    Anderson, Roger Y.

    2001-02-01

    Sediment-trapping investigations in Pyramid Lake, Nevada show that medium- to coarse-grained clastic sediments suspended in streamflow after periods of low flow can be transported several kilometers in plumes of freshwater discharged over the surface of a saline lake. Analogous conditions are postulated to explain changes in the abundance of detrital quartz in lake clay near the center of Estancia Basin, New Mexico during the Late Pleistocene. Abrupt increases in the abundance of quartz grains mark the onset of lake freshening, and ostracode and trace-metal proxies for salinity indicate repeated, brief episodes of streamflow and lake freshening during the Last Glacial Maximum (LGM).

  5. A late Pleistocene tephra layer in the southern Great Basin and Colorado Plateau derived from Mono Craters, California

    Science.gov (United States)

    Madsen, D.B.; Sarna-Wojcicki, A. M.; Thompson, R.S.

    2002-01-01

    A newly identified tephra in stratified deposits in southwestern Utah, dated ???14,000 14C yr B.P., may aid in correlating late Pleistocene deposits across parts of the southern Great Basin and west-central Colorado Plateau. Geochemical analyses of the ash suggest the tephra originated from Mono Craters, California, and most probably correlates with Wilson Creek ash #3. Because the ash is 2 mm thick ???550 km from its source, the event may have been larger than others correlated to Mono Craters eruptions. ?? 2002 University of Washington.

  6. The Eastern Beringian vole Microtus deceitensis (Rodentia, Muridae, Arvicolinae) in Late Pliocene and Early Pleistocene faunas of Alaska and Yukon

    Science.gov (United States)

    Storer, John E.

    2003-07-01

    The fossil vole Microtus deceitensis occurs in Early Pleistocene deposits at Fort Selkirk, Yukon Territory, and Late Pliocene beds at the type locality, Cape Deceit, Alaska. Analyses of simple vs complex morphotypes in the cheek teeth, and of differentiation of tooth enamel, show that the Cape Deceit sample of M. deceitensis is less derived, and thus appears to be older, than the Fort Selkirk sample. The fossiliferous deposits at Fort Selkirk are well constrained by fission-track and radiometric dates and are 1.5 to 1.7 myr. Sediments at Cape Deceit bear a normal magnetic polarity, are correlated with the Olduvai subchron, and probably are latest Pliocene.

  7. Late Pleistocene to Holocene soil development and environments in the Long Gang Volcanic Field area, Jilin Province, NE China

    Science.gov (United States)

    Sauer, Daniela; Zhang, Xinrong; Knöbel, Jette; Maerker, Lutz

    2014-05-01

    Late Pleistocene to Holocene shifts of climate and vegetation in the Long Gang Volcanic Field in NE China have been reconstructed, e. g. by Steblich et al. (2009), based on Maar lake sediment cores. In this study, we investigated soil development during the Late Pleistocene and Holocene and linked it to the climate and vegetation reported in the literature. Three pedons were described and analyzed on a crater wall surrounding a maar. The lower part of the slope is covered by basic pyroclastics that are obviously younger than the maar itself. Pedon 1 is located on the upper slope, where the younger pyroclastics are not present; thus it developed over the entire Holocene and part of the Late Pleistocene. Pedon 2 is on the toe slope and developed from the young basic pyroclastics. Vegetation remains, charred by fire that was caused by the volcanic ash fall, were found in the lowermost part of the pyroclastics layer, on top of a paleosol. Charcoal fragments were dated to 18950-18830 cal BP (using INTCAL 09). Thus, pedon 2 developed since around 18.9 ka BP, whereas the development of the paleosol that was buried under the pyroclastics (pedon 3), was stopped at this time. Pedons 1 and 2 are Vitric Andosols, developed mainly from basic pyroclastics, as evidenced by the composition of rock fragments in the soils, comprising 78 / 81 mass % lapilli and 22 / 19 mass % gneiss fragments, respectively. Pedon 3 is a Cutanic Luvisol (Chromic) that developed entirely from gneiss fragments produced by the maar explosion. Lab data suggest increasing intensity of pedogenesis in the direction: Pedon 3 (paleosol) forest cover, it most likely started developing during the Eemian. Steblich et al. (2009) reconstructed for the period 16.7-14.45 ka BP steppe with Betula (and minor proportions of Larix, Alnus, Picea and Salix). We assume a similar environment for the time of the deposition of the pyroclastics (18.9 ka BP) in the toe slope profile. The character of the steppe was probably more open at this time, but the presence of at least few scattered trees over the steppe is evidenced by a charred tree trunk that was found in the profile. During Holocene, vegetation consisted mainly of deciduous forest, until anthropogenic influence increased from around 1850 AD on. Reference: Steblich, M., Mingram, J., Han, J., Liu, Y. (2009): Late Pleistocene spread of (cool-)temperate forests in Northeast China and climate changes synchronous with the North Atlantic region. Global and Planetary Change, 65, 56-70.

  8. Late Pleistocene Southeast Amazonia Paleoenvironmental reconstruction inferred by bulk, isotopic and molecular organic matter. Saci lake-Para-Brazil

    Science.gov (United States)

    Martins, G. S.; Cordeiro, R. C.; Turcq, B.; Moreira, L. S.; Bouloubassi, I.; Sifeddine, A.

    2014-12-01

    Bulk, Isotope and biolomecular analysis supported by 22 14C AMS dates, allowed the reconstruction of environmental changes during the last 35 000 years BP in the Southeast Amazonian basin. A terrestrial origin has been inferred for the odd carbon-numbered long-chain (>C27) n-alkanes. The entire n-alkane ?13C range between -31.7‰ and -36.8‰, which is the isotopic range occupied by C3 vegetation. The C29:C31 ratio shows that a gramineae contribution is higher during the Pleistocene than in Holocene. The n-alkanes concentration decrease between 32 000 - 18 000, suggesting a increase in arid conditions. The ACL index confirm this interpretation showing high values due the Pleistocene linked to more hydrological stress. A shift in the abundance of n-alkane and isotopic values are observed across the late Pleistocene glacial-Holocene interglacial climate change, suggesting a climate-induced vegetational change. During the middle Holocene the n-alcanes values decreases indicating rain forest regression accompanied by increase in the ACL values confirming the dry climate conditions. Comparison with other South American records, our record indicates regression/expansion of the rain forest linked to the South American System monsoon activity since 35 kyrs.

  9. Drainage system inversion in the Guadalentin Depression during the Late Pleistocene-Holocene (Murcia, Spain)

    International Nuclear Information System (INIS)

    This article presents the results of studies conducted in the central sector of Guadalentin depression (Murcia) for the abnormal accumulation (more than 17 m) of Pleistocene and Holocene deposits upstream of Romeral tectonic threshold (Librilla). 14C dating. ruins and archaeological sites, together with its stratigraphic analysis show that the three sequences that constitute the Holocene detrital filling of the Depression, prograded are superimposed on the upper Pleistocene travertine upstream from the confluence of the River Guadalentin the Rambla de Librilla. Between Librilla and threshold Romeral Holocene deposits only appear along the left bank (15-17m). By contrast the right side shows significant lifting of the Pleistocene travertine up area Romeral threshold, where the substrate allora Neogene. (Author) 11 refs.

  10. Submarine glacial landforms record Late Pleistocene ice-sheet dynamics, Inner Hebrides, Scotland

    Science.gov (United States)

    Dove, Dayton; Arosio, Riccardo; Finlayson, Andrew; Bradwell, Tom; Howe, John A.

    2015-09-01

    We use ?7000 km2 of high-resolution swath bathymetry data to describe and map the submarine glacial geomorphology, and reconstruct Late Pleistocene ice sheet flow configurations and retreat dynamics within the Inner Hebrides, western Scotland. Frequently dominated by outcrops of structurally complex bedrock, the seabed also comprises numerous assemblages of well-preserved glacigenic landforms typical of grounded ice sheet flow and punctuated ice-margin retreat. The occurrence and character of the glacially streamlined landforms is controlled in part by the shallow geology and topography, however these factors alone cannot account for the location, orientation, and configuration of the observed landforms. We attribute the distribution of these elongate streamlined landforms to the onset zone of the former Hebrides Ice Stream (HIS) - part of a major ice stream system that drained 5-10% of the last British-Irish Ice Sheet (BIIS). We suggest this geomorphic signature represents the transition from slow 'sheet flow' to 'streaming flow' as ice accelerated out from an environment characterized by numerous bedrock obstacles (e.g. islands, headlands), towards the smooth, sediment dominated shelf. The majority of streamlined landforms associated with the HIS indicate ice sheet flow to the southwest, with regional-scale topography clearly playing a major role in governing the configuration of flow. During maximal glacial conditions (?29-23 ka) we infer that the HIS merged with the North Channel-Malin Shelf Ice Stream to form a composite ice stream system that ultimately reached the continental shelf edge at the Barra-Donegal Trough-Mouth Fan. Taken collectively however, the pattern of landforms now preserved at seabed (e.g. convergent flow indicators, cross-cutting flow sets) is more indicative of a thinning ice mass, undergoing reorganization during overall ice sheet retreat (during latter stages of Late Weischselian glaciation). Suites of moraines overprinting the streamlined landforms suggest partial stabilization of the HIS prior to the ice sheet retreating to more isolated, topographically confined troughs and basins. Retreat from the shelf towards, and back into the Inner Hebrides may have been rapid due the prevalence of overdeepened troughs. Within the near-shore fjord-like troughs and deeps, basin-aligned streamlined landforms indicate the subsequent flow of thinner topographically partitioned ice masses, and overprinted moraines record further ice margin retreat, potentially along tide-water margins. This work provides the first geomorphological constraints for this large marine-influenced sector of the former BIIS. We also shed new light on the glacial geomorphic record found at the transition from terrestrial to marine continental-shelf settings, and examine the interplay between substrate geology, bed topography/bathymetry, and grounding-line positions - relationships which are important for characterizing contemporary marine ice sheet margins.

  11. Late Pleistocene and Holocene uplift history of Cyprus: implications for active tectonics along the southern margin of the Anatolian microplate

    Science.gov (United States)

    Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.

    2013-01-01

    The nature of the southern margin of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding active plate-margin tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the margins of the Troodos Ophiolite and re-activation of its low-angle, basal shear zone.

  12. Small mammal diversity loss in response to late-Pleistocene climatic change.

    Science.gov (United States)

    Blois, Jessica L; McGuire, Jenny L; Hadly, Elizabeth A

    2010-06-10

    Communities have been shaped in numerous ways by past climatic change; this process continues today. At the end of the Pleistocene epoch about 11,700 years ago, North American communities were substantially altered by the interplay of two events. The climate shifted from the cold, arid Last Glacial Maximum to the warm, mesic Holocene interglacial, causing many mammal species to shift their geographic distributions substantially. Populations were further stressed as humans arrived on the continent. The resulting megafaunal extinction event, in which 70 of the roughly 220 largest mammals in North America (32%) became extinct, has received much attention. However, responses of small mammals to events at the end of the Pleistocene have been much less studied, despite the sensitivity of these animals to current and future environmental change. Here we examine community changes in small mammals in northern California during the last 'natural' global warming event at the Pleistocene-Holocene transition and show that even though no small mammals in the local community became extinct, species losses and gains, combined with changes in abundance, caused declines in both the evenness and richness of communities. Modern mammalian communities are thus depauperate not only as a result of megafaunal extinctions at the end of the Pleistocene but also because of diversity loss among small mammals. Our results suggest that across future landscapes there will be some unanticipated effects of global change on diversity: restructuring of small mammal communities, significant loss of richness, and perhaps the rising dominance of native 'weedy' species. PMID:20495547

  13. Late Pliocene and Early Pleistocene vegetation history of northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    Science.gov (United States)

    Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M.

    2014-05-01

    The 318 m thick lacustrine sediment record from Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities for the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments demonstrate their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.5-3.35 Myr BP, the vegetation at Lake El'gygytgyn, now an area of tundra was dominated by spruce-larch-fir-hemlock forests. After ca. 3.35 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental change took place ca. 3.31-3.28 Myr BP, corresponding to the Marine Isotope Stage (MIS) M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.043-3.025, 2.935-2.912, and 2.719-2.698 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Peaks in observed green algae colonies (Botryococcus) around 2.53, 2.45, 2.32-2.305, 2.20 and 2.16-2.15 Myr BP suggest a spread of shallow water environments. A few intervals (i.e., 2.55-2.53, ca. 2.37, and 2.35-2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively short-term climate ameliorations during Early Pleistocene glacial periods.

  14. Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene

    Science.gov (United States)

    Jovanovska, E.; Cvetkoska, A.; Hauffe, T.; Levkov, Z.; Wagner, B.; Sulpizio, R.; Francke, A.; Albrecht, C.; Wilke, T.

    2015-09-01

    Ancient lakes, like lakes Ohrid and Prespa on the Balkan Peninsula, have become model systems for studying the link between geological and biotic evolution. Recently the scientific deep drilling program "Scientific Collaboration on Past Speciation Conditions in Lake Ohrid" (SCOPSCO) has been launched to better understand the environmental, climatic and limnological evolution of the lake. It revealed that Lake Ohrid experienced a number of environmental disturbances during its ca. 2.0 million year long history. They comprise disturbances that lasted over longer periods of times ("press events") such as Heinrich events as well as sudden and short disturbances ("pulse events") like the deposition of volcanic ashes. The latter include one of the most severe volcanic episodes during the Late Pleistocene, the eruption of the Campanian Ignimbrite (known as Y-5 marine tephra layer) from the Campi Flegrei caldera, dated at 39.6 ± 0.1 ka ago. The event is recorded by the deposition of a ca. 15 cm thick Y-5 tephra layer in sediment cores of lakes Ohrid (DEEP-5045-1) and Prespa (Co1204). This pulse event is overlain by the Heinrich event 4 (H4), 40.0-38.0 ka ago. In the current paper, diatoms were used as proxies to compare the responses of these lakes to the Y-5 (pulse) and the H4 (press) disturbances. Based on stratigraphically constrained incremental sum of squares cluster (CONISS) and unconstrained Partitioning Around Medoids (PAM) analyses, we found only little evidence that the diatom community compositions in either lake responded to the H4 event. However, the Y-5 influx caused clear and rapid diatom community changes. After the initial response, community composition in Lake Ohrid and, to a lesser extent, in Lake Prespa slowly returned to their quasi pre-disturbance state. Moreover, there is no evidence for disturbance-related extinction events. The combined evidence from these findings suggests that lakes Ohrid and Prespa likely did not experience regime shifts. It is therefore concluded that both lakes show resilience to environmental disturbance. However, it seems that Lake Ohrid is more resilient than Lake Prespa as the recovery of diatom communities is more pronounced and as its estimated recovery time is only ca. 1400 years vs. ca. 3600 years in Lake Prespa. The reasons for the differential responses remain largely unknown, but differences in geology, lake age, limnology, and intrinsic parameters of the diatom proxies may play a role. Given the relative robust results obtained, this study provides important new insights into the response of lakes to (multiple) environmental disturbances. Moreover, it contributes to one of the major goals of the SCOPSCO project - to evaluate the influence of major geological events onto the evolution of endemic taxa in Lake Ohrid.

  15. Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene

    Directory of Open Access Journals (Sweden)

    E. Jovanovska

    2015-09-01

    Full Text Available Ancient lakes, like lakes Ohrid and Prespa on the Balkan Peninsula, have become model systems for studying the link between geological and biotic evolution. Recently the scientific deep drilling program "Scientific Collaboration on Past Speciation Conditions in Lake Ohrid" (SCOPSCO has been launched to better understand the environmental, climatic and limnological evolution of the lake. It revealed that Lake Ohrid experienced a number of environmental disturbances during its ca. 2.0 million year long history. They comprise disturbances that lasted over longer periods of times ("press events" such as Heinrich events as well as sudden and short disturbances ("pulse events" like the deposition of volcanic ashes. The latter include one of the most severe volcanic episodes during the Late Pleistocene, the eruption of the Campanian Ignimbrite (known as Y-5 marine tephra layer from the Campi Flegrei caldera, dated at 39.6 ± 0.1 ka ago. The event is recorded by the deposition of a ca. 15 cm thick Y-5 tephra layer in sediment cores of lakes Ohrid (DEEP-5045-1 and Prespa (Co1204. This pulse event is overlain by the Heinrich event 4 (H4, 40.0–38.0 ka ago. In the current paper, diatoms were used as proxies to compare the responses of these lakes to the Y-5 (pulse and the H4 (press disturbances. Based on stratigraphically constrained incremental sum of squares cluster (CONISS and unconstrained Partitioning Around Medoids (PAM analyses, we found only little evidence that the diatom community compositions in either lake responded to the H4 event. However, the Y-5 influx caused clear and rapid diatom community changes. After the initial response, community composition in Lake Ohrid and, to a lesser extent, in Lake Prespa slowly returned to their quasi pre-disturbance state. Moreover, there is no evidence for disturbance-related extinction events. The combined evidence from these findings suggests that lakes Ohrid and Prespa likely did not experience regime shifts. It is therefore concluded that both lakes show resilience to environmental disturbance. However, it seems that Lake Ohrid is more resilient than Lake Prespa as the recovery of diatom communities is more pronounced and as its estimated recovery time is only ca. 1400 years vs. ca. 3600 years in Lake Prespa. The reasons for the differential responses remain largely unknown, but differences in geology, lake age, limnology, and intrinsic parameters of the diatom proxies may play a role. Given the relative robust results obtained, this study provides important new insights into the response of lakes to (multiple environmental disturbances. Moreover, it contributes to one of the major goals of the SCOPSCO project – to evaluate the influence of major geological events onto the evolution of endemic taxa in Lake Ohrid.

  16. Late Triassic - Early Jurassic successions of the Atuel depocenter: sequence stratigraphy and tectonic controls

    Directory of Open Access Journals (Sweden)

    Silvia Lanés

    2008-12-01

    Full Text Available Biostratigraphic correlations of the Late Triassic - Early Jurassic successions of the Atuel depocenter allowed determining the accommodation changes and the possible tectonic controls on sedimentation. The Rhaetian - late Early Sinemurian deposits contain facies of slope-type fan deltas, braided fluvial systems and low sinuosity rivers with alternate bars deposited during a synrift phase. The late Early Sinemurian - Toarcian series host facies of intermediate (Gilbert to shelf type fan deltas, braided and low sinuosity fluvial systems, wave-dominated estuaries, transgressive storm-dominated and turbidite-influenced marine shelves which record the sag phase. According to different criteria two stratigraphic schemes are proposed, the first one considering tectosedimentary units (TSU and the second one using "Exxon-like" sequences. In the first scheme the synrift TSU matches the actual Precuyo Mesosequence and the sag TSU is partly equivalent to the Cuyo Mesosequence, mainly keeping the current mesosequence scheme for the Neuquén basin but assigning the fandeltaic deposits to the Precuyo Mesosequence. The second sequence scheme considers the whole Late Triassic - Early Jurassic succession as a part of the Cuyo Mesosequence, where the synrift deposits composes the detached lowstand system tract (LST and most of the sag deposits makes the transgressive system tract (TST. The basal sequence boundary does not crop out, the flooding surface at the TST base and the maximum flooding surface at the TST top are respectively marked by the lowest estuarine levels and by black shales with suboxic-compatible bivalves (Bositra sp..

  17. Sedimentary effects of cataclysmic late Pleistocene glacial outburst flooding, Altay Mountains, Siberia

    Science.gov (United States)

    Rudoy, A. N.; Baker, V. R.

    1993-05-01

    Pleistocene glacial outburst floods were released from ice-dammed lakes of the Altay Mountains, south-central Siberia. The Kuray-Chuja lake system yielded peak floods in excess of 1 × 106 m3 s-1 and as great as 18 × 106 m3 s-1. The phenomenally high bed shear stresses and stream powers generated in these flows produced a main-channel, coarse-grained facies of coarse gravel in (1) foreset-bedded bars as much as 200 m high and several kilometers long, and (2) degradational, boulder-capped river terraces. Giant current ripples, 50 to 150 m in spacing, composed of pebble and cobble gravel, are locally abundant. The whole sedimentary assemblage is very similar to that of the Channeled Scabland, produced by the Pleistocene Missoula Floods of western North America.

  18. Late Paleocene–early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    Indian Academy of Sciences (India)

    A Samanta; A Sarkar; M K Bera; Jyotsana Rai; S S Rathore

    2013-02-01

    Late Paleocene to early Eocene (?56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene–Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope (13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the ‘out of India’ hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  19. Aeolian to shallow-marine shelf architecture off a major desert since the Late Pleistocene (northern Mauritania)

    Science.gov (United States)

    Hanebuth, T. J. J.; Mersmeyer, H.; Kudrass, H. R.; Westphal, H.

    2013-12-01

    Continental shelves off major desert regions are not expected to host substantial amounts of sediments due to long-lasting and unfocused material supply and a high re-mobilization potential of aeolian material. This study, in contrast, demonstrates that significant volumes of sediments have accumulated on the northern Mauritanian shelf under the arid climate conditions and prevail over consecutive climatic cycles. Eight late Pleistocene to Holocene depositional units, each formed under contrasting depositional conditions, are identified in high-resolution seismo-acoustic data and dated sediment cores. These are: (1) a highly differentiated Pleistocene paleo-landscape older than the past climatic cycle, (2) a continental dune complex (MIS-4), (3) a thick regressive shallow-water clinoform (late MIS-3), (4) a regressive to lowstand shore deposit (latest MIS-3), and (5) a local transgressive cover (LGM to deglacial). Additionally, (6) an open-shelf highstand cover, (7) an outer-shelf highstand wedge and (8) mid-shelf mud depocenters have formed during the Holocene sea-level highstand. The common local offshore formation and preservation of confined stratigraphic units, in particular from during MIS-3, mark the interplay of: a) episodes of pronounced arid climatic conditions resulting in enhanced aeolian and coastal sediment input, b) shelf current patterns focusing sediment deposition locally, and c) early post-depositional sediment stabilization providing protection against erosion. Prominent internal surfaces at 63 and 115 m modern water depths indicate widespread and intense erosional activity during late MIS-3 regression and MIS-2 lowstand to post-LGM transgression, hosting coarse shell sands and gravels from beach and shoreface paleo-environments. The reasons for the high preservation potential of confined stratigraphic units are: a) carbonaceous cementation, b) sediment composition (massive widespread shore-related gravel and shell beds with subtle minor admixtures of cohesive material), and c) morphological protection (inside seafloor depressions and behind sheltering relief).

  20. Phylogeography of the Alcippe morrisonia (Aves: Timaliidae): long population history beyond late Pleistocene glaciations

    OpenAIRE

    Li Shouhsien; Yin Zuohua; Qu Yanhua; Song Gang; Liu Naifa; Lei Fumin

    2009-01-01

    Abstract Background The role of Pleistocene glacial oscillations in current biodiversity and distribution patterns varies with latitude, physical topology and population life history and has long been a topic of discussion. However, there had been little phylogeographical research in south China, where the geophysical complexity is associated with great biodiversity. A bird endemic in Southeast Asia, the Grey-cheeked Fulvetta, Alcippe morrisonia, has been reported to show deep genetic diverge...

  1. Late Pleistocene piedmont glaciations in the Eastern Mediterranean; insights from cosmogenic 36Cl dating of hummocky moraines in southern Turkey

    Science.gov (United States)

    Çiner, Attila; Sar?kaya, Mehmet Akif; Y?ld?r?m, Cengiz

    2015-05-01

    We report the presence of Late Pleistocene piedmont glaciers represented by the largest hummocky moraine field observed in the Eastern Mediterranean. The piedmont glaciers originated from the Geyikda? ice cap (?40 km2), situated between 2350 and 2650 m above sea level (a.s.l.) (Central Tauride Mountains of Turkey), and deeply carved the north-facing hillslopes before reaching the Namaras Valley (2000-2050 m a.s.l). The hummocky moraines resulted from in-situ deposition of stagnant glacier ice where debris cover was heterogeneously distributed on the glacier surface. Thirty-four boulders from hummocky, disintegration, lateral and terminal moraines from the Namaras Valley and the tributary Susam Valley (2100-2200 m a.s.l.) were dated by cosmogenic 36Cl surface exposure dating. The moraine ages indicate three phases of deglaciation during the Late Pleistocene. The oldest deglaciation occurred in the Namaras Valley at 18.0 ± 1.1 ka (ka: thousand years ago) towards the end of the Last Glacial Maximum (LGM) and is recorded entirely by hummocky moraines. We speculate that hummocky moraine forming processes with cycles of relief inversion gave rise to boulder apparent ages up to a few thousand years younger in our study area. Therefore, 18.0 ± 1.1 ka should be regarded as a minimum age with a probable true age much closer to the local-LGM values (?20 ka) as observed in the surrounding mountains. Paleo-piedmont glaciers also deposited several lateral moraines that are ?50 m higher than the hummocky moraines. Although the lateral moraines probably represent the build-up and the hummocky moraines the final phase of the same local-LGM-pulse, both lateral moraines started to retreat from the Late-glacial (14.0 ± 2.7 ka) and gradually disappeared by mid-Holocene (5.2 ± 1.0 ka), encompassing the Younger Dryas (YD) stadial. In the Susam Valley, the Late-glacial is represented by a terminal moraine (13.4 ± 1.5 ka). The glacier retreat was very fast as indicated by an almost instantaneous disappearance of 5 km long Susam Valley glacier, represented by disintegration and hummocky moraines (14.0 ± 1.3 ka). Alternatively, in case the oldest boulder age is taken into account, the Susam Valley glacier can be also attributed to the late LGM (?17 ka) to Late-glacial (?14 ka) transition. Near the exit of the Susam Valley a right lateral moraine was deposited 11.6 ± 1.3 ka ago, confirming the presence of the YD in Geyikda?. Comparable glacial chronologies were obtained from other Turkish and Mediterranean mountains.

  2. Aeolian stratigraphy and thermoluminescence dating of sediments of late Holocene age from Sola, southwest Norway

    International Nuclear Information System (INIS)

    Thermoluminescence age determinations were performed on four aeolian sand samples of late Holocene sediments from Stavanger airport, Sola, in southwest Norway. The locality is well suited for testing thermoluminescence dating because of a good agreement between radiocarbon ages and age information based on archaeological typology and sea level changes. The conclusion from a comparison of thermoluminescence and radiocarbon dates is that it is possible to date well bleached sediments as young as 1600 years with thermoluminescence. 57 refs., 7 figs., 6 tabs

  3. The stratigraphy and sedimentology of the Dunscombe Mudstone Formation (late Triassic) of south-west England

    OpenAIRE

    Gallois, Ramues W.; Porter, R J

    2006-01-01

    The mid to late Triassic Mercia Mudstone Group exposed on the east Devon coast between Sidmouth and Seaton consists of c. 450 m of predominantly red mudstones that were deposited in low-relief sabkha environments in hot deserts. In marked contrast to this, the Dunscombe Mudstone Formation in the middle part of the group consists of 35-40 m of interbedded and interlaminated green, purple and grey mudstones, breccias, muddy limestones and lenticular siltstones/sandstones that were d...

  4. The stratigraphy of the Penarth Group (Late Triassic) of the East Devon coast

    OpenAIRE

    Gallois, Ramues W.

    2008-01-01

    The cliff and foreshore exposures in the Devon part of the Dorset and East Devon Coast World Heritage Site expose an unbroken late Triassic to early Jurassic succession. The change from the terrestrial, red-bed facies of the Triassic Mercia Mudstone Group to the fully marine conditions of the Jurassic Lias Group takes place via the Penarth Group, a succession of mudstones, siltstones and limestones deposited in lagoonal and sheltered shallow-marine environments of varying salinities....

  5. Genetic consequences of population expansions and contractions in the common hippopotamus (Hippopotamus amphibius) since the Late Pleistocene

    DEFF Research Database (Denmark)

    Stoffel, Céline; Dufresnes, Christophe

    2015-01-01

    Over the past two decades, an increasing amount of phylogeographic work has substantially improved our understanding of African biogeography, in particular the role played by Pleistocene pluvial-drought cycles on terrestrial vertebrates. However, still little is known on the evolutionary history of semi-aquatic animals, which faced tremendous challenges imposed by unpredictable availability of water resources. In this study, we investigate the Late Pleistocene history of the common hippopotamus (Hippopotamus amphibius), using mitochondrial and nuclear DNA sequence variation and range-wide sampling. We documented a global demographic and spatial expansion approximately 0.1-0.3 My ago, most likely associated with an episode of massive drainage overflow. These events presumably enabled a historical continent-wide gene flow among hippopotamus populations, and hence no clear continental-scale genetic structuring remains. Nevertheless, present-day hippopotamus populations are genetically disconnected, probably as aresult of the mid-Holocene aridification and contemporary anthropogenic pressures. This unique pattern contrasts with the biogeographic paradigms established for savannah-adapted ungulate mammals and should be further investigated in other water-associated taxa. Our study has important consequences for the conservation of the hippo, an emblematic but threatened species that requires specific protection to curtail its long-term decline. This article is protected by copyright. All rights reserved.

  6. Didelphidae marsupials (Mammalia, Didelphimorphia) from the late Pleistocene deposit of the Gruta dos Moura Cave, northern Brazil.

    Science.gov (United States)

    Nova, Patricia Villa; Avilla, Leonardo S; Oliveira, Édison V

    2015-03-01

    The present study acknowledges the diversity of fossil marsupials from the Gruta dos Moura cave, as well as environmental and climatic aspects during the Quaternary. The results show that this is the largest diversity of Pleistocene marsupials recorded in a single cave: Didelphis albiventris, D. aurita, Gracilinanus agilis, G. microtarsus, Marmosa murina, Monodelphis brevicaudata, M. domestica and Sairadelphys tocantinensis. Furthermore, the described specimens are also part of the only fossil assemblage unequivocally referable to the late Pleistocene. Paleontological studies suggest an intimate association with dry and open environments with high abundance of water sources. Since most of the identified taxa are characteristic of open forests and gallery forests, this could represent the actual environment around the Gruta dos Moura cave. Recent studies identified sympatric occurrences between species from open and dry environments and species from humid forests that were identified among our material and are characteristic of humid regions. Therefore, these species could inhabit gallery forests and capons, or even ecotones, inside a dry and open environment. Moreover, the extinction of Sairadelphys could also indicate that the climatic and environmental conditions changed or that the past environment was more heterogeneous than the current environment of the region. PMID:25806985

  7. Investigating the role of climate change during the late Pleistocene on landscape evolution: a case study from New Mexico, USA

    Science.gov (United States)

    Yetemen, O.; Flores Cervantes, J. H.; Istanbulluoglu, E.; Vivoni, E. R.

    2010-12-01

    This study examines the role of climate change during the late Pleistocene-Holocene transition on landscape morphology in a semi-arid basin in central New Mexico through a modeling experiment, corroborated with field observations. In central New Mexico transition from a wetter and cooler climate to recent drier and warmer climate have led to changes in vegetation types from forests dominated in low elevations to shrubs and grasses. Such vegetation changes with the intensification of monsoon caused significant increase in regional erosion rates. In order to reveal the influence of vegetation change on erosion dynamics, we use the CHILD landscape evolution model with moisture-dependent vegetation growth functions and accounting for the impacts of spatial distribution of solar radiation. Pleistocene-Holocene transition is represented by a sinusoidal function for annual precipitation. Potential evapotranspiration is estimated in relation to annual precipitation based on regionally constructed relationships. We used the model to investigate how the water and energy-driven vegetation dynamics impact the tempo of landscape evolution and identify the factors that lead to the observed landscape morphology in the region.

  8. Fossils in Late Cretaceous to early Palaeocene flint nodules embedded in pleistocene glaciofluvial sediments near Fukov (D??ín District, Northern Bohemia).

    Czech Academy of Sciences Publication Activity Database

    Pokorný, R.; Kaše, J.; Kva?ek, J.; Zágoršek, K.; Ko?í, T.; Žítt, Ji?í

    2012-01-01

    Ro?. 68, 3/4 (2012), s. 119-131. ISSN 0036-5343 Institutional support: RVO:67985831 Keywords : Erratic boulders * Flint * Glaciofluvial sediments * Late Cretaceous * Northern Bohemia * Palaeocene * Pleistocene glaciation * Taphocoenosis Subject RIV: DB - Geology ; Mineralogy http://www.nm.cz/publikace/archiv.php?id=4&rok=68&kcislu=3-4&f_=Zobrazit

  9. New results on the paleoclimate record of the late Pleistocene cave sediments (Moravian Karst, Czech Republic); the case study based on mineral magnetic properties and facial analyses.

    Czech Academy of Sciences Publication Activity Database

    Lisá, Lenka; Nerudová, Z.; Chadima, Martin; Bajer, A.

    Prague : Institute of Geology AS CR, v. v. i, 2011 - (Koptíková, L.; Hladil, J.; Adamovi?, J.). s. 34-36 Institutional research plan: CEZ:AV0Z30130516 Keywords : cave sediments * Late Pleistocene * facial analyses Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://home.gli.cas.cz/hladil/KRS2011/IGCP580-Prague-2011-AbstractVolume--.pdf

  10. Leafcutter bee nests and pupae from the Rancho La Brea Tar Pits of southern California: Implications for understanding the paleoenvironment of the Late Pleistocene

    Science.gov (United States)

    The Rancho La Brea Tar Pits is the world’s richest and most important Late Pleistocene fossil locality and best renowned for numerous fossil mammals and birds excavated over the past century. Less researched are insects, even though these specimens frequently serve as the most valuable paleoenvironm...

  11. Late Quaternary stratigraphy, sedimentology, and geochemistry of an underfilled lake basin in the Puna (north-west Argentina)

    Science.gov (United States)

    McGlue, Michael M.; Cohen, Andrew S.; Ellis, Geoffrey S.; Kowler, Andrew L.

    2013-01-01

    Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogues. To address this, we present new stratigraphic, sedimentological and geochemical analyses of four radiocarbon-dated sediment cores from the Pozuelos Basin (PB; northwest Argentina) that capture the evolution of this low-accommodation Puna basin over the past ca. 43 cal kyr. Strata from the PB are interpreted as accumulations of a highly variable, underfilled lake system represented by lake-plain/littoral, profundal, palustrine, saline lake and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich highstand deposits underlying thicker, organic-poor regressive deposits. The major controls on depositional architecture and basin palaeogeography are tectonics and climate. Accommodation space was derived from piggyback basin-forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American summer monsoon, and perennial lake deposits correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna plateau. Our results shed new light on lake expansion–contraction dynamics in the PB in particular and provide a deeper understanding of Puna basin lakes in general.

  12. The sedimentary sequence from the Lake ??ži outcrop, central Latvia: implications for late glacial stratigraphy

    Directory of Open Access Journals (Sweden)

    Tiiu Koff

    2011-06-01

    Full Text Available Sediment samples from an outcrop in the near-shore area of Lake ??ži (Vidzeme Heights, Central Latvia were investigated using palaeobotanical (pollen and macrofossil analysis and lithological (grain-size analysis methods and accelerator mass spectrometry 14C dating. A dark, organic-rich sediment layer was found below 1.7 m of sandy layers approximately 30 cm above the present lake level. Radiocarbon dating of a wood sample from the lowermost layer (11 050 ± 60 14C BP, 13 107–12 721 cal BP shows that the layer is of late glacial age. The composition of the pollen spectra is characterized by Betula nana, Cyperaceae pollen and spores of Equisetum, confirming that the lowermost sediments were formed during the late glacial. Fossils of obligate aquatic organisms in the upper layer, which include oospores of Characeae and seeds of Potamogeton, indicate an open water environment. Pollen of Myriophyllum and Potamogeton and non-pollen palynomorphs, such as algal Botryococcus and Pediastrum cf. boryanum, confirm this conclusion. The pollen assemblage from the greyish loam layer following this lacustrine phase shows a pattern characteristic of the Younger Dryas vegetation before the start of the real expansion of birch forests at the beginning of the Holocene.

  13. First accelerator mass spectrometry {sup 14}C dates documenting contemporaneity of nonanalog species in late Pleistocene mammal communities

    Energy Technology Data Exchange (ETDEWEB)

    Stafford, T.W. Jr.; Semken, H.A. Jr.; Graham, R.W.; Klippel, W.F.; Markova, A.; Smirnov, N.G.; Southon, J.

    1999-10-01

    Worldwide late Pleistocene terrestrial mammal faunas are characterized by stratigraphic associations of species that now have exclusive geographic ranges. These have been interpreted as either taphonomically mixed or representative of communities that no longer exist. Accelerator mass spectrometry {sup 14}C dates (n = 60) on single bones of stratigraphically associated fossil micromammals from two American and two Russian sites document for the first time that currently allopatric mammals occurred together between 12,000 and 22,000 yr B.P. on two continents. The existence of mammal communities without modern analogs demonstrates that Northern Hemisphere biological communities are ephemeral and that many modern biomes are younger than 12 ka. Future climate change may result in new nonanalog communities.

  14. Late Pleistocene and Early Holocene Rock Art from the Mongolian Altai: The Material and its Cultural Implications

    Directory of Open Access Journals (Sweden)

    Esther Jacobson-Tepfer

    2013-09-01

    Full Text Available Rock-pecked images from the northern Mongolian Altai attest to the presence of human communities within the high valleys of that region during the Late Pleistocene and Early Holocene. The material provides evidence that is hitherto largely missing from the archaeological record of that region. This paper reviews the rock art, its find sites and larger physical contexts and uses evidence from paleoenvironmental studies to propose dating and cultural significance. The material is compared with other sites said to have Paleolithic imagery from Mongolia and the adjoining Russian Altai. The body of presented material offers a major resource for the study of early hunter-gatherer communities at the interface of Central and North Asia.

  15. Tocuila Mammoths, Basin of Mexico: Late Pleistocene-Early Holocene stratigraphy and the geological context of the bone accumulation

    Science.gov (United States)

    Gonzalez, Silvia; Huddart, David; Israde-Alcántara, Isabel; Dominguez-Vazquez, Gabriela; Bischoff, James

    2014-07-01

    We report new stratigraphic, tephrochronology and dating results from the Tocuila Mammoth site in the Basin of Mexico. At the site there is evidence for a thin meteorite airburst layer dated between 10,878 and 10,707 cal BC at the onset of the Younger Dryas (YD) cool period. The Upper Toluca Pumice (UTP) tephra marker, caused by a Plinian eruption of the Nevado de Toluca volcano, dated from 10,666 to 10,612 cal BC, is above that layer. The eruption must have caused widespread environmental disruption in the region with evidence of extensive reworking and channelling by the Lake Texcoco shoreline and contributed to the widespread death and/or extinction of megafaunal populations, as suggested by earlier authors, but the new work reinforces the view that both catastrophic events must have caused large environmental disruption in a short time period of around two hundred years. There is no evidence for megafauna (mammoths, sabre toothed cats, camels, bison, glyptodonts) after the UTP volcanic event and subsequent lahars in the Basin of Mexico. At Tocuila, although there are some in situ tephra markers in nearshore lake sediments, such as the Great Basaltic Ash (GBA) and the UTP Ash, there is evidence of much reworking of several tephra populations in various combinations. The mammoth bone accumulation is reworked in a lahar sequence (volcanic mudflow) derived from several source sediments but associated with the major UTP Plinian eruption. Paleoindian populations were also present in the Basin of Mexico during the YD period, where several Paleoindian skeletons were found associated with the UTP ash deposits, e.g. Metro Man, Chimalhuacan Man and Tlapacoya Man.

  16. Sedimentology and diagenesis of windward-facing fore-reef calcarenites, Late Pleistocene of Barbados, West Indies

    Energy Technology Data Exchange (ETDEWEB)

    Humphrey, J.D.; Kimbell, T.N.

    1989-03-01

    Late Pleistocene reef terraces in southeastern Barbardos developed extensive fore-reef sand facies during deposition in response to high-energy windward-facing conditions. Sedimentology and diagenesis of these deposits illustrate significant contrasts with previous studies from the leeward west coast. These calcarenites are dominantly skeletal packstones with less common grainstones and wackestones present. The fore-reef sand facies occurs within progradational reef sequences, being conformably overlain by deep-water head coral facies. Medium-bedded, laterally continuous sand sheets retain original depositional slopes, dipping seaward at 10/degrees/-15/degrees/. These fore-reef deposits, in places, are over 30 m thick (average 20 m) and developed rapidly during late Pleistocene glacio-eustatic sea level highstands. Sedimentation rate ranges from 2 to 5 m/1000 years. Areal extent of fore-reef calcarenites in southeastern Barbados is estimated to be 8-10 km/sup 2/. Lithologically, the packstones are composed of an abundance of coralline red algae and the benthic foraminifer Amphistegina sp. Other volumetrically significant allochems include echinoids, mollusks, rhodoliths, peloids, and micritized grains. Micrite in the wackestone and packstone lithologies is likely derived from intense physical/mechanical abrasion of shoal-water reef facies. Diagenesis of these lithologies reflects a complex interplay of meteoric, mixing zone, and marine environments as a result of glacio-eustasy. Differences in diagenetic character are derived from differences in terrace ages, terrace geometry, a paleotopographic control on meteoric ground-water distribution, and high-energy coastal conditions. Diagenetic fabrics include equant, blocky meteoric phreatic calcite; limpid dolomite of mixing zone origin: and peloidal and isopachous fibrous cements from marine precipitation.

  17. Late Holocene stratigraphy of coastal deposits between Auckland and Dunedin, New Zealand

    International Nuclear Information System (INIS)

    Three chronostratigraphic units based on accumulative deposits and their respective soils are proposed for late Holocene coastal deposits between Auckland and Dunedin, New Zealand: Tamatean Chronozone (c. 1,800 to 450 years BP), Ohuan Chronozone (c. 450 to 150 years BP), and Hoatan Chronozone (c. 150 years to present day). The chronozones represent depositional episodes each consisting of two phases: a high rate of deposition (unstable phase), followed by a low rate of deposition and soil formation (stable phase). Vegetation on soils formed during the stable phases is inferred principally from landsnails recovered from archaeological sites. Forest on Tamatean soil (600 to 450 years BP) advanced almost to the coast in the Manawatu, the southeast Wairarapa, and on the East Coast. Sediment thickness measured at sections along the eastern North Island coast show that rates of deposition during unstable phases have decreased during the last 650 years. The depositional episodes appear to be unrelated to sea level changes, tectonic activity, volcanic eruptions or cultural influence. Unstable phases appear to correlate with times of high temperatures, and stable phases with time of low temperatures; it is suggested that the episodes may be related to changes in the frequency of tropical and extratropical cyclones. Inferred climate during unstable phases is windy and dry, and during stable phases, less windy and moist

  18. Late Quaternary stratigraphy and sedimentology of the central North Atlantic: A progress report

    International Nuclear Information System (INIS)

    The marine geological research program of the Department of Sedimentary Geology at the Free University of Amsterdam focuses on three areas: Banda Sea, central North Atlantic and the Mediterranean. Late Quaternary deep-sea cores taken in these areas are analysed in order to reconstruct changes in paleoceanography as reflected in the sedimentary record. Radiocarbon datings through the cores provide the necessary stratigraphic framework. The Utrecht tandem Accelerator Mass Spectrometer (AMS) allows radiocarbon dating on minutes samples (10-25 mg carbonate) and is therefore an excellent tool for core studies. This paper concentrates on results obtained from the central North Atlantic material. The Atlantic CaCO3 profile shows a maximum at the last climate optimum at 6 ka and a minimum at the last glacial maximum at 18 ka. This is also observed in our material, and confirmed by radiocarbon dating. It is shown that sedimentation rates are distinctly higher during the period of deglaciation. The dating also provides a framework for the timing of the retreat of the polar front. A surface layer of pteropod shells covers parts of the Atlantic Ocean floor at about 3000 m depth. Many shells show Fe/Mn staining. The AMS technique allows dating of single shells, and proves that the stained specimens are considerably oder than the unstained shells. Implications for this phenomenon and for the contribution of aragonite to the sediment are given. (orig.)

  19. Late Pleistocene and Holocene palaeoenvironments in and around the middle Caspian basin as reconstructed from a deep-sea core

    Science.gov (United States)

    Leroy, Suzanne A. G.; López-Merino, Lourdes; Tudryn, Alina; Chalié, Françoise; Gasse, Françoise

    2014-10-01

    Late Pleistocene and/or Holocene high-resolution palynological studies are available for the south basin of the Caspian Sea (CS), the world's largest lake. However, the north and middle basins have not been the object of high-resolution palynological reconstructions. This new study presents the pollen, spores and dinoflagellate cysts records obtained from a 10 m-long sediment core recovered in the middle basin, which currently has brackish waters and is surrounded by arid and semi-arid vegetation. An age-depth model built based on six radiocarbon dates on ostracod shells indicates that the sequence spans the period from 14.47 to 2.43 cal. ka BP. The present palaeoenvironmental study focuses on the top 666 cm, or from 12.44 to 2.43 cal. ka BP. At the vegetation level, the Younger Dryas is characterised by an open landscape dominated by desert vegetation composed by Amaranthaceae with shrubs and salt-tolerant plants. However, although the Early Holocene is also characterised by desert vegetation, it is enriched in various shrubs such as Ephedra and Calligonum, but tree expansion is not important at the Holocene onset. After a major shift at 8.19 cal. ka BP, the Middle Holocene displays now both the character of desert and of steppe, although some trees such as Quercus and Corylus slightly spread. The Late Holocene records steppe vegetation as dominant, with more tree diversity. Regarding the lacustrine signal, the dinocyst assemblage record fluctuates between slightly brackish conditions highlighted by Pyxidinopsis psilata and Spiniferites cruciformis, and more brackish ones - similar to the present day - with the dominance of Impagidinium caspienense. The Late Pleistocene is characterised by low salinities, related to the Khvalynian highstand. From 11.56 cal. ka BP, slightly more saline waters are reconstructed with an increase of I. caspienense for a period of 1000 years, which could be attributed to the Mangyshlak lowstand. From 10.55 cal. ka BP, low salinity conditions return with remains such as Anabaena and Botryococcus abundant until 8.83 cal. ka BP, followed by a slow, progressive decrease of P. psilata and S. cruciformis until 4.11 cal. ka BP, which is the main assemblage change at lacustrine scale. Since then, higher salinities, similar to the present one, are reconstructed. Finally, Lingulodinium machaerophorum starts its development only at 2.75 cal. ka BP, in the Late Holocene. The present research revealed fundamental differences from previously published sea-level curves, in that a 6000 yr-long highstand suggested by low salinities is shown between 10.55 and 4.11 cal. ka BP. Amongst other arguments, using a comparison to a similar palynological regard but in the south basin, a N-S salinity gradient that is the reverse of the present one across the CS, suggests that the Amu Darya was flowing in the CS. Hence the CS levels during the Late Pleistocene and Holocene were influenced by a combination of precipitation over the high European latitudes and the indirect influence of the Indian summer monsoon over the Pamirs.

  20. The Tendaguru Formation (Late Jurassic to Early Cretaceous, southern Tanzania: definition, palaeoenvironments, and sequence stratigraphy

    Directory of Open Access Journals (Sweden)

    R. Bussert

    2009-08-01

    Full Text Available The well-known Late Jurassic to Early Cretaceous Tendaguru Beds of southern Tanzania have yielded fossil plant remains, invertebrates and vertebrates, notably dinosaurs, of exceptional scientific importance. Based on data of the German-Tanzanian Tendaguru Expedition 2000 and previous studies, and in accordance with the international stratigraphic guide, we raise the Tendaguru Beds to formational rank and recognise six members (from bottom to top: Lower Dinosaur Member, Nerinella Member, Middle Dinosaur Member, Indotrigonia africana Member, Upper Dinosaur Member, and Rutitrigonia bornhardti-schwarzi Member. We characterise and discuss each member in detail in terms of derivation of name, definition of a type section, distribution, thickness, lithofacies, boundaries, palaeontology, and age. The age of the whole formation apparently ranges at least from the middle Oxfordian to the Valanginian through Hauterivian or possibly Aptian. The Tendaguru Formation constitutes a cyclic sedimentary succession, consisting of three marginal marine, sandstone-dominated depositional units and three predominantly coastal to tidal plain, fine-grained depositional units with dinosaur remains. It represents four third-order sequences, which are composed of transgressive and highstand systems tracts. Sequence boundaries are represented by transgressive ravinement surfaces and maximum flooding surfaces. In a more simple way, the depositional sequences can be subdivided into transgressive and regressive sequences/systems tracts. Whereas the transgressive systems tracts are mainly represented by shallow marine shoreface, tidal channel and sand bar sandstones, the regressive systems tracts predominantly consist of shallow tidal channel, tidal flat, and marginal lagoonal to supratidal deposits. doi:10.1002/mmng.200900004

  1. Integrated Late Eocene-Oligocene Stratigraphy of the Alabama Coastal Plain: Correlation of Hiatuses and Stratal Surfaces to Glacioeustatic Lowerings

    Science.gov (United States)

    Miller, Kenneth G.; Thompson, Peter R.; Kent, Dennis V.

    1993-04-01

    We integrated strontium and oxygen isotopic, biostratigraphic, and magnetostratigraphic studies of two upper Eocene-Oligocene boreholes drilled near Bay Minette and St. Stephens Quarry (SSQ), Alabama. Continuous coring provided fresh, unweathered material for magnetostratigraphic studies, minimizing problems reported from nearby outcrops. Difficulties with each technique were encountered because of diagenesis, absence of marker fossils, and the presence of unconformities; however, by integrating results from isotopic stratigraphy, biostratigraphy, and magnetostratigraphy, we correlated these relatively shallow-water deposits to the geomagnetic polarity time scale (GPTS). At the SSQ borehole, the upper Eocene to lower Oligocene section is apparently complete within our stratigraphic resolution (0.2-0.5 m.y.), allowing us to estimate the ages of several stratal surfaces. Late Eocene Sr isotope age estimates are as expected at the SSQ borehole, but Oligocene ages are ˜1 m.y. older than expected due to diagenesis. At the Bay Minette borehole, a latest Eocene-earliest Oligocene and a late early Oligocene hiatus were detected. We correlate these two hiatuses and stratal surfaces at SSQ with global ?18O increases inferred to represent glacioeustatic lowerings and with evidence for hiatuses on other continental margins: (1) a distinct disconformity at the base of the Chickasawhay Limestone at both boreholes and a hiatus at Bay Minette correlates with a global ?18O increase; we revise the age of this surface (equivalent to the TB 1.1 sequence boundary) making it ˜2 m.y. older than previously reported; and (2) a surface at the top of the Shubuta Member (lowermost Oligocene) has been interpreted both as a condensed section and a disconformity; this surface at SSQ and a hiatus at Bay Minette correlate with a sharp global ?18O increase and with hiatuses on the New Jersey and Irish margins. The timing of the hiatuses and stratal surfaces correlates with the inflection of the ?18O increases and not with the maximum values, supporting models that indicate that unconformities form during the maximum rates of sea level fall.

  2. Mammoth tracks indicate a declining Late Pleistocene population in southwestern Alberta, Canada

    Science.gov (United States)

    McNeil, Paul; Hills, L. V.; Kooyman, B.; Tolman, Shayne M.

    2005-05-01

    Much debate has raged over the role that early humans played in this most recent large extinction. Fossil mammoth ( Mammuthus primigenius) footprints were discovered at the St. Mary Reservoir in southwestern Canada (Wally's Beach DhPg-8). They are located in aeolian sediment dated at 11,300-11,000 years BP. By comparing the size distribution of these tracks with those of modern African elephants ( Loxodonta africana), the age distribution of this mammoth population was determined. Containing far fewer juveniles than would be expected for an expanding or stable population, these tracks provide the first evidence that a living mammoth population, coexisting with human inhabitants, was in decline. Additionally, the same site provides corroborating evidence of humans hunting megafauna (horse and bovids). This suggests that humans, in addition to climate change, played a role in the end Pleistocene extinctions in North America.

  3. Late Pleistocene carbonate aeolianites on Mallorca, Western Mediterranean: a luminescence chronology

    Science.gov (United States)

    Fornós, Joan J.; Clemmensen, Lars B.; Gómez-Pujol, Lluís; Murray, Andrew S.

    2009-12-01

    Coastal outcrops of Upper Pleistocene deposits in north-eastern Mallorca (Balearic Islands, Spain) have been examined and a chronological framework established using Optically Stimulated Luminescence (OSL) dating. The outcrops record a complex interaction between aeolian, colluvial and alluvial fan deposition that result in a variable stratigraphical architecture. Dating and facies analysis make it possible to identify four aeolian activity episodes during MIS 5c/b, 4 and 3, and also add to the understanding of the environmental history of north-eastern Mallorca over the last 100 ka. The new data suggest enhanced aeolian transport and dune formation during cold climatic intervals when sea level was low, sediment supply (exposed marine carbonate sediment) was high, winter windiness was high, and vegetation on coastal plains at a minimum.

  4. Late ordovician stratigraphy, zircon provenance and tectonics, Lachlan Fold Belt, southeastern Australia

    International Nuclear Information System (INIS)

    Ordovician quartz turbidites of the Lachlan Fold Belt in southeastern Australia accumulated in a marginal sea and overlapped an adjoining island arc (Molong volcanic province) developed adjacent to eastern Gondwana. The turbidite succession in the Shoalhaven River Gorge, in the southern highlands of New South Wales, has abundant outcrop and graptolite sites. The succession consists of, from the base up, a unit of mainly thick-bedded turbidites (undifferentiated Adaminaby Group), a unit with conspicuous bedded chert (Numeralla Chert), a unit with common thin-bedded turbidites [Bumballa Formation (new name)] and a unit of black shale (Warbisco Shale). Coarse to very coarse sandstone in the Bumballa Formation is rich in quartz and similar to sandstone in the undifferentiated Adaminaby Group. Detrital zircons from sandstone in the Bumballa Formation, and from sandstone at a similar stratigraphic level from the upper Adaminaby Group of the Genoa River area in eastern Victoria, include grains as young as 453-473 Ma, slightly older than the stratigraphic ages. The dominant detrital ages are in the interval 500-700 Ma (Pacific Gondwana component) with a lessor concentration of Grenville ages (1000-1300 Ma). This pattern resembles other Ordovician sandstones from the Lachlan Fold Belt and also occurs in Triassic sandstones and Quaternary sands from eastern Australia. The Upper Ordovician succession is predominantly fine grained, which reflects reduced clastic inputs from the source in the Middle Cambrian to earliest Ordovician Ross-Delamerian Fold Belts that developed along the eastern active margin of Gondwana. Development of subduction zones in the Late Ordovician marginal sea are considered to be mainly responsible for the diversion of sediment and the resulting reduction in the supply of terrigenous sand to the island arc and eastern part of the marginal sea. Sixty zircons from each sample were analysed and results are presented. Methods following standard procedures were undertaken on SHRIMP I, the analyses comprised four scans through the mass spectrum (Williams 1998 and references therein). The U/Pb ratios have been calibrated relative to the AS3 Duluth Gabbro reference zircon (Paces and Miller 1993) and relative probability plots with stacked histograms were compiled using ISOPLOT/EX (Ludwig 1999). Copyright (2002) Geological Society of Australia

  5. Compilation of information on the climate and evaluation of the hydrochemical and isotopic composition during Late Pleistocene and Holocene

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Cecilia [Intera KB (Sweden)

    1998-01-01

    This report summarises and evaluates some of the existing information on the Late Pleistocene and Holocene climates, i.e. the last 130 000 years. An estimation of the conditions at the Aespoe island (southeast Sweden) has also been made during this time span. The knowledge about Late Pleistocene (Eemian Interglacial and Weichselian glacial) is not yet fully understood. There are still a lot of assumptions concerning this period and more information is needed to be able to establish the climatic conditions. This is not the case for the Weichselian deglaciation and the present interglacial, Holocene, for which the environmental conditions are quite certain. It has been concluded, however, that the Eemian climatic development probably was similar to the Holocene but perhaps somewhat warmer and more humid. The Eemian Baltic Sea level was probably also higher than the present Baltic Sea level and there was a connection between it and the White Sea in the northeast. Aespoe was probably situated below sea level during the greater part of Eemian. Not much is known about the last glacial period, the Weichselian glaciation, until the final deglaciation. The ice sheet during Early Weichselian was probably mostly concentrated to the Scandinavian mountain area and in northern Scandinavia. At least two intervals with higher temperatures have been recorded, the Broerup and Odderade interstadials. The Middle Weichselian substage is characterised by fluctuations, melting and re-advances. Aespoe was probably not glaciated until the middle or latter part of Middle Weichselian. The maximum extension of the Weichselian ice sheet occurred in Late Weichselian, around 20 to 18 ka BP, which was succeeded by the final deglaciation. The retreat of the Weichselian ice sheet is described by for example end moraines and glacial varved clay. The Aespoe area was glaciated until 12 500 BP. Huge quantities of glacial meltwater was released into the Baltic basin as the ice receded. Due to different causes the basin was sometimes in contact with the sea and, sometimes large freshwater lakes were formed in it. Aespoe island was situated below sea or lake level to around 3000 years BP. 72 refs, 17 figs, 1 tab.

  6. Giant seismites and megablock uplift in the East African Rift: Evidence for large magnitude Late Pleistocene earthquakes

    Science.gov (United States)

    Hilbert-Wolf, Hannah; Roberts, Eric

    2015-04-01

    Due to rapid population growth and urbanization of many parts of East Africa, it is increasingly important to quantify the risk and possible destruction from large-magnitude earthquakes along the tectonically active East African Rift System. However, because comprehensive instrumental seismic monitoring, historical records, and fault trench investigations are limited for this region, the sedimentary record provides important archives of seismicity in the form of preserved soft-sediment deformation features (seismites). Extensive, previously undescribed seismites of centimeter- to dekameter-scale were identified by our team in alluvial and lacustrine facies of the Late Quaternary-Recent Lake Beds Succession in the Rukwa Rift Basin, of the Western Branch of the East African Rift System. We document the most highly deformed sediments in shallow, subsurface strata close to the regional capital of Mbeya, Tanzania, primarily exposed at two, correlative outcrop localities ~35 km apart. This includes a remarkable, clastic 'megablock complex' that preserves remobilized sediment below vertically displaced breccia megablocks, some in excess of 20 m-wide. The megablock complex is comprised of (1) a 5m-tall by 20m-wide injected body of volcanic ash and silt that hydraulically displaced (2) an equally sized, semi-consolidated, volcaniclastic megablock; both of which are intruded by (3) a clastic injection dyke. Evidence for breaching at the surface and for the fluidization of cobbles demonstrates the susceptibility of the substrate in this region to significant deformation via seismicity. Thirty-five km to the north, dekameter-scale asymmetrical/recumbent folds occur in a 3 m-thick, flat lying lake floor unit of the Lake Beds Succession. In between and surrounding these two unique sites, smaller-scale seismites are expressed, including flame structures; cm- to m-scale folded beds; ball-and-pillow structures; syn-sedimentary faults; sand injection features; and m-dkm-scale clastic injection dykes. Our documentation provides evidence for M 6-7.5+ Late Pleistocene earthquakes, similar to the M7.4 earthquake at the same location in 1910, extending the record of large-magnitude earthquakes beyond the last century. Our study not only expands the database of seismogenic sedimentary structures, but also attests to repeated, large-magnitude, Late Pleistocene-Recent earthquakes along the Western Branch of the East African Rift System. Understanding how seismicity deforms the crust is critical for predicting and preparing for modern seismic hazards, especially along the East African Rift System and other tectonically active, developing regions.

  7. Compilation of information on the climate and evaluation of the hydrochemical and isotopic composition during Late Pleistocene and Holocene

    International Nuclear Information System (INIS)

    This report summarises and evaluates some of the existing information on the Late Pleistocene and Holocene climates, i.e. the last 130 000 years. An estimation of the conditions at the Aespoe island (southeast Sweden) has also been made during this time span. The knowledge about Late Pleistocene (Eemian Interglacial and Weichselian glacial) is not yet fully understood. There are still a lot of assumptions concerning this period and more information is needed to be able to establish the climatic conditions. This is not the case for the Weichselian deglaciation and the present interglacial, Holocene, for which the environmental conditions are quite certain. It has been concluded, however, that the Eemian climatic development probably was similar to the Holocene but perhaps somewhat warmer and more humid. The Eemian Baltic Sea level was probably also higher than the present Baltic Sea level and there was a connection between it and the White Sea in the northeast. Aespoe was probably situated below sea level during the greater part of Eemian. Not much is known about the last glacial period, the Weichselian glaciation, until the final deglaciation. The ice sheet during Early Weichselian was probably mostly concentrated to the Scandinavian mountain area and in northern Scandinavia. At least two intervals with higher temperatures have been recorded, the Broerup and Odderade interstadials. The Middle Weichselian substage is characterised by fluctuations, melting and re-advances. Aespoe was probably not glaciated until the middle or latter part of Middle Weichselian. The maximum extension of the Weichselian ice sheet occurred in Late Weichselian, around 20 to 18 ka BP, which was succeeded by the final deglaciation. The retreat of the Weichselian ice sheet is described by for example end moraines and glacial varved clay. The Aespoe area was glaciated until 12 500 BP. Huge quantities of glacial meltwater was released into the Baltic basin as the ice receded. Due to different causes the basin was sometimes in contact with the sea and, sometimes large freshwater lakes were formed in it. Aespoe island was situated below sea or lake level to around 3000 years BP

  8. Are Late-Pleistocene Climate Reconstructions from Cirque and Valley Moraines Possible in Regions of Decaying Ice Sheets?

    Science.gov (United States)

    Menounos, B.; Goehring, B. M.; osborn, G.; Clague, J. J.; Davis, P. T.; Lakeman, T.; Schaefer, J. M.; Koch, J.; Clarke, G. K.

    2012-12-01

    The extent of glaciers in the past has commonly been used to infer past climates. Both abrupt climate change and geomorphic factors, however, are required to explain the timing and apparent magnitude of latest Pleistocene advances at high latitudes in western Canada and southernmost Patagonia. At the southern end of the Andes, north and west of Ushuaia, Argentina, 10Be surface exposure ages from glaciated bedrock beyond cirque moraines indicate that alpine areas were deglaciated by ca. 15.5 ka (kilo calendar yr BP). One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many cirques in this region. The mean of five 10Be ages from two of the moraines is 14.82-13.16 ka, whereas a smaller recessional moraine in one cirque returned a minimum-limiting AMS radiocarbon age of 12.38-12.01 ka. The ages imply that following regional deglaciation, cirque glaciers first advanced during the Antarctic Cold Reversal (ACR) [14.5-12.9 ka] and then advanced again or remained near their ACR limits during the Younger Dryas Chronozone (YD) [12.9-11.7 ka]. The moraines are restricted to topographic highs that were deglaciated before 15.5 ka. In western Canada, glaciers also advanced during the YD, but the magnitude of this advance differs markedly throughout the region. 10Be and 14C ages on moraines at high elevations in the Canadian Rockies and the southern Coast Mountains indicate that many glaciers built moraines during the YD that were only hundreds of meters beyond those constructed during the later part of the Little Ice Age [0.30-0.15 ka]. In contrast, 10Be ages [13.10-12.00 ka] on three moraines in northwest British Columbia indicate that glaciers up to 10 km beyond LIA glacier limits during the YD. We argue that the different responses of alpine glaciers in western Canada to climate deterioration during the YD is due to the presence of the decaying Cordilleran ice sheet. Top-down melting of the Cordilleran ice sheet allowed many high alpine sites to become ice-free prior to cirque glacier growth during the YD. Conversely, in some valleys Cordilleran ice sheet outlet glaciers advanced in response to the YD to positions far beyond LIA limits. An implication of this study is that late Pleistocene climate reconstructions based on alpine moraines may be problematic in regions with decaying ice sheets. We are currently using numerical ice sheet models, forced with GCM simulations, to further examine the roles played by climatic and geomorphic factors on the spatial distribution of latest Pleistocene glaciers in western Canada and southernmost Patagonia.

  9. Deciphering magnetoclimatological patterns of late Early to early Middle Pleistocene loess-paleosol sequences in the western Chinese Loess Plateau

    Science.gov (United States)

    Wang, Xisheng; Yang, Zhenyu; Chen, Yun; Hu, Jianyong; Tang, Ling; Sheng, Mei; Løvlie, Reidar

    2015-07-01

    A detailed environmental magnetic investigation in conjunction with geochemical, bulk grain size and redness analyses of late Early to early Middle Pleistocene loess-paleosol sequences at the Jiuzhoutai and Caotan loess sections has been carried out, aimed to explore the reliability of magnetic parameters as paleoclimatic proxies in the western Chinese Loess Plateau (CLP). The results show that magnetic enhancement of early- to mid-Pleistocene loess-paleosol sequences at both sites is not solely due to the neoformation of ultrafine magnetic particles through pedogenesis, but in the case of several loess layers (e.g., L8 and L9) is more attributed to the significant input of coarse-grained magnetic minerals associated with the advance of desert margin and/or with significant changes in local sediment input. Since the magnetoclimatological signals studied here are obviously controlled by both pedogenesis and wind vigor, measurements of magnetic susceptibility (?) and saturation isothermal remanent magnetization (SIRM), both of which are responsive to both ultrafine pedogenic magnetic particles and eolian coarse-grained pseudo-single domain/multi-domain magnetic particles, could not provide unambiguous interpretation of the magnetic response to the East Asian summer monsoon intensity. In contrast, anhysteretic remanent magnetization (ARM) and the percentage of frequency-dependent magnetic susceptibility (?fd%), which are notably responsive to ultrafine magnetic particles, can aptly trace changes in the concentration of pedogenic magnetic particles and can therefore be used as reliable proxies of pedogenic intensity. The magnetic grain size dependent proxies, e.g., ARM/? and ARM/Ms (Ms, saturation magnetization), geochemical indices (e.g., chemical index of alteration, Zr/Rb and Al/Si ratios), and bulk grain size records all exhibit concordant variations and are more straightforward proxies for addressing the East Asian monsoon variability. Therefore the combination of multi-parameter mineral magnetic, geochemical and grain size analyses is very useful for distinguishing, delimiting and correlating loess sequences, and for accurately deciphering their paleoclimatic signals embedded in the weakly weathered loess. As the classical precipitation-driven pedogenic model for magnetic susceptibility enhancement is not entirely applicable to the early- to mid-Pleistocene loess developed in the semi-arid western CLP, considerable caution should also be warranted in using magnetic susceptibility measurements alone in the quantitative reconstruction of paleoprecipitation.

  10. The late Early Pleistocene human dental remains from Uadi Aalad and Mulhuli-Amo (Buia), Eritrean Danakil: macromorphology and microstructure.

    Science.gov (United States)

    Zanolli, Clément; Bondioli, Luca; Coppa, Alfredo; Dean, Christopher M; Bayle, Priscilla; Candilio, Francesca; Capuani, Silvia; Dreossi, Diego; Fiore, Ivana; Frayer, David W; Libsekal, Yosief; Mancini, Lucia; Rook, Lorenzo; Medin Tekle, Tsegai; Tuniz, Claudio; Macchiarelli, Roberto

    2014-09-01

    Fieldwork performed during the last 15 years in various Early Pleistocene East African sites has significantly enlarged the fossil record of Homo erectus sensu lato (s.l.). Additional evidence comes from the Danakil Depression of Eritrea, where over 200 late Early to early Middle Pleistocene sites have been identified within a ?1000 m-thick sedimentary succession outcropping in the Dandiero Rift Basin, near Buia. Along with an adult cranium (UA 31), which displays a blend of H. erectus-like and derived morpho-architectural features and three pelvic remains, two isolated permanent incisors (UA 222 and UA 369) have also been recovered from the 1 Ma (millions of years ago) Homo-bearing outcrop of Uadi Aalad. Since 2010, our surveys have expanded to the nearby (4.7 km) site of Mulhuli-Amo (MA). This is a fossiliferous area that has been preliminarily surveyed because of its exceptional concentration of Acheulean stone tools. So far, the site has yielded 10 human remains, including the unworn crown of a lower permanent molar (MA 93). Using diverse analytical tools (including high resolution ?CT and ?MRI), we analysed the external and internal macromorphology and microstructure of the three specimens, and whenever possible compared the results with similar evidence from early Homo, H. erectus s.l., H. antecessor, H. heidelbergensis (from North Africa), Neanderthals and modern humans. We also assessed the UA 369 lower incisor from Uadi Aalad for root completion timing and showed that it compares well with data for root apex closure in modern human populations. PMID:24852385

  11. First record of Bison antiquus from the Late Pleistocene of southern Mexico

    Science.gov (United States)

    Jiménez-Hidalgo, Eduardo; Cabrera-Pérez, Lucía; MacFadden, Bruce J.; Guerrero-Arenas, Rosalía

    2013-03-01

    In Mexico, just 54% of the reported Pleistocene Bison material has been identified to species. Current paleontological research in northwestern Oaxaca, southern Mexico, has allowed collection of several specimens of Bison antiquus that are part of the Viko Vijin Local Fauna. B. antiquus had a very wide geographic distribution, from lowlands to mountainous landscapes of North and Central America. The B. antiquus record from southern Mexico links their former records from central Mexico and middle Central America and confirms this wide geographic distribution. The univariate mesowear score of the B. antiquus specimens from Oaxaca is in the lower extreme of grazers and the upper end of mixed-feeders, suggesting that they had a less abrasive diet than the modern plains Bison, as has been observed in other samples of this species from diverse parts of North America. The presence of B. antiquus in the Viko Vijin L. F. constrains the age of this fossil assemblage within a range from 60 Ka to 11.7 Ka.

  12. A discontinuity in the late Pleistocene alluvial deposits, Hwacheon-ri, Gyeongju, Korea: Occurrences and paleoenvironmental implications

    Science.gov (United States)

    Paik, In Sung; Kyeong Seol, Weon; Kim, Hyun Joo; Lee, Ho Il; Kang, Hee Cheol

    2015-04-01

    Sedimentary discontinuity surface occurs in the late Pleistocene alluvial deposits exposed along the cliff (about 10 m thick and over 140 m in length) in stream side, Gyeongju, Korea. The discontinuity surface is laterally extensive and marked by distinct carbonaceous dark horizon in the middle part of the deposits. The deposits are divided into lower and upper units by the discontinuity surface. The lower unit overlies unconformably the Cretaceous andesitic rock (basement), and consists of braided-river deposits. Lower part of the lower unit is mainly composed of lenticular-bedded and clast-supported conglomeratic deposits, whereas gray to dark gray sandy to muddy channel-plug deposits occur in the uppermost part of the lower unit. It is characteristic that iron-oxide crusts occur in the lower unit. They are cutting across the lower unit and truncated by the overlying upper unit. Rootlets mineralized by vivianite are present in the channel-plug deposits below the discontinuity surface. The upper unit overlying the lower unit with erosive contact (discontinuity surface) is mostly composed of matrix-supported conglomeratic alluvial fan deposits. Hornfelsic gravels are common in the lower unit, whereas andesitic gravels are predominant in the upper unit, suggesting the provenance change from the lower unit to the upper unit. OSL ages for the lower and the upper units are 125±9 ka and 94±9 ka, respectively, suggesting that the lower unit was deposited in MIS5e and the upper unit was formed in MIS5c to 5b. It is thus interpreted that the shift of depositional environment from a fluvial plain (lower unit) to an alluvial fan (upper unit) was an alluvial response to sea level change inducing fall of base level in an alluvial basin from the interglacial to the glacial stages. The development of iron-oxide crusts and diagenetic vivianite in the discontinuity surface suggest that humid condition persisted during the paleoclimatic shift from the last interglacial to the last glacial stages. Key words: Late Pleistocene, Alluvial deposits, Discontinuity, Iron-oxides, Vivianite

  13. Late Pleistocene-Holocene earthquake-induced slumps and soft-sediment deformation structures in the Acequion River valley, Central Precordillera, Argentina

    Directory of Open Access Journals (Sweden)

    Perucca Laura P

    2014-07-01

    Full Text Available Evidence of earthquake-induced liquefaction features in the Acequión river valley, central western Argentina, is analysed. Well-preserved soft-sediment deformation structures are present in Late Pleistocene deposits; they include two large slumps and several sand dikes, convolutions, pseudonodules, faults, dish structures and diapirs in the basal part of a shallow-lacustrine succession in the El Acequión River area. The water-saturated state of these sediments favoured deformation.

  14. New results on the palaeoclimate record of the Late Pleistocene cave sediments (Moravian Karst, Czech Republic); the case srudy based on mineral magnetic properties and facial analyses.

    Czech Academy of Sciences Publication Activity Database

    Lisá, Lenka; Nerudová, Z.; Neruda, P.; Chadima, Martin; Bajer, A.

    Pozna? : Adam mickewicz University Pozna?, 2011 - (Issmer, K.; Makohonienko, M.; Hildebrandt-Radke, I.; Wis?iewski, A.). s. 14-16 [Geoarchaeological Workshop : Actual stage of the environmental archaeology investigations in southern Poland and northern Czech and their implications for palaeoclimatic changes versus new delimitations of the Quaternary. 25,10.2011, Pozna?] Institutional research plan: CEZ:AV0Z30130516 Keywords : geoarchaeology * cave sediments * Late Pleistocene Subject RIV: AC - Archeology, Anthropology, Ethnology

  15. Leafcutter Bee Nests and Pupae from the Rancho La Brea Tar Pits of Southern California: Implications for Understanding the Paleoenvironment of the Late Pleistocene

    OpenAIRE

    Holden, Anna R.; KOCH, Jonathan B.; Griswold, Terry, L.; Erwin, Diane M.; Hall, Justin

    2014-01-01

    The Rancho La Brea Tar Pits is the world’s richest and most important Late Pleistocene fossil locality and best renowned for numerous fossil mammals and birds excavated over the past century. Less researched are insects, even though these specimens frequently serve as the most valuable paleoenvironemental indicators due to their narrow climate restrictions and life cycles. Our goal was to examine fossil material that included insect-plant associations, and thus an even higher potential for si...

  16. Late Pliocene and early Pleistocene environments of the north-eastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    OpenAIRE

    Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M.

    2013-01-01

    The 318 m thick lacustrine sediment record in Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities allowing the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments show their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.50–3.35 My...

  17. Abnormal carbonate diagenesis in Holocene-late Pleistocene sapropel-associated sediments from the Eastern Mediterranean; Evidence from Emiliania huxleyi coccolith morphology

    DEFF Research Database (Denmark)

    Crudeli, D.; Young, J.R.; Erba, E.; De Lange, G.J.; Henriksen, K.; Kinkel, Hanno; Slomp, C.P.; Ziveri, P.

    2004-01-01

    In studying the Holocene-late Pleistocene record of the Eastern Mediterranean, considerable Emiliania huxleyi size/shape variation not clearly assignable to primary or secondary calcification was observed. Accordingly, different morphotypes were distinguished by light microscope (LM). A subsequent scanning electron microscope (SEM) analysis of selected samples has indicated that Emiliania huxleyi coccoliths are variably affected by carbonate diagenesis in these sediments. A series of diagenetic ...

  18. Geomorphic and Modeling Evidence for a Late Pleistocene Cirque Glacier in Southwest England

    Science.gov (United States)

    Knight, J.; Harrison, S.; Rowan, A. V.

    2014-12-01

    Several small ice caps have been identified outside of the margins of the last (late Devensian) British ice sheet, but few sites in the uplands of southwest England show evidence for late Devensian niche/cirque glaciers and/or perennial snowbanks. Here we present evidence for the southernmost site yet discovered, in west Penwith, Cornwall. Here, a NE-facing hollow developed on granite bedrock is surrounded by tors with deep bedrock fractures and displaced angular blocks. Bedrock is exposed at the base of the hollow but sediments form a subdued ridge, interpreted as a terminal moraine, at the front of the hollow. The sediments comprise gravelly diamicton containing facetted clasts that are occasionally striated, interbedded with sand lenses. Sediments are deformed by periglacial involutions. We used a 2-D glacier energy balance and iceflow model (Plummer and Phillips, 2003, Quat Sci Rev) to discover if the climatic conditions during the late Devensian could have sustained a cirque glacier at this site. Met Office regional climate data (1981-2010) were used to define mean monthly air temperatures, lapse rate, precipitation, cloudiness and relative humidity, and surface energy fluxes were calculated based on solar position during the present day and last glacial maximum (LGM). We ran a range of different glacier model simulations to test an envelope of late Devensian paleoclimate conditions inferred from other climate proxies. Model results suggest that a cirque glacier could have formed at this site under conditions equivalent to a change in temperature from present-day values of -8.5°C accompanied by a 20% decrease in precipitation, which is consistent with the regional LGM. Response times for these simulations are greater than 500 years, indicating that it is unlikely that such cirque glaciers maintained steady state and were instead short-lived features.

  19. Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA

    Science.gov (United States)

    Hoppe, Kathryn A.; Koch, Paul L.

    2007-11-01

    We used analyses of the strontium isotope ( 87Sr/ 86Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low 87Sr/ 86Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of 87Sr/ 86Sr ratios. Some individuals in each taxon displayed low 87Sr/ 86Sr ratios that suggest they ranged locally, while other animals had high 87Sr/ 86Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower 87Sr/ 86Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.

  20. Evidence for prolonged El Nino-like conditions in the Pacific during the Late Pleistocene: a 43 ka noble gas record from California groundwaters

    Science.gov (United States)

    Kulongoski, J.T.; Hilton, David R.; Izbicki, J.A.; Belitz, K.

    2009-01-01

    Information on the ocean/atmosphere state over the period spanning the Last Glacial Maximum - from the Late Pleistocene to the Holocene - provides crucial constraints on the relationship between orbital forcing and global climate change. The Pacific Ocean is particularly important in this respect because of its dominant role in exporting heat and moisture from the tropics to higher latitudes. Through targeting groundwaters in the Mojave Desert, California, we show that noble gas derived temperatures in California averaged 4.2 ?? 1.1 ??C cooler in the Late Pleistocene (from ???43 to ???12 ka) compared to the Holocene (from ???10 to ???5 ka). Furthermore, the older groundwaters contain higher concentrations of excess air (entrained air bubbles) and have elevated oxygen-18/oxygen-16 ratios (??18O) - indicators of vigorous aquifer recharge, and greater rainfall amounts and/or more intense precipitation events, respectively. Together, these paleoclimate indicators reveal that cooler and wetter conditions prevailed in the Mojave Desert from ???43 to ???12 ka. We suggest that during the Late Pleistocene, the Pacific ocean/atmosphere state was similar to present-day El Nino-like patterns, and was characterized by prolonged periods of weak trade winds, weak upwelling along the eastern Pacific margin, and increased precipitation in the southwestern U.S.

  1. Conceptual hydrochemical model of late Pleistocene aquifers at the Samario-Sitio Grande petroleum reservoir, Gulf of Mexico, Mexico

    International Nuclear Information System (INIS)

    Carbon-14 concentrations between 0.83 and 11.79 pmC of formation water from the Activo Samaria-Sitio Grande petroleum reservoir in SE-Mexico, extracted from 3500 to 4500 m.b.s.l., indicate a common infiltration event of surface water during the late Pleistocene period. Mixing of two components - meteoric water and seawater, previously evaporated at the surface - explain the widespread mineralization (TDI = 15-257 g/L) of Na-Cl and Na-Ca-Cl type reservoir water. Statistical discrimination by clustering and a heterogeneous chemical-isotopic fluid composition indicate the existence of 4 different water types as part of local aquifer systems, which are separated by normal and thrust faults. Tectonic horst and graben structures show an ambiguous, individual hydraulic behaviour - as permeable conduits and/or as impermeable barriers, causing the local limitation of aquifer extent. The recent increase of water production in petroleum wells is not related to the injection of surface water, but the long-term extraction of oil reserves is modifying the original position and flow direction of the reservoir aquifers. The rise of the initial groundwater level reflects the final stage of an exhausted petroleum reservoir with coning effects of underlying aquifer systems. The flexible change towards superior production intervals could represent a feasible technique to avoid the abrupt closure of invaded production wells

  2. The role of cryptotephra in refining the chronology of Late Pleistocene human evolution and cultural change in North Africa

    Science.gov (United States)

    Barton, R. N. E.; Lane, C. S.; Albert, P. G.; White, D.; Collcutt, S. N.; Bouzouggar, A.; Ditchfield, P.; Farr, L.; Oh, A.; Ottolini, L.; Smith, V. C.; Van Peer, P.; Kindermann, K.

    2015-06-01

    Sites in North Africa hold key information for dating the presence of Homo sapiens and the distribution of Middle Stone Age (MSA), Middle Palaeolithic (MP) and Later Stone Age (LSA) cultural activity in the Late Pleistocene. Here we present new and review recently published tephrochronological evidence for five cave sites in North Africa with long MSA/MP and LSA cultural sequences. Four tephra horizons have been identified at the Haua Fteah (Cyrenaica, Libya). They include cryptotephra evidence for the Campanian Ignimbrite (CI) eruption dating to ˜39 ka that allows correlation with other Palaeolithic sequences in the eastern Mediterranean and as far north as Russia. Cryptotephra have also been recorded from the Moroccan sites of Taforalt, Rhafas and Dar es-Soltane 1. At Taforalt the geochemical composition suggests a provenance in the Azores, while examples from Sodmein (Egypt) appear to derive from central Anatolia and another unknown source. In these latter examples chemical compositional data from relevant proximal volcanic centres is currently lacking so the identification of tephra in layers of known age and cultural association provides the first reliable age determinations for distal volcanic events and their geographical extent. The future potential for tephrochronological research in North Africa is also discussed.

  3. Forces driving late Pleistocene (ca. 77-12 ka) landscape evolution in the Cimarron River valley, southwestern Kansas

    Science.gov (United States)

    Layzell, Anthony L.; Mandel, Rolfe D.; Ludvigson, Greg A.; Rittenour, Tammy M.; Smith, Jon J.

    2015-07-01

    This study presents stratigraphic, geomorphic, and paleoenvironmental (?13C) data that provide insight into the late Pleistocene landscape evolution of the Cimarron River valley in the High Plains of southwestern Kansas. Two distinct valley fills (T-1 and T-2) were investigated. Three soils occur in the T-2 fill and five in the T-1 fill, all indicating periods of landscape stability or slow sedimentation. Of particular interest are two cumulic soils dating to ca. 48-28 and 13-12.5 ka. ?13C values are consistent with regional paleoenvironmental proxy data that indicate the prevalence of warm, dry conditions at these times. The Cimarron River is interpreted to have responded to these climatic changes and to local base level control. Specifically, aggradation occurred during cool, wet periods and slow sedimentation with cumulic soil formation occurred under warmer, drier climates. Significant valley incision (~ 25 m) by ca. 28 ka likely resulted from a lowering of local base level caused by deep-seated dissolution of Permian evaporite deposits.

  4. Late and middle Pleistocene ungulates dietary diversity in Western Europe indicate variations of Neanderthal paleoenvironments through time and space

    Science.gov (United States)

    Rivals, Florent; Schulz, Ellen; Kaiser, Thomas M.

    2009-12-01

    Mesowear and microwear on enamel from 763 teeth of middle and late Pleistocene ungulates were analysed to infer the potential of dental wear analysis of faunal remains as a paleoenvironmental and paleoclimatic proxy in relation to climatic changes and diversity of vegetation available in the environment. Fossil localities including levels belonging to two glacial and two interglacial stages were selected in Germany, France, and Spain. At a temporal scale, results indicate that the dietary diversity in ungulates is higher during interglacial phases (MIS 5 and 3) than during pleniglacial phases (MIS 8 and 4). Dietary diversity is concluded to be related to climate-driven vegetation changes which during interglacials lead to increased variety of potential food items available to ungulates. At the geographical scale, during interglacials, changes in diet composition are evident along geographical gradients. The corresponding dietary gradients are proposed to be related to climate and vegetation gradients reflecting more arid climates in the Mediterranean area compared to North-Western Europe. Species consistently represented at all localities investigated are Cervus elaphus (Cervidae, Artiodactyla) and Equus ferus (Equidae, Perissodactyla). C. elaphus populations are found to consistently have less abrasive diets than E. ferus populations but dietary traits of both species varied largely, revealing a significant plasticity in the feeding adaptation of both species. Those traits are concluded to be related to differences in vegetation structure at each locality and complement the evidence that ungulates have broader dietary habits than what is usually assumed.

  5. On the Physical Significance of Statistically Significant Millennial Peaks in Late Pleistocene Glacial Intervals of Marine Sediment Cores.

    Science.gov (United States)

    Obrochta, S. P.; Crowley, T. J.

    2005-12-01

    Multitaper and maximum entropy methods were used to determine the statistical significance and frequency, respectively, of millennial-band peaks in late Pleistocene glacial intervals of geochemical, petrological, and physical property time series generated from marine sediment cores, including ODP Site 980 and IODP Site U1308 (Reoccupied DSDP Site 609). A preliminary age model for Site U1308 was created by correlating the sediment lightness (L*) record to the Site 980 ?18O record. Marine Isotope Stages (MIS) 2-3 (Wisconsin glaciation), 6 (Penultimate glaciation), 8, 10, and 12 were analyzed as individual time series and interpolated to the average sampling resolution of each respective glacial interval. Results indicate the existence of many peaks statistically significant at a 95% or greater confidence interval within each individual glacial-interval time series. One may be tempted to accept each of these peaks as physically significant; however, the probability that a particular peak is significant by chance alone (i.e., 5% chance given a 95% confidence interval), must be considered. For example, Hyde and Crowley (2002) generated millennial-scale peaks significant at a 95% confidence interval in a 120 k.y. model run forced by white noise at a 100-year time step. Given these model results, we exercise caution in the interpretation of physical significance of peaks in the sediment core time series, placing physical significance only on peaks that consistently appear in most of the series.

  6. Late-Pleistocene to Holocene sedimentary fills of the Ç?narc?k Basin of the Sea of Marmara

    Science.gov (United States)

    Eri?, K. Kadir; Ça?atay, Nam?k; Beck, Christian; Mercier de Lepinay, Bernard; Corina, Campos

    2012-12-01

    A giant RV Marion Dufresne piston core MD01-2425 recovered from the 1276 m-deep Ç?narc?k Basin of the Sea of Marmara documents characteristics of deep basin sedimentation influenced by large-scale gravity-controlled mass-wasting processes and associated turbidite deposition during the Late Pleistocene to Holocene. A visual lithological description of the core reveals twenty major seismoturbidite layers (> 20 cm thick), intercalated in hemipelagic-type fine-grained calcareous and slightly siliceous clays. The thickness and frequency of the sesimoturbidite layers deposited during the lacustrine period (prior to 12.3 cal ka BP) is much greater than during the Holocene marine period. The sedimentary processes during deposition of seismoturbidites in the basin have been determined in this study using a combination of grain-size parameters. Often the seismoturbidites show strong grain segregation with a sharp boundary between a coarse lower and a homogeneous upper part. The traction carpet deposits formed at the base of a turbulent suspension and were produced in the lower coarse-grained part, whereas the homogeneous upper part was deposited by uniform suspensions following bedload deposition.

  7. Limestone percussion tools from the late Early Pleistocene sites of Barranco León and Fuente Nueva 3 (Orce, Spain).

    Science.gov (United States)

    Barsky, Deborah; Vergès, Josep-María; Sala, Robert; Menéndez, Leticia; Toro-Moyano, Isidro

    2015-11-19

    In recent years, there is growing interest in the study of percussion scars and breakage patterns on hammerstones, cores and tools from Oldowan African and Eurasian lithic assemblages. Oldowan stone toolkits generally contain abundant small-sized flakes and their corresponding cores, and are characterized by their structural dichotomy of heavy- and light-duty tools. This paper explores the significance of the lesser known heavy-duty tool component, providing data from the late Lower Pleistocene sites of Barranco León and Fuente Nueva 3 (Orce, Spain), dated 1.4-1.2 Myr. Using quantitative and qualitative data from the large-sized limestone industries from these two major sites, we present a new methodology highlighting their morpho-technological features. In the light of the results, we discuss the shortfalls of extant classificatory methods for interpreting the role of percussive technology in early toolkits. This work is rooted in an experimental program designed to reproduce the wide range of percussion marks observed on the limestone artefacts from these two sites. A visual and descriptive reference is provided as an interpretative aid for future comparative research. Further experiments using a variety of materials and gestures are still needed before the elusive traces yield the secrets of the kinds of percussive activities carried out by hominins at these, and other, Oldowan sites. PMID:26483530

  8. Geomorphological and sedimentary evidence for late Pleistocene to Holocene hydrological change along the Río Mamoré, Bolivian Amazon

    Science.gov (United States)

    Plotzki, A.; May, J.-H.; Preusser, F.; Veit, H.

    2013-11-01

    Aerial photography and satellite imagery reveal manifold geomorphological evidence of a dynamic evolution of past and present rivers in the Bolivian Amazon. Comparison of oxbow lake and meander scar dimensions along an inactive meander belt of the Río Mamoré (Llanos de Moxos, north-eastern Bolivia) and its modern counterpart suggests significant regional paleohydrological variability. We used these features as geomorphological and sedimentary archives to enhance our understanding of longer-term variations of the fluvial system. Late Pleistocene to Holocene hydrological changes of the Río Mamoré are inferred from: (i) the analysis of satellite imagery, (ii) discharge estimates from meander morphology, (iii) stratigraphic, and (iv) chronological information based on luminescence and radiocarbon dating. The combined data from three oxbows indicate that the now abandoned meander belt - the paleo-Mamoré - continued to be active at least until ?5 ka, and likely even postdating 3 ka. An up to threefold increase in discharge is estimated for the modern Río Mamoré versus the paleo-Mamoré. The altered runoff regime may have triggered an avulsive shift towards the currently active Río Mamoré. The preceding increase in discharge in turn, was possibly related to a shift in climatic conditions, which changed markedly between the mid- and late Holocene in tropical South America. In addition, it may have been the indirect result of capturing the avulsive Río Grande system to the east of the Río Mamoré. Alternative explanations for the differences in dimensions of the paleo versus the modern Río Mamoré, i.e. contemporaneous activity of both rivers or alteration of site factors such as the channel/floodplain relationship, are considered to be unlikely.

  9. Late Pliocene - Early Pleistocene paleoenvironmental reconstruction based on stable isotope compositions of Stephanorhinus sp. and Mammut sp. teeth

    Science.gov (United States)

    Szabó, Péter; Kovács, János; Kocsis, László; Gasparik, Mihály; Vennemann, Torsten; Demény, Attila; Virág, Attila

    2014-05-01

    Stable isotope measurements of skeletal apatite from herbivorous mammals are often used to provide information on the terrestrial paleoenvironment and paleoclimate. In this study fossil teeth of Stephanorhinus Kretzoi 1942 (rhinoceros) and Mammut Blumenbach 1799 (mastodon), amongst others, were investigated from the Carpathian Basin. According to the biostratigraphy, the age of the samples has a range from Late Pliocene to Early Pleistocene. Reconstructing paleoclimate and paleoenvironment of this era is important as it can be an analogue for the future climate. Oxygen and carbon isotopic compositions were measured from the tooth enamel, because it is believed to be the most resistant to diagenetic alteration (e.g., Kohn & Cerling, 2002). The carbon isotopic composition in the carbonate fraction of apatite can be related to the diet of the animal (Kohn & Cerling, 2002). Hence, it can reflect the photosynthetic pathway (C3 or C4) of the plants consumed by these herbivores. The ?18O values were determined in the phosphate fraction of apatite. In the case of large mammals that are obligate drinkers, the ?18O values closely track those of the environmental water (Bryant & Froelich, 1995). Knowing the ?18O values of environmental water and relating it to local precipitation, the mean annual temperature (MAT) of the site can be calculated (Dansgaard, 1964). The ?13C values range from -10 to -15 o (VPDB). The result clearly shows that these animals consumed C3 plants. Most of the ?13C values indicate mixed grassland-open woodland rather than a closed canopy forest. Although there is variation in the ?18O values (mean 14.2 ± 1.0 o VSMOW, n=17), most of the samples would support a MAT range of 8-12 ° C. This is in good agreement with other proxies for the localities and time period (Kovács et al., 2013). Bryant, D.J. & Froelich, P.N. (1995) A model of oxygen-isotope fractionation in bodywater of large-mammals. Geochimica et Cosmochimica Acta 59, 4523-4537. Dansgaard, W. (1964) Stable isotopes in precipitation. Tellus 16, 436-468. Kohn, M.J. & Cerling, T.E. (2002) Stable isotope compositions of biological apatite. Reviews in Mineralogy and Geochemistry 48, 455-488. Kovács, J. et al. (2013) Clay Mineralogy of Red Clay Deposits from the Central Carpathian Basin (Hungary): Implications for Plio/Pleistocene Chemical Weathering and Paleoclimate. Turkish J. Earth. Sci. 22, 414-426.

  10. Didelphidae marsupials (Mammalia, Didelphimorphia) from the Late Pleistocene deposit of the Gruta dos Moura Cave, northern Brazil

    Scientific Electronic Library Online (English)

    Patricia Villa, Nova; Leonardo S., Avilla; Édison V., Oliveira.

    2015-03-01

    Full Text Available Neste estudo pretende-se reconhecer a diversidade de marsupiais fósseis da Gruta dos Moura além dos seus aspectos ambientais e climáticos durante o Quaternário. Constatou-se que esta é a maior diversidade de marsupiais Pleistocênicos coletados em uma única caverna: Didelphis albiventris, D. aurita, [...] Gracilinaus agilis, G. microtarsus, Marmosa murina, Monodelphis brevicaudata, M. domestica e Sairadelphys tocantinensis. Além disso, esses marsupiais também reúnem a única assembleia fossilífera que seguramente está associada ao Neopleistoceno. Estudos paleontológicos realizados sugerem uma íntima associação com ambientes secos, abertos e de alta profusão de recursos hídricos. Assim, como a maioria dos táxons identificados são característicos de florestas abertas e matas de galerias, essa poderia ser de fato a paisagem do entorno da Gruta dos Moura. Estudos recentes identificaram simpatria entre espécies de ambientes secos/abertos e de florestas úmidas dos táxons aqui identificados e característicos de regiões úmidas. Assim, essas espécies poderiam habitar matas de galeria e capões, ou até ecótonos, em um ambiente mais seco e aberto. Além disso, a extinção de Sairadelphys pode ser outro indício de que as condições climático-ambientais mudaram ou que o ambiente pretérito era mais heterogêneo que o encontrado atualmente na região. Abstract in english The present study acknowledges the diversity of fossil marsupials from the Gruta dos Moura cave, as well as environmental and climatic aspects during the Quaternary. The results show that this is the largest diversity of Pleistocene marsupials recorded in a single cave: Didelphis albiventris, D. aur [...] ita, Gracilinanus agilis, G. microtarsus, Marmosa murina, Monodelphis brevicaudata, M. domestica and Sairadelphys tocantinensis. Furthermore, the described specimens are also part of the only fossil assemblage unequivocally referable to the late Pleistocene. Paleontological studies suggest an intimate association with dry and open environments with high abundance of water sources. Since most of the identified taxa are characteristic of open forests and gallery forests, this could represent the actual environment around the Gruta dos Moura cave. Recent studies identified sympatric occurrences between species from open and dry environments and species from humid forests that were identified among our material and are characteristic of humid regions. Therefore, these species could inhabit gallery forests and capons, or even ecotones, inside a dry and open environment. Moreover, the extinction of Sairadelphys could also indicate that the climatic and environmental conditions changed or that the past environment was more heterogeneous than the current environment of the region.

  11. Pollen evidence for late pleistocene bering land bridge environments from Norton Sound, Northeastern Bering Sea, Alaska

    Science.gov (United States)

    Ager, T.A.; Phillips, R.L.

    2008-01-01

    After more than half a century of paleoenvironmental investigations, disagreements persist as to the nature of vegetation type and climate of the Bering land bridge (BLB) during the late Wisconsin (Sartan) glacial interval. Few data exist from sites on the former land bridge, now submerged under the Bering and Chukchi Seas. Two hypotheses have emerged during the past decade. The first, based on pollen data from Bering Sea islands and adjacent mainlands of western Alaska and Northeast Siberia, represents the likely predominant vegetation on the Bering land bridge during full-glacial conditions: graminoid-herb-willow tundra vegetation associated with cold, dry winters and cool, dry summer climate. The second hypothesis suggests that dwarf birch-shrub-herb tundra formed a broad belt across the BLB, and that mesic vegetation was associated with cold, snowier winters and moist, cool summers. As a step towards resolving this controversy, a sediment core from Norton Sound, northeastern Bering Sea was radiocarbon dated and analyzed for pollen content. Two pollen zones were identified. The older, bracketed by radiocarbon ages of 29,500 and 11,515 14C yr BP, contains pollen assemblages composed of grass, sedge, wormwood, willow, and a variety of herb (forb) taxa. These assemblages are interpreted to represent graminoid-herb-willow tundra vegetation that developed under an arid, cool climate regime. The younger pollen zone sediments were deposited about 11,515 14C yr BP, when rising sea level had begun to flood the BLB. This younger pollen zone contains pollen of birch, willow, heaths, aquatic plants, and spores of sphagnum moss. This is interpreted to represent a Lateglacial dwarf birch-heath-willow-herb tundra vegetation, likely associated with a wetter climate with deeper winter snows, and moist, cool summers. This record supports the first hypothesis, that graminoid-herb-willow tundra vegetation extended into the lowlands of the BLB during full glacial conditions of the late Wisconsin. ?? 2008 Regents of the University of Colorado.

  12. Late Piocene - Pleistocene evolution of river terrace in Zhongwei Basin, northeastern margin of Tibetan Plateau, China

    Science.gov (United States)

    Liang, H.; Zhang, K.

    2014-12-01

    Northeastern margin of the Tibetan Plateau is a key area to understand the formation and evolution of the plateau. We describe the feature of terraces derived from deposit or down-cutting of the Yellow River in Zhongwei Basin that records the evolution of landform in this region. After clarifying the correlation among terrace remnants, we determine the age of certain terraces by TCN and ESR. The TCN dating yields age for lowest terrace buried in the basin of 2.40±0.38 Ma, and the ESR dating for upper three terraces on hillslope adjacent the margin of the basin of 2.08±0.21Ma, 1.88±0.35Ma and 1.48±0.11Ma respectively. The fact that buried terrace is older than the ones distribute on high elevation suggests that spatial variation in vertical motions of the basin. Taken with the observation and ages of these landform features, we infer to a deceleration of depression in center of the basin after terrace was buried in Late Piocene, then the basin started to uplift rapidly, causing the river gradient to steepen locally and erosion of the channel to intensify, resulting to the terrace on high elevation nearby the basin.

  13. Stable carbon isotope reconstructions of diet and paleoenvironment from the late Middle Pleistocene Snake Cave in Northeastern Thailand

    Science.gov (United States)

    Pushkina, Diana; Bocherens, Herve; Chaimanee, Yaowalak; Jaeger, Jean-Jacques

    2010-03-01

    Thailand’s geographical location in the tropics and almost complete, relatively uninterrupted forest cover makes it valuable for paleodiet and paleoclimate research. We present the first dietary and environmental reconstructions in Northeastern Thailand, using stable isotope abundances in mammalian tooth enamel from the late Middle Pleistocene locality, Tham Wiman Nakin (Snake Cave), which reflect a much higher (over 70%) than modern (13%) occurrence of C4 plants. Bovids and cervids appear to have had almost entirely a C4 plant diet. Carnivores consumed a mixture of C3 (suids) and C4 (bovids, cervids) consumers. Rhinoceroses and orangutan appear to have maintained their preference through time for forested or open C3 environment, respectively. 13C/12C from bone bioapatite, horn and hair of modern Southeast Asian mammals almost exclusively demonstrate C3 vegetation dominance. C4 consumption is rare in analysed modern species and it could be related to anthropogenic influences such as ingestion of domestic crops or livestock. Interesting implications emerge in the C4 vegetation distribution in southern Eurasian ecosystems, indicating that Southeast Asia, south of the Tibet, could be part of the global C4 vegetation spread, which occurred around 7 Ma. However, the C4 percentage in ecosystems varied geographically. Despite modern reversal towards C3 habitats due to factors such as increasing CO2, we think that anthropological influences may be responsible for habitat and dietary changes in extant species. Bovids demonstrate the most significant shift in diet and habitat through time, from C4-dominated open habitats to C3-dominated habitats indicative of dense forest understory.

  14. Evidence of Late Pliocene-Early Pleistocene marine environments in the deep subsurface of the Lihue Basin, Kauai, Hawaii

    Science.gov (United States)

    Izuka, S.K.; Resig, J.M.

    2008-01-01

    Cuttings recovered from two deep exploratory wells in the Lihue Basin, Kauai, Hawaii, include fossiliferous marine deposits that offer an uncommon opportunity to study paleoenvironments from the deep subsurface in Hawaii and interpret the paleogeography and geologic history of Kauai. These deposits indicate that two marine incursions gave rise to protected shallow-water, low-energy embayments in the southern part of the Lihue Basin in the late Pliocene-early Pleistocene. During the first marine incursion, the embayment was initially zoned, with a variable-salinity environment nearshore and a normal-marine reef environment offshore. The offshore reef environment eventually evolved to a nearshore, variable-salinity environment as the outer part of the embayment shallowed. During the second marine incursion, the embayment had normal-marine to hypersaline conditions, which constitute a significant departure from the variable-salinity environment present during the first marine incursion. Large streams draining the southern Lihue Basin are a likely source of the freshwater that caused the salinity fluctuations evident in the fossils from the first marine incursion. Subsequent volcanic eruptions produced lava flows that buried the embayment and probably diverted much of the stream flow in the southern Lihue Basin northward, to its present point of discharge north of Kalepa Ridge. As a result, the embayment that formed during the second marine incursion received less freshwater, and a normal-marine to hypersaline environment developed. The shallow-water marine deposits, currently buried between 86 m and 185 m below present sea level, have implications for regional tectonics and global eustasy. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

  15. Stable carbon isotope reconstructions of diet and paleoenvironment from the late Middle Pleistocene Snake Cave in Northeastern Thailand.

    Science.gov (United States)

    Pushkina, Diana; Bocherens, Herve; Chaimanee, Yaowalak; Jaeger, Jean-Jacques

    2010-03-01

    Thailand's geographical location in the tropics and almost complete, relatively uninterrupted forest cover makes it valuable for paleodiet and paleoclimate research. We present the first dietary and environmental reconstructions in Northeastern Thailand, using stable isotope abundances in mammalian tooth enamel from the late Middle Pleistocene locality, Tham Wiman Nakin (Snake Cave), which reflect a much higher (over 70%) than modern (13%) occurrence of C4 plants. Bovids and cervids appear to have had almost entirely a C4 plant diet. Carnivores consumed a mixture of C3 (suids) and C4 (bovids, cervids) consumers. Rhinoceroses and orangutan appear to have maintained their preference through time for forested or open C3 environment, respectively. (13)C/(12)C from bone bioapatite, horn and hair of modern Southeast Asian mammals almost exclusively demonstrate C3 vegetation dominance. C4 consumption is rare in analysed modern species and it could be related to anthropogenic influences such as ingestion of domestic crops or livestock. Interesting implications emerge in the C4 vegetation distribution in southern Eurasian ecosystems, indicating that Southeast Asia, south of the Tibet, could be part of the global C4 vegetation spread, which occurred around 7 Ma. However, the C4 percentage in ecosystems varied geographically. Despite modern reversal towards C3 habitats due to factors such as increasing CO(2), we think that anthropological influences may be responsible for habitat and dietary changes in extant species. Bovids demonstrate the most significant shift in diet and habitat through time, from C4-dominated open habitats to C3-dominated habitats indicative of dense forest understory. PMID:20127068

  16. Tapping the Late Pleistocene-Holocene environmental change and alluvial geoarchaeology in Central Asia

    Science.gov (United States)

    Macklin, Mark; Panyushkina, Irina; Toonen, Willem; Chang, Claudia; Seitkaliyev, Meyram; Voyakin, Dmitry

    2015-04-01

    We integrate the environmental history derived from spatial-temporal variability of multi proxies and the prehistory of arid lands from archaeological data in Central Asia in order to determine the relationship between the Holocene river dynamics, climate change and floodwater farming. This study addresses to developing fluvial achieves and geoarcheological records from the Talgar catchment, a south-bank tributary of the Ili River and the Talas catchment, a east-bank tributary of the Syr Darya River, in the southern Kazakhstan. The catchments of these steppe rivers flowing northwest had favorable habitats for farming from the Eneolithic to the medieval period as appears from human settlement histories documented with archaeological surveys and in some cases excavations. The river development has been reconstructed over the last 20,000 years and the key archaeological sites have been dated with radiocarbon. Periods of Holocene river aggradation and high water in downstream Lake Balkhash and Aral Sea correspond with cooler and wetter neoglacial episodes while river entrenchment and floodplain soil development are associated with warmer and drier conditions. Floodwater farming in the Talgar River reached its height in the late Iron Age (400-200 cal. BC) with more than 70 settlement sites and 700 burial mounds, and in the Talas River during the medieval period. This corresponds to a period of reduced flood flows, river stability and glacier retreat in the Tien Shan headwaters. A new hydroclimatic-based model for the spatial and temporal dynamics of floodwater farming is proposed, which explains settlement patterns since the first documented use of irrigation in the Iron Age and medieval times. The undertaken research highlights the Holocene human adaptations to the environmental change of floodplains in Central Asia.

  17. Paleohydrology of the southern Great Basin, with special reference to water table fluctuations beneath the Nevada Test Site during the Late Pleistocene

    International Nuclear Information System (INIS)

    The magnitude of water table rise during Pleistocene pluvial climates, and of the resultant shortening of ground-water flow path and reduction in unsaturated zone thickness, is investigated. The distribution of calcitic veins in alluvium and lakebeds, and of tufa deposits, between the Ash Meadows spring discharge area and the Nevada Test Site suggests that discharge from the regional Paleozoic carbonate aquifer during the Late Pleistocene occurred at distances as much as 14 kilometers northeast of Ash Meadows and at altitudes up to 50 meters higher than at present. Use of the underflow equation (relating discharge to transmissivity, aquifer width, and hydraulic gradient), and various assumptions regarding pluvial recharge, transmissivity, and altitude of ground-water base level, suggest possible rises in potentiometric level in the carbonate aquifer of 6 to 90 meters beneath central Frenchman Flat, 58 kilometers northeast of Ash Meadows. During Wisconsin time the rise probably did not exceed 30 meters. Water-level rises beneath Frenchman Flat during future pluvials are unlikely to exceed 30 meters, and future levels might even be 10 meters lower than the modern one, 210 meters beneath the center of the valley. Neither the cited rise in potentiometric level in the regional carbonate aquifer, nor the shortened flow path during the Late Pleistocene precludes utilization of the NTS as a repository for high-level or transuranic-element radioactive wastes provided other requisite conditions are met at this site. Deep water tables, attendant thick (up to several hundred meter) unsaturated zones, and ground-water flow paths tens of kilometers in length characterized the region during Wisconsin time and possibly throughout the Pleistocene, and are likely to so characterize it during future pluvial climates

  18. Late Pleistocene Climate Events and The Origin of Agriculture In SW Asia

    Science.gov (United States)

    Rossignol-Strick, M.

    In the Eastern Mediterranean sea, the climate succession of the last deglaciation is documented and dated in marine cores by the d18-O variation of foraminiferal cal- cite and pollen records. The Last Glacial Maximum is identified by a large abundance of grass pollen from a prairie-type vegetal cover with low annual precipitation in the mountainous north and east borderlands of the sea, where the pollen mainly origi- nates. During the first phase of the last deglaciation, the Bolling/Allerod chronozone, the moisture availability increases and makes possible the spread of a deciduous for- est, as shown by the increasing pollen abundance of the deciduous oak. The cold and arid Younger Dryas is identified by a reversal to semi-desert conditions, with the in- crease of sage-brush (Artemisia) and the saline-tolerant Chenopodiaceae. The climate of the earliest Holocene is Optimum for at least 3000 years (9000-6000yr BP), with the largest spread of the deciduous forest at low-middle elevations signalling wet sum- mers and of the Pistacia woodland at low elevations signalling mild, no-frost winters. This is the time when the most recent sapropel deposited in the eastern Mediterranean under anoxic bottom conditions generated by a surface lid of lower salinity due to the concomitant largest floods of the Nile River fed by the strongest African monsoon rains in the Ethiopian Highlands. In SW Asia, the pollen records of lakes and marshes have been correlated with those of the marine cores, thereby obtaining a robust time-frame. In that area, the archaeo- logical data of human settlements are independently dated by 14C. Thus the archaeo- logical succession can be securely set against the well-dated climatic succession. The Late Palaeolithic populations of SW Asia were wandering hunter-gatherers in the prairies of the Last Glacial Maximum, where they already collected wild wheat, barley and fruit. With the Bolling/Allerod wetter and warmer climate, they began to settle in favourable locations, on a year-long or semi-permanent basis. They exploited, proba- bly more widely, the vegetal food resources of wild cereals and pulses. In Palestine, this culture is called Natufian. In Syria on the Middle Euphrates, the settlement at Tel Abu Hureira displays a first phase of occupation that yielded wild emmer wheat and two-row barley. These wild varieties of cereals are characterized by a brittle rachis of the ear that insures the wide dispersion of the spikelets at maturity. This Phase I came to an end with the abandonment of the site for several hundred years. The following occupation Phase II immediately yields the domesticated form of cereals, which are 1 mainly identified by the non-brittle, solid rachis at maturity. This mutant form makes possible for man to more efficiently collect the seeds with a sickle or a stick. Based on the local 14C dates, the settlement interruption is coeval with the cold, arid Younger Dryas, and the incipience of Phase II is coeval with the Climate Optimum of the early Holocene. It is striking that the domestication of emmer wheat appears to have taken place during the Younger Dryas. This strong climatic shift must somehow have constrained this most fundamental step in the globally earliest emergence of agriculture, that of SW Asia. The accumulation of grain surplus supported the human population increase that eventually led to the earliest emergence of urban civilization in SW Asia. 2

  19. A multiproxy reconstruction of the palaeoenvironment and palaeoclimate of the Late Pleistocene in northeastern Iberia: Cova dels Xaragalls, Vimbodí-Poblet, Paratge Natural de Poblet, Catalonia

    Science.gov (United States)

    López-García, Juan Manuel; Blain, Hugues-Alexandre; Bennàsar, Maria; Euba, Itxaso; Bañuls, Sandra; Bischoff, James; López-Ortega, Esther; Saladié, Palmira; Uzquiano, Paloma; Vallverdú, Josep

    2012-01-01

    The Cova dels Xaragalls is a small open karst system, located in the municipality of Vimbodí-Poblet (Tarragona, Catalonia, NE Spain). It is an important Holocene archaeological site that was inspected in the 1970s but from which little has been published. New excavations starting in 2008 have exposed a deep Late Pleistocene stratigraphical sequence. In this paper, we present for the first time palaeoenvironmental and palaeoclimatic reconstructions of this Late Pleistocene succession on the basis of both the small-vertebrate assemblages and the charcoals. Results from the small-vertebrate associations along the sequence indicate that the landscape had open-woodland habitats in the vicinity of the Cova del Xaragalls, with wet points in the surrounding area. Woodland habitats were dominant throughout the sequence, as evidenced by the abundance of the species Apodemus sylvaticus, but were better developed during warm periods (layers C5 and C8), whereas during cold periods (layers C4 and C3) the environment was slightly more humid in response to higher mean annual precipitation and the opening of the landscape. The charcoal analysis indicates that the woodland surrounding the cave was composed mainly of Pinus (more than 90% was identified as Pinus), but that during the cold period (C3–C4) it incorporated some Quercus ilex/coccifera and Angiosperm indet., probably linked with greater precipitation. Comparisons are made with other long palaeoenvironmental sequences from the northeastern Iberian Peninsula and with global marine isotopic curves, providing a scenario for the palaeoclimatic and palaeoenvironmental changes that occurred during the Late Pleistocene in the woodland areas surrounding the Cova dels Xaragalls.

  20. Influence of Late Pleistocene and Holocene climate on vegetation distributions in southwest Africa elucidated from sedimentary n-alkanes - Differences between 12°S and 20°S

    Science.gov (United States)

    Badewien, Tanja; Vogts, Angela; Dupont, Lydie; Rullkötter, Jürgen

    2015-10-01

    Global and local climatic forcing, e.g. concentration of atmospheric CO2 or insolation, influence the distribution of C3 and C4 plants in southwest Africa. C4 plants dominate in more arid and warmer areas and are favoured by lower pCO2 levels. Several studies have assessed past and present continental vegetation by the analysis of terrestrial n-alkanes in near-coastal deep sea sediments using single samples or a small number of samples from a given climatic stage. The objectives of this study were to evaluate vegetation changes in southwest Africa with regard to climatic changes during the Late Pleistocene and the Holocene and to elucidate the potential of single sample simplifications. We analysed two sediment cores at high resolution, altogether ca. 240 samples, from the Southeast Atlantic Ocean (20°S and 12°S) covering the time spans of 18 to 1 ka and 56 to 2 ka, respectively. Our results for 20°S showed marginally decreasing C4 plant domination (of ca. 5%) during deglaciation based on average chain length (ACL27-33 values) and carbon isotopic composition of the C31 and C33n-alkanes. Values for single samples from 18 ka and the Holocene overlap and, thus, are not significantly representative of the climatic stages they derive from. In contrast, at 12°S the n-alkane parameters show a clear difference of plant type for the Late Pleistocene (C4 plant domination, 66% C4 on average) and the Holocene (C3 plant domination, 40% C4 on average). During deglaciation vegetation change highly correlates with the increase in pCO2 (r² = 0.91). Short-term climatic events such as Heinrich Stadials or Antarctic warming periods are not reflected by vegetation changes in the catchment area. Instead, smaller vegetation fluctuations during the Late Pleistocene occur in accordance with local variations of insolation.

  1. Major features of Sundadonty and Sinodonty, including suggestions about East Asian microevolution, population history, and late Pleistocene relationships with Australian aboriginals.

    Science.gov (United States)

    Turner, C G

    1990-07-01

    The eight diagnostic morphological traits of the Sundadont and Sinodont divisions of the Mongoloid dental complex are identified. Intra- and intergroup variation for these crown and root features is plotted. The univariate frequency distributions provide useful evidence for several suggestions about East Asian prehistory, dental microevolution, and intergroup relationships. The case for local evolution of Sundadonty is strengthened by finding Australian teeth to be very similar to this pattern. Australian Aboriginal teeth are also generally like those of Jomonese and some Ainus, suggesting that members of the late Pleistocene Sundaland population could have initially colonized Sahulland as well as the continental shelf of East Asia northward to Hokkaido. PMID:2375382

  2. On the timing and forcing mechanisms of late Pleistocene glacial terminations: Insights from a new high-resolution benthic stable oxygen isotope record of the eastern Mediterranean

    Science.gov (United States)

    Konijnendijk, T. Y. M.; Ziegler, M.; Lourens, L. J.

    2015-12-01

    Benthic oxygen isotope records of deep marine sedimentary archives have yielded a wealth of information regarding ice sheet dynamics and climate change during the Pleistocene. However, since they often lack independent age control, these records are generally bound by a fixed phase relationship between orbital forcing and the climate response, e.g. ice volume changes. We present the first long (?1.2 Ma) benthic oxygen isotope record from the eastern Mediterranean, based on ODP Sites 967 and 968, which clearly reflects the behavior of global climate on a glacial-interglacial scale throughout the late Pleistocene time period. The age model for our record is based on tuning the elemental ratio of titanium versus aluminum (Ti/Al) against insolation. The Ti/Al record is dominated by the precession-related changes in northern African climate, i.e. monsoonal forcing, and hence largely independent of glacial-interglacial variability. We found the largest offset between our chronology and that of the widely applied, open ocean stacked record LR04 (Lisiecki and Raymo, 2005) for TVII (?624 ka), which occurred ?9 kyr earlier according to our estimates, though in agreement with the AICC2012 ?Dice chronology of EPICA Dome C (Bazin et al., 2013). Spectral cross-correlation analysis between our benthic ?18O record and 65°N summer insolation reveals significant amounts of power in the obliquity and precession range, with an average lag of 5.5 ± 0.8 kyr for obliquity, and 6.0 ± 1.0 kyr for precession. In addition, our results show that the obliquity-related time lag was smaller (3.0 ± 3.3 kyr) prior to ?900 ka than after (5.7 ± 1.1 kyr), suggesting that on average the glacial response time to obliquity forcing increased during the mid-Pleistocene transition, much later than assumed by Lisiecki and Raymo (2005). Finally, we found that almost all glacial terminations have a consistent phase relationship of ?45 ± 45° with respect to the precession and obliquity-driven increases in 65°N summer insolation, consistent with the general consensus that both obliquity and precession are important for deglaciation during the Late Pleistocene. Exceptions are glacial terminations TIIIb, T36 and potentially T32 (and TVII T24 and T34), which show this consistent phase relationship only with precession (only with obliquity). Our findings point towards an early (>1200 ka) onset of the Mid Pleistocene Transition. Vice versa, the timing of TVII, which can only be explained as a response to obliquity forcing, indicates that the transition lasted until at least after MIS 15.

  3. Sediment production and transport in the New Zealand Southern Alps - Canterbury sedimentary system during the Late Pleistocene: the influence of alpine glacial erosion on the marine stratigraphic record.

    Science.gov (United States)

    Villaseñor, T. G.; Jaeger, J. M.; Foster, D. A.

    2014-12-01

    Quaternary mountain glaciations have greatly modified landscape and sediment production, especially after the Mid Pleistocene Transition. However, the impact of increased glacigenic sediment yields on continental margin sedimentation is poorly documented during this period in which eustasy is proposed as the dominant control on margin development. We study the provenance of sediment accumulated in the continental shelf during the Late Pleistocene, by performing 40Ar/39Ar geochronology of the bulk silt-size fraction on sediment samples from three sites drilled during IODP Expedition 317 to Canterbury Basin, New Zealand. The results show ages that range from 25 to 90 Ma, which are significantly younger than the cooling ages of the potential rock sources (>100 Ma). Bedrock cooling ages similar to our results are found adjacent to the Main Divide Fault Zone, located near the main drainage divide in Central Southern Alps. This suggests that a large proportion of sediment accumulating in the continental shelf is sourced in this region of highest elevation and maximum glacial erosion. Sediment bulk ages in the cores show younger ages up-section, suggesting that contribution of young sediment has increased and/or that glaciers have eroded younger rocks with time. In addition, sediment ages are younger in the most landward site, while the most offshore site observes young ages later indicating that the input of young sediment across the continental shelf is progressive, likely by means of sediment reworking during sea level transgression and shoreline migration during sea level fall. We propose that sediment transfer from source to sink occurs in steps in which sediment undergoes several cycles of transport and storage until final accumulation. Glacial erosion plays a very important role in this sedimentary system, supplying sediment that is likely eroded in a zone of rock weakness. The age signature of the muddy sediment accumulating in the continental shelf likely reflects Late Pleistocene landscape evolution in the Southern Alps.

  4. Late Pleistocene and Holocene-Age Columbia River Sediments and Bedforms: Hanford Reach Area, Washington - Part 2

    Energy Technology Data Exchange (ETDEWEB)

    K.R. Fecht, T.E. Marceau

    2006-03-28

    This report presents the results of a geologic study conducted on the lower slopes of the Columbia River Valley in south-central Washington. The study was designed to investigate glaciofluvial and fluvial sediments and bedforms that are present in the river valley and formed subsequent to Pleistocene large-scale cataclysmic flooding of the region.

  5. Quantification of climate and vegetation from Southern African Middle Stone Age sites - an application using Late Pleistocene plant material from Sibudu, South Africa

    Science.gov (United States)

    Bruch, A. A.; Sievers, C.; Wadley, L.

    2012-04-01

    The isolated geographical situation of South Africa makes the unraveling of various parameters that influence its regional climate in time challenging. If the South African climate does not exhibit a linear correlation with global archives as suggested by some authors then the contribution of independent local data that provides direct information on the environment at a certain place and time is crucial. Fossil plant remains provide valuable information on past environmental conditions. Although few paleobotanical data are available from Southern Africa, some sites reveal rich and diverse fossil floras, most notably, Sibudu Cave, KwaZulu-Natal, South Africa, with its numerous fruits, seeds, pollen and charcoal flora. Such plant remains not only provide information on past vegetation, but also serve as a sound base for paleoclimate quantification with the Coexistence Approach (CA). Sibudu Cave has pulses of Middle Stone Age occupation separated by hiatuses that are as long as 10 ka. Pre-Still Bay, Still Bay, Howiesons Poort, post-Howiesons Poort and late and final Middle Stone Age industries are present. Variations in vegetation and the animals preyed on through time suggest that subtle environmental changes could have occurred during MIS4 and MIS3 in the Sibudu area. Whilst always semi-forested, the region may have comprised a mosaic of uneven and changeable patches of coastal forest and savanna. These in turn might have influenced the numbers of forest versus plains animals in the area. Cultural factors could also have played a part in the faunal variability observed in Sibudu. Preliminary analyses of Sibudu Cave material confirm the potential of the CA for its application on Late Pleistocene African floras. In the future, comparison with other contemporaneous sites will help quantify spatial differences in the climate of the Late Pleistocene in South Africa, and may answer if environmental changes effected the cultural development from Still Bay to late MSA industries.

  6. Acoustic stratigraphy of Bear Lake, Utah-Idaho: late Quaternary sedimentation patterns in a simple half-graben

    Science.gov (United States)

    Colman, Steven M.

    2006-01-01

    A 277-km network of high-resolution seismic-reflection profiles, supplemented with a sidescan-sonar mosaic of the lake floor, was collected in Bear Lake, Utah–Idaho, in order to explore the sedimentary framework of the lake's paleoclimate record. The acoustic stratigraphy is tied to a 120 m deep, continuously cored drill hole in the lake. Based on the age model for the drill core, the oldest continuously mapped acoustic reflector in the data set has an age of about 100 ka, although older sediments were locally imaged. The acoustic stratigraphy of the sediments below the lake indicates that the basin developed primarily as a simple half-graben, with a steep normal-fault margin on the east and a flexural margin on the west. As expected for a basin controlled by a listric master fault, seismic reflections steepen and diverge toward the fault, bounding eastward-thickening sediment wedges. Secondary normal faults west of the master fault were imaged beneath the lake and many of these faults show progressively increasing offset with depth and age. Several faults cut the youngest sediments in the lake as well as the modern lake floor. The relative simplicity of the sedimentary sequence is interrupted in the northwestern part of the basin by a unit that is interpreted as a large (4 × 10 km) paleodelta of the Bear River. The delta overlies a horizon with an age of about 97 ka, outcrops at the lake floor and is onlapped by much of the uppermost sequence of lake sediments. A feature interpreted as a wave-cut bench occurs in many places on the western side of the lake. The base of this bench occurs at a depth (22–24 m) similar to that (20–25 m) of the distal surface of the paleodelta. Pinch-outs of sedimentary units are common in relatively shallow water on the gentle western margin of the basin and little Holocene sediment has accumulated in water depths of less than 30 m. On the steep eastern margin of the basin, sediments commonly onlap the hanging wall of the East Bear Lake Fault. However, no major erosional or depositional features suggestive of shoreline processes were observed on acoustic profiles in water deeper than about 20–25 m.

  7. Secuencias pleistocenas «lujanenses» en su sección tipo: Primeras dataciones 14C e implicancias estratigráficas, arqueológicas e históricas, Luján - Jáuregui, provincia de Buenos Aires / Pleistocene Lujanense sequences in the type section: First 14C datings and their implications on stratigraphy, archaeology and history, Luján Jauregui, provincia de Buenos Aires

    Scientific Electronic Library Online (English)

    M.J., Toledo.

    2005-06-01

    Full Text Available Se dan a conocer las primeras dataciones 14C del Pleistoceno terminal o "Lujanense" en su sección tipo. Se propone un modelo secuencial preliminar en vista a ordenar las unidades litoestratigráficas y proveer un marco temporal a los descubrimientos arqueológicos del siglo XIX. Las secuencias lujanen [...] ses se datan entre >40.000 AP y >11.000 AP y se discuten las evidencias de poblamiento arcaico en este período. Se identifica la discordancia intralujanenense atribuida al comienzo del último máximo glaciario (LGM) en 30.000 AP. Son resultados preliminares de un proyecto de caracterización estratigráfica y arqueológica del Pleistoceno del nordeste pampeano. Abstract in english The main purpose of this note is to communicate the first 14C dating of the Pleistocene sequences in the Lujan type section. A preliminary sequence stratigraphy model is presented in order to organize the lithostratigrafic units and provide a coherent stratigraphic framework to XIX century archeolog [...] ical discoveries. "Lujanense" sequences are dated between > 40,000 and >11,000 BP and is discussed the peopling evidence within this time interval. The base sequence boundary of the last glacial maximum (LGM) is identified and called "intralujanense" at 30.000 BP. This is a preliminary result of an integral project on sequence stratigraphy and archeological characterization of the Pleistocene of the northeastern pampas.

  8. Preliminary Findings of the Balkan Paleo Project: Evidence of Human Activity at the “Gateway” of Europe During the Late Pleistocene

    Directory of Open Access Journals (Sweden)

    Tsanko Tzankov

    2012-12-01

    Full Text Available This paper describes the initial findings of the Balkan Paleo Project (BPP. The project seeks: 1 – to augment the evidence that can be used to test hypotheses about hominin and faunal dispersals into and out of Europe during the Pleistocene; 2 – to gather data for testing the hypotheses regarding the adaptation of early human populations to Eurasian ecosystems, the adjustment of their tool technologies, anatomical characteristics and behaviors in response to local climates and faunal evidence.These research objectives can only be achieved by identifying and excavating a broad spectrum of archaeological and paleontological sties that span the Pleistocene within the Balkan Peninsula. Results of BPP activities conducted in southern Bulgaria are reported here. These include excavations at the Arkata rockshelter and associated caves overlooking the Arda River near (Eastern Rhodopes, Krumovgrad district, the Leyarna caves and the previously known paleontological locality of Mechata Dupka (Strandzha Mountains, Malko Tarnovo district. These activities have expanded our understanding of ecological conditions along a potentially important pathway along which early humans may have dispersed into and out of Europe, and have for the first time documented the presence of Pleistocene humans within southeastern Bulgaria.

  9. Orogénesis y drenaje en la región del Valle de Lerma (cordillera oriental, Salta, Argentina durante el Pleistoceno Tardío Orogeny and drainage in the Lerma Valley region (Eastern Cordillera, Salta, Argentina during the late Pleistocene

    Directory of Open Access Journals (Sweden)

    Gustavo González Bonorino

    2012-03-01

    Full Text Available En el Pleistoceno tardío, luego de la incipiente elevación de las serranías subandinas, la contracción retornó al interior del orógeno. En aquel tiempo un piedemonte conectaba los contrafuertes occidentales de la Cordillera Oriental (sierras de Lesser y Obispo con la llanura subandina, a través de la región que hoy7 ocupan el valle de Lerma y la serranía Mojotoro-Castillejo. La contracción dio origen a las elevaciones interiores en la sierra de Vaqueros y los Cerrillos de San Miguel, y luego se propagó al este una falla que derivó en el desarrollo de la serranía Mojotoro-Castillejo y el cierre del valle de Lerma. Algunos ríos incidieron a través de las nacientes barreras topográficas mientras que otros fueron a una cuenca endorreica inundada por un antiguo lago Lerma. La capacidad de incisión fue mayor en el valle de Lerma septentrional, donde los ríos llegaban con gradientes de cauce elevados a los sitios de ascenso topográfico, y donde el río Mojotoro persistió como cauce antecedente. En el sur, el lago Lerma colmató la cuenca hasta un punto de derrame por bajos estructurales en capas del Grupo Salta, y el agua labró el cauce subsecuente del actual río Juramento a través de la sierra de Castillejo. Más de 800 m de sedimento (aquí denominado Grupo Valle de Lerma se acumularon en el valle de Lerma durante el Pleistoceno tardío. Información de subsuelo permite hacer una revisión crítica de la estratigrafía de este relleno y proponer una subdivisión más detallada. En particular se acota la extensión geográfica de la Formación Tajamar y se revisan las extrapolaciones que de ella se han hecho.In the late Pleistocene, following uplift of the first subandean ranges, contraction returned to the orogen interior. At the time, a wide piedmont connected the western ramparts of the Eastern Cordillera (Lesser and Obispo ranges to the subandean plain, spanning the zone presently occupied by the Lerma Valley and the Mojotoro and Castillejo ranges. Contraction gave rise to the interior Vaqueros Range and the San Mguel Hills, and then propagated eastward with a regional reverse fault that derived in the development of the Mojotoro and Castillejo ranges and closure of the Lerma Valley. Some river courses incised across the rising barriers, whereas others were diverted to an internally drained basin flooded by ancient Lake Lerma. Incision power was greater in the northern Lerma Valley, where the rivers reached the sites of topographic uplift with high bed gradients, and where the Mojotoro River persisted as an antecedent course. In the south, Lake Lerma filled the basin to a pour point through structural lows in Salta Group strata, and the issuing water carved the subsequent channel of the present Juramento River across the Castillejo Range. More than 800 m of sediment (herein designated Lerma Valley Group accumulated in the Lerma Valley during the late Pleistocene. Subsurface information allowed a critical revision of the stratigraphy of this fill and a more detailed subdivision. In particular, the geographical extension of the Tajamar Formation is restricted and previously proposed extrapolations for it are revised.

  10. Orogénesis y drenaje en la región del Valle de Lerma (cordillera oriental, Salta, Argentina) durante el Pleistoceno Tardío / Orogeny and drainage in the Lerma Valley region (Eastern Cordillera, Salta, Argentina) during the late Pleistocene

    Scientific Electronic Library Online (English)

    Gustavo, González Bonorino; Liliana, Del Valle Abascal.

    2012-03-01

    Full Text Available En el Pleistoceno tardío, luego de la incipiente elevación de las serranías subandinas, la contracción retornó al interior del orógeno. En aquel tiempo un piedemonte conectaba los contrafuertes occidentales de la Cordillera Oriental (sierras de Lesser y Obispo) con la llanura subandina, a través de [...] la región que hoy7 ocupan el valle de Lerma y la serranía Mojotoro-Castillejo. La contracción dio origen a las elevaciones interiores en la sierra de Vaqueros y los Cerrillos de San Miguel, y luego se propagó al este una falla que derivó en el desarrollo de la serranía Mojotoro-Castillejo y el cierre del valle de Lerma. Algunos ríos incidieron a través de las nacientes barreras topográficas mientras que otros fueron a una cuenca endorreica inundada por un antiguo lago Lerma. La capacidad de incisión fue mayor en el valle de Lerma septentrional, donde los ríos llegaban con gradientes de cauce elevados a los sitios de ascenso topográfico, y donde el río Mojotoro persistió como cauce antecedente. En el sur, el lago Lerma colmató la cuenca hasta un punto de derrame por bajos estructurales en capas del Grupo Salta, y el agua labró el cauce subsecuente del actual río Juramento a través de la sierra de Castillejo. Más de 800 m de sedimento (aquí denominado Grupo Valle de Lerma) se acumularon en el valle de Lerma durante el Pleistoceno tardío. Información de subsuelo permite hacer una revisión crítica de la estratigrafía de este relleno y proponer una subdivisión más detallada. En particular se acota la extensión geográfica de la Formación Tajamar y se revisan las extrapolaciones que de ella se han hecho. Abstract in english In the late Pleistocene, following uplift of the first subandean ranges, contraction returned to the orogen interior. At the time, a wide piedmont connected the western ramparts of the Eastern Cordillera (Lesser and Obispo ranges) to the subandean plain, spanning the zone presently occupied by the L [...] erma Valley and the Mojotoro and Castillejo ranges. Contraction gave rise to the interior Vaqueros Range and the San Mguel Hills, and then propagated eastward with a regional reverse fault that derived in the development of the Mojotoro and Castillejo ranges and closure of the Lerma Valley. Some river courses incised across the rising barriers, whereas others were diverted to an internally drained basin flooded by ancient Lake Lerma. Incision power was greater in the northern Lerma Valley, where the rivers reached the sites of topographic uplift with high bed gradients, and where the Mojotoro River persisted as an antecedent course. In the south, Lake Lerma filled the basin to a pour point through structural lows in Salta Group strata, and the issuing water carved the subsequent channel of the present Juramento River across the Castillejo Range. More than 800 m of sediment (herein designated Lerma Valley Group) accumulated in the Lerma Valley during the late Pleistocene. Subsurface information allowed a critical revision of the stratigraphy of this fill and a more detailed subdivision. In particular, the geographical extension of the Tajamar Formation is restricted and previously proposed extrapolations for it are revised.

  11. Thorough assessment of DNA preservation from fossil bone and sediments excavated from a late Pleistocene-Holocene cave deposit on Kangaroo Island, South Australia

    Science.gov (United States)

    Haouchar, Dalal; Haile, James; McDowell, Matthew C.; Murray, Dáithí C.; White, Nicole E.; Allcock, Richard J. N.; Phillips, Matthew J.; Prideaux, Gavin J.; Bunce, Michael

    2014-01-01

    Fossils and sediments preserved in caves are an excellent source of information for investigating impacts of past environmental changes on biodiversity. Until recently studies have relied on morphology-based palaeontological approaches, but recent advances in molecular analytical methods offer excellent potential for extracting a greater array of biological information from these sites. This study presents a thorough assessment of DNA preservation from late Pleistocene-Holocene vertebrate fossils and sediments from Kelly Hill Cave Kangaroo Island, South Australia. Using a combination of extraction techniques and sequencing technologies, ancient DNA was characterised from over 70 bones and 20 sediment samples from 15 stratigraphic layers ranging in age from >20 ka to ˜6.8 ka. A combination of primers targeting marsupial and placental mammals, reptiles and two universal plant primers were used to reveal genetic biodiversity for comparison with the mainland and with the morphological fossil record for Kelly Hill Cave. We demonstrate that Kelly Hill Cave has excellent long-term DNA preservation, back to at least 20 ka. This contrasts with the majority of Australian cave sites thus far explored for ancient DNA preservation, and highlights the great promise Kangaroo Island caves hold for yielding the hitherto-elusive DNA of extinct Australian Pleistocene species.

  12. Stratigraphy, foraminiferal assemblages and paleoenvironments in the Late Cretaceous of the Upper Magdalena Valley, Colombia (part I)

    Science.gov (United States)

    Vergara, Luis S.

    1997-03-01

    The present work focuses on the Cretaceous record (Middle Albian-Maastrichtian) of the Upper Magdalena Valley (UMV), with a scope that covers facies and biofacies. The nomenclatural scheme previously stated for the Girardot-Guataqui area is here extended and proposed for all the basin, the following fomational units being characterized in detail. The Hondita Formation (Middle Albian-late Turonian), placed on top of the Caballos Formation, is separated from the Lomagorda Formation (late Turonian-early Santonian) by a chert interval within a succession of predominantly dark shales deposited in outer shelf environments. The Olini Group (early Santonian-late Campanian) presents two conspicuous chert units (Lidita Inferior and Superior) overlain by the Nivel de Lutitas y Arenas (early Maastrichtian). The sandstones of La Tabla and finally the mudstones of the Seca Formation (Maastrichtian) represent diverse littoral environments of the end of the Cretaceous. In the UMV, the Cretaceous system attains approximately 1350 m of thickness. Within the paleogeographic scenario, the drowning of the basin and of the adjacent Central Cordillera during most of the Late Cretaceous enabled upwelling currents and the development of widespread pelagic sediments. These sediments graded to shallower water deposits towards the south of the basin. In the Upper Cretaceous, four sequences of second order can be identified. The longer cycle begins at the base of the Hondita Formation and exhibits the maximum flooding in the Cenomanian condensed section of this unit. Following this cycle, three successive sudden sea level drops mark the boundaries of complete sequences, each comprising well developed lowstand, transgressive and highstand system tracts. After the last cycle was completed, the basin was uplifted and rocks of the Seca Formation were cannibalized by fluvial processes during the Tertiary. An angular unconformity that truncates this unit represents the uppermost sequence boundary of the Cretaceous megasequence.

  13. LITHIC TECHNOLOGY STUDIES IN COLOMBIA DURING THE LATE PLEISTOCENE AND EARLY HOLOCENE / ESTUDIOS DE LA TECNOLOGÍA LÍTICA EN COLOMBIA ENTRE EL PLEISTOCENO FINAL Y EL HOLOCENO TEMPRANO

    Scientific Electronic Library Online (English)

    Francisco Javier, Aceituno; Sneider, Rojas-Mora.

    Full Text Available En este artículo se presenta una sinopsis de las investigaciones arqueológicas que se refieren a la tecnología lítica de los grupos humanos que poblaron el territorio colombiano entre el Pleistoceno Final y el Holoceno Temprano. Como metodología se ha optado por documentar y comparar regionalmente l [...] os análisis de tecnología y así demostrar las diferencias en los enfoques teóricos y metodológicos aplicados en las diferentes investigaciones que se han ocupado del tema. Abstract in english This paper provides an overview of the lithic technology of human groups that inhabited Colombian territory between the Late Pleistocene and the early Holocene. The chosen methodology was to document and compare the lithic technology regionally, in order to show the differences in theoretical and me [...] thodological approaches applied.

  14. LITHIC TECHNOLOGY STUDIES IN COLOMBIA DURING THE LATE PLEISTOCENE AND EARLY HOLOCENE / ESTUDIOS DE LA TECNOLOGÍA LÍTICA EN COLOMBIA ENTRE EL PLEISTOCENO FINAL Y EL HOLOCENO TEMPRANO

    Scientific Electronic Library Online (English)

    Francisco Javier, Aceituno; Sneider, Rojas-Mora.

    2015-03-01

    Full Text Available En este artículo se presenta una sinopsis de las investigaciones arqueológicas que se refieren a la tecnología lítica de los grupos humanos que poblaron el territorio colombiano entre el Pleistoceno Final y el Holoceno Temprano. Como metodología se ha optado por documentar y comparar regionalmente l [...] os análisis de tecnología y así demostrar las diferencias en los enfoques teóricos y metodológicos aplicados en las diferentes investigaciones que se han ocupado del tema. Abstract in english This paper provides an overview of the lithic technology of human groups that inhabited Colombian territory between the Late Pleistocene and the early Holocene. The chosen methodology was to document and compare the lithic technology regionally, in order to show the differences in theoretical and me [...] thodological approaches applied.

  15. Geomagnetic modulation of the late Pleistocene cosmic-ray flux as determined by 10Be from Blake Outer Ridge marine sediments

    International Nuclear Information System (INIS)

    The cosmic-ray flux incident upon the Earth during the late Pleistocene, 20-60 kyr B.P., was studied by measuring the cosmogenic radionuclide 10Be from a marine sediment core at site CH88-10P on the Blake Outer Ridge. The paleointensity of the geomagnetic field for this core was determined by various methods. The variance in the concentration of 10Be in the authigenic fraction of the sediments from Blake Ridge closely correlates with the inverse of the variance in the paleointensity of the geomagnetic field. The 10Be signal lags, up to 1000 years of sedimentation, the measured paleointensity of the sediments. In contrast, the data from several other elements, some climatically sensitive, and from beryllium show relationship neither to 10Be nor to the paleomagnetic data. The relationship between 10Be concentration and the dipole field intensity (M/Mo) as measured in the sediments is consistent with theoretical models

  16. The Palos Verdes Fault offshore Southern California: Late Pleistocene to present tectonic geomorphology, seascape evolution, and slip rate estimate based on AUV and ROV surveys

    Science.gov (United States)

    Brothers, Daniel S.; Conrad, James E.; Maier, Katherine L.; Paull, Charles K.; McGann, Mary; Caress, David W.

    2015-07-01

    The Palos Verdes Fault (PVF) is one of few active faults in Southern California that crosses the shoreline and can be studied using both terrestrial and subaqueous methodologies. To characterize the near-seafloor fault morphology, tectonic influences on continental slope sedimentary processes and late Pleistocene to present slip rate, a grid of high-resolution multibeam bathymetric data, and chirp subbottom profiles were acquired with an autonomous underwater vehicle (AUV) along the main trace of PVF in water depths between 250 and 600 m. Radiocarbon dates were obtained from vibracores collected using a remotely operated vehicle (ROV) and ship-based gravity cores. The PVF is expressed as a well-defined seafloor lineation marked by subtle along-strike bends. Right-stepping transtensional bends exert first-order control on sediment flow dynamics and the spatial distribution of Holocene depocenters; deformed strata within a small pull-apart basin record punctuated growth faulting associated with at least three Holocene surface ruptures. An upper (shallower) landslide scarp, a buried sedimentary mound, and a deeper scarp have been right-laterally offset across the PVF by 55 ± 5, 52 ± 4 , and 39 ± 8 m, respectively. The ages of the upper scarp and buried mound are approximately 31 ka; the age of the deeper scarp is bracketed to 17-24 ka. These three piercing points bracket the late Pleistocene to present slip rate to 1.3-2.8 mm/yr and provide a best estimate of 1.6-1.9 mm/yr. The deformation observed along the PVF is characteristic of strike-slip faulting and accounts for 20-30% of the total right-lateral slip budget accommodated offshore Southern California.

  17. Leafcutter bee nests and pupae from the Rancho La Brea Tar Pits of Southern California: implications for understanding the paleoenvironment of the Late Pleistocene.

    Science.gov (United States)

    Holden, Anna R; Koch, Jonathan B; Griswold, Terry; Erwin, Diane M; Hall, Justin

    2014-01-01

    The Rancho La Brea Tar Pits is the world's richest and most important Late Pleistocene fossil locality and best renowned for numerous fossil mammals and birds excavated over the past century. Less researched are insects, even though these specimens frequently serve as the most valuable paleoenvironemental indicators due to their narrow climate restrictions and life cycles. Our goal was to examine fossil material that included insect-plant associations, and thus an even higher potential for significant paleoenviromental data. Micro-CT scans of two exceptionally preserved leafcutter bee nest cells from the Rancho La Brea Tar Pits in Los Angeles, California reveal intact pupae dated between ?23,000-40,000 radiocarbon years BP. Here identified as best matched to Megachile (Litomegachile) gentilis Cresson (Hymenoptera: Megachilidae) based on environmental niche models as well as morphometrics, the nest cells (LACMRLP 388E) document rare preservation and life-stage. The result of complex plant-insect interactions, they offer new insights into the environment of the Late Pleistocene in southern California. The remarkable preservation of the nest cells suggests they were assembled and nested in the ground where they were excavated. The four different types of dicotyledonous leaves used to construct the cells were likely collected in close proximity to the nest and infer a wooded or riparian habitat with sufficient pollen sources for larval provisions. LACMRLP 388E is the first record of fossil Megachile Latreille cells with pupae. Consequently, it provides a pre-modern age location for a Nearctic group, whose phylogenetic relationships and biogeographic history remain poorly understood. Megachile gentilis appears to respond to climate change as it has expanded its distribution across elevation gradients over time as estimated by habitat suitability comparisons between low and high elevations; it currently inhabits mesic habitats which occurred at a lower elevation during the Last Glacial Maximum ?21,000 years ago. Nevertheless, the broad ecological niche of M. gentilis appears to have remained stable. PMID:24718701

  18. Late Pliocene and early Pleistocene environments of the north-eastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    Directory of Open Access Journals (Sweden)

    A. A. Andreev

    2013-08-01

    Full Text Available The 318 m thick lacustrine sediment record in Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities allowing the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments show their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.50–3.35 Myr BP the vegetation at Lake El'gygytgyn, in nowadays tundra area, was dominated by spruce-larch-fir-hemlock forests. After ca. 3.4 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental changes took place at ca. 3.305–3.275 Myr BP, corresponding with the Marine Isotope Stage (MIS M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated in the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.04–3.02, 2.93–2.91, and 2.725–2.695 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Revealed peaks in green algae colonies (Botryococcus around 2.53, 2.45, 2.320–2.305 and 2.175–2.150 Myr BP suggest a spread of shallow water environments. Few intervals (i.e. 2.55–2.53, ca. 2.37, and 2.35–2.32 Myr BP with a higher presence of coniferous taxa (mostly pine and larch document some relatively short-term climate ameliorations.

  19. Late Pliocene and early Pleistocene environments of the north-eastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    Science.gov (United States)

    Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M.

    2013-08-01

    The 318 m thick lacustrine sediment record in Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities allowing the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments show their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.50-3.35 Myr BP the vegetation at Lake El'gygytgyn, in nowadays tundra area, was dominated by spruce-larch-fir-hemlock forests. After ca. 3.4 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental changes took place at ca. 3.305-3.275 Myr BP, corresponding with the Marine Isotope Stage (MIS) M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated in the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.04-3.02, 2.93-2.91, and 2.725-2.695 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Revealed peaks in green algae colonies (Botryococcus) around 2.53, 2.45, 2.320-2.305 and 2.175-2.150 Myr BP suggest a spread of shallow water environments. Few intervals (i.e. 2.55-2.53, ca. 2.37, and 2.35-2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively short-term climate ameliorations.

  20. Sedimentation and erosion processes in Middle to Late Pleistocene sequences exposed in the brickyard of Langenlois/Lower Austria

    DEFF Research Database (Denmark)

    Thiel, Christine; Terhorst, Birgit

    2011-01-01

    The correlation of sedimentary and pedogenetic processes in Lower Austria is difficult due to significant discontinuities and local variability in soil formation. This hampers landscape reconstruction at a regional scale. However, at a local scale distinct landscape formation processes represented by a shift from fluvial to aeolian deposition can be observed in the brickyard of Langenlois, Lower Austria. Sedimentological and mineralogical analyses in combination with palaeontological finds suggest that the fluvial deposition took place during the Middle Pleistocene. This attribution is confirmed by infra-red stimulated luminescence (IRSL) dating, which gives a minimum age of 300 ka for the palaeosurface on which the fluvial sediments were deposited. This is consistent with a small faunal assemblage including Stephanorhinus sp., Dama sp. and an alcine cervid. Such a fauna is previously unknown in Austria; it indicates a Middle Pleistocene interglacial period. The low degree of weathering as well as Cryosols found in the loess sequence point to loess accumulation during the Last Glacial; the dating results (35–55 ka) indicate prolonged loess deposition. No signs of pedogenesis could be found; this is surprising because in other areas this period is known for weak soil development. The lack of soil formation seems to be specific to the western part of Lower Austria, as is the complete erosion of the last glacial maximum (LGM) loess, which can not be found at Langenlois.

  1. K-Ar ages and paleomagnetism of Pliocene-Pleistocene pyroclastic rocks from northern Tokachi, Hokkaido

    International Nuclear Information System (INIS)

    K-Ar ages were determined on five samples of pyroclastic rocks from northern Tokachi, Hokkaido, and the results were discussed in reference to paleomagnetic, stratigraphic, and paleontological evidence for these rocks. All K-Ar ages obtained are consistent rather well with the stratigraphy and also with the magnetostratigraphy of the rocks. A sample of Meto welded tuff and a rhyolitic welded tuff collected from the downstream of the Osoushi River give nearly the same age of about 2.8 m.y., indicating successive extrusion in the late Pliocene. The Upper Osarushinai Formation is supposed to have been deposited in the early Pleistocene, based on the age obtained from an obsidian clast included in it. The Pliocene-Pleistocene boundary is not defined strictly, but it is supposed to exist in some horizon between the Ikeda and the Upper Osarushinai Formations. (author)

  2. Late Pleistocene-Holocene ground surface heat flux changes reconstructed from borehole temperature data (the Urals, Russia)

    Science.gov (United States)

    Demezhko, D. Y.; Gornostaeva, A. A.

    2015-04-01

    We use geothermal reconstruction of the ground surface temperature (GST) history early obtained in the Middle Urals to determine the surface heat flux (SHF) history over the past 35 kyr. A new algorithm of GST-SHF transformation was applied to solve this problem. The timescale of geothermal reconstructions has been corrected by comparing the estimated heat flux and annual insolation at the latitude of 60° N. The consistency of SHF and insolation changes on the interval 35-6 kyr BP with the linear correlation coefficient R = 0.99 points to orbital factors as the main cause of climatic changes during the Pleistocene-Holocene transition. The amplitude of SHF variations is about 1.3% of the insolation change amplitude. The increase of carbon dioxide concentrations lagged by 2-3 kyr from the SHF increase and occurred synchronously with GST changes.

  3. Stratigraphy and Structure of Late Oligocene-Early Miocene Ignimbrite-filled Paleovalleys, Northern Sierra Nevada, California

    Science.gov (United States)

    Rood, D. H.; Busby, C. J.; Wagner, D.

    2003-12-01

    Mapping of a Late Oligocene-Early Miocene (31-25 Ma) paleovalley system filled with ignimbrites erupted from calderas in present-day Nevada provides relationships necessary to deduce paleotopographic vs. structural controls on the paleogeography of the Sierra Nevada and its transition into the Basin and Range in Early Tertiary time. A paleovalley filled with five distinctive ignimbrites is well-exposed in the Diamond Mountains about 2 -3 km west of the Honey Lake fault zone, a segment of the northern Walker Lane fault zone. We map a N-S trending paleovalley approximately 7.2 km wide, using ignimbrite distributions and thicknesses of ignimbrites and sedimentary rocks, as well as compaction foliation, cooling joints, welding zonation and lateral variations within each ignimbrite. Paleotopographic relief in the metamorphic and granitic basement reaches approximately 223 m; metamorphic roof pendants form steep-sided paleo-ridges and spires, while the granitic basement forms stepped relief controlled by pre-existing joints. The five ignimbrites are composed of at least nine mappable cooling units that vary laterally, from ca. 260 m thick paleovalley axis deposits to ca. 70 m thick paleovalley wall deposits, with dramatic thickening of vitrophyres toward paleovalley walls. The lowest three ignimbrites are confined to the paleovalley, the fourth passes upward from confined to unconfined, and the fifth is entirely unconfined. All of the ignimbrites are cut by two N-S trending, steeply W-dipping faults; the first, near the axis of the paleovalley, shows maximum 85 m of dip-slip displacement, and the second, near the eastern margin of the paleovalley, shows ca. 40 m of dip slip displacement. These N-S faults parallel the paleovalley and are oblique to the modern (NW-trending) Honey Lake fault zone, suggesting they may be older. Evidence for syndepositional faulting is present along the paleovalley axis fault, where sedimentary rocks between ignimbrites 3 and 4 thicken from several meters to 60 m onto the downthrown block, and along the fault near the eastern paleovalley margin, where ignimbrite 4 thickens from 50 to 90 m onto the downthrown block. We correlate ignimbrite units 3, 4 and 5 of the Diamond Mountains with ignimbrites filling paleovalley erosional remnants near Frenchman Lake (26 km to the SSE), Haskell Peak (52 km to the SSW), and Soda Springs (91 km to the S). At Soda Springs (located 8 km SW of Donner Pass) the N-S trending paleovalley is about 6 km wide. The western paleovalley wall is composed of metamorphic basement rock and is steep, with paleotopographic relief of at least 280 m, whereas the eastern side of the paleovalley is predominantly granitic and is characterized by less dramatic relief. The paleovalley contains seven ignimbrites composed of at least ten cooling units. We correlate units 1, 4 and 7 of the Soda Springs paleovalley with units 3, 4, and 5 of the Diamond Mountains paleovalley, on the basis of petrographic and outcrop characteristics. The ignimbrite sequence is 323 m thick, and has mappable erosional unconformities with relief of up to 30 m between units 4, 5 and 6. The upper three units locally spread beyond the paleovalley walls. We have not recognized any faults in this paleovalley. Late Oligocene-Early Miocene ignimbrite-filled paleovalleys in the Diamond Mountains, Frenchman Lake, Haskell Peak and Soda Springs may represent remnants of a once-continuous valley 117 km long that trended obliquely to, and presumably crossed, the modern range front faults prior to their development.

  4. Possible Late Pleistocene volcanic activity on Nightingale Island, South Atlantic Ocean, based on geoelectrical resistivity measurements, sediment corings and (14)C dating

    DEFF Research Database (Denmark)

    BjØrk, Anders Anker; Björck, Svante

    2011-01-01

    Tristan da Cunha is a volcanic island group situated in the central South Atlantic. The oldest of these islands, Nightingale Island, has an age of about 18Ma. In the interior of the island, there are several wetlands situated in topographic depressions. The ages of these basins have been unknown, and their genesis has been debated. Aiming towards the reconstruction of the geomorphological history of these basins, we conducted geoelectrical resistivity measurements to map the subsurface topography, extracted peat and sediment cores and dated the onset of sedimentation applying the radiocarbon method. The irregular shapes of the basins and the lack of clear erosional features indicate that they are not eruption craters and were not formed by erosion. Instead, we regard them as morphological depressions formed between ridges of trachytic lava flows and domes at a late stage of the formation of the volcanic edifice. The onset of sedimentation within these basins appears to have occurred between 24 and 37 ka with the highest situated wetland yielding the highest ages. These ages are very young compared to the timing of the main phase of the formation of the island, implying volcanic activity on the island during the Late Pleistocene.

  5. Evidence for geographic variation in the diets of late Pleistocene and early Holocene Bison in North America, and differences from the diets of recent Bison

    Science.gov (United States)

    Rivals, Florent; Solounias, Nikos; Mihlbachler, Matthew C.

    2007-11-01

    During the late Pleistocene and early Holocene , Bison was widely dispersed across North America and occupied most regions not covered by ice sheets. A dietary study on Bison paleopopulations from Alaska, New Mexico, Florida, and Texas was performed using two methods that relate dental wear patterns to diet, mesowear analysis and microwear analysis. These data were compared to a mixed sample of extant Bison from the North American central plains, extant wood Bison from Alberta (Canada) and a variety of other modern ungulates. Mesowear relates macroscopic molar facet shape to levels of dietary abrasion. The mesowear signature observed on fossil Bison differs significantly from the hyper-abrasive grazing diet of extant Bison. Tooth microwear examines wear on the surface of enamel at a microscopic scale. The microwear signal of fossil samples resembles to modern Bison, but the fossil samples show a greater diversity of features, suggesting that fossil Bison populations regularly consumed food items that are texturally inconsistent with the short-grass diet typical of modern plains Bison. Mesowear and microwear signals of fossil Bison samples most closely resemble a variety of typical mixed feeding ungulates, all with diets that are substantially less abrasive than what is typical for modern plains Bison. Furthermore, statistical tests suggest significant differences between the microwear signatures of the fossil samples, thus revealing geographic variability in Pleistocene Bison diets. This study reveals that fossils are of value in developing an understanding of the dietary breadth and ecological versatility of species that, in recent times, are rare, endangered, and occupy only a small remnant of their former ranges.

  6. Sequence stratigraphy and architectural variability in Late Eocene lacustrine strata of the Dongying Depression, Bohai Bay Basin, Eastern China

    Science.gov (United States)

    Feng, Youliang; Li, Sitian; Lu, Yongchao

    2013-09-01

    Stratigraphic sequences and architectural variability in the Late Eocene lacustrine strata of the Dongying Depression, eastern China, were investigated using the interpretation of 2-D and 3-D high-resolution seismic profiles, analysis of spontaneous potential and resistivity curves, and observation of drill cores. Four third-order sequences controlled by syndepositional faults or fault slope break zones were identified, based on the characteristics of sequence boundaries and sedimentary successions. The architecture of the sequences in the different structural belts of the depression is complicated by the relationship between the rate at which fault-controlled accommodation was created and the rate of sediment supply. At fault margins, the rate of sediment supply exceeded accommodation space. Here, lowstand systems tracts consist of lowstand fan deltas with small progradational to retrogradation stacking patterns controlled by steeply dipping, parallel and cross-shaped syndepositional faults or fault slope-break zones; transgressive systems tracts consist of fan deltas with retrogradational to aggradational stacking patterns; and highstand systems tracts consist of fan deltas with normal regressive or progradational stacking pattern. At hinged margins, the rate of sediment supply was equal to or exceeded accommodation controlled by faults. Lowstand systems tracts at hinged margins consist of incised channel fills deposited on the landward side of gently dipping parallel and broom-shaped syndepositional faults or fault slope break zones and lowstand fans or sublacustrine fans deposited on the shores of lakes. Transgressive systems tracts consist of delta systems and shore to shallow-lake subfacies with retrogradational stacking patterns. Highstand systems tracts consist of braided deltas and fluvial delta systems with progradational or normal regressive and aggradational stacking patterns. Along the axis, the rate of sediment supply far exceeded accommodation. Only the lowstand systems tracts developed, consisting of lowstand deltas deposited on the landward side of the syndepositional faults or fault slope break zones, and lowstand fans or sublacustrine fans deposited on the lakeward side of the zones. Here, transgressive systems tracts consist of thin, deep lacustrine deposits and fluvial delta systems with retrogradational or transgressive stacking patterns; and highstand systems tracts consist of thick fluvial delta systems with a progradational configuration or normal regressive stacking patterns. The four kinds of syndepositional fault slope-break zones controlled the stratal architecture of sequences and the distribution of lowstand systems tracts. Sand bodies within lowstand systems tracts provide suitable conditions for the formation of hydrocarbon reservoirs when they are overlain by sediments from transgressive systems tracts, and are therefore favorable sites for lithostratigraphic trap exploration.

  7. Late Holocene coastal stratigraphy of Sitkinak Island reveals Aleutian-Alaska megathrust earthquakes and tsunamis southwest of Kodiak Island

    Science.gov (United States)

    Nelson, A. R.; Briggs, R. W.; Kemp, A.; Haeussler, P. J.; Engelhart, S. E.; Dura, T.; Angster, S. J.; Bradley, L.

    2012-12-01

    Uncertainty in earthquake and tsunami prehistory of the Aleutian-Alaska megathrust westward of central Kodiak Island limit assessments of southern Alaska's earthquake hazard and forecasts of potentially damaging tsunamis along much of North America's west coast. Sitkinak Island, one of the Trinity Islands off the southwest tip of Kodiak Island, lies at the western end of the rupture zone of the 1964 Mw9.2 earthquake. Plafker reports that a rancher on the north coast of Sitkinak Island observed ~0.6 m of shoreline uplift immediately following the 1964 earthquake, and the island is now subsiding at about 3 mm/yr (PBO GPS). Although a high tsunami in 1788 caused the relocation of the first Russian settlement on southwestern Kodiak Island, the eastern extent of the megathrust rupture accompanying the tsunami is uncertain. Interpretation of GPS observations from the Shumagin Islands, 380 km southwest of Kodiak Island, suggests an entirely to partially creeping megathrust in that region. Here we report the first stratigraphic evidence of tsunami inundation and land-level change during prehistoric earthquakes west of central Kodiak Island. Beneath tidal and freshwater marshes around a lagoon on the south coast of Sitkinak Island, 27 cores and tidal outcrops reveal the deposits of four to six tsunamis in 2200 years and two to four abrupt changes in lithology that may correspond with coseismic uplift and subsidence over the past millennia. A 2- to 45-mm-thick bed of clean to peaty sand in sequences of tidal sediment and freshwater peat, identified in more than one-half the cores as far inland as 1.5 km, was probably deposited by the 1788 tsunami. A 14C age on Scirpus seeds, double 137Cs peaks at 2 cm and 7 cm depths (Chernobyl and 1963?), a consistent decline in 210Pb values, and our assumption of an exponential compaction rate for freshwater peat, point to a late 18th century age for the sand bed. Initial 14C ages suggest that two similar extensive sandy beds, identified in eight cores at higher tidal and freshwater sites, date from about 1.5 ka and 2.0 ka, respectively. A younger silty sand bed, <10 cm beneath the now-eroding low marsh around the lagoon, may record the 1964 tsunami. Correlations of two to three other sandy beds are too uncertain to infer their deposition by tsunamis. Stratigraphic contacts found only in cores and outcrops of the <0.8- to 1-ka tidal section fringing the lagoon may mark coseismic uplift (peat over tidal mud, sometimes with intervening sand) or subsidence (tidal mud over peat, sometimes with intervening sand). We collected samples of modern tidal foraminifera along three elevational transects for the baseline dataset needed to use fossil assemblages to measure the amount of uplift or subsidence recorded by contacts. Foraminiferal assemblages above and below one contact confirm rapid uplift a few hundred years before the 1788 tsunami, but cores are too few to correlate this contact with any of the sandy beds that we infer were deposited by tsunamis farther inland. These initial results demonstrate the promise of this previously unexplored island and similar sites for using stratigraphic evidence of sudden land-level changes and high tsunamis to map prehistoric ruptures of the Aleutian-Alaskan megathrust.

  8. Simulated Trends in African Glacial and Interglacial Vegetation: Implications for Late-Pleistocene Hominid-Plant Interactions

    Science.gov (United States)

    Cowling, S. A.; Cox, P. M.; Jones, C. D.; Maslin, M. A.; Spall, S. A.

    2004-12-01

    Most theories of human evolution in south, central and eastern Africa are predicated on the assumption that savannas and grasslands almost exclusively dominated Pleistocene (glacial) landscapes. It was our aim to evaluate this assumption using a state-of-the-art fully-coupled earth system model (HadCM3LC), which we used to predict potential palaeovegetation following representative glacial and interglacial climate-forcing. Our glacial simulations indicate that tropical broadleaf forest was not severely displaced by grassland expanding into central Africa, although the outer extent of closed forest decreases, particularly in the north. Our vegetation-climate simulations also indicate that the extent of closed tropical forest during typical interglacials is not represented by today's observed vegetation distributions. Simulated interglacial climate results in expansion of tropical forest from coast-to-coast across much of central Africa. Our modelling experiments have implications for interpreting biogeography and phylogenies of various African plant and animal species, including the evolution of our own species, Homo sapiens sapiens.

  9. East-west genetic differentiation in Musk Ducks (Biziura lobata) of Australia suggests late Pleistocene divergence at the Nullarbor Plain

    Science.gov (United States)

    Guay, P.-J.; Chesser, R.T.; Mulder, R.A.; Afton, A.D.; Paton, D.C.; McCracken, K.G.

    2010-01-01

    Musk Ducks (Biziura lobata) are endemic to Australia and occur as two geographically isolated populations separated by the Nullarbor Plain, a vast arid region in southern Australia. We studied genetic variation in Musk Duck populations at coarse (eastern versus western Australia) and fine scales (four sites within eastern Australia). We found significant genetic structure between eastern and western Australia in the mtDNA control region (??ST = 0. 747), one nuclear intron (??ST = 0.193) and eight microsatellite loci (FST = 0.035). In contrast, there was little genetic structure between Kangaroo Island and adjacent mainland regions within eastern Australia. One small population of Musk Ducks in Victoria (Lake Wendouree) differed from both Kangaroo Island and the remainder of mainland eastern Australia, possibly due to genetic drift exacerbated by inbreeding and small population size. The observed low pairwise distance between the eastern and western mtDNA lineages (0.36%) suggests that they diverged near the end of the Pleistocene, a period characterised by frequent shifts between wet and arid conditions in central Australia. Our genetic results corroborate the display call divergence and Mathews' (Austral Avian Record 2:83-107, 1914) subspecies classification, and confirm that eastern and western populations of Musk Duck are currently isolated from each other. ?? 2010 Springer Science+Business Media B.V.

  10. The recovery of ancient DNA from Dasypus bellus provides new possibilities for investigating late Pleistocene mammal response to climate change

    Science.gov (United States)

    Letts, Brandon; Shapiro, Beth

    2010-05-01

    Dasypus bellus, the 'beautiful armadillo,' is well known as a casualty of the Pleistocene megafaunal mass extinction event. Appearing in the fossil record about 2.5 Mya, D. bellus was widespread throughout the mid to southern United States and Mexico until it went extinct by about 10 kya. It was replaced by D. novemcinctus, the nine-banded armadillo, which is morphologically identical but smaller. The exact taxonomic status of D. bellus and its phylogenetic relationship with D. novemcinctus has been a subject of debate. In particular, it remains unresolved whether D. bellus was more closely related to North American than South American D. novemcinctus. To address this, we extracted and sequenced fragments of ancient mitochondrial DNA from surprisingly well-preserved remains of D. bellus recovered from Mefford Cave in Florida. Our results reveal a surprisingly close relationship between the extinct D. bellus and North American D. novemcinctus. Although southern climates have been considered inhospitable for the preservation of ancient DNA, thousands of bones per individual and the propensity of the armadillo to seek out shelter in caves makes preservation more likely than for other organisms. The armadillo may therefore make an excellent proxy organism for investigating the influence of climate change on animal populations south of the cold permafrost regions.

  11. Age calibration of carbonate rind thickness in late Pleistocene soils for surficial deposit age estimation, Southwest USA

    Science.gov (United States)

    Amoroso, L.

    2006-01-01

    Carbonate rinds have been used for cross-correlation of landforms as well as a quantitative indicator of soil age. Using the measured rind thickness of clasts found within a deposit, whose age has been independently determined, allows the construction of a calibrated surface-age proxy. Measurements were taken at sites within the Mojave Desert, the northwestern Sonoran Desert, the southern Great Basin, and the western Colorado Plateau. These sites are all within about 300 km of the intersection of the borders of the states of California, Arizona, and Nevada. In the study area, elevation varied from 200 to 1200 m, MAP was from 95 to 195 mm, and MAT was from 18.4?? to 23.3??. The calibrated proxy, while not accounting for the effects of parent material or climate on rind development, does show a strong correlation (R2 = 0.74, P Pleistocene age. The calibrated chronosequence, rind thickness = 0.0889 + 0.0079 [surface age]), is in general valid over a large region of southwestern United States. This statistical relation suggests that parent material, climate, and elevation may not be as strong a control on carbonate accumulation as is age for younger soils.

  12. Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling

    Directory of Open Access Journals (Sweden)

    J. Etourneau

    2013-08-01

    Full Text Available The largest increase in export production in the eastern Pacific of the last 5.3 Myr (million years occurred between 2.2 and 1.6 Myr, a time of major climatic and oceanographic reorganization in the region. Here, we investigate the causes of this event using reconstructions of export production, nutrient supply and oceanic conditions across the Pliocene–Pleistocene in the eastern equatorial Pacific (EEP for the last 3.2 Myr. Our results indicate that the export production peak corresponds to a cold interval marked by high nutrient supply relative to consumption, as revealed by the low bulk sedimentary 15N/14N (?15N and alkenone-derived sea surface temperature (SST values. This ?0.6 million year long episode of enhanced delivery of nutrients to the surface of the EEP was predominantly initiated through the upwelling of nutrient-enriched water sourced in high latitudes. In addition, this phenomenon was likely promoted by the regional intensification of upwelling in response to the development of intense Walker and Hadley atmospheric circulations. Increased nutrient consumption in the polar oceans and enhanced denitrification in the equatorial regions restrained nutrient supply and availability and terminated the high export production event.

  13. late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

    Science.gov (United States)

    Adam, David P.; Byrne, Roger; Luther, Edgar

    1981-01-01

    A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, California, has yielded a pollen record for the period between about 30,000 B. P. and roughly 5000 B. P. Three pollen zones are recognized. The earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2°C to 3°C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

  14. A late-Middle Pleistocene (Marine Isotope Stage 6) vegetated surface buried by Old Crow tephra at the Palisades, interior Alaska

    Science.gov (United States)

    Reyes, A.V.; Jensen, B.J.L.; Zazula, G.D.; Ager, T.A.; Kuzmina, S.; La, Farge C.; Froese, D.G.

    2010-01-01

    A 40??cm thick primary bed of Old Crow tephra (131??????11??ka), an important stratigraphic marker in eastern Beringia, directly overlies a vegetated surface at Palisades West, on the Yukon River in central Alaska. Analyses of insect, bryophyte, and vascular plant macrofossils from the buried surface and underlying organic-rich silt suggest the local presence of an aquatic environment and mesic shrub-tundra at the time of tephra deposition. Autochthonous plant and insect macrofossils from peat directly overlying Old Crow tephra suggest similar aquatic habitats and hydric to mesic tundra environments, though pollen counts indicate a substantial herbaceous component to the regional tundra vegetation. Trace amounts of arboreal pollen in sediments associated with the tephra probably reflect reworking from older deposits, rather than the local presence of trees. The revised glass fission-track age for Old Crow tephra places its deposition closer to the time of the last interglaciation than earlier age determinations, but stratigraphy and paleoecology of sites with Old Crow tephra indicate a late Marine Isotope Stage 6 age. Regional permafrost degradation and associated thaw slumping are responsible for the close stratigraphic and paleoecological relations between Old Crow tephra and last interglacial deposits at some sites in eastern Beringia. ?? 2009 Elsevier Ltd.

  15. A late-Middle Pleistocene (Marine Isotope Stage 6) vegetated surface buried by Old Crow tephra at the Palisades, interior Alaska

    Science.gov (United States)

    Reyes, Alberto V.; Jensen, Britta J. L.; Zazula, Grant D.; Ager, Thomas A.; Kuzmina, Svetlana; La Farge, Catherine; Froese, Duane G.

    2010-03-01

    A 40 cm thick primary bed of Old Crow tephra (131 ± 11 ka), an important stratigraphic marker in eastern Beringia, directly overlies a vegetated surface at Palisades West, on the Yukon River in central Alaska. Analyses of insect, bryophyte, and vascular plant macrofossils from the buried surface and underlying organic-rich silt suggest the local presence of an aquatic environment and mesic shrub-tundra at the time of tephra deposition. Autochthonous plant and insect macrofossils from peat directly overlying Old Crow tephra suggest similar aquatic habitats and hydric to mesic tundra environments, though pollen counts indicate a substantial herbaceous component to the regional tundra vegetation. Trace amounts of arboreal pollen in sediments associated with the tephra probably reflect reworking from older deposits, rather than the local presence of trees. The revised glass fission-track age for Old Crow tephra places its deposition closer to the time of the last interglaciation than earlier age determinations, but stratigraphy and paleoecology of sites with Old Crow tephra indicate a late Marine Isotope Stage 6 age. Regional permafrost degradation and associated thaw slumping are responsible for the close stratigraphic and paleoecological relations between Old Crow tephra and last interglacial deposits at some sites in eastern Beringia.

  16. Large-scale cement stratigraphy in cavern porosity, Mallorca, Spain

    Energy Technology Data Exchange (ETDEWEB)

    Pomar, L.

    1989-03-01

    Rapid precipitation of carbonate cements occurs at the air-water interface in the zone of mixed fresh and marine waters in karstic caverns near the coast of Mallorca, Spain,. These cements, which have been precipitating at least since the middle Pleistocene, occur as fibrous calcite, rhombic calcite, and fibrous aragonite, which have accumulated in superimposed bands reaching total thicknesses of a few centimeters to a few meters. Calcite overgrown on aragonite without evidence of aragonite dissolution is common, although in some places the calcite shows later dissolution. Recent fibrous calcite with rapid rates of growth is precipitated in the few-decimenters-thick zone of tidal fluctuation (atmospheric pressure tides). Carbon-14 dating of these cements gives growth rates of 72.5 mm/1000 years. Extensive coatings of these cements extend 55 m vertically, from 40 m above to 15 m below the water table. Uranium-thorium and SER dating of some of the coatings shows that the cycles of precipitation recorded in the cements over the least 700,000 years are on the order of 100,000 years (Milankovich cyclicity). Precipitation of these cements occurred in the upper phreatic zone, whose position was tied to sea level changes during the Pleistocene-Holocene. The stratigraphy of these cements therefore provides an excellent record of late Quaternary sea level history in the western Mediterranean.

  17. Late Pleistocene leopards across Europe - northernmost European German population, highest elevated records in the Swiss Alps, complete skeletons in the Bosnia Herzegowina Dinarids and comparison to the Ice Age cave art

    Science.gov (United States)

    Diedrich, Cajus G.

    2013-09-01

    European leopard sites in Europe demonstrate Early/Middle Pleistocene out of Africa lowland, and Late Pleistocene Asian alpine migrations being driven by climatic changes. Four different European Pleistocene subspecies are known. The final European Late Pleistocene “Ice Age leopard” Panthera pardus spelaea (Bächler, 1936) is validated taxonomically. The skull shows heavy signs of sexual dimorphism with closest cranial characters to the Caucasian Panthera pardus ciscaucasica (Persian leopard). Late Pleistocene leopards were distributed northernmost, up to S-England with the youngest stratigraphic records by skeletons and cave art in the MIS 2/3 (about 32,000-26,000 BP). The oldest leopard painting left by Late Palaeolithics (Aurignacians/Gravettians) in the Chauvet Cave (S-France) allows the reconstruction of the Ice Age leopard fur spot pattern being close to the snow or Caucasian leopards. The last Ice Age glacial leopard habitat was the mountain/alpine boreal forest (not mammoth steppe lowland), where those hunted even larger prey such as alpine game (Ibex, Chamois). Into some lairs, those imported their prey by short-term cave dwelling (e.g. Baumann's Cave, Harz Mountains, Germany). Only Eurasian Ice Age leopards specialized, similar as other Late Pleistocene large felids (steppe lions), on cave bear predation/scavenging partly very deep in caves. In Vjetrenica Cave (Dinarid Mountains, Bosnia Herzegovina), four adult leopards (two males/two females) of the MIS 3 were found about two km deep from the entrance in a cave bear den, near to one cave bear skeleton, that remained articulated in its nest. Leopards died there, partly being trapped by raising water levels of an active ponor stream, but seem to have been killed possibly either, similar as for lions known, in battles with cave bears in several cave bear den sites of Europe (e.g. Baumann's Cave, Wildkirchli Cave, Vjetrenica Cave). At other large cave sites, with overlap of hyena, wolf and dhole dens at the cave entrances, leopard bones with bite damages indicate their remains to have been imported and consumed by predators in alpine regions due to reduced prey availability. The best models for the competition/taphonomy of large predators - felids, hyenids, canids - within large cave bear dens of Europe is represented in combination of the Zoolithen Cave and Vjetrenica Cave taphonomy.

  18. Humidity changes in southern Tunisia during the Late Pleistocene inferred from U-Th dating of mollusc shells

    International Nuclear Information System (INIS)

    Calcareous deposits, mainly consisting of mollusc shell accumulations, which have been dated by the U/Th disequilibrium method, mark the shorelines of paleolake highstands in the Great Chotts Area of Southern Tunisia. The 5 sites studied consist of discontinuous accumulations of fossils of marine-like organisms e.g.: Cerastoderma glaucum, Melania tuberculata, Melanopsis praemorsa, Cerithium rupestre. U/Th isochron plots and age frequency histograms for 39 shell samples are reported here. Limited variations for U content and 234U/238U activity ratios (AR) of shells support the hypothesis of closure of the geochemical system with respect to this element. It is remarkable that 234U/238U AR of shells collected in Chott Fejej or Chott Jerid are clustered around different values, reflecting probably different groundwater recharge from the Continental Intercalaire (CI) or Complexe Terminal (CT) aquifers. Furthermore waters collected near Wadi el Akarit show 234U/238U AR values comparable to those observed for shells. 14C determinations made on aliquots of some of these samples suggested an age distribution between 18 and 34 ka BP. The U/Th data of these 39 shell samples imply that 4 distinct flood episodes of these lakes occurred at about 30, 95-100, 130-150 and 180-200 ka. For the episode centred around 30 ka, the frequency histogram of ages shows a multimodal age group that could represent the existence of several humid pulses rather than a unique event. Moreover, the comparison of ?13C and ?18O with those of older humid Pleistocene phases, when very large palaeolakes have been recorded, suggests that these young carbonate shells are not related to a true highstand lake. It is suggested that they represent a period of less humid climatic conditions with carbonate accumulation in minor water ponds in which intensive biological activity could have taken place. It should be noted that this period was less arid than the present

  19. Late Pleistocene fault slip rate, earthquake recurrence, and recency of slip along the Pyramid Lake fault zone, northern Walker Lane, United States

    Science.gov (United States)

    Briggs, Richard W.; Wesnousky, Steven G.

    2004-08-01

    Up to 25% of Pacific-North America plate relative transform motion is accommodated east of the Sierra Nevada. Most of that 25% is taken up by deformation in the Walker Lane, a discontinuous zone of strike-slip and normal faults approximately parallel to the San Andreas. The Pyramid Lake fault zone is a northwest trending right-lateral fault in the northern Walker Lane, Nevada. Recent geodetic surveys report 6 ± 2 mm/year of right-lateral shear strain accumulation across the northern Walker Lane. Interpretation of displaced geomorphic features preserved in post-Lake Lahontan (˜15,500 cal. yr B.P.) surfaces indicate the Pyramid Lake fault zone has accommodated at least 2.6 ± 0.3 mm/year of right-lateral shear during the late Pleistocene. Additionally, a minimum of two earthquakes have occurred since deposition of the Mazama tephra (˜7630 cal. yr B.P.), and at least four earthquakes have occurred on the fault after desiccation of Lake Lahontan (˜15.5 ka), with the most recent earthquake occurring after 1705 ± 175 cal. yr B.P. The observations indicate that the Pyramid Lake fault zone accommodates the major portion (?25%-70%) of right-lateral slip east of the Sierra Nevada at the latitude of ˜39°45'N.

  20. The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

    Science.gov (United States)

    Enzel, Yehouda; Amit, Rivka; Dayan, Uri; Crouvi, Onn; Kahana, Ron; Ziv, Baruch; Sharon, David

    2008-02-01

    Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60-12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone-physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15'. The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.

  1. Stratigraphic context and paleoenvironmental significance of minor taxa (Pisces, Reptilia, Aves, Rodentia) from the late Early Pleistocene paleoanthropological site of Buia (Eritrea).

    Science.gov (United States)

    Rook, L; Ghinassi, M; Carnevale, G; Delfino, M; Pavia, M; Bondioli, L; Candilio, F; Coppa, A; Martínez-Navarro, B; Medin, T; Papini, M; Zanolli, C; Libsekal, Y

    2013-01-01

    The Buia Homo site, also known as Wadi Aalad, is an East African paleoanthropological site near the village of Buia that, due to its very rich yield from the late Early Pleistocene, has been intensively investigated since 1994. In this paper, which reports on the finds of the 2010-2011 excavations, we include new fossil evidence on previously identified taxa (i.e., reptiles), as well as the very first description of the small mammal, fish and bird remains discovered. In particular, this study documents the discovery of the first African fossil of the genus Burhinus (Aves, Charadriiformes) and of the first rodent from the site. This latter is identified as a thryonomyid rodent (cane rat), a relatively common taxon in African paleoanthropological faunal assemblages. On the whole, the new occurrences documented within the Buia vertebrate assemblage confirm the occurrence of taxa characterized by strong water dependence. The paleoenvironmental characteristics of the fauna are confirmed as fully compatible with the evidence obtained through sedimentology and facies analysis, documenting the sedimentary evolution of fluvio-deltaic and lacustrine systems. PMID:23159190

  2. Geothermal properties and groundwater flow estimated with a three-dimensional geological model in a late Pleistocene terrace area, central Japan

    Science.gov (United States)

    Funabiki, A.; Takemura, T.; Hamamoto, S.; Komatsu, T.

    2012-12-01

    1. Introduction The ground source heat pump (GSHP) is a highly efficient and renewable energy technology for space heating and cooling, with benefits that include energy conservation and reductions in greenhouse gas emissions. One result of the huge Tohoku-oki earthquake and tsunami and the subsequent nuclear disasters is that GSHPs are receiving more attention from the media and they are being introduced by some local governments. Heat generated by underground GSHP installation, however, can pollute the geothermal environment or change groundwater flow patterns . In this study, we estimated possible effects from the use of GSHPs in the Tokyo area with a three-dimensional (3D) geological model. 2. Geological model The Tokyo Metropolitan Area is surrounded by the Late Pleistocene terraces called the Musashino uplands. The terrace surfaces are densely populated residential areas. One of these surfaces, the Shimosueyohi surface, formed along the Tama River during the last deglacial period. The CRE-NUCHS-1 core (Funabiki et al., 2011) was obtained from this surface, and the lithology, heat transfer coefficients, and chemical characteristics of the sediments were analyzed. In this study, we used borehole log data from a 5 km2 area surrounding the CRE-NUCHS-1 core site to create a 3D geological model. In this area, the Pleistocene Kazusa Group is overlain by terrace gravels and a volcanic ash layer called the Kanto Loam. The terrace gravels occur mainly beneath the Kanda, Kitazawa, and Karasuyama rivers , which flow parallel to the Tama River, whereas away from the rivers , the Kanto Loam directly overlies the Kazusa Group sediments. 3. Geothermal disturbance and groundwater flow Using the geological model, we calculated the heat transfer coefficients and groundwater flow velocities in the sediments. Within the thick terrace gravels, which are at relatively shallow depth (8-20 m), heat transfer coefficients were high and groundwater flow was relatively fast. The amount of disturbance of the geothermal environment and groundwater flow caused by the use of GSHPs, therefore, would depend on the thickness of these gravels. Reference Funabiki, A., Nagoya, K., Kaneki, A., Uemura, K., Kurihara, M., Obara, H., Goto, A., Chiba, T., Naya, T., Ueki, T., and Takemura, T. (2011) Sedimentary facies and physical properties of the sediment core CRE-NUCHS-1 in Setagaya district, Tokyo, central Japan. Abstracts, The 118th Annual Meeting of theGeological Society of Japan. Acknowledgement This work was supported by the Core Research for Evolutional Science and Technology (CREST) program of the Japan Science and Technology Agency (JST).

  3. Palaeohydrological and palaeoecological studies on South Cameroonian alluvial sedimentary basins - New evidence on the palaeoenvironmental evolution of western Central Africa since the Late Pleistocene

    Science.gov (United States)

    Sangen, M.

    2009-04-01

    A new valuable and innovative contribution will be presented to ascertain the timing and extension of climatic and ecological changes in western equatorial Africa. Main focus is laid on the dynamics of climate, fluvial systems and the high sensitive tropical ecosystems (dense evergreen and semi-deciduous rain forest and savanna-rain forest margin) since the Late Pleistocene (~50 kyrs. BP). For this purpose extended fieldworks were carried out in South Cameroon (2004-2008) by the ReSaKo-Project (sub-project of DFG-Project 510) with abundant investigations on alluvial sedimentary basins of equatorial tropical fluvial systems. Suitable alluvial sediment-archives for palaeoenvironmental research were uncovered along selected braiding, meandering and anabranching/anastomosing reaches of major southwestern, into the Gulf of Guinea (Ntem, Nyong and Sanaga) and southeastern, into the Congo basin (Boumba, Dja and Ngoko) draining rivers (RUNGE et al. 2006, SANGEN 2008). Among geomorphological investigations and cross section discussions, 150 corings (Edelman, 20 cm layers) reaching maximum depths of 550 cm were carried out on river benches, levees, cut-off and periodical branches, islands and terraces as well as in seasonal inundated floodplains and backswamps. Corresponding sedimentary profiles and catenae recovered multilayered, sandy to clayey alluvia containing sedimentary form-units and palaeosurfaces which contribute to the reconstruction of palaeoenvironmental conditions in western equatorial Africa. Several (59) radiocarbon (AMS) dated samples (Erlangen and Lecce) from fossil organic layers and macro-rests embedded in these units yielded Late Pleistocene to recent ages (14C-ages around 48 to 0.2 kyrs. BP), spanning also the Last Glacial Maximum (LGM) and Holocene record. Abrupt grain-size modifications and alternating form-units (sandy and clayey layers, palaeosurfaces) in the stratigraphic records display fluctuations in the fluvial-morphological response of the fluvial systems to climatic variability and other extrinsic and intrinsic impacts. Although the sedimentary record varies among the studied river reaches, fossil organic sediment layers (palaeosurfaces) containing valuable proxy data were found in almost all alluvia basins of examined southern Cameroonian rivers. Around 56 ^13C-values corresponding to the dated samples (-31.4 to -18.0 ) evidence that despite major disturbances of the African rain forest over geological times (MALEY 2001) mainly rain forest ecosystems have prevailed during the corresponding time periods, presumably as gallery forests, which were able to persist in this fluvial habitat ("fluvial refuge"), even during arid periods (e.g. LGM). The results are consistent with earlier findings from lacustrine (SERVANT & SERVANT-VILDARY 2000), marine (WELDEAB et al. 2007) and additional sediment archives (GASSE et al. 2008) and will add additional insights and information to the unravelling of the complex respond of the African monsoon, the Central African ecosystems and fluvial systems to Late Quaternary climatic and environmental fluctuations within a globally teleconnected system. References: GASSE, F., CHALIé, F., VINCENS, A., WILLIAMS, M.A.J. & WILLIAMSON, D. (2008): Climatic patterns in equatorial and southern Africa from 30,000 to 10,000 years ago reconstructed from terrestrial and near-shore proxy data. Quaternary Science Reviews, 27 (25-26), 2316-2340. MALEY, J. (2001): The impact of arid phases on the African rain forest through geological history. In: WEBER, W., WHITE, L., VEDDER, A., NAUGHTON-TREVES, L. (Eds.): African rain forest ecology and conservation - An interdisciplinary perspective. Yale University Press, New Haven, 68-87. RUNGE, J., EISENBERG, J., SANGEN, M. (2006): Geomorphic evolution of the Ntem alluvial basin and physiogeographic evidence for Holocene environmental changes in the rain forest of SW Cameroon (Central Africa) - preliminary results. Z. Geomorph. N.F., Suppl. Bd. 145, 63-79. SERVANT, M. & SERVANT-VILDARY, S. (2000): Dynamique à long terme des

  4. Age estimates and uplift rates for Late Pleistocene marine terraces: Southern Oregon portion of the Cascadia Forearc

    Science.gov (United States)

    Muhs, Daniel R.; Kelsey, Harvey M.; Miller, Gifford H.; Kennedy, George L.; Whelan, Joseph F.; McInelly, Galan W.

    1990-05-01

    Marine terraces are prominent landforms along the southern Oregon coast, which forms part of the forearc region of the Cascadia subduction zone. Interest in the Cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes. In addition, other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates. With these hypotheses in mind, we generated new uranium series, amino acid, and stable isotope data for southern Oregon marine terrace fossils. These data, along with terrace elevations and two alternative estimates of sea level at the time of terrace formation, allow us to determine terrace ages and uplift rates. Uranium series analysis of fossil coral yields an age of 83±5 ka for the Whisky Run terrace at Coquille Point in Bandon, Oregon. A combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at Cape Blanco. These ages indicate uplift rates of 0.45-1.05 and 0.81-1.49 m/kyr for Coquille Point and Cape Blanco, respectively. Late Quaternary uplift rates of marine terraces yield information about deformation in the overriding plate, but it is unclear if such data vary systematically with convergent margin type. In order to assess the utility of the southern Oregon uplift rates for predicting the behavior of the Cascadia subduction zone, we compared late Quaternary uplift rates derived from terrace data from subduction zones around the world. On the basis of this comparison the southern Oregon rates of vertical deformation are not unusually high or low. Furthermore, late Quaternary uplift rates show little relationship to the type of convergent margin. These observations suggest that local structures may play a large role in uplift rate variability. In addition, while the type of convergent margin may place an upper limit on possible uplift rate, greater upper limits serve to increase the range of possible uplift rates. In the case of the southern Oregon coast, variability in uplift rate probably reflects local structures in the overriding plate, and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern Cascadia subduction zone.

  5. No surface breaking on the Ecemi? Fault, central Turkey, since Late Pleistocene (~ 64.5 ka); new geomorphic and geochronologic data from cosmogenic dating of offset alluvial fans

    Science.gov (United States)

    Sar?kaya, M. A.; Y?ld?r?m, C.; Çiner, A.

    2015-05-01

    The Ecemi? Fault Zone (EF) has been recognized as a major left lateral strike-slip fault in the Central Anatolian Fault Zone (CAFZ) of Turkey. However, its Quaternary slip-rate has been challenging to determine due to the difficulty of dating offset markers. Using high-precision offset measurements and 36Cl cosmogenic nuclide dating, we present the first geochronologically determined Late Quaternary slip-rate for the EF. Our study focuses on the excellent exposures of offset alluvial fan surfaces, originating from the Alada?lar, a Late Quaternary glaciated mountain. Analysis of airborne orthophotogrametry and GNSS (Global Navigation Satellite System) surveys indicates 168 ± 2 m left lateral and 31 ± 1 m vertical displacements. In-situ terrestrial cosmogenic 36Cl geochronology obtained from eleven surface boulders provides a minimum abandonment/incision age of 104.2 ± 16.5 ka for the oldest offset alluvial fan surface. Our geomorphic observations together with Self-potential geophysical surveys revealed the presence of an unfaulted alluvial fan terrace, which allows us to constrain the timing of deformation. The abandonment/incision age of this fan is 64.5 ± 5.6 ka based on thirteen 36Cl depth profile samples. Accordingly, we obtained a geologic fault slip-rate of 4.2 ± 1.9 mm a- 1 horizontally and 0.8 ± 0.3 mm a- 1 vertically for the time frame between 104.2 ± 16.5 ka and 64.5 ± 5.6 ka. Our analysis indicates that the EF has not been producing a major surface breaking earthquake on the main strand at least since 64.5 ± 5.6 ka (mid-Late Pleistocene). This could be the result of abandonment of the main strand and accommodation of deformation by other faults within the EF. Nevertheless, a recently occurred (30 September 2011) low magnitude (ML: 4.3) left lateral strike-slip earthquake indicates recent seismic activity of the EF. Comparison of the recent GPS velocity field with the longer slip history along the CAFZ indicates a constant but low strain release without surface breaking and very long large earthquake recurrence intervals.

  6. The influence of Late Pleistocene geomorphological inheritance and Holocene hydromorphic regimes on floodwater farming in the Talgar catchment, southeast Kazakhstan, Central Asia

    Science.gov (United States)

    Macklin, Mark G.; Panyushkina, Irina P.; Toonen, Willem H. J.; Chang, Claudia; Tourtellotte, Perry A.; Duller, Geoff A. T.; Wang, Hong; Prins, Maarten A.

    2015-12-01

    In comparison to Southwest Asia and the Indian subcontinent, the relationship between Holocene river dynamics, climate change and floodwater farming in Central Asia is significantly under researched. To address this, a multi-disciplinary research project was begun in 2011 centred on the Talgar catchment, a south-bank tributary of the Ili River, southeast Kazakhstan. Building on archaeological excavations and surveys conducted over the past 20 years, we have undertaken investigations of Holocene human adaptations to changing hydromorphic regimes in the Tien Shan piedmont region, Central Asia. Fluvial geochronologies have been reconstructed over the last 20,000 years using Optically Stimulated Luminescence and 14C dating, and are compared with human settlement histories from the Eneolithic to the medieval period. Phases of Late Pleistocene and Holocene river aggradation at c. 17,400-6420, 4130-2880 and 910-500 cal. BC and between the mid-18th and early 20th centuries were coeval with cooler and wetter neoglacial episodes. Entrenchment and floodplain soil development (c. 2880-2490 cal. BC and cal. AD 1300-1640) coincided with warmer and drier conditions. Prior to the modern period, floodwater farming in the Talgar River reached its height in the late Iron Age (400 cal. BC - cal. AD 1) with more than 70 settlement sites and 700 burial mounds. This period of agricultural expansion corresponds to a phase of reduced flooding, river stability and glacier retreat in the Tien Shan Mountains. Late Iron age agriculturists appear to have been opportunistic by exploiting a phase of moderate flows within an alluvial fan environment, which contained a series of partially entrenched distributary channels that could be easily 'engineered' to facilitate floodwater farming. Holocene climate change was therefore not a proximate cause for the development and demise of this relatively short-lived (c. 200 years) period of Iron Age farming. River dynamics in the Tien Shan piedmont are, however, strongly coupled with regional hydroclimatic fluctuations, and they have likely acted locally as both 'push' and 'pull' factors for riparian agriculturists.

  7. Chronostratigraphy and changes of environment of Late Pleistocene and Holocene at Starunia palaeontological site and vicinity (Carpathian region, Ukraine

    Directory of Open Access Journals (Sweden)

    Tadeusz SOKO?OWSKI

    2009-01-01

    Full Text Available This paper presents the results of absolute dating and biostratigraphical analysis carried out for alluvial sediments of an abandoned Starunia ozokerite mine located in the Velyky Lukavets River valley, in which large mammal remains were discovered in the first half of the 20th century. The sediments build up three terrace levels. The highest one, up to 8 m high (terrace II, is likely to be associated with a stage of aggradation, as well as with a short episode of valley broadening, which occurred in the Weichselian Late Pleniglacial. The lower one, 4 m high (terrace I, is most likely to be linked with the Holocene, despite a considerable transformation of its top due to mining activity. The lower part of this terrace cover bears coarse-grained channel sediments dated to 120.6-58.9 ka BP (Eemian Interglacial?-Early Pleniglacial - OIS 5e, 4 and 3, and overbank (distal floodplain mud with intercalations of biogenic deposits (peat, peat mud and biogenic mud. The overbank deposits are dated to 48.2-11.11 ka BP (Glinde Interstadial?-Younger Dryas, OIS 3-2 and are overlain by Holocene (OIS 1 mud and biogenic deposits. In boreholes drilled in the vicinity of the present-day river channel, younger sediments occur more frequently. These include sediments originating from the Late Weichselian overlain by Holocene sediments. However, sediments originating exclusively from the Holocene are infrequent. The deposition of sediments took place in specific conditions of a permanent saturation of the environment with brine, petroleum and thickened bitumen. In the longest period of deposition (48.2-1.27 ka BP, ephemeral swamps, ponds and lakes were developed in different parts of the floodplain. They were marked by the presence of: Juncus glaucus/effusus, J. articulatus, Typha sp., Batrachium sp., Potamogeton filliformis, Bidens tripartita, Ranunculus sceleratus and Phragmites communis, as well as by halophytic species, like: Zannichellia palustris, Triglochin maritimum, Schoenoplectus tabernemontani, Puccinelia distans and Eleocharis palustris. Rhythmic oscillations between cold and warm climatic conditions, typical of the Weichselian age and well identified in Western Europe, are here marked by the changes of plant communities (woody assemblages passing into steppe and tundra, but are not noticeably recorded in the sediments of the Velyky Lukavets River. This shows that the greatest part of the discussed period involved the formation of poorly differentiated silty overbank sediments with intercalations of biogenic sediments. However, the variability of sediments provides evidence for extreme events which occurred in the Holocene.

  8. Tectonic control on the stratigraphic framework of Late Pleistocene and Holocene deposits in Marajó Island, State of Pará, eastern Amazonia

    Directory of Open Access Journals (Sweden)

    Dilce F. Rossetti

    2010-06-01

    Full Text Available The traditional view that the Brazilian Amazonia is located in a tectonically stable area since the Cretaceous is changing in front of the increasing documentation of fault reactivations even during the Holocene. How the sedimentary record has responded to these events is an issue that remains to be approached with basis on field data. This work focuses on the stratigraphic correlation of late Quaternary deposits from eastern Marajó Island, with the goal of demonstrating the role of fault reactivation on the origin and preservation of these deposits. Despite the location in a stable platform of a continental passive margin, three studied stratigraphic units display significant vertical offsets that define two depocenters that are better explained through tectonic displacements. This interpretation is reinforced by several morphostructural features related to faults that occur between the studied drills. Without the influence of tectonics, sediment preservation in this characteristically low-lying terrain would have been negligible. The results of the present work motivate to look for other tectonically-influenced areas in Amazonia, which similarly might have acted as sites for sediment accommodation during the late Quaternary. These sedimentary records have great potential to be the source of valuable information for reconstructing Quaternary geological events in Northern Brazil.A visão tradicional de que a Amazônia brasileira localiza-se em ma área tectonicamente estável desde o Cretáceo está mudando perante a crescente documentação de reativações de falha, até mesmo durante o Holoceno. Como o registro sedimentar respondeu a esses eventos é um tema que permanece por ser abordado com base em dados de campo. Este trabalho enfatiza a correlação estratigráfica de depósitos quaternários tardios no leste da Ilha do Marajó, com o objetivo de demonstrar a importância de reativações de falha na origem e preservação desses depósitos. Apesar da localização em área de plataforma de uma margem continental passiva, três unidades estratigráficas estudadas mostram significantes rejeitos verticais, que definem dois depocentros, explicados por deslocamentos tectônicos. Esta interpretação é reforçada por várias feições morfoestruturais relacionadas com falhas localizadas entre os poços estudados. Sem influência tectônica, a preservação de sedimentos nesse terreno, caracteristicamente plano, seria imperceptível. Os resultados do presente trabalho motivam a procurar outras áreas tectonicamente influenciadas da Amazônia, que possam ter atuado como sítios de acomodação de sedimentos durante o Quaternário tardio. Esses registros sedimentares têm grande potencial de serem fontes de informações valiosas para auxiliar na reconstrução de eventos geológicos quaternários no norte do Brasil.

  9. Tectonic control on the stratigraphic framework of Late Pleistocene and Holocene deposits in Marajó Island, State of Pará, eastern Amazonia

    Scientific Electronic Library Online (English)

    Dilce F., Rossetti.

    2010-06-01

    Full Text Available A visão tradicional de que a Amazônia brasileira localiza-se em ma área tectonicamente estável desde o Cretáceo está mudando perante a crescente documentação de reativações de falha, até mesmo durante o Holoceno. Como o registro sedimentar respondeu a esses eventos é um tema que permanece por ser ab [...] ordado com base em dados de campo. Este trabalho enfatiza a correlação estratigráfica de depósitos quaternários tardios no leste da Ilha do Marajó, com o objetivo de demonstrar a importância de reativações de falha na origem e preservação desses depósitos. Apesar da localização em área de plataforma de uma margem continental passiva, três unidades estratigráficas estudadas mostram significantes rejeitos verticais, que definem dois depocentros, explicados por deslocamentos tectônicos. Esta interpretação é reforçada por várias feições morfoestruturais relacionadas com falhas localizadas entre os poços estudados. Sem influência tectônica, a preservação de sedimentos nesse terreno, caracteristicamente plano, seria imperceptível. Os resultados do presente trabalho motivam a procurar outras áreas tectonicamente influenciadas da Amazônia, que possam ter atuado como sítios de acomodação de sedimentos durante o Quaternário tardio. Esses registros sedimentares têm grande potencial de serem fontes de informações valiosas para auxiliar na reconstrução de eventos geológicos quaternários no norte do Brasil. Abstract in english The traditional view that the Brazilian Amazonia is located in a tectonically stable area since the Cretaceous is changing in front of the increasing documentation of fault reactivations even during the Holocene. How the sedimentary record has responded to these events is an issue that remains to be [...] approached with basis on field data. This work focuses on the stratigraphic correlation of late Quaternary deposits from eastern Marajó Island, with the goal of demonstrating the role of fault reactivation on the origin and preservation of these deposits. Despite the location in a stable platform of a continental passive margin, three studied stratigraphic units display significant vertical offsets that define two depocenters that are better explained through tectonic displacements. This interpretation is reinforced by several morphostructural features related to faults that occur between the studied drills. Without the influence of tectonics, sediment preservation in this characteristically low-lying terrain would have been negligible. The results of the present work motivate to look for other tectonically-influenced areas in Amazonia, which similarly might have acted as sites for sediment accommodation during the late Quaternary. These sedimentary records have great potential to be the source of valuable information for reconstructing Quaternary geological events in Northern Brazil.

  10. High-resolution Stable Isotope Record From Lago Cardiel (49° S), Argentina - Implications for Past Hydroclimatic Conditions in Patagonia Since the Late Pleistocene

    Science.gov (United States)

    Gilli, A.; Ariztegui, D.; Anselmetti, F. S.; McKenzie, J. A.; Markgraf, V.

    2004-12-01

    Lacustrine authigenic carbonates are excellent archives of the prevailing water conditions at the time of precipitation. Their stable carbon and oxygen isotope compositions provide powerful proxies to reconstruct past environmental conditions in a high-resolution mode. Our study site, Lago Cardiel, is a large closed basin located at the southern tip of Patagonia (Argentina) on the eastern edge of the modern rain shadow caused by the combination of persistent westerly winds and the topographic barrier of the Andes. This geographical setting combined with the fact that the lake catchment area was not glaciated during the Last Glaciation makes it very sensitive to past atmospheric changes in the hydrological conditions. Previous studies on shorelines and seismic sequence stratigraphy calibrated with sedimentary core data revealed former large lake level fluctuations, which can now be assessed and constrained using stable isotope data from authigenic precipitated carbonates. During the last ca. 16,000 years Lago Cardiel underwent substantial changes in volume. The oxygen isotope record is to a large extend controlled by the precipitation/evaporation ratio leading to more negative oxygen isotopic values in times of wetter hydroclimatic conditions and vice versa. A clear stepwise structure characterized the Late Glacial-Holocene transition (LG-H) with the lowest lake level between 13,160 and 12,900 cal yr BP revealing relative positive oxygen isotope values. Conversely, a rapid lake level rise between 12,600 and 10,300 cal yr BP is characterized by a decrease in the oxygen isotope value of more than 3 \\permil. The oxygen isotope record reveals a mid-Holocene lake level highstand and indicates highly variable environmental conditions in the late Holocene as a result of an intensification of the El Niño/Southern Oscillation (ENSO). The observed changes in the hydroclimatic condition of Patagonia are of more than just regional significance since they have substantial intra-hemispheric linkages controlling partly the dust content of Antarctic ice cores. The comparison of these results with those from other Patagonian sites shows a significant latitudinal gradient at critical time windows such as the LG-H transition. The latter point towards the complexity of the climate system and the need for more refined climate models.

  11. Reconstruction of mass balance of Nevado Coropuna glaciers (Southern Peru) for Late Pleistocene, Little Ice Age and the present.

    Science.gov (United States)

    Ubeda, J.; Palacios, D.

    2009-04-01

    The Nevado Coropuna volcanic complex (15th 31'S-72 ° 39 ° W) is the quaternary stratovolcano northernmost of the central volcanic zone (CVZ) in the western flank of the Central Andes (Southern Peru). This consists in four adjacent volcanic buildings that are occupied over 5.100-5.700 masl by a system of glaciers covering an area of 47 Km2 in 2007 (Ubeda et al, 2008). The maximum expansion of glaciers during the Pleistocene affected an area of ~449 Km2, dropping to altitudes around 3.600-4800 m (Ubeda et al, 2007). In this work were mapped several hundreds of moraines which constitute a record of climate change since the last glacial maximum (LGM). Current glacier system is formed by dozen of glaciers descending slope down in all directions. Coropuna complex is an excellent laboratory for to investigate the control that climate change, tectonics and volcanism exert on the dynamics of glaciers, a scale of tens of years (by studying current glaciers) and also of tens of thousands of years (by analyzing the geomorphological evidence of its evolution in the past). Ubeda et al. (2008) analyzed the evolution of eighteen glaciers of Nevado Coropuna using indicators as surfaces and Equilibrium Line Altitudes (ELAs) of ice masses in 2007, 1986, 1955, Little the Ice Age (LIA) and Last Glacial Maximum (LGM). The glaciers were grouped into two sets: NE group (seven glaciers) and SE group (eleven glaciers). The work included statistical series of ELAs in each phase, estimates by Area x Altitud Balance Ratio (AABR) method, which was proposed by Osmaston (2005), in addition with estimates of timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The work included statistical series of ELAs in each phase, estimates by the method Area x Altitud Balance Ratio (AABR) proposed by Osmaston (2005), and in addition estimates of the timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The objective of this work is to estimate the current and past mass balance of glaciers in these phases (2007, 1986, 1955, LIA and LGM) in order to assess the current state of glaciers and deduct the regimes of temperature and precipitation for present and for LGM. To achieve this target were installed in 2007 in the gorge of Queñua Ranra (NE quadrant of Coropuna complex) four stations, that are respectively at 4886 m (E1), 5564 m (E2), 5694 (E3) m and 5822 m (E4). The stations consist of a sensor in air and one (E3) or two sensors in ground (E1). The sensors record temperature at intervals of 30 minutes (sensors 12, 13, 22 and 32) or 45 minutes (11, 21, 31 and 41), with precision of tenths of a degree Celsius (° C). The first digit of the name of the sensors referred to the station (arranged in increasing altitude) and the second at his position (eg 11-air, 12-ground and 13-deep ground, in the station E1). The records of Ta and Ts have allowed to define homogeneous data sets of 365 days (12-11-2007/11-11-2008). With these data have been calculated for each day and each sensor the average temperatures, and the minimum and maximum temperature variations and was used to estimate the vertical thermal gradient (^T/^Z) between the stations. In E1, Ta = 3.9 ° C and Ts =6.8°C. At E3, Ta=-2.9°C and Ts=1.3°C. The rain has been extrapolated from the average of the 1965-2003 series (39 years) from the station of Andahua (15 Ë? 29'36 "S-72 Ë? 20'56" W, 3587 m), 20 km to NE of the eastern summit of Coropuna, resulting in the level E1 (4886 m) a value of P = 494 mm. The availability of the temperature series has allowed develop the model of mass balance using an adaptation of the method Klein et al. (1999) developed from an earlier proposal (Kaser 1995). The method is to solve two equations. Equation 1: a=?m/Lm[(Qr+?(Ta-Ts)], where a is the value of the ablation (mm), ?m duration of ablation (days), Lm the latent heat of fusion (3.34x105J/kg), Qr heat available for melting in the form of net radiation (MJ/day/m), ? a coefficient of mass transferred by heat sensitive (0864 MJ/day), and Ta and Ts air a

  12. Late Pleistocene glaciation of the Kodar Mountains, south-central Siberia, constrained by Be-10 exposure dating

    Science.gov (United States)

    Margold, Martin; Jansen, John D.; Gurinov, Artem L.; Reznichenko, Natalya V.; Codilean, Alexandru T.; Fink, David

    2014-05-01

    The glacial history of the mountainous Transbaikalia region NE of Lake Baikal, Siberia, has so far received little attention. The Kodar Mountains exceed 3000 m in elevation and small cirque glaciers currently occur in the central parts of the range. Yet, greatly expanded glaciation in the past is evidenced by massive moraine complexes at the mouth of glacial valleys in the Chara Depression (part of the Baikal rift system), and along the Vitim River valley to the NW. The moraines document the existence of large valley glaciers that reached to over 120 kilometres in length. We applied Be-10 exposure dating to determine the timing of glacier advances that formed the major moraines: 19 samples from boulders on 8 moraine ridges in 5 moraine complexes. Our results indicate extensive glaciation in the Kodar Mountains at the time of the Last Glacial Maximum, with our ages spanning from about 20 ka to the Late Glacial. We attribute the age spread on some of the moraines to boulder exhumation linked to permafrost dynamics.

  13. Late Pleistocene sea surface warming as a trigger for catastrophic ice sheet wasting in the North Pacific Ocean

    Science.gov (United States)

    Taylor, M.; Hendy, I. L.; Pak, D. K.

    2013-12-01

    A new, high-resolution planktonic foraminiferal Mg/Ca-based temperature record offshore of Vancouver Island, BC captures the interplay between SSTs and ocean-ice sheet dynamics during the deglacial. The SST record of thermocline dwelling N. pachyderma shows variability through the Last Glacial Maximum and the deglacial, with two distinct warming steps of 2.5 and 3.5°C respectively at 17.2-16.5 and 15.3-14.7 ka from ~3 to 9°C. The SST record of surface dwelling G. bulloides remains a relatively constant 5-6°C during the late glacial, warming to 9°C at the Bølling-Ållerød, close to the average modern winter SSTs in the northern NE Pacific. Throughout the interval of the maximum Cordilleran Ice Sheet extent (~20-17 ka), SSTs were sufficiently warm (5-6°C) to induce significant melt at the ice terminus. Moreover, SST warming of ~3°C coincide with the presence of ice rafted debris at MD02-2496, indicating that ocean thermal forcing played an important role in Cordilleran Ice Sheet retreat. We hypothesize that submarine melting was the dominant mode of ice removal resulting from both subglacial meltwater discharge and warm SSTs during early deglaciation of the CIS, promoting iceberg calving events and rapid evacuation of straits and fjords of the BC region.

  14. Foraminíferos y ostrácodos del Pleistoceno tardío (Mar Chiquita, provincia de Buenos Aires, Argentina) / Late Pleistocene Foraminifera and Ostracoda (Mar Chiquita, Buenos Aires Province, Argentina)

    Scientific Electronic Library Online (English)

    Laura, Ferrero.

    2009-12-01

    Full Text Available Sobre la base del estudio de foraminíferos y ostrácodos, se describe la evolución de ambientes marino- costeros al sudeste de la provincia de Buenos Aires afectados por las variaciones del nivel del mar durante el Pleistoceno tardío. Fueron estudiadas dos perforaciones realizadas al sur de la laguna [...] Mar Chiquita. En las secciones inferiores de las perforaciones (A y B) se registran ambientes marinos marginales que pueden ser asignados a la Formación Canal 5 correlacionable con el último máximo interglacial (subestadio isotópico 5e). En los niveles fértiles inferiores de la perforadión A y en toda la sección B las asociaciones de foraminíferos, dominadas por Ammonia beccarii (Linné), permiten inferir ambientes marinos litorales a lagunas costeras. Las asociaciones de ostrácodos indican ambientes de depositación costeros, litorales a de plataforma interna cercanos a estuarios o lagunas costeras, con niveles relativamente altos de energía que han provocado mezcla de material por transporte y retrabajo. Estos ambientes pueden ser asociados al ascenso del nivel del mar durante la última transgresión pleistocena y asignados a la Facies Los Médanos de la Formación Canal 5. Hacia arriba (en la Perforación A), estos ambientes gradan a otros con mayor influencia continental, lagunares, oligo-mesohalinos, de baja energía, evidenciados por el aumento de las proporciones de taxones mixohalinos (Cyprideis) y dulceacuícolas-oligohalinos, por el buen estado de preservación de los ejemplares y la coexistencia de adultos y juveniles de los taxones de ostrácodos, así como por asociaciones de foraminíferos con baja diversidad dominadas por Ammonia beccarii. Estos ambientes pueden ser asignados a la Facies Santa Ana de la misma Formación. Sobreyacen sedimentos continentales no microfosilíferos. Abstract in english The evolution of Late Pleistocene marginal marine environments in the southeast of Buenos Aires province are described based upon the associations of foraminifera and ostracoda. Two drilling performed in the southern coastal plain of Mar Chiquita coastal lagoon were studied. The lowest sections of t [...] he drillings (A and B) indicate marginal marine environments that could be assigned to Canal 5 Formation and correlated to Last Interglacial Maximum, (marine oxygen isotope substage 5e). Along the whole studied section of drilling B and the lowest levels of drilling A, foraminiferal associations are dominated by Ammonia beccarii (Linné) and could be interpreted as characterizing littoral marine environments or coastal lagoons. Ostracoda associations suggest littoral marine environments close to an estuary or a coastal lagoon, with relatively high energetic conditions shown by reworked and mixed material. These environments represent the transgressive/ highstand phase of the Late Pleistocene transgression and could be assigned to Los Médanos Facies of Canal 5 Formation. Upward (Drilling A) increasing percentages of mixohaline (Cyprideis) and non-marine taxa, along with a good preservation of valves, tests and the presence of juvenile and adults of ostracoda and lower diversity associations of foraminifera dominated by Ammonia becarii, suggest the evolution towards lagoonal, low energy environments. These levels represent the regressive phase corresponding to Santa Ana Facies of Canal 5 Formation and are covered by non-microfossiliferous continental muds.

  15. Holocene late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California

    Science.gov (United States)

    Halfar, Jochen; Godinez-Orta, Lucio; Goodfriend, Glenn A.; Mucciarone, David A.; Ingle, James C.; Holden, Peter

    2001-10-01

    Using high-resolution seismic reflection profiling and dating of (1) shallow marine vibracores and (2) sediments collected from uplifted marine terraces we reconstruct the tectonic history and sediment accumulation patterns of Holocene to late Pleistocene warm-temperate to subtropical carbonates in the southern Gulf of California, Mexico. The study was conducted in the vicinity of La Paz where carbonates form along the fault bounded narrow western shelf of the tectonically active Gulf of California rift basin. The non-tropical nature of the setting is responsible for (1) poor cementation of the bioclastic carbonates, and (2) a composition which is dominated by rhodoliths (coralline red algae), corals and mollusks. Unrimmed carbonate flats forming in small pocket bays and a rhodolith bioherm, which has a surface area of more than 20 km 2 and is up to 16 m thick, constitute the major carbonate factories. Holocene carbonate accumulation rates were deduced from seismic and core data and are highest on the rhodolith bioherm (260 cm/ka) and in subtidal zones of pocket bays (210 cm/ka), and lowest on the inner and middle shelf (100 cm/ka). Taken together, rates of carbonate accumulation are intermediate in magnitude between higher rates recorded in fully tropical carbonate settings and lower rates typical of cool-water carbonates. Seismic reflection profiles demonstrate that Isla Espiritu Santo in the center of the study area is a west dipping fault block, which is tectonically influenced by two distinct faults, the La Paz and Espiritu Santo faults. The latter fault accommodates at least 700 m of east-side down normal offset, and forms a steep eastern escarpment leading into the La Paz slope basin. Some of the sediments produced in the shallow carbonate factories of the narrow La Paz shelf are transported across this escarpment and are redeposited in the slope basin at a water depth of 750 m. Uranium-series dates of marine terraces exposed on Isla Espiritu Santo indicate that late Pleistocene uplift along the eastern side of the island could be as high as 310 mm/ka whereas downdropping along the western side of the island occurred at a rate of up to 15 mm/ka. Isla Espiritu Santo therefore constitutes part of the uplifted shoulder of the western margin of the Gulf of California rift basin. Patterns of vertical tectonic movements of Isla Espiritu Santo together with fault offsets on the surrounding seafloor and slump features on steep submarine slopes, point to continuous activity of the La Paz and Espiritu Santo faults. Results of this study will assist in recognizing and interpreting similar settings along ancient non-tropical rift basin margins worldwide and especially in the Neogene of the Gulf of California.

  16. Late Pleistocene (Rancholabrean) Glyptodont and Pampathere (Xenarthra, Cingulata) from Sonora, Mexico / Gliptodonte y Pampaterio (Xenarthra, Cingulata) del Pleistoceno tardío (Rancholabreano) de Sonora, México

    Scientific Electronic Library Online (English)

    Jim I., Mead; Sandra L., Swift; Richard S., White; H. Greg, McDonald; Arturo, Baez.

    2007-12-01

    Full Text Available Los yacimientos ricos en fósiles de Térapa (área centro-oriental de Sonora) contienen más de 60 taxon zoológicas, muchos con afinidades tropicales como Crocodylus (crocodrilo), Hydrochaeris (capibara), y muchas aves. Los depósitos contienen además la dermis ósea de oído (osteodermis) de dos xenartro [...] s extintos, un gliptodonte (Glyptotherium cylindricum) y un armadillo gigante (Pampatherium cf. mexicanum) (Mammalia, Xenarthra). También se han hallado restos de gliptodonte en otras localidades de Sonora menos estudiadas. Las faunas de estas localidades contienen además el género Bison, lo cual indica que los depósitos son del Rancholabreano (Rancholabrean Land Mammal Age), Pleistoceno tardío. La presencia de Pampatherium en Térapa y de Glyptotherium en Térapa y los sitios del Río Mayo/Río Yaqui representa el primer recuento publicado de estas especies en Sonora y extiende grandemente su distribución conocida durante el Rancholabreano, o pleistoceno tardío, en unos 1,100 kms hacia el noroeste de México. Abstract in english The fossil-rich deposits of Térapa (east-central Sonora) contain more than 60 zoological taxa, many with tropical affinities such as Crocodylus (crocodylian), Hydrochaeris (capybara), and many birds. The deposits also contain the dermal ossicles (osteoderms) of two extinct xenarthrans, a glyptodont [...] (Glyptotherium cylindricum) and a pampathere (giant armadillo; Pampatherium cf. mexicanum). Glyptodont remains are also known from other less-well studied localities in Sonora. The faunas from these localities also contain the genus Bison, which indicates that the deposits are of the Rancholabrean Land Mammal Age, late Pleistocene. The presence of Pampatherium at Térapa and the presence of Glyptotherium at Térapa and the Río Mayo/Río Yaqui sites represent the first published accounts of these species from Sonora, and greatly extends their known geographical distribution during the Rancholabrean by about 1,100 km into northwestern Mexico.

  17. New data on the Late Pleistocene and Holocene glacial, climate and relative sea-level changes at Fildes Peninsula, King George Island (South Shetlands Islands, West Antarctica)

    Science.gov (United States)

    Verkulich, Sergey; Pushina, Zina; Tatur, Andrej

    2010-05-01

    New data on the Late Pleistocene and Holocene glacial, climate and relative sea-level changes at Fildes Peninsula, King George Island (South Shetlands Islands, West Antarctica) Verkulich S. R. (Arctic and Antarctic Research Institute, St. Petersburg, Russia) Pushina Z.V. (Arctic and Antarctic Research Institute, St. Petersburg, Russia) Tatur A. (Department of Antarctic Biology, Polish Academy of Sciences, Warsaw, Poland) During the 2008-2009 austral summer, co-operative Russian - Polish paleogeographical investigations allowed to refine the understanding of the past environmental events at Fildes Peninsula, King George Island. Old marine deposits (ca. 30000 yrs BP) with shells, whale bones and marine algae in situ were found in the western coastal and northern inland territories at the altitudes of 20-40 m a.s.l. that evidences the covering of considerable part of the peninsula by relatively warm sea waters before the Last Glacial Maximum. Quite good preservation of these deposits supposes relatively small thickness and weak erosional potential of ice masses overlying the area during the LGM. The early Holocene phase of the peninsula deglaciation was caused by both climate warming and marine transgression, which left the deposits with fossil flora and fauna at heights up to 15 m a.s.l. (maximum rise of the relative sea-level 7000-8000 yrs BP). During the middle Holocene, glacier contraction in the area continued (on the whole) due to mainly favorable climatic conditions. The presence of marine and terrestrial deposit blocks (with shells, algae, mosses) in moraine ridges on the surface of Collins Ice Cap signifies that this glacier could vanish from the peninsula during climate optimum (ca. 4000-3000 yrs BP). The processes of new formation and growth of the ice cap started probably ca. 2000 yrs BP; within the last 1000 years the limited advance of the glacier occurred (likely corresponding to the Little Ice Age), and was replaced then by modern process of its decay.

  18. Hippidion saldiasi Roth, 1899 (Mammalia, Perissodactyla en el Pleistoceno tardío de Calama, norte de Chile Late Pleistocene Hippidion saldiasi Roth, 1899 (Mammalia, Perissodactyla from Calama, northern Chile

    Directory of Open Access Journals (Sweden)

    MARÍA TERESA ALBERDI

    2007-06-01

    Full Text Available Se describen restos del género Hippidion procedentes de la zona del desierto de Atacama (Calama, Segunda Región de Chile. El conjunto analizado corresponde a un esqueleto bastante completo proveniente del yacimiento Betecsa 1, así como escasas unidades del yacimiento Kamac Mayu. En ambos sitios se identifica H. saldiasi. A partir de dos dataciones radiométricas por AMS del ejemplar estudiado, los restos se sitúan estratigráficamente en el Pleistoceno Superior (21.070 ± 100 AP y 21.380 ± 100 14C AP. Se infieren datos ambientales y de dieta a partir de análisis de isótopos estables en los restos de Hippidion saldiasi del sitio Betecsa 1 cuyo valor de ?13C en hueso fue de -15,45 y el valor en esmalte de dientes fue de -16,68, sugiriendo una alimentación con pastos C3. El cráneo recuperado es el primero conocido de esta especieThis paper describes the Hippidion bones recovered from the Atacama Desert (Calama, Second Region of Chile. The analyzed assemblage corresponds to a nearly complete skeleton from Betecsa 1 site and more poorly preserved remains from Kamac Mayu site. In both H. saldiasi is identified. Two 14C radiometric determinations indicate late Pleistocene age for these remains (21,070 ± 100 BP and 21,380 ± 100 BP. Environmental and diet inferences from stable isotope analysis are also presented. The ?13C value from Betecsa 1 horses (-15.45 from bone sample and -16.68 from enamel sample suggest a dietary adaptation exclusively C3 feeders. This is the first skull and associated skeleton recovered of this species

  19. Hippidion saldiasi Roth, 1899 (Mammalia, Perissodactyla) en el Pleistoceno tardío de Calama, norte de Chile / Late Pleistocene Hippidion saldiasi Roth, 1899 (Mammalia, Perissodactyla) from Calama, northern Chile

    Scientific Electronic Library Online (English)

    MARÍA TERESA, ALBERDI; JOSÉ LUIS, PRADO; PATRICIO, LÓPEZ; RAFAEL, LABARCA; ISMAEL, MARTÍNEZ.

    2007-06-01

    Full Text Available Se describen restos del género Hippidion procedentes de la zona del desierto de Atacama (Calama, Segunda Región de Chile). El conjunto analizado corresponde a un esqueleto bastante completo proveniente del yacimiento Betecsa 1, así como escasas unidades del yacimiento Kamac Mayu. En ambos sitios se [...] identifica H. saldiasi. A partir de dos dataciones radiométricas por AMS del ejemplar estudiado, los restos se sitúan estratigráficamente en el Pleistoceno Superior (21.070 ± 100 AP y 21.380 ± 100 14C AP). Se infieren datos ambientales y de dieta a partir de análisis de isótopos estables en los restos de Hippidion saldiasi del sitio Betecsa 1 cuyo valor de ?13C en hueso fue de -15,45 y el valor en esmalte de dientes fue de -16,68, sugiriendo una alimentación con pastos C3. El cráneo recuperado es el primero conocido de esta especie Abstract in english This paper describes the Hippidion bones recovered from the Atacama Desert (Calama, Second Region of Chile). The analyzed assemblage corresponds to a nearly complete skeleton from Betecsa 1 site and more poorly preserved remains from Kamac Mayu site. In both H. saldiasi is identified. Two 14C radiom [...] etric determinations indicate late Pleistocene age for these remains (21,070 ± 100 BP and 21,380 ± 100 BP). Environmental and diet inferences from stable isotope analysis are also presented. The ?13C value from Betecsa 1 horses (-15.45 from bone sample and -16.68 from enamel sample) suggest a dietary adaptation exclusively C3 feeders. This is the first skull and associated skeleton recovered of this species

  20. Moluscos marinos bentónicos del Cuaternario de Bahía Anegada (sur de Buenos Aires, Argentina): variaciones faunísticas en el Pleistoceno tardío y Holoceno / Quaternary marine benthic molluscs from Anegada Bay (southern Buenos Aires, Argentina): faunistic variations in the late Pleistocene and Holocene

    Scientific Electronic Library Online (English)

    Melisa P., Charó; Enrique E., Fucks; Sandra, Gordillo.

    2013-08-01

    Full Text Available A lo largo del área costera del Atlántico sudoccidental se observan depósitos marinos que representan los dos últimos eventos transgresivos del Cuaternario (Pleistoceno tardío y Holoceno). La región de Bahía Anegada, sur de la provincia de Buenos Aires, se caracteriza por la buena preservación y abu [...] ndancia de fauna marina fósil, en especial de gasterópodos y bivalvos en los cordones litorales. Estos registros no han sido investigados con anterioridad desde el punto de vista paleontológico, y son de utilidad como indicadores de cambios ambientales del Cuaternario. El objetivo de este trabajo ha sido describir y comparar la fauna de moluscos del Pleistoceno tardío y Holoceno en Bahía Anegada. Para ello se analizaron dos áreas de la región: Canal Villalonga y Los Pocitos. Los depósitos marinos pleistocenos (asociados al estadio isotópico marino MIS5e) analizados para Bahía Anegada mostraron mayor número de especies, tanto de gasterópodos (17 versus 9) como bivalvos (14 versus 12) respecto al Holoceno. En los depósitos pleistocenos de Canal Villalonga se destaca la presencia de Crassostrea rhizophorae (Guilding) y Abra aequalis (Say) que actualmente tienen un área de distribución en latitudes bajas. En cuanto a los micromoluscos, se menciona por primera vez Turbonilla argentina Doello -Jurado para el Pleistoceno. Con base en estos análisis se concluye para la región estudiada que el Pleistoceno tardío registró mayor número de especies, tanto de bivalvos como gasterópodos, respecto al Holoceno, y que la abundancia de las especies del Pleistoceno se ha mantenido durante el Holoceno. Dichas variaciones se interpretan en asociación con cambios de la temperatura e indicarían condiciones más cálidas para el Pleistoceno tardío (último interglacial). Abstract in english Marine deposits representing the last two transgressive Quaternary events (late Pleistocene and Holocene) are observed along the coastal area of the southwestern Atlantic. Littoral deposits in the Anegada Bay region, southern province of Buenos Aires, are characterized by good preservation and abund [...] ance of fossil marine shells, especially gastropods and bivalves. These records, which have not been previously investigated from a paleontological viewpoint, are here useful as indicators of Quaternary environmental changes. The aim of this study was to describe and to compare the molluscan fauna of late Pleistocene with the equivalent of the Holocene. For that, we analyzed two areas within this region: Canal Villalonga and Los Pocitos. Compared to the Holocene, Pleistocene marine deposits (associated to Marine Isotope Stage MIS5e) from Anegada Bay showed a greater number of species, in both gastropods (17 versus 9) and bivalves (14 versus 12). In the Pleistocene deposits of Canal Villalonga is remarkable the presence of Crassostrea rhizophorae (Guilding) and Abra aequalis (Say), which are today displaced toward low latitudes. In relation to micromolluscs, Turbonilla argentina Doello-Jurado is for the first time mentioned for the Pleistocene. Our data indicate that the number of species of bivalves and gastropods was higher during the late Pleistocene than in the Holocene, and that the abundance of species during the Pleistocene has also remained during the Holocene. These variations are interpreted in association with changes in temperature, indicating warmer conditions for the late Pleistocene (last interglacial).

  1. Palaeovegetation dynamics of an ecotone forest-savanna in southern Brazilian Amazon during the late Pleistocene and Holocene based on carbon isotopes of soil organic matter

    International Nuclear Information System (INIS)

    This study was carried out in the Brazilian southern Amazon region (Rondonia state and Humaita, southern Amazon state). Carbon isotope data on soil organic matter have been collected along an ecosystem transect of about 750 km that includes a savanna, a wooded savanna (cerrado), a tropical semideciduous forest (cerradao), a forest transition type and a tropical forest. The main objective is to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Late Pleistocene (Late Glacial) and Holocene. Large ranges in ?13 values were observed in soil organic matter collected from profiles in the savanna (-27 to -14 per mille and forest regions (-26 to -19 per mille) reflecting changing distribution of 13C-depleted C3 forest and 13C enriched C4 savanna vegetation in response to climate change. 14C data of humin fraction and buried charcoal indicate that the organic matter in these soils is at least 17,000 years BP at 300-cm depth. In this period, the entire ecosystem transect are characterized by ?13C soil depth profiles, generated typically by C3 plants (forest), inferring a humid climate in the southern Amazon region after the end of last glaciation. 13C data also indicate that C4 plants (grasses) have influenced significantly the vegetation at the transitional forest and the cerrado sites of southern Rondonia state and two distinct points in the forest ecosystem in the southern Amazon state. These typical C4 type isotopic signatures probably reflect a drier climate during about 9000-8000 yr BP to 3000 yr BP and the savanna and wooded savanna expansion in distinct points of the transect. The 13C records representing the 3000 yr show an expansion of the forest, due to a climatic improvement, in areas previously occupied by savanna vegetation. This study adds to the mounting evidence that extensive forested areas existed in the Amazon during the last glacial and that savanna vegetation expanded in response to warm and dry conditions during the early to middle Holocene. (author)

  2. Cosmogenic dating of rock avalanches constraining Quaternary stratigraphy and regional neotectonics in the Argentine Central Andes (32° S)

    Science.gov (United States)

    Moreiras, Stella M.; Hermanns, Reginald L.; Fauqué, Luis

    2015-03-01

    This paper provides a comprehensive review of the chronostratigraphy of six rock avalanches clustered in the northern extreme of the Cordon del Plata range. These rock avalanches are stratigraphically related to Pleistocene glacial drifts and valley-fill deposits documenting the regional neotectonic activity. We used cosmogenic dating (TCN) to directly date block surfaces of rock-avalanche deposits, as well as optically stimulated luminescence dating (OSL) of paleo-lakes dammed by these rock avalanches. Our new direct dates (17 TCN and 4 OSL) determine the Middle-to-Late Pleistocene age of these collapses. These are in contrast to the previously established chronostratigraphy based on relative dating techniques, paleontological context, and tephrochronology. These new data help to redefine the geomorphological evolution of the Mendoza River valley. Especially, the new data indicate that the glacial stratigraphy earlier proposed must be reconsidered. We redefine this stratigraphy as far as possible with our data and discuss the data in relation with other recently published results. However, it becomes clear that the glacial history of the Mendoza valley has to be studied anew by using modern dating techniques. In addition, our data suggest that the Carrera Fault system bounding the valleys of the Cordillera del Plata has been active more recently than proposed earlier.

  3. Dark humic alluvial paleosols in Central and Southern Mexico: Micromorphological indicators of Late Pleistocene megafauna habitats Paleosuelos aluviales con humus oscuro en el Centro y Sur de México: indicadores micromorfológicos de los hábitats de la megafauna del Pleistoceno tardío Paleosolos aluviais com húmus escuro no Centro e Sul do México: indicadores micromorfológicos dos habitats da megafauna do Pleistocénico tardio

    OpenAIRE

    Rosa E. Tovar; Sergey Sedov; Berenice Solís; Elizabeth Solleiro

    2013-01-01

    During the Late Pleistocene, Mexico had a richer fauna than today with many different forms of megafauna that are now extinct. However, the ecosystems they inhabited and the particular ecological niches that they occupied are still poorly understood. Most of the findings of Pleistocene megafauna have been in alluvial deposits that present rich opportunities for paleoecological studies using paleopedological records. Floodplain paleosols commonly are poorly developed. However, micromorphologic...

  4. Late Pleistocene to early Holocene aeolian and flash-flood sedimentation and soil formation in a small hilly catchment in SW-Germany (Palatinate forest)

    Science.gov (United States)

    Dotterweich, M.; Kühn, P.; Tolksdorf, J. F.; Müller, S.; Nelle, O.

    2012-04-01

    This paper focuses on the dynamics of sedimentation processes and soil development in a steep slope 0-order catchment in the sandy Lower Bunter of the south-western mid-range mountains in Germany during the transition period from the late Glacial to the early Holocene. Italso discusses how late Palaeolithic gatherers and hunters may have influenced these processes by sedentary land occupation. The investigated dry valley covers an area of around 16.6 ha and is characterized by short and steep slopes of 30° to 60°. A significant amount of the sediments from the adjacent slopes had been captured along the wide and rather flat valley bottom and at the small outlet. Several exposures, pits, and percussion liner drillings revealed a weak to highly weathered reddish sandy material at the base and eight subsequent layers of incoherent sandy and charcoal (from pines) enriched sediments with different colours ranging from olive-brown to dull reddish brown. By stratigraphical means, the lowermost sediment can be ascribed to the early Lateglacial when the deposition of aeolian sands under cold conditions with scarce vegetation cover was a widespread phenomenon. The subsequent layer contains a higher amount of silt and dates into the Allerød as suggested by radiocarbon dating. This is corroborated by the occurrence of LST that indicate that these sediments have been near to the surface around 12,900 yr BP. It shows characteristics of a palaeosol with Bwb and BwAhb horizons (Brunic Arenosols dystric) and with greyish Ahb and Eb horizons (Albic Arenosols dystric) similar to the Usselo/Finow soils in north-eastern Germany. In the material above, many remnants of roots and organic particles and rounded bone fragments were revealed by micromorphological analyses. Then, an alternation of reddish brown coarse to fine sands and small, partly rounded stones with some small intercalate aggregations of humic material rich in charcoal which dates to around 10,000 yr BP were deposited. The layers are overlain by very clear visible wavy and frequently distributed clay-illuviation bands typical for a Luvisol. The upper meter looks duller and more homogenous which is typical for a Bv-horizion of a Cambisol. The embedded deposition shows structures in this sediment package that are typical for a flash-flood event. Records of soil erosion during this time period are sparse and it is generally assumed that sediments were fixed by forest vegetation. In contrast, these presented results indicate that the manipulation of forest vegetation by fire by sedentary Mesolithic hunter-gatherers created an open area and enabled soil erosion with a high geomorphological impact on a local scale. This geoarchive provides first time high resolution data on a natural (and anthropogenic) soil-sediment formation during the Late Pleistocene and Early Holocene in SW-Germany.

  5. Potential Interference Among The Campanian Ignimbrite Eruption, Heinrich Event 4 and The Middle/upper Palaeolithic Shift In Late Pleistocene Europe

    Science.gov (United States)

    Fedele, F. G.; Giaccio, B.; Isaia, R.; Orsi, G.

    The Campanian Ignimbrite (CI) eruption (Phlegraean Fields Caldera) was the largest volcanic eruption in the Greater Mediterranean area over the past 200 Ka (at least 150 km3 DRE). Ash layers correlated with CI have been found in sediments of the eastern Mediterranean Sea (Y5) and East Europe, from Italy to the former USSR. The recent dating of the CI eruption at 39.3 Ka BP draws attention to the coincidence be- tween this volcanic catastrophe and the suite of coeval biocultural modifications in Old World prehistory, here termed the European Late Pleistocene shift (ELPS). These included the Middle to Upper Palaeolithic cultural transition and the supposed change from Neanderthal to "modern" Homo sapiens anatomy, still a subject of sustained de- bate. The first results of our investigations show that: (1) at several archaeological sites of peninsular Italy a distinct tephra layer corresponding to the CI is regularly interbedded between the last documented Middle Palaeolithic and the earliest appear- ance of unquestionable Upper Palaeolithic assemblages; (2) at the same sites the CI tephra coincides with a interruption of occupation, several millennia long; (3) in the GISP2 Greenland ice-core, Lago Grande di Monticchio (southern Italy) lacustrine se- quences, and KET 8003 Tyrrhenian sea-core, a large volcanogenic sulfate signal (375 ppb, at 40,062 yr BP) to be correlated with the CI eruption and/or CI tephra layer occurs just before a sharp climatic shift which coincides with the onset of Heinrich event 4 (HE4). The concurrence of the CI eruption, Palaeolithic site abandonment and beginning of HE4 suggests that the overlapping of CI eruption and HE4 climatic im- pacts induced ecosystem crisis on a fairly large scale - human systems included - and well beyond the direct-impact zone. Moreover, the occurrence of the CI eruption just before HE4 probably corroborates the positive climate-volcanism feedback supposed for other high magnitude eruptions (e.g. Toba, 74 Ka). Without obviously claiming for the CI an overall evolutionary relevance within the ELPS, on the available data we nevertheless suggest that it deserves careful consideration as a contributing factor to the regional expression - or re-orientation - of cultural and population change.

  6. Pollen and lithological data from the Bukovynka Cave deposits as recorders of the Late Pleistocene and Holocene climatic change in the eastern foothills of the Carpathian Mountains (Ukraine

    Directory of Open Access Journals (Sweden)

    Nataliia GERASIMENKO

    2015-11-01

    Full Text Available The study of clastic sediments of the BukovynkaCaveshows biotic and climatic changes during the Middle Pleniglacial (the Trapeznyi Chamber, Late Glacial and Holocene (the Sukhyi Chamber in the south-eastern part of the Ukrainian Carpathians. The artesian BukovynkaCaveis located near the villageof Stal’nivtsi(the Chernivtsi region, in the PrutRiver basin. It is developed in the Miocene gypsum strata. The Quaternary clastic infilling of the cave, as well as mammal taphonomy has been previously studied in the Trapeznyi Chamber (Vremir et al., 2000; Ridush, 2004; Ridush et al., 2012, whereas palaeomagnetic research and its palaeoenvironmental implication has been provided for the Sukhyi Chamber (Bondar and Ridush, 2014. The results of pollen and grain-size studies of clastic deposits in both chambers, supported by mammal finds, are presented in this paper. In the Chernivtsi region, the pollen study has been previously performed (without 14C-dating on the Upper Pleistocene loess-paleosol section of Snyatyn and on the Onut site of the Holocene flood-plain deposits of the River Prut (Artyushenko et al., 1982. 39 samples from the cave sediments have been processed for grain-size analyses using the ‘pipette’ technique by Kachinsky (1965. In order to get pollen from clastic sediments, the following technique has been applied: heating with 10% HCl and 10% KOH, cold treatment with HF, disintegration in a solution of Na4P2O7 and separation in heavy liquid (CdI2 and KI with a specific gravity 2.2. The abundance and good preservation of pollen show that the cave chambers turned periodically into sedimentation traps. Mammal bones are also mostly well preserved. Re-deposited pollen are abundant in the Trapeznyi Chamber but occur very rarely in the Suchyi Chamber. The present-day vegetation near the cave is a meadow-steppe surrounded by Carpinus-Quercus forest. The high proportion of Pinus sylvestris pollen in the surface soil samples (30-40% does not correspond to the limited role that pine has in the modern vegetation. On the basis of this fact, pine pollen in the cave deposits are also regarded as over-represented because of its ability to travel farther on the wind than other pollen and its better preservation in rocks.

  7. Radiocarbon date on megafauna from the late Pleistocene-early Holocene of Córdoba province, Argentina: Stratigraphic and paleoclimatic significance / Fechamiento por radiocarbono de megafauna del Peistoceno tardío-Holoceno temprano de la provincia de Córdoba, Argentina: significado estratigráfico y paleoclimático

    Scientific Electronic Library Online (English)

    Laura Edith, Cruz; María Susana, Bargo; Eduardo Pedro, Tonni; Aníbal Juan, Figini.

    2010-12-01

    Full Text Available Se presenta el primer fechamiento por radiocarbono (7550 ± 60 yr 14C AP) para la provincia de Córdoba, obtenido a partir de colagéno presente en huesos de Scelidotherium leptocephalum, un perezoso terrestre extinto. Los materiales fósiles fueron exhumados de sedimentos asignados a la Formación La In [...] vernada, en el Departamento de Río Cuarto, provincia de Córdoba, Argentina. Lafecha aquí presentada soporta la asignación temporal de la Formación La Invernada al Pleistoceno tardío-Holoceno temprano y permite la correlación de estos sedimentos con los eventos climáticos que tuvieron lugar durante ese periodo. Asimismo, es uno de los fechamientos por radiocarbono más jóvenes de megamamíferos de Argentina. Abstract in english A radiocarbon date (7550 ± 60 yr 14C BP) was obtained from bone collagen of an extinct ground sloth (Scelidotherium leptocephalum) from the locality of Río Cuarto (Córdoba province, Argentina). The fossil remains were recovered from the La Invernada Formation (late Pleistocene- Holocene). The date p [...] resented in this paper is the first radiocarbon date obtainedfrom megafauna in Córdoba province, Argentina. It supports the temporal assignation of the La Invernada Formation to the late Pleistocene-early Holocene, and it will allow correlation of these sediments with climatic events that took place during this time. Moreover, it is the youngest radiocarbon date from megamammals recorded in central Argentina.

  8. The presence of Ursus ex gr. minimus-thibetanus in the late villányian and its position among the Pliocene and Pleistocene black bears in Europe.

    Czech Academy of Sciences Publication Activity Database

    Wagner, Jan; ?ermák, Stanislav; Horá?ek, I.

    -, ?. 4 (2011), s. 39-58. ISSN 1771-1150 R&D Projects: GA ?R GA205/09/0184 Institutional research plan: CEZ:AV0Z30130516 Keywords : Black bear * MN17 * Ursus aff. thibetanus * Villány 3 * Central Europe - Hungary * Ursus * Pleistocene * Pliocene Subject RIV: DB - Geology ; Mineralogy

  9. Tendencias climáticas para los pastizales pampeanos durante el Pleistoceno tardío-Holoceno: estimaciones cuantitativas basadas en secuencias polínicas fósiles / Climatic trends for the pampa grasslands during the late Pleistocene-Holocene: quantitative estimations based on fossil pollen sequences

    Scientific Electronic Library Online (English)

    Marcela Sandra, Tonello; Aldo Raúl, Prieto.

    2010-12-01

    Full Text Available Se presentan los modelos de calibración polen-clima de temperatura media anual (Tan), precipitación anual (Pan) y eficiencia de la precipitación (EP) para la región de los pastizales pampeanos (33º-41ºS y 56º-67ºO). Los modelos de Pan y EP fueron óptimos (r² boot s=0,669 y 0,717 respectivamente; RMS [...] EPboots= 16%) para obtener estimaciones cuantitativas aplicando la Técnica del Análogo Moderno a datos polínicos fósiles de dos sucesiones aluviales del Pleistoceno tardío-Holoceno. En el centro de los pastizales los valores de Pan y EP fueron entre 100 y 200 mm menores a los actuales durante el Pleistoceno tardío (16.000-12.000 años cal AP) y similares a los actuales durante la transición Pleistoceno-Holoceno, el Holoceno temprano y el Holoceno tardío. En el sudoeste los valores de Pan y EP fueron c. 200 mm mayores a los actuales durante el Holoceno medio (5500-3000 años cal AP) y disminuyeron durante el Holoceno tardío alcanzando valores similares a los actuales durante los últimos 500 años cal. Las inferencias climáticas son coincidentes con las interpretaciones paleoclimáticas previas al señalar condiciones secas a semiáridas durante el Pleistoceno tardío y subhúmedas húmedas durante la transición Pleistoceno-Holoceno y el Holoceno temprano. Sin embargo, existen discrepancias a partir de 5000 años cal AP, probablemente por la diferente sensibilidad de los registros proxies de clima. El gradiente NE-SO de precipitación durante los últimos c. 5500 años cal habría sido más pronunciado que en la actualidad. Estas estimaciones son las primeras reconstrucciones climáticas cuantitativas para la región de los pastizales pampeanos, y deberían considerarse como tendencias hasta que nuevas reconstrucciones permitan su convalidación. Abstract in english Pollen-climate calibration models for mean annual temperature (Tan), annual precipitation (Pan) and precipitation efficiency (EP) are presented for the Pampa grasslands region (33º-41ºS and 56º-67ºW). The Pan and EP models were optimal (r²boots =0,669 and 0,717; RMSEPboots= 16%) to apply Modern Anal [...] og Technique and to obtain late Pleistocene-Holocene quantitative climatic estimations based on fossil pollen from two alluvial sequences. In the central Pampa grasslands, Pan and EP values were 100 to 200 mm lower than present ones during the late Pleistocene (16000-12000 yr cal BP). During the Pleistocene- Holocene transition, early Holocene and late Holocene the values were similar to modern ones. In the southwest, Pan and EP values were c. 200 mm higher than present ones during the mid-Holocene (5500-3000 yr cal BP), and decreased during the late Holocene reaching similar modern values during the last 500 years cal. The climatic inferences agree with previous paleoclimatic interpretations that state dry to semiarid conditions during the late Pleistocene, and subhumid humid conditions during the Pleistocene-Holocene transition and early Holocene. However, there are discrepancies as from 5000 yr cal BP, probably related to the different sensitivity of the climate proxy data. The NE-SW precipitation gradient during the last c. 5500 yr cal may have been steeper than at present. These estimations are the first quantitative climatic reconstructions for the Pampa grasslands region, and should be taken as trends until new reconstructions confirm them.

  10. Correlation of Lithology to Sequence Stratigraphy: Canterbury Basin, New Zealand

    Science.gov (United States)

    Ryan-Mishkin, K.; McHugh, C. M.; Fulthorpe, C.; Morgan, D.; Shipboard Scientific Party, E.

    2010-12-01

    A major objective of IODP Expedition 317 to the Canterbury Basin, New Zealand was to date and sample clinoformal seismic sequences, sequence boundaries, and their associated facies to understand the role of eustasy in shaping sedimentation on this continental margin. Canterbury Basin stratigraphy has also been influenced by tectonics and along strike currents that must also be taken into consideration when evaluating the evolution of the margin. Sesimic stratigraphic analysis provided the large-scale framework for understanding margin architecture and for drilling Sites U1351 through U1354 across the shelf and upper slope. Nineteen regional seismic sequence bounding surfaces (U1-U19) were identified from the middle Miocene to Holocene in the sediments offshore of Canterbury Basin, New Zealand. Correlation of the lithology to seismic stratigraphy permits the identification of sedimentary packages with boundaries near the predicted depths of sequence boundaries U1-U19. These sedimentary packages have sharp basal contacts that separate coarse-grained sediment above from fine grained beneath. The coarse-grained sediment above the contacts is composed of greenish gray, fine to medium muddy sand or sandy mud containing abundant shells. Each sedimentary package can be as thick as 6 m. In contrast, the sediment beneath is composed of fine-grained mud that is heavily bioturbated. Remarkable correlation was found between the depths at which some basal contacts occur and the depths predicted for sequence boundaries U11-U19 (early Pliocene to Holocene) across the shelf and upper slope. Heterolithic lithologies characterize the depositional environments within mid- and late Pleistocene seismic sequences. In contrast, alternations of gray and green mud are common in the early Pleistocene and Pliocene. Marlstones with wavy laminations, ripples and sand lenses suggestive of current activity are typical of Miocene lithologies beneath the slope while chalks and limestones dominate the Oligocene sequences. These lithologic changes are also manifested in the architecture of the margin that evolved from a ramp morphology to a progradational margin with steeper slopes and abrupt shelf breaks. Further studies of the facies within depositional sequences and the associated sedimentary packages will permit improved correlation between lithology and seismics and a better understanding of the relative contributions of eustasy, along-strike currents and tectonics to sedimentation. Sesimic stratigraphic analysis will also permit comparison with other margins where similar sea level studies are underway, such as New Jersey.

  11. Contribution to the stratigraphy of the onshore Paraiba Basin, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Rossetti, Dilce F.; Valeriano, Marcio M., E-mail: rossetti@dsr.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Divisao de Sensoriamento Remoto; Goes, Ana M.; Brito-Neves, Benjamim B. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Inst. de Geociencias; Bezerra, Francisco H.R.; Ochoa, Felipe L. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Centro de Ciencias Exatas e da Terra. Departamento de Geologia

    2012-06-15

    Several publications have contributed to improve the stratigraphy of the Paraiba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono- sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraiba Basin. Except for a few outcrops of carbonatic-rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraiba Basin. (author)

  12. Digital landscapes and Late Pleistocene environments of deglaciation: The use of LiDAR data to test outburst flood hypotheses of lowland river gorge formation

    Science.gov (United States)

    Thorndycraft, Varyl; Cripps, Jonathan; Passmore, Dave; Oldknow, Christopher; Eades, Gwilym

    2013-04-01

    We report on the quantitative interrogation of DEMs developed from airborne LiDAR data for the identification and reconstruction of Late Pleistocene glacial lake outburst floods (GLOFs). There is much importance attached to the quantification of geomorphic processes associated with deglaciation given global warming and current observations of rapidly melting glaciers and ice caps (e.g. Greenland). Given the period of direct observation is short, recourse can be made to the study of past ice sheets and associated landforms in order to reconstruct the rates and magnitudes of change during deglaciation. Meltwater channels, lakes and outflow channels are examples of landforms that can be used to identify the position, timing and retreat of former ice margins. With regards lake drainage there is a need to distinguish 'instantaneous' outburst floods from long term downcutting in order to improve our interpretations on the rates and magnitudes of geomorphic processes. There has been success in this regards at the megaflood scale but less attention has been paid to low magnitude outburst floods that can nevertheless have important regional implications for geomorphic processes. Here we use 5m DEMs and 2m resolution LiDAR data using ArcMap10, in combination with fieldwork, to investigate outflow channels in lowland environments of northern England, and develop methodological guidelines to aid the identification of GLOF events in previously glaciated landscapes. We identified a suite of distinguishing landforms from the 2m LiDAR data, not always identifiable in the 5m DEM, that indicate rapid erosion as opposed to long-term incision: 1) abandoned head cuts; 2) spillways representing sudden incision events once a downstream blockage has failed; 3) headcut extension of incised gorges upstream of the breach site; and 4) sedimentary deposits of 'chaotic' poorly sorted, water-lain sediments mapped at low elevations in the gorge; and run-up bars at higher elevations. All of these features are present in the River Till gorge, previously thought to be the outflow of Glacial Lake Milfield in northern England but here interpreted as a new drainage pathway resulting from an outburst event. Our reconstruction of the Till flood shows complex initial flow hydraulics with water flooding over undulating drumlin terrain. However once the gorge has incised we quantify palaeodischarges of between 2000-4000 m3/s, based on hydraulic modelling using the DEM-derived topography, with floodwater elevations delimited by terrace levels associated with incision phases (caused by the sudden failure of downstream blockages). This suggests that the 1.27 km3 lake took less than one week to drain, during this time eroding approximately 0.04 km3 of material from the gorge. We also briefly report on results from another UK site, the River Derwent outflow gorge of Glacial Lake Pickering.

  13. The origin, nature and stratigraphy of Pleistocene-Holocene palaeosols in Wadi Es-Salqa (Gaza Strip, Palestine) / Sobre El Origen, Naturaleza Y Estratigrafía De Los Paleosuelos Pleistoceno-Holocenos En Wadi Es-Salqa (firanja De Gaza, Palestina)

    Scientific Electronic Library Online (English)

    Khalid F, Ubeid.

    2013-12-01

    Full Text Available La firanja de Gaza se encuentra en la parte suroeste de Palestina. Su topografía es definida por tres cordones (localmente llamado “cordones o crestas kurkar “) que son paralelas a la costa mediterránea. Las mismas se componen de areniscas calcáreas (kurkar) y depósitos de grano fino de color rojizo [...] (Hamra) del Pleistoceno - Holoceno (kurkar). Las crestas son interceptadas por tres cauces principales, de norte a sur: Beit Hanoun, Gaza y Es- Salqa (Silka). Durante el invierno Es- Salqa recoge las aguas de una cuenca de 40 km². La sección geológica de Es-Salqa muestra que la sucesión consiste en kurkar y Hamra de la Formación Gaza (Pleistoceno-Holoceno), que se incluye en el Grupo Kurkar del Plioceno-Holoceno y se superpone en contacto neto al Grupo Saqia. Las sucesiones aforantes en Es-Salqa consisten en paleosuelos de color marrón rojizo asignados a la Formación Gaza. Estos paleosuelos están constituidos por material loésico desarrollados en suelos firancos a firanco-arenosos, y suelos arenosos. El modelo de distribución del suelo loésico lo vincula genéticamente al desierto del Sinaí y el sur del Sahara, mientras que los suelos arenosos son derivados de materiales parentales de arena que generalmente cubre la parte occidental de la llanura costera del sur de Palestina. Abstract in english The Gaza Strip is located in the southwestern part of Palestine. Its topography is defined by three ridges (locally termed “kurkar ridges”) that are parallel to the Mediterranean coastline. The ridges consist of Pleistocene-Holocene calcareous sandstones (kurkar) and reddish fine-grained deposits (h [...] amra). The ridges are intersected by three main wadis, firom north to south: Wadi Beit Hanoun, Wadi Gaza, and Wadi Es-Salqa (Wadi Silka). During winter Wadi Es-Salqa collects water firom a 40 km² catchment area. The subcrop geological cross-section at Wadi Es-Salqa shows that the succession consists of kurkar and hamra of the Pleistocene-Holocene Gaza Formation, which belongs to the Pliocene-Holocene Kurkar Group and sharply overlies the Saqia Group. The outcrop successions in Wadi Es-Salqa consist of reddish-brown palaeosols of Gaza Formation. These palaeosols are loessial soils that developed in loam to sandy loam soils, as well as sandy soils. The model distribution of the loessial soil grains refects atmospheric dust that accumulated firom the Sinai and Saharan Deserts. The sandy soils are derived firom sandy parent materials that generally cover the western part of the southern coastal plain of Palestine.

  14. Late Pleistocene variations in Antarctica sea ice. I - Effect of orbital isolation changes. II - Effect of interhemispheric deep-ocean heat exchange

    Science.gov (United States)

    Crowley, Thomas J.; Parkinson, Claire L.

    1988-01-01

    A dynamic-thermodynamic sea-ice model is presently used to ascertain the effects of orbitally-induced insolation changes on Antarctic sea-ice cover; the results thus obtained are compared with modified CLIMAP reconstructions of sea-ice 18,000 years ago. The minor influence exerted by insolation on Pleistocene sea-ice distributions is attributable to a number of factors. In the second part of this investigation, variations in the production of warm North Atlantic Deep Water are proposed as a mechanism constituting the linkage between climate fluctuations in the Northern and Southern hemispheres during the Pleistocene; this hypothesis is tested by examining the sensitivity of the dynamic-thermodynamic model for Antarctic sea-ice changes in vertical ocean heat flux, and comparing the simulations with modified CLIMAP sea-ice maps for 18,000 years ago.

  15. Climatic characteristics of the late Pleistocene and Holocene continental deposits from southwestern Syria based on palynological data / Características climaticas de los depósitos continentales del Pleistoceno tardío y Holoceno del suroeste de Siria sobre la base de datos palinológicos

    Scientific Electronic Library Online (English)

    Kamal M., Hussein.

    2006-12-01

    Full Text Available El objetivo de esta investigación fue reconstruir la vegetación, el clima y los cambios que han tenido lugar durante el Pleistoceno tardío y el Holoceno, en el suroeste de Siria. Esta reconstrucción se basó en datos palinológicos obtenidos del análisis de 27 sedimentos y muestras de superficie (con [...] un espesor total de 4,55 m) coleccionadas durante el verano de 1998 en el lago Al-Hijaneh (Pleistoceno tardío) y en el valle del rio Al-Aouaj (Holoceno), y analizadas en 1999. Se establecieron tres zonas de alemacenamiento de polen. La más antigua (zona A) corresponde al Pleistoceno tardío en los depósitos lacustres del lago Al-Hijaneh. Las zonas B y C quedaron definidas en los depósitos lacustres del Holoceno del valle del rio Al-Aouaj. Las tres zonas polínicas son correlativas con zonas de polen similar en territorios del Mediterráneo del este. Los climas presentes y pasados de la región, y su vegetación son tema de discusión. Abstract in english The goal of this research was to reconstruct the vegetational and climatic changes that took place during the late Pleisocene and Holocene in southwestern Syria. This reconstruction was based on palynological data obtained from the analysis of 27 sediments and surface samples (with a total thickness [...] of 4.55 m) collected from Al-Hijaneh Lake basin (late Pleistocene) and from Al-Aouaj River valley (Holocene). Three pollen zones were established. The oldest one (zone A) corresponds to the late Pleistocene lacustrine deposits of Lake Al-Hijaneh. Zones B and C were defined in the Holocene fluvial- lacustrine deposits of the Al-Aouaj River valley. These three pollen assemblage zones are correlated to synchronic and similar C14 dated pollen zones from Syria, Turkey, Iran and Greece. This allows a more definite age determination for the deposits of this study. The region's past climates and vegetation are discussed.

  16. Paudorf locus typicus (Lower Austria) revisited – The potential of the classic loess outcrop for Middle to Late Pleistocene landscape reconstructions

    DEFF Research Database (Denmark)

    Sprafke, Tobias; Terhorst, Birgit; Peticzka, Robert; Thiel, Christine

    2013-01-01

    The more than 12 m thick loess-paleosol sequence in Paudorf, Lower Austria, has been known for decades as locus typicus of the “Paudorfer Bodenbildung” (Paudorf paleosol). The upper section of the outcrop contains an up to 1 m thick pedocomplex that developed during MIS 5. The differentiated sequence of loess-like sediment below, including a more than 2 m thick pedocomplex in its basal part, is an exceptional archive of landscape evolution from the Middle Pleistocene. Herein we present detailed ...

  17. Macroecological analyses support an overkill scenario for late Pleistocene extinctions Análises macroecológicas apoiam o cenário de sobreexploração para as extinções do final do Pleistoceno

    OpenAIRE

    Diniz-Filho, J.A.F

    2004-01-01

    The extinction of megafauna at the end of Pleistocene has been traditionally explained by environmental changes or overexploitation by human hunting (overkill). Despite difficulties in choosing between these alternative (and not mutually exclusive) scenarios, the plausibility of the overkill hypothesis can be established by ecological models of predator-prey interactions. In this paper, I have developed a macroecological model for the overkill hypothesis, in which prey population dynamic para...

  18. Late Pleistocene steppe lion Panthera leo spelaea (Goldfuss, 1810) footprints and bone records from open air sites in northern Germany - Evidence of hyena-lion antagonism and scavenging in Europe

    Science.gov (United States)

    Diedrich, Cajus G.

    2011-07-01

    Bone remains and a trackway of Pantheraichnus bottropensis nov. ichg. ichnsp. of the Late Pleistocene lion Panthera leo spelaea ( Goldfuss, 1810) have been recovered from Bottrop and other open air sites in northern Germany. Some of these bones are from open air hyena den sites. A relative high proportion of lion bones (20%) exhibit bite, chew or nibble marks, or bone crushing and nibbling caused by a large carnivore. Repeated patterns of similar bone damage have been compared to bone remains found at hyena dens in gypsum karst areas and cave sites in northern Germany. Ice Age spotted hyenas have been the main antagonists and the main scavengers on lion carcasses. The remains appear to have been imported often by hyenas into their communal dens, supporting the theory of strong hyena-lion antagonism, similar to the well documented antagonism between modern African lions and spotted hyenas. Most of the lion bones from the open air hyena den at Bottrop are probably a result of such antagonism, as are the rare remains of these carnivores found within large hyena prey bone accumulations along the Pleistocene rivers. The Emscher River terrace also has the largest quantity of hyena remains from open air river terrace sites in northern Germany. Their cub remains, and incomplete chewed prey bones from mammoths and woolly rhinoceroses, typical of hyena activity, underline the character of these sites as cub-raising and communal dens, where their prey was accumulated along the riverbanks in a similar manner to modern African hyenas.

  19. First reported occurrence of Palaeolama mirifica (Camelidae, Lamini) from the Late Pleistocene (Rancholabrean) of Puebla, central Mexico / Primera localización de Paleolama mirifica (Camelidae, Lamini) en el Pleistoceno (Rancholabreano) de Puebla, México central

    Scientific Electronic Library Online (English)

    Victor M., Bravo-Cuevas; Eduardo, Jiménez-Hidalgo.

    Full Text Available Palaeolama fue un camélido poco común en Norteamérica durante el Pleistoceno. En este trabajo damos a conocer el primer registro de P. mirifica en el Pleistoceno tardío de Puebla, México. Se trata del registro más austral de P. mirifica en Norteamérica y complementa su distribución geográfica con el [...] registro de esta especie en Costa Rica. La unidad fosilífera consiste de limo, arena fina y escasa grava, la cual es parcialmente correlacionable con la secuencia de Axamilpa, Puebla, considerada de edad MIS 2-3. Datos isotópicos y de Mesodesgaste III indican que P. mirifica de Barranca Xocoa tuvo hábito alimentario mixto. Abstract in english Palaeolama was a relatively rare camelid in North America during the Pleistocene. Here we report the first occurrence of P. mirifica in the Late Pleistocene of Puebla, central Mexico. This is the southernmost record of P. mirifica in North America, and fills in a geographic gap with a record of the [...] species in Costa Rica. The fossil-bearing unit is composed of silt, fine sand, and scarce pebbles. This unit is partially correlative with the alluvial sequence of Axamilpa, Puebla, considered to be MIS 2 - 3 in age. Isotopic data and Mesowear III values indicate that P. mirifica from Barranca Xocoa was an intermediate feeder.

  20. Size and shape stasis in late Pleistocene mammals and birds from Rancho La Brea during the Last Glacial-Interglacial cycle

    Science.gov (United States)

    Prothero, Donald R.; Syverson, Valerie J.; Raymond, Kristina R.; Madan, Meena; Molina, Sarah; Fragomeni, Ashley; DeSantis, Sylvana; Sutyagina, Anastasiya; Gage, Gina L.

    2012-11-01

    Conventional neo-Darwinian theory views organisms as infinitely sensitive and responsive to their environments, and considers them able to readily change size or shape when they adapt to selective pressures. Yet since 1863 it has been well known that Pleistocene animals and plants do not show much morphological change or speciation in response to the glacial-interglacial climate cycles. We tested this hypothesis with all of the common birds (condors, golden and bald eagles, turkeys, caracaras) and mammals (dire wolves, saber-toothed cats, giant lions, horses, camels, bison, and ground sloths) from Rancho La Brea tar pits in Los Angeles, California, which preserves large samples of many bones from many well-dated pits spanning the 35,000 years of the Last Glacial-Interglacial cycle. Pollen evidence showed the climate changed from chaparral/oaks 35,000 years ago to snowy piñon-juniper forests at the peak glacial 20,000 years ago, then back to the modern chaparral since the glacial-interglacial transition. Based on Bergmann's rule, we would expect peak glacial specimens to have larger body sizes, and based on Allen's rule, peak glacial samples should have shorter and more robust limbs. Yet statistical analysis (ANOVA for parametric samples; Kruskal-Wallis test for non-parametric samples) showed that none of the Pleistocene pit samples is statistically distinct from the rest, indicating complete stasis from 35 ka to 9 ka. The sole exception was the Pit 13 sample of dire wolves (16 ka), which was significantly smaller than the rest, but this did not occur in response to climate change. We also performed a time series analysis of the pit samples. None showed directional change; all were either static or showed a random walk. Thus, the data show that birds and mammals at Rancho La Brea show complete stasis and were unresponsive to the major climate change that occurred at 20 ka, consistent with other studies of Pleistocene animals and plants. Most explanations for such stasis (stabilizing selection, canalization) fail in this setting where climate is changing. One possible explanation is that most large birds and mammals are very broadly adapted and relatively insensitive to changes in their environments, although even the small mammals of the Pleistocene show stasis during climate change, too.

  1. Palaeoecology of well-preserved coral communities in a siliciclastic environment from the Late Pleistocene (MIS 7), Kish Island, Persian Gulf (Iran): the development of low-relief reef frameworks (biostromes) in increasingly restricted environments

    Science.gov (United States)

    Mossadegh, Zahra Karimi; Parker, Justin; Gischler, Eberhard; Oschmann, Wolfgang; Blakeway, David; Eisenhauer, Anton

    2013-03-01

    Major changes in community structure and depositional relief of high-latitude coral communities in the southern Persian Gulf between marine isotope stage (MIS) 7 and the present day suggest that the area has become increasingly restricted. Corals and bivalves from outcrops on Kish Island, Iran, were identified in order to interpret the Late Pleistocene palaeoenvironmental setting. U/Th disequilibrium dating was used to constrain the ages of the stratigraphic units. During MIS 7, two coral-bearing sequences were deposited on what is now Kish Island. The lower sequence is dated as MIS 7.5 and changes laterally from an assemblage dominated by Cyphastrea sp. and Platygyra daedalea in the west to one characterized by branching Montipora in the east. By contrast, the upper sequence, dated as MIS 7.1, transitions from an assemblage dominated by platy Montipora in the west to a diverse assemblage of Platygyra and other faviids in the east. The assemblages of both sequences are within a marl matrix and bounded by thin lithified mollusc-rich layers. Corals and bivalves indicate that the sequences were deposited on gentle slopes in sheltered environments less than 20 m deep. The MIS 7 deposits may be classified as coral carpets or biostromes that developed a low-relief framework. During MIS 5, coral communities were no longer framework building and are now limited to an Acropora-rich layer of coral rubble that covers large parts of the island, and two small incipient reefs with sparse faviids. Similarities between the MIS 5 and modern nearshore coral communities suggest that the environmental conditions during MIS 5 were comparable to those of today. The late Pleistocene coral carpets and non-framework coral communities of the southern Persian Gulf may serve as models for coral biostromes in the fossil record, which formed under restricted environmental conditions such as elevated terrigenous input, high turbidity, and strong seasonal changes in temperature and/or salinity.

  2. A new record of Equus (Mammalia: Equidae) from the Late Pleistocene of central-south Chile / Un nuevo registro de Equus (Mammalia: Equidae) para el Pleistoceno Superior de Osorno, Chile

    Scientific Electronic Library Online (English)

    OMAR P, RECABARREN; MARIO, PINO; INÉS, CID.

    2011-12-01

    Full Text Available Se analizan e interpretan 14 fósiles correspondientes a dientes y huesos de caballo registrados en el sitio Pilauco, Osorno (40°39' S-73°07' W). El sitio se formó asociado a un pantano en un borde del antiguo río Damas; en él se ha conservado abundante material de mastofauna y flora pleistocénica. U [...] na fecha radiocarbónica de 11457 ± 140 A.P obtenida de un molar, es concordante con el modelo de edad del sitio. La identificación taxonómica permite asociar a los fósiles a la especie Equus (Amerhippus) andium, lo que confirma la presencia de la especie en el centro-sur de Chile. Por otra parte, la posición geográfica de los hallazgos y la reconstrucción del paisaje indicarían que se trata de ejemplares cuyas adaptaciones en los metapodios son concordantes para el paisaje pleistocénico de Pilauco dominado por suelos volcánicos blandos, con presencia de bosquetes dispersos en grandes extensiones de praderas de gramíneas. Abstract in english Fourteen dental and bone parts of a horse excavated from the Pilauco paleontological site, Osorno (40°39' S-73°07' W) are analysed and interpreted. This site was formed in association with a peat bog located on the banks of the old Damas River and has conserved abundant late Pleistocene mammalian fa [...] una and flora materials. A date of 11457 ± 140 14C yrs B.P. was obtained from a molar and agrees with our stratigraphic age model. We have identified the fossils as pertaining to the species Equus (Amerhippus) andium, which confirms its presence in central-south Chile. Furthermore, the recorded geographic location indicate that the metapodial adaptations of the specimens previously described agree with the reconstructed late Pleistocene landscape of Pilauco, dominated by soft volcanic soils and isolated forest patches over large extensions of grasslands.

  3. A new record of Equus (Mammalia: Equidae from the Late Pleistocene of central-south Chile Un nuevo registro de Equus (Mammalia: Equidae para el Pleistoceno Superior de Osorno, Chile

    Directory of Open Access Journals (Sweden)

    OMAR P RECABARREN

    2011-12-01

    Full Text Available Fourteen dental and bone parts of a horse excavated from the Pilauco paleontological site, Osorno (40°39' S-73°07' W are analysed and interpreted. This site was formed in association with a peat bog located on the banks of the old Damas River and has conserved abundant late Pleistocene mammalian fauna and flora materials. A date of 11457 ± 140 14C yrs B.P. was obtained from a molar and agrees with our stratigraphic age model. We have identified the fossils as pertaining to the species Equus (Amerhippus andium, which confirms its presence in central-south Chile. Furthermore, the recorded geographic location indicate that the metapodial adaptations of the specimens previously described agree with the reconstructed late Pleistocene landscape of Pilauco, dominated by soft volcanic soils and isolated forest patches over large extensions of grasslands.Se analizan e interpretan 14 fósiles correspondientes a dientes y huesos de caballo registrados en el sitio Pilauco, Osorno (40°39' S-73°07' W. El sitio se formó asociado a un pantano en un borde del antiguo río Damas; en él se ha conservado abundante material de mastofauna y flora pleistocénica. Una fecha radiocarbónica de 11457 ± 140 A.P obtenida de un molar, es concordante con el modelo de edad del sitio. La identificación taxonómica permite asociar a los fósiles a la especie Equus (Amerhippus andium, lo que confirma la presencia de la especie en el centro-sur de Chile. Por otra parte, la posición geográfica de los hallazgos y la reconstrucción del paisaje indicarían que se trata de ejemplares cuyas adaptaciones en los metapodios son concordantes para el paisaje pleistocénico de Pilauco dominado por suelos volcánicos blandos, con presencia de bosquetes dispersos en grandes extensiones de praderas de gramíneas.

  4. New insights for the Late Pleistocene to Mid Holocene landscape reconstruction in the Western part of the Thessaloniki Plain (Greece): evidence for an abrupt transition and consequences on the settling history

    Science.gov (United States)

    Psomiadis, D.; Ghilardi, M.; Demory, F.; Delanghe-Sabatier, D.

    2012-04-01

    The Neolithic site of Nea Nikomideia is located at the western limit of the Thessaloniki Plain, Northern Greece and the archaeological excavations conducted in the 1960s suggested that the settlement was located close to an ancient coastline during its early occupation. Recently published results indicated that palaeoenvironmental transitions in the area influenced the human occupation from the early Holocene (6000/5800 cal. B.C.). It was also established that a freshwater lake occupied the vicinity of the Neolithic settlement at the early stages (Ghilardi et al., under press). However, the Late Pleistocene landscape configuration has not been clearly established, despite of some attempts (Lykousis, 2001). This study presents new data, which are correlated with more densely dated proxies in order to thoroughly investigate the Late Pleistocene - Holocene transition as well as the impact of following environmental alterations on the settlement. Special attention is given on periods of soil coverage which are considered indicative of periods with favourable conditions for human occupation. A new sequence is used, based on 3 new boreholes, for laser grain size analysis, loss-on-ignition and carbonate content, magnetic susceptibility measurements, microfaunal inspection and radiocarbon datings (A.M.S.) and it is intercorrelated with other sequences from the area. The synthesis of the proxies reveals distinct events of palaeoenvironmental alterations in a very well constructed chronostratigraphic framework of more than 10.000 years. The Pleistocene subsurface is found in circa 9 meters deep and clearly indicates the presence of a large alluvial fan deposition (calm environment) from Aliakmon River. The abrupt transition with early Holocene sediments reveals that an important influx of fresh water helped in creating a limnic environment of deposition. From Neolithic times to the present day, the area turned into a marine bay and subsequently into a freshwater lake where palaeosoils are clearly identified and dated from Bronze Age and Medieval Times. These two periods of high anthropogenic activities within the newly created plain could also be related to arid climatic events which affected the shape of the recent Holocence palaeo-lake.

  5. Sobre la presencia de un supuesto Haplodontheriinae (Mammalia, Toxodontidae) en el Pleistoceno tardío de la provincia de Corrientes (Argentina) / On the presence of an alleged Haplodontheriinae (Mammalia, Toxodontidae) from the late Pleistocene of the Corrientes province (Argentina)

    Scientific Electronic Library Online (English)

    Ángel R., Miño-Boilini; Alfredo E., Zurita; Mariano, Bond; Analía, Francia; Esteban, Soibelzon.

    2012-06-01

    Full Text Available En el extremo sur de Sudamérica se han postulado varias áreas que podrían haber actuado como reservorio de taxones supérstites, especialmente en el lapso Mioceno-Pleistoceno tardío ("Araucanense"-Lujanense). Así, en el Pleistoceno tardío (ca. 58-28 ka) de la provincia de Corrientes, Argentina, se ha [...] reconocido la persistencia de ciertos taxones ya desaparecidos en la región pampeana de Argentina, particularmente entre los Xenarthra Glyptodontidae, Artiodactyla Cervidae y Notoungulata "Haplodontheriinae". Aquí se efectua una revisión con criterios taxonómicos modernos de los materiales (3 restos dentarios) asignados a Toxodontidae Haplodontheriinae, cuyos registros últimos en la región pampeana provienen del Montehermosense (Plioceno). El estudio comparado indica que los 2 "caniniformes" superiores derechos (CTES-PZ 1608, 1609) corresponden en realidad a un Xenarthra Phyllophaga (Lestodon), en tanto que el tercero (CTES-PZ 1610) debe ser asignado a un Notoungulata (Toxodon), ambos géneros típicos del Pleistoceno de América del Sur. Por último, las revisiones sistemáticas que se llevan a cabo son claves para refinar el registro paleontológico regional, y brindar un aporte fundamental al esquema bioestratigráfico en áreas extra-pampeanas. Abstract in english In southern South America, some regions have been postulated as containing supersite taxa, especially during the Miocene-late Pleistocene lapse. Thus, from the Late Pleistocene (ca. 58-28 ka) of the current territory of the Corrientes Province, Argentina, it has been recognized the presence of some [...] taxa, which were extinct from the Pampean region of Argentina: Xenarthra Glyptodontidae, Artiodactyla Cervidae and Notoungulata "Haplodontheriinae". In this contribution, we carried out a review with modern taxonomic criteria of the materials belonging to Toxodontidae "Haplodontheriinae" (represented by 3 teeth), whose last record in the Pampean region corresponds to Montehermosan Age/Stage (Pliocene). The comparative study clearly shows that 2 of the 3 teeth (CTES-PZ 1608, 1609) belong to the Xenrthra Phyllophaga (Lestodon), whereas the other (CTES-PZ 1610) corresponds to the Notoungulata (Toxodon). Both genera are typical of the Pleistocene of South America. Finally, this kind of taxonomic revisions are essentials to depurate the regional paleontological record, and thus to provide a key contribution to the biostratigraphic scheme in extra-pampean areas.

  6. Sobre la presencia de un supuesto Haplodontheriinae (Mammalia, Toxodontidae en el Pleistoceno tardío de la provincia de Corrientes (Argentina On the presence of an alleged Haplodontheriinae (Mammalia, Toxodontidae from the late Pleistocene of the Corrientes province (Argentina

    Directory of Open Access Journals (Sweden)

    Ángel R. Miño-Boilini

    2012-06-01

    Full Text Available En el extremo sur de Sudamérica se han postulado varias áreas que podrían haber actuado como reservorio de taxones supérstites, especialmente en el lapso Mioceno-Pleistoceno tardío ("Araucanense"-Lujanense. Así, en el Pleistoceno tardío (ca. 58-28 ka de la provincia de Corrientes, Argentina, se ha reconocido la persistencia de ciertos taxones ya desaparecidos en la región pampeana de Argentina, particularmente entre los Xenarthra Glyptodontidae, Artiodactyla Cervidae y Notoungulata "Haplodontheriinae". Aquí se efectua una revisión con criterios taxonómicos modernos de los materiales (3 restos dentarios asignados a Toxodontidae Haplodontheriinae, cuyos registros últimos en la región pampeana provienen del Montehermosense (Plioceno. El estudio comparado indica que los 2 "caniniformes" superiores derechos (CTES-PZ 1608, 1609 corresponden en realidad a un Xenarthra Phyllophaga (Lestodon, en tanto que el tercero (CTES-PZ 1610 debe ser asignado a un Notoungulata (Toxodon, ambos géneros típicos del Pleistoceno de América del Sur. Por último, las revisiones sistemáticas que se llevan a cabo son claves para refinar el registro paleontológico regional, y brindar un aporte fundamental al esquema bioestratigráfico en áreas extra-pampeanas.In southern South America, some regions have been postulated as containing supersite taxa, especially during the Miocene-late Pleistocene lapse. Thus, from the Late Pleistocene (ca. 58-28 ka of the current territory of the Corrientes Province, Argentina, it has been recognized the presence of some taxa, which were extinct from the Pampean region of Argentina: Xenarthra Glyptodontidae, Artiodactyla Cervidae and Notoungulata "Haplodontheriinae". In this contribution, we carried out a review with modern taxonomic criteria of the materials belonging to Toxodontidae "Haplodontheriinae" (represented by 3 teeth, whose last record in the Pampean region corresponds to Montehermosan Age/Stage (Pliocene. The comparative study clearly shows that 2 of the 3 teeth (CTES-PZ 1608, 1609 belong to the Xenrthra Phyllophaga (Lestodon, whereas the other (CTES-PZ 1610 corresponds to the Notoungulata (Toxodon. Both genera are typical of the Pleistocene of South America. Finally, this kind of taxonomic revisions are essentials to depurate the regional paleontological record, and thus to provide a key contribution to the biostratigraphic scheme in extra-pampean areas.

  7. Middle-Late Pleistocene marine terraces and fault activity in the Sant'Agata di Militello coastal area (north-eastern Sicily)

    Science.gov (United States)

    Giunta, Giuseppe; Gueli, Anna M.; Monaco, Carmelo; Orioli, Silvia; Ristuccia, Gloria M.; Stella, Giuseppe; Troja, Sebastiano O.

    2012-04-01

    The coastal sector of Sant'Agata di Militello (north-eastern Sicily) is characterized by a flight of raised Middle-Upper Pleistocene marine terraces occurring at different heights with respect to present sea level. In particular, the geomorphological survey and the analysis of stereo-pairs of aerial photographs allowed to recognize at least five main orders of well preserved Quaternary surfaces and relative deposits mostly located at the hanging wall and at the footwall of the Pleistocene northwest-dipping Capo d'Orlando normal fault, which controlled the geomorphological evolution of the coastal area. The marine terraces show an overall good morphological continuity and are formed by marine platforms overlain by littoral deposits made up of yellow littoral sand and gravels in a sandy matrix. The continental sedimentary cover of the 3rd order terrace contains mammal-bearing deposits that were previously dated 200 ± 40 ka BP by isoleucine epimerization method, allowing to relate them to MIS 7.1 high-stand. In order to better define the whole terrace chronology, deposit samples were analyzed by Optically Stimulated Luminescence (OSL) methodology, a conventional SAR protocol used with sand-sized quartz. New datings, together with the detailed morphostructural analysis, allow to relate the 2nd and 4th order terraces to MIS 5.5 and 8.5, respectively, and to reconstruct the tectonic evolution of this coastal area, constraining the activity of the Capo d'Orlando fault.

  8. Pollen analyses of Pleistocene hyaena coprolites from Montenegro and Serbia

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    Argant Jacqueline

    2007-01-01

    Full Text Available The results of pollen analyses of hyaena coprolites from the Early Pleistocene cave of Trlica in northern Montenegro and the Late Pleistocene cave of Baranica in southeast Serbia are described. The Early Pleistocene Pachycrocuta brevirostris, and the Late Pleistocene Crocuta spelaea are coprolite-producing species. Although the pollen concentration was rather low, the presented analyses add considerably to the much-needed knowledge of the vegetation of the central Balkans during the Pleistocene. Pollen extracted from a coprolite from the Baranica cave indicates an open landscape with the presence of steppe taxa, which is in accordance with the recorded conditions and faunal remains. Pollen analysis of the Early Pleistocene samples from Trlica indicate fresh and temperate humid climatic conditions, as well as the co-existence of several biotopes which formed a mosaic landscape in the vicinity of the cave.

  9. Late Oligocene larger foraminifera from Nosara (Nicoya Peninsula, Costa Rica) and Indward (Carriacou, Lesser Antilles), calibrated by 87SR/86SR isotope stratigraphy

    International Nuclear Information System (INIS)

    The late Oligocene first occurrence of Miogypsina gunteri Cole and Miogypsina tani Drooger is verified in the light of larger foraminiferal assemblages from Nosara (Nicoya Peninsula, Costa Rica) and Windward (Carriacou, Grenada, Lesser Antilles). At Windward, they co-occur with planktonic foraminifera and nannofossils studied by earlier workers. 87SR/86SR isotope ratios were measured in calcite of larger foraminifera at both sites to determine independent absolute ages of the two outcrops. Late Oligocene shallow water formations unconformably overlie Paleocene-Eocene distal turbidites and siliceous shales in the outcrops in Costa Rica. The shallow-water lithostratigraphy includes near shore volcanic sandstones that alternate with sandy bioclastic limestones. The latter have yielded rich assemblages of larger foraminifera that have been studied in oriented sections, SEM for split material and polished rock thin sections for transmitted light and cathodoluminescence (CL) observation. The association of larger foraminifera includes Heterostegina antillea Cushman, Miogypsina tani Drooger, Miogypsina gunteri Cole, Miogypsina c.f (Miolepidocyclina) panamensis (Cushman), Miogypsina sp., Lepidocyclina (nephrolepidina) vaughani Cushman, Lepidocyclina yurnagurensis Cushman, Lepidocyclina undosa Cushman. At Windward, scattered outcrops of the Belvedere Formation expose mass flow deposits rich in larger foraminifera associated with an early late Oligocene (NP24) planktonic foraminifa assemblage. Planktonic foraminifera and nannofossils recovered in rocks slightly downsection indicate an upper Middle Oligocene age. Larger foraminifera species collected just north of Windward include Lepidocyclina undosa Cushman and Miogypsina gunteri Cole. The 87SR/86SR ratio was measured in 11 specimens of megalosphaeric Lepidocyclina spp., mechanically extracted from 2 rock samples collected at Punta Peladas (Costa Rica) Ratios range from 0.709088 to 0.708196, which correspond to a model age of 27.4 to 24.94 Ma. Very similar ratios, ranging from 0.708150 to 0.708167 were obtained from Windward Village (Carriacou). All measured 87SR/86SR ratios fall within a Chattian (Late Oligocene) age. Nannofossils, planktonic foraminifera and identical 87SR/86SR ratios from Punta Peladas and Windward clearly indicate a Chattian (Upper Oligocene) first occurrence of Miogypsina gunteri and Miogypsina tani and confirm this age range for the other larger foraminifera cited above. The first occurrence of Miogypsina gunteri in the lower Aquitanian and Miogypsina tani in the upper Aquitanian as proposed by European workers cannot be confirmed. (author)

  10. Late Triassic - Early Jurassic successions of the Atuel depocenter: sequence stratigraphy and tectonic controls / Sucesiones del Triásico Tardío - Jurásico Temprano del depocentro Atuel: estratigrafía secuencial y controles tectónicos

    Scientific Electronic Library Online (English)

    Silvia, Lanés; Laura, Giambiagi; Florencia, Bechis; Maisa, Tunik.

    2008-12-01

    Full Text Available La correlación bioestratigráfica de las sucesiones del Triásico Tardío - Jurásico Temprano del depocentro Atuel permitió determinar los cambios del espacio de acomodación y los posibles controles tectónicos de la sedimentación. La sección del Retiano - Sinemuriano Temprano tardío contiene facies de [...] abanicos deltaicos de talud, ríos entrelazados y ríos de baja sinuosidad con desarrollo de barras alternas, depositados durante una fase de sinrift. La sucesión del Sinemuriano Temprano tardío - Toarciano alberga facies de abanicos deltaicos intermedios (entre los de tipo Gilbert y los de plataforma), ríos entrelazados, ríos de baja sinuosidad, estuarios dominados por oleaje y plataformas marinas transgresivas (desde plataformas dominadas por tormentas hasta otras influídas por corrientes de turbidez), todos los cuales registran la fase de sag. Se proponen dos esquemas estratigráficos según diferentes criterios: el primero considerando unidades tectosedimentarias (TSU) y el segundo usando secuencias depositacionales (o de tipo "Exxon"). En el primer esquema la TSU de sinrift se corresponde con la Mesosecuencia Precuyo y la TSU de sag equivale parcialmente a la Mesosecuencia Cuyo, manteniendo en gran parte el esquema de mesosecuencias vigente para la cuenca Neuquina aunque asignando los depósitos de abanicos deltaicos a la Mesosecuencia Precuyo. En el segundo esquema se considera a toda la sucesión del Triásico Tardío - Jurásico Temprano como parte de la Mesosecuencia Cuyo, donde los depósitos de sinrift componen el cortejo de mar bajo (LST) y la mayoría de los depósitos de sag forman parte del cortejo transgresivo (TST). El límite de secuencia basal no aflora, la superficie de inundación en la base del TST y la superficie de máxima inundación en el tope del TST están marcados, respectivamente, por los niveles estuáricos más bajos y por las lutitas negras con bivalvos subóxicos (Bositra sp.). Abstract in english Biostratigraphic correlations of the Late Triassic - Early Jurassic successions of the Atuel depocenter allowed determining the accommodation changes and the possible tectonic controls on sedimentation. The Rhaetian - late Early Sinemurian deposits contain facies of slope-type fan deltas, braided fl [...] uvial systems and low sinuosity rivers with alternate bars deposited during a synrift phase. The late Early Sinemurian - Toarcian series host facies of intermediate (Gilbert to shelf) type fan deltas, braided and low sinuosity fluvial systems, wave-dominated estuaries, transgressive storm-dominated and turbidite-influenced marine shelves which record the sag phase. According to different criteria two stratigraphic schemes are proposed, the first one considering tectosedimentary units (TSU) and the second one using "Exxon-like" sequences. In the first scheme the synrift TSU matches the actual Precuyo Mesosequence and the sag TSU is partly equivalent to the Cuyo Mesosequence, mainly keeping the current mesosequence scheme for the Neuquén basin but assigning the fandeltaic deposits to the Precuyo Mesosequence. The second sequence scheme considers the whole Late Triassic - Early Jurassic succession as a part of the Cuyo Mesosequence, where the synrift deposits composes the detached lowstand system tract (LST) and most of the sag deposits makes the transgressive system tract (TST). The basal sequence boundary does not crop out, the flooding surface at the TST base and the maximum flooding surface at the TST top are respectively marked by the lowest estuarine levels and by black shales with suboxic-compatible bivalves (Bositra sp.).

  11. Late Triassic - Early Jurassic successions of the Atuel depocenter: sequence stratigraphy and tectonic controls Sucesiones del Triásico Tardío - Jurásico Temprano del depocentro Atuel: estratigrafía secuencial y controles tectónicos

    Directory of Open Access Journals (Sweden)

    Silvia Lanés

    2008-12-01

    Full Text Available Biostratigraphic correlations of the Late Triassic - Early Jurassic successions of the Atuel depocenter allowed determining the accommodation changes and the possible tectonic controls on sedimentation. The Rhaetian - late Early Sinemurian deposits contain facies of slope-type fan deltas, braided fluvial systems and low sinuosity rivers with alternate bars deposited during a synrift phase. The late Early Sinemurian - Toarcian series host facies of intermediate (Gilbert to shelf type fan deltas, braided and low sinuosity fluvial systems, wave-dominated estuaries, transgressive storm-dominated and turbidite-influenced marine shelves which record the sag phase. According to different criteria two stratigraphic schemes are proposed, the first one considering tectosedimentary units (TSU and the second one using "Exxon-like" sequences. In the first scheme the synrift TSU matches the actual Precuyo Mesosequence and the sag TSU is partly equivalent to the Cuyo Mesosequence, mainly keeping the current mesosequence scheme for the Neuquén basin but assigning the fandeltaic deposits to the Precuyo Mesosequence. The second sequence scheme considers the whole Late Triassic - Early Jurassic succession as a part of the Cuyo Mesosequence, where the synrift deposits composes the detached lowstand system tract (LST and most of the sag deposits makes the transgressive system tract (TST. The basal sequence boundary does not crop out, the flooding surface at the TST base and the maximum flooding surface at the TST top are respectively marked by the lowest estuarine levels and by black shales with suboxic-compatible bivalves (Bositra sp..La correlación bioestratigráfica de las sucesiones del Triásico Tardío - Jurásico Temprano del depocentro Atuel permitió determinar los cambios del espacio de acomodación y los posibles controles tectónicos de la sedimentación. La sección del Retiano - Sinemuriano Temprano tardío contiene facies de abanicos deltaicos de talud, ríos entrelazados y ríos de baja sinuosidad con desarrollo de barras alternas, depositados durante una fase de sinrift. La sucesión del Sinemuriano Temprano tardío - Toarciano alberga facies de abanicos deltaicos intermedios (entre los de tipo Gilbert y los de plataforma, ríos entrelazados, ríos de baja sinuosidad, estuarios dominados por oleaje y plataformas marinas transgresivas (desde plataformas dominadas por tormentas hasta otras influídas por corrientes de turbidez, todos los cuales registran la fase de sag. Se proponen dos esquemas estratigráficos según diferentes criterios: el primero considerando unidades tectosedimentarias (TSU y el segundo usando secuencias depositacionales (o de tipo "Exxon". En el primer esquema la TSU de sinrift se corresponde con la Mesosecuencia Precuyo y la TSU de sag equivale parcialmente a la Mesosecuencia Cuyo, manteniendo en gran parte el esquema de mesosecuencias vigente para la cuenca Neuquina aunque asignando los depósitos de abanicos deltaicos a la Mesosecuencia Precuyo. En el segundo esquema se considera a toda la sucesión del Triásico Tardío - Jurásico Temprano como parte de la Mesosecuencia Cuyo, donde los depósitos de sinrift componen el cortejo de mar bajo (LST y la mayoría de los depósitos de sag forman parte del cortejo transgresivo (TST. El límite de secuencia basal no aflora, la superficie de inundación en la base del TST y la superficie de máxima inundación en el tope del TST están marcados, respectivamente, por los niveles estuáricos más bajos y por las lutitas negras con bivalvos subóxicos (Bositra sp..

  12. Isotopic Constraints (U, Th, Pb, Sr, Ar) on the Timing of Magma Generation, Storage and Eruption of a Late-Pleistocene Subvolcanic Granite, Alid Volcanic Center, Eritrea

    Science.gov (United States)

    Lowenstern, J. B.; Charlier, B. L.; Wooden, J. L.; Lanphere, M. A.; Clynne, M. A.; Bullen, T. D.

    2001-12-01

    Isotopic analyses demonstrate that a shallow granophyric intrusion from the Alid volcanic center (AVC) was generated, intruded and crystallized over a 20,000-year period in the latest Pleistocene. The granophyre is not exposed, but was ejected as unmelted blocks within a ~1 km3 pyroclastic flow deposit around 15 ka and is a subvolcanic equivalent of the erupted rhyolitic pumice (Lowenstern et al., 1997: J Petrol 12, p. 1707-1721). The rock contains 2.59) is 15.2+/- 5.8 ka (all errors are 2 ? ). Two other splits with lower density (thus higher in Na) yielded ages older than 24 ka, and may retain some excess Ar. Thus, the time between intrusion and complete crystallization for the granophyre was http://wrgis.wr.usgs.gov/docs/geologic/jlwnstrn/alid/ Alidpage.html

  13. Macroecological analyses support an overkill scenario for late Pleistocene extinctions Análises macroecológicas apoiam o cenário de sobreexploração para as extinções do final do Pleistoceno

    Directory of Open Access Journals (Sweden)

    J. A. F. Diniz-Filho

    2004-08-01

    Full Text Available The extinction of megafauna at the end of Pleistocene has been traditionally explained by environmental changes or overexploitation by human hunting (overkill. Despite difficulties in choosing between these alternative (and not mutually exclusive scenarios, the plausibility of the overkill hypothesis can be established by ecological models of predator-prey interactions. In this paper, I have developed a macroecological model for the overkill hypothesis, in which prey population dynamic parameters, including abundance, geographic extent, and food supply for hunters, were derived from empirical allometric relationships with body mass. The last output correctly predicts the final destiny (survival or extinction for 73% of the species considered, a value only slightly smaller than those obtained by more complex models based on detailed archaeological and ecological data for each species. This illustrates the high selectivity of Pleistocene extinction in relation to body mass and confers more plausibility on the overkill scenario.A extinção da megafauna no final do Pleistoceno tem sido tradicionalmente explicada por grandes mudanças climáticas ou pelo efeito de "sobreexploração" por parte dos primeiros caçadores (overkill. Apesar das dificuldades e controvérsias na distinção desses dois cenários não mutuamente exclusivos, a plausibilidade do cenário de sobreexploração pode ser avaliada por modelos de interação predador-presa. Neste estudo, demonstrou-se como um modelo macroecológico determinístico (isto é, utilizando parâmetros derivados de relações alométricas para diferentes espécies pode ser utilizado para avaliar a dinâmica das presas potenciais dos primeiros caçadores na América. Esse modelo previu corretamente o destino de 73% das espécies, valor apenas pouco inferior ao obtido por outros modelos mais complexos para o cenário. Isso ilustra a elevada seletividade do cenário de sobreexploração em relação ao tamanho do corpo e sua plausibilidade como explicação para as extinções da megafauna no final do Pleistoceno.

  14. Macroecological analyses support an overkill scenario for late Pleistocene extinctions / Análises macroecológicas apoiam o cenário de sobreexploração para as extinções do final do Pleistoceno

    Scientific Electronic Library Online (English)

    J. A. F., Diniz-Filho.

    2004-08-01

    Full Text Available A extinção da megafauna no final do Pleistoceno tem sido tradicionalmente explicada por grandes mudanças climáticas ou pelo efeito de "sobreexploração" por parte dos primeiros caçadores (overkill). Apesar das dificuldades e controvérsias na distinção desses dois cenários não mutuamente exclusivos, a [...] plausibilidade do cenário de sobreexploração pode ser avaliada por modelos de interação predador-presa. Neste estudo, demonstrou-se como um modelo macroecológico determinístico (isto é, utilizando parâmetros derivados de relações alométricas para diferentes espécies pode ser utilizado para avaliar a dinâmica das presas potenciais dos primeiros caçadores na América. Esse modelo previu corretamente o destino de 73% das espécies, valor apenas pouco inferior ao obtido por outros modelos mais complexos para o cenário. Isso ilustra a elevada seletividade do cenário de sobreexploração em relação ao tamanho do corpo e sua plausibilidade como explicação para as extinções da megafauna no final do Pleistoceno. Abstract in english The extinction of megafauna at the end of Pleistocene has been traditionally explained by environmental changes or overexploitation by human hunting (overkill). Despite difficulties in choosing between these alternative (and not mutually exclusive) scenarios, the plausibility of the overkill hypothe [...] sis can be established by ecological models of predator-prey interactions. In this paper, I have developed a macroecological model for the overkill hypothesis, in which prey population dynamic parameters, including abundance, geographic extent, and food supply for hunters, were derived from empirical allometric relationships with body mass. The last output correctly predicts the final destiny (survival or extinction) for 73% of the species considered, a value only slightly smaller than those obtained by more complex models based on detailed archaeological and ecological data for each species. This illustrates the high selectivity of Pleistocene extinction in relation to body mass and confers more plausibility on the overkill scenario.

  15. Stratigraphy and structural geology

    Science.gov (United States)

    Carr, M. H.; Wilhelms, D. E.; Greeley, R.; Guest, J. E.

    1976-01-01

    The immediate goal of stratigraphy and structural geology is to reduce the enormous complexity of a planetary surface to comprehensible proportions by dividing the near-surface rocks into units and mapping their distribution and attitude.

  16. Analysis of Pleistocene paleodrainage evolution in the Po Basin (Italy) by multivariate statistical techniques

    OpenAIRE

    Vezzoli, Giovanni

    2008-01-01

    In order to obtain a high-resolution Pleistocene stratigraphy, eleven continuously cored boreholes, 100 to 220m deep were drilled in the northern part of the Po Plain by Regione Lombardia in the last five years. Quantitative provenance analysis (QPA, Weltje and von Eynatten, 2004) of Pleistocene sands was carried out by using multivariate statistical analysis (principal component analysis, PCA, and similarity analysis) on an integrated data set, including high-resolution bulk ...

  17. Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: reassessing the age of Wally's Beach, Canada.

    Science.gov (United States)

    Waters, Michael R; Stafford, Thomas W; Kooyman, Brian; Hills, L V

    2015-04-01

    The only certain evidence for prehistoric human hunting of horse and camel in North America occurs at the Wally's Beach site, Canada. Here, the butchered remains of seven horses and one camel are associated with 29 nondiagnostic lithic artifacts. Twenty-seven new radiocarbon ages on the bones of these animals revise the age of these kill and butchering localities to 13,300 calibrated y B.P. The tight chronological clustering of the eight kill localities at Wally's Beach indicates these animals were killed over a short period. Human hunting of horse and camel in Canada, coupled with mammoth, mastodon, sloth, and gomphothere hunting documented at other sites from 14,800-12,700 calibrated y B.P., show that 6 of the 36 genera of megafauna that went extinct by approximately 12,700 calibrated y B.P. were hunted by humans. This study shows the importance of accurate geochronology, without which significant discoveries will go unrecognized and the empirical data used to build models explaining the peopling of the Americas and Pleistocene extinctions will be in error. PMID:25831543

  18. Calibration of amino acid racemization (AAR) kinetics in United States mid-Atlantic Coastal Plain Quaternary mollusks using 87Sr/ 86Sr analyses: Evaluation of kinetic models and estimation of regional Late Pleistocene temperature history

    Science.gov (United States)

    Wehmiller, J. F.; Harris, W.B.; Boutin, B.S.; Farrell, K.M.

    2012-01-01

    The use of amino acid racemization (AAR) for estimating ages of Quaternary fossils usually requires a combination of kinetic and effective temperature modeling or independent age calibration of analyzed samples. Because of limited availability of calibration samples, age estimates are often based on model extrapolations from single calibration points over wide ranges of D/L values. Here we present paired AAR and 87Sr/ 86Sr results for Pleistocene mollusks from the North Carolina Coastal Plain, USA. 87Sr/ 86Sr age estimates, derived from the lookup table of McArthur et al. [McArthur, J.M., Howarth, R.J., Bailey, T.R., 2001. Strontium isotopic stratigraphy: LOWESS version 3: best fit to the marine Sr-isotopic curve for 0-509 Ma and accompanying Look-up table for deriving numerical age. Journal of Geology 109, 155-169], provide independent age calibration over the full range of amino acid D/L values, thereby allowing comparisons of alternative kinetic models for seven amino acids. The often-used parabolic kinetic model is found to be insufficient to explain the pattern of racemization, although the kinetic pathways for valine racemization and isoleucine epimerization can be closely approximated with this function. Logarithmic and power law regressions more accurately represent the racemization pathways for all amino acids. The reliability of a non-linear model for leucine racemization, developed and refined over the past 20 years, is confirmed by the 87Sr/ 86Sr age results. This age model indicates that the subsurface record (up to 80m thick) of the North Carolina Coastal Plain spans the entire Quaternary, back to ???2.5Ma. The calibrated kinetics derived from this age model yield an estimate of the effective temperature for the study region of 11??2??C., from which we estimate full glacial (Last Glacial Maximum - LGM) temperatures for the region on the order of 7-10??C cooler than present. These temperatures compare favorably with independent paleoclimate information for the region. ?? 2011 Elsevier B.V.

  19. Taxonomía y hábito alimentario de Equus conversidens (Perissodactyla, Equidae) del Pleistoceno Tardío (Rancholabreano) de Hidalgo, centro de México / Taxonomy and dietary behavior of Equus conversidens (Perissodactyla, Equidae) from the late Pleistocene (Rancholabream) of Hidalgo, central Mexico

    Scientific Electronic Library Online (English)

    Víctor M., Bravo-Cuevas; Eduardo, Jiménez-Hidalgo; Jaime, Priego-Vargas.

    2011-04-01

    Full Text Available El estudio comparado de material craneal y dental perteneciente a équidos, recuperado de sedimentos pleistocénicos innominados de origen fluvio-lacustre ubicados en la parte suroriental de Hidalgo, permitió caracterizar y asignar la muestra disponible a Equus conversidens. Este registro aporta evide [...] ncia adicional acerca de la amplia distribución que tuvo esta especie a lo largo del territorio nacional y del subcontinente Norteamericano en conjunto durante los últimos dos millones de años. Por otra parte, la interpretación del hábito alimentario mediante la implementación del método de mesodesgaste, reveló que el patrón de desgaste observado en los elementos dentales considerados en el análisis, caracterizado por una combinación de relieve oclusal bajo y cúspides romas, es estrechamente cercano al que distingue a la especie pacedora reciente Bison bison. Los resultados obtenidos indican que la población de équidos hidalguense tuvo una dieta conformada predominantemente por recursos abrasivos con un alto contenido de sílice y/o fitolitos (pastos, polvo y/o arena). El comportamiento alimentario propuesto evidencia la presencia de zonas de vegetación abierta en lo que ahora es parte del centro de México durante la segunda mitad del Pleistoceno; aunado a esto, las formas herbívoras asociadas al registro de équidos sugieren que, además de áreas donde posiblemente predominaron los pastos y otras herbáceas, también existieron zonas más arboladas, lo cual es indicativo de un hábitat heterogéneo. Abstract in english A comparative study of equid cranial and dental material, recovered from unnamed fluvio-lacustrine deposits of late Pleistocene age that crop out in southeastern Hidalgo, allowed to assign the fossil sample to Equus conversidens. The record gives additional evidence on the widespread distribution of [...] this species throughout the North American subcontinent during the last two million years. On the other hand, we evaluated the dietary behavior of this Equus population from Hidalgo by the extended mesowear analysis method. The observed mesowear pattern is comparable to that of the recent grazer species Bison bison. These species display a particular combination of low occlusal relief and blunt cusps. This suggests that the horse population from Hidalgo was a grass feeder that incoporated abrasive food items into its diet (grass and/or extrinsic grit). The results provide evidence for the existence of local grazing habitats in central Mexico during the late Pleistocene; furthermore, the associated herbivore fauna indicates wooded areas as well, thus suggesting a heterogeneous habitat.

  20. A Late Pleistocene macrobenthic assemblage in Caleta Patillos, northern Chile: paleoecological and paleobiogeographical interpretations / Un ensamble macrobéntico del Pleistoceno Tardío en Caleta Patillos, norte de Chile: interpretaciones paleoecológicas y paleobiogeográflcas

    Scientific Electronic Library Online (English)

    Marcelo M, Rivadeneira; Erico R, Carmona.

    2008-01-01

    Full Text Available En este trabajo se describe y analiza la estructura de un ensamble fósil marino macrobentónico del Pleistoceno Tardío (posiblemente último interglacial) en Caleta Patillos, norte de Chile (20°45'S, 70°12'O). Un análisis tafonómico sugiere la existencia de un ambiente de depositación submareal somero [...] , primariamente de fondo blando, de alta energía, e intensa mezcla de especies desde varios tipos de habitats bentónicos. El total de 38 taxa identificados, correspondientes en su mayoría a especies de moluscos, gastrópodos y bivalvos, no fue distinto de lo registrado en otros ensambles pleistocénicos tardíos en el norte de Chile. A una escala biogeográfica, la composición del ensamble de moluscos mostró notables similitudes con la fauna actual, y no se registraron especies extralimitales. A una escala local, sin embargo, una comparación con el ensamble viviente en el mismo sitio de estudio mostró una dramática alteración en la composición de especies, un resultado que no puede ser explicado por sesgos de muestreo. Se plantea una profunda y quizás muy reciente (i.e., en tiempos históricos) alteración en la estructura de los ensambles macrobentónicos locales Abstract in english In the present study, we describe and analyze the structure of a Late Pleistocene (likely last interglacial) marine macrobenthic assemblage in Caleta Patillos (20°45'S, 70°12'W), northern Chile. A taphonomic analysis suggests the existence of a shallow subtidal paleonvironment, mainly soft-bottom, o [...] f high energy and intense mixing from several benthic habitats. The total number of 38 taxa recorded, mainly gastropods and bivalves, was not different than the ones reported in other Late Pleistocene assemblages in northern Chile. At a biogeographic scale, the composition of mo Husk species showed remarkable similarities with present-day fauna, and no extralimital species were recorded. At local scale, however, a comparison with the living assemblage in the same area of study showed a dramatic shift in the species' composition, a result that cannot be explained by sampling bias. A deep and perhaps very recent (i.e., at historical times) alteration of the structure of local macrobenthic assemblages is hypothesized

  1. Ancient feeding ecology and extinction of Pleistocene horses from the Pampean Region (Argentina)

    OpenAIRE

    Sánchez Chillón, Begoña; Prado, José L.; Alberdi Alonso, María Teresa

    2006-01-01

    To reconstruct the diet and habitat preference of fossil horses, we measured the carbon and oxygen isotope composition of 35 bone and tooth samples of Equus (Amerhippus) neogeus Lund, Hippidion principale (Lund), and Hippidion devillei (Gervais) from 10 different Pleistocene localities in the Pampean region (Argentina). To compare the three species by stratigraphic age, we divided the samples into three groups: lower Pleistocene, middle-late Pleistocene and latest Pleistocene. Sam...

  2. Stratigraphy of the Harwell boreholes

    International Nuclear Information System (INIS)

    Seven boreholes, five of them partially cored, were drilled at the Atomic Energy Research Establishment at Harwell as part of a general investigation to assess the feasibility of storing low- and intermediate-level radioactive waste in underground cavities. Two of the deeper boreholes were almost wholly cored to provide samples for hydrogeological, hydrochemical, mineralogical, geochemical, geotechnical, sedimentological and stratigraphical studies to enable variations in lithology and rock properties to be assessed, both vertically and laterally, and related to their regional geological setting. This report describes the lithologies, main faunal elements and stratigraphy of the Cretaceous, Jurassic, Triassic and Carboniferous sequences proved in the boreholes. More detailed stratigraphical accounts of the late Jurassic and Cretaceous sequences will be prepared when current studies of the faunal assemblages are complete. (author)

  3. Pleistocene seismic sequences may result from eustatic change but can they be used for global correlations? New Insights from the Canterbury Basin, New Zealand

    Science.gov (United States)

    McHugh, C. M.; Fulthorpe, C.; Hoyanagi, K.; Blum, P.

    2013-12-01

    To understand the influence of eustasy on continental margin sedimentation and test the concepts of sequence stratigraphy, Integrated Ocean Drilling Program Expedition 317 drilled four sites on the continental shelf and upper slope of the Canterbury Basin, eastern South Island, New Zealand. We present results from upper slope Site U1352 (320 m water depth). A high-resolution multiproxy approach involving geochemical elemental analyses, lithostratigraphy and biostratigraphy, calibrated to an oxygen isotope scale, was applied to understand sedimentation over the past ~1.8 million years. Multichannel seismic data (EW00-01 survey) provided a seismic sequence stratigraphic framework against which to interpret the data. Seismic sequence boundaries are represented by a unique geochemical signature and arrangement of overlying sedimentary facies. However, several such geochemical-lithologic units are commonly contained within each seismic sequence. These higher frequency, intrasequence geochemical units generally correlate with100 ky glacial-interglacial Milankovic variability in the late Pleistocene, revealing that it took several glacio-eustatic cycles to build each seismic sequence. These findings support prior results obtained from Pleistocene sediments recovered by Ocean Drilling Program Leg 174A that drilled on the New Jersey margin with similar objectives to those of Expedition 317. In both northern and southern hemisphere siliciclastic settings there is a strong correlation between seismic sequences and glacio-eustasy, but the correlation between isotopic cycles and sequence boundaries is not one-to-one: only a subset of the glacioeustatic cycles result in a preserved seismic sequence boundary. Furthermore, late Pleistocene sequence boundaries on the two margins are not synchronous. Local conditions cause different isotopic peaks to be preferentially preserved as sequence boundaries in each location and preserved seismic sequences contain different groupings of marine isotope stages. Therefore, high-frequency Pleistocene seismic sequences may not correlate globally even though they are driven by glacio-eustasy.

  4. Paudorf locus typicus (Lower Austria) revisited – The potential of the classic loess outcrop for Middle to Late Pleistocene landscape reconstructions

    DEFF Research Database (Denmark)

    Sprafke, Tobias; Terhorst, Birgit

    2013-01-01

    The more than 12 m thick loess-paleosol sequence in Paudorf, Lower Austria, has been known for decades as locus typicus of the “Paudorfer Bodenbildung” (Paudorf paleosol). The upper section of the outcrop contains an up to 1 m thick pedocomplex that developed during MIS 5. The differentiated sequence of loess-like sediment below, including a more than 2 m thick pedocomplex in its basal part, is an exceptional archive of landscape evolution from the Middle Pleistocene. Herein we present detailed paleopedological and sedimentological surveys, as well as first micromorphological observations to address the sequence in its entirety and the processes leading to its genesis. Furthermore, high resolution color and carbonate analyses, as well as detailed texture analyses, have resulted in a substantial database. The studies show that the loess sediments were subject to a polygenetic development under periglacial conditions reflected in eolian silt and fine sand accumulation, admixture of local material during (mostly solifluidal) redeposition and in situ processes. Horizons with signs of pedogenesis, particularly the two pedocomplexes, document longer phases of stability; the stages of development can be correlated to equivalent sequences and seen as paleoclimatic signals where chronological data are available. The upper pedocomplex is a Chernozem of the early last glacial (MIS 5c–[a?]), which developed in a solifluidal redeposited (MIS 5d) interglacial Cambisol (MIS 5e). Cryosols, typical for MIS 6 sequences, are present in the loess sediment below. The lower pedocomplex formed during several warm stages of varying intensities, with interruptions caused by colluvial processes and admixture of eolian sediment during colder stages.

  5. Super-High-Resolution Seismic-Reflection-Based Analysis of the Late Pleistocene- Holocene Highstand-Active Newport Channel and Its Distributaries, Southern California Borderland

    Science.gov (United States)

    Temeng, A.; Covault, J. A.; Paull, C. K.; Ryan, H.; Sliter, R.; Graham, S. A.

    2008-12-01

    Super-high-resolution multibeam bathymetry (vertical resolution of 0.15-m and horizontal resolution of 1 m at 50 m survey altitude) and chirp seismic-reflection profiles (3.5 kHz; vertical resolution of 0.11 m) were collected by Monterey Bay Aquarium Research Institute's Autonomous Underwater Vehicle (AUV) in order to examine fine-scale details of the Holocene-active Newport channel and its distributaries offshore southern California. The resolution afforded by these data greatly exceeds industry-standard multichannel seismic- reflection data (typically 10 to 25 m vertical resolution). Recently acquired sparker data (100 to 4000 Hz), older Huntec deep-tow boomer (800 to 1200 Hz) and WesternGeco multichannel seismic-reflection data collected since the 1970's are available to analyze coarser-scale channel geometry and longer-term depositional evolution. As many as 48 radiocarbon ages from 16 piston cores are available in order to establish a chronostratigraphic framework for the latest Pleistocene and Holocene. Data show up to three coalescing, southwestward-trending, low-relief distributary channels at 800 m water depth in the western survey, whose features stand in sharp contrast with gentle, nearly flat topography in the eastern survey. The surveys are separated by the left-lateral Carlsbad Ridge Fault. Chirp profiles show the cut-and-fill organization of distributary channel-filling turbidites, which have an average thickness of ~ 2 m. Distributary channels are depressions history and relationship to the main Newport channel. Additionally, the fine-scale stratigraphic architecture will be correlated with well-documented southern California allogenic influences of sedimentation, including climate, basin tectonics and sea level. This study provides insight into the finer-scale geometries and internal characteristics of deep-water channel scours and fill and the processes and controls on their formation.

  6. Spain as an emergency air traffic hub during volcanic air fall events? Evidence of past volcanic ash air fall over Europe during the late Pleistocene.

    OpenAIRE

    Hardiman, Mark; Lane, Christine S.; Blockley, Simon P. E.; Moreno, Ana; Valero-Garces, Blas; Ortiz Menéndez, José Eugenio; Torres Pérez-Hidalgo, Trinidad José; Lowe, John J; Menzies, Martin A.

    2010-01-01

    Past volcanic eruptions often leave visible ash layers in the geological record, for example in marine or lake sedimentary sequences. Recent developments, however, have shown that non-visible volcanic ash layers are also commonly preserved in sedimentary deposits. These augment the record of past volcanic events by demonstrating that past ash dispersals have been more numerous and widely disseminated in Europe than previously appreciated. The dispersal ‘footprints’ of some large late Pleistoc...

  7. Diagenetic rejuvenation of raised coral reefs and precision of dating. The contribution of the Red Sea reefs to the question of reliability of the Uranium-series datings of middle to late Pleistocene key reef-terraces of the world

    Directory of Open Access Journals (Sweden)

    Choukri Abdelmajid

    2008-03-01

    Full Text Available This paper is a general review of the dating of reefs on the coasts of the Red Sea, including those of Egypt, Jordan, Sudan, Eritrea, Saudi Arabia and Djibouti. New methods of sampling and dating (U/Th already tested on the reefs and associate deposits of the African coast of Egypt have demonstrated that processes of rejuvenation shown to exist in the best-preserved corals are probably attributable to the diagenesis of the organic material in their bio-minerals, thus justifying a revision of a great many datings of corals supposedly younger or older than the age assigned to the high-level isotopic substage (?18O MIS 5.5 (= 5e. During this late Pleistocene substage, a rapid lowering of sea level, short and limited to about ten meters, was detected and associated with a glacio-eustatic episode of global influence. A comparison of these Middle East reef chronologies with those of New Guinea, Australia and the western Atlantic that are referred only with difficulty to the ?18O global sea-level curves, casts doubt on the reliability of many regional reconstructions. Moreover the most "classic" reef chronologies, more or less out-of-phase with global isotopic records calls for a reexamination of the chronologic basis of the reference curves derived from marine isotopic data.

  8. Reconstructing the Late Pleistocene Southern Ocean biological pump using the vertical gradient of Cd/Ca in planktic and benthic foraminifera

    Science.gov (United States)

    Charidemou, Miros; Hall, Ian; Ziegler, Martin

    2015-04-01

    The Southern Ocean is a particularly important region in the global carbon cycle because its wind-driven upwelling regime brings CO2-rich deep waters to the ocean surface. However, outgassing of CO2 to the atmosphere is ultimately determined by the efficiency of the soft-tissue biological pump which transfers carbon back into the deep sea. Biological productivity in the Southern Ocean on glacial-interglacial timescales is thought to be influenced by the availability of iron from terrestrial dust sources (Martin, 1990). However, the exact nature of the relationship between productivity and dust flux is still debated (Ziegler et al., 2013; Martinez-Garcia et al., 2014) and remains unclear for earlier times such as during the Middle Pleistocene Transition (MPT). Changes in the strength of the soft-tissue biological pump can be reconstructed with relative ease by measuring carbon isotopes in planktic and benthic foraminifera and quantifying the vertical gradient between them (Ziegler et al., 2013). Our ultimate aim is to use this technique to reconstruct changes in the biological pump in the Southern Ocean during the MPT, when a sharp rise in dust flux is observed in the sedimentary record (Martinez-Garcia et al., 2011). This will allow us to assess the contribution of changes in the Southern Ocean biological pump to the climatic reorganisation that occurred during the MPT. However, before the ??13C record is constructed for the MPT it is vital to confirm that this method is indeed a reliable proxy for the soft-tissue biological pump. Records of ??13C can be influenced by changes in the whole ocean inventory of ?13C, changes in circulation and changes in the degree of fractionation between the ocean and the atmosphere. The impact of inventory and circulation changes can be minimised by careful selection of study sites and by targeting foraminifera that live within specific water masses. However, deviations of ??13C from the biological signal could certainly arise due to ?13C fractionation between the ocean and the atmosphere. Due to the similarity in the distribution of phosphate and cadmium (Cd) in the ocean and the incorporation of this trace metal into the calcite tests of foraminifera, Cd/Ca ratios can provide an additional proxy for reconstructing the vertical nutrient distribution in the ocean in the same way as ?13C. We present downcore records of Cd/Ca in the deep-dwelling planktic species, Globorotalia truncatulinoides (s) and the benthic species, Cibicidoides wuellerstorfi from sediment core MD02-2588. A new core a core-top calibration of Cd/Ca in G. truncatulinoides, combined with the established calibration for benthic species allows us to estimate seawater Cd within intermediate and deep water masses that bath the study site and to reconstruct the vertical seawater Cd gradient (?Cdsw) over the past 150,000 years. Comparison of ?Cdsw to ??13C from the same samples from core MD02-2588 in the Southern Ocean indicate a very similar downcore variability which supports the use of the ??13C method to reconstruct the biological pump during the MPT.

  9. New Zealand Quaternary stratigraphy: An overview

    Science.gov (United States)

    Pillans, Brad

    New Zealand Quaternary strata, including marine sediments, loess, volcanic and glacial deposits, offer detailed records of Quaternary environmental change from a geographically significant location. Time-stratigraphic subdivision of New Zealand Quaternary strata, based on marine biostratigraphy and climatostratigraphy, has resulted in a series of locally defined stages and substages. The Plio/Pleistocene boundary as defined at Vrica in Italy, and dated at ca. 1.63 Ma, lies near the top of the Nukumaruan Stage in New Zealand. The first faunal evidence of cooling in New Zealand Plio/Pleistocene sequences occurs much earlier, at the base of the Nukumaruan Stage ca. 2.4 Ma, with the appearance in central New Zealand of the subantarctic taxa Chlamys delicatula and Jacquinotia edwardsii. Although glacial deposits of the South Island have long been central to New Zealand Quaternary stratigraphy, they are poorly dated and lack continuity. More complete records of Quaternary events are found within uplifted marine strata and associated terrestrial deposits of the North Island, such as in Wanganui Basin. The use of widespread rhyolite tephra for precise correlation and dating in North Island offers much for improved land-sea correlations. Direct correlation of on-land sequences, using tephra, with Oxygen Isotope Stages of deep sea cores may negate the need for further local time-stratigraphic subdivision in the New Zealand Quaternary. However, there will still be scope for regional comparisons highlighting climatic changes not apparent in deep sea cores.

  10. THE EL PALTO PHASE OF NORTHERN PERÚ: CULTURAL DIVERSITY IN THE LATE PLEISTOCENE-EARLY HOLOCENE / LA FASE EL PALTO EN EL NORTE DE PERÚ: DIVERSIDAD CULTURAL EN EL PLEISTOCENO TARDÍO-HOLOCENO TEMPRANO

    Scientific Electronic Library Online (English)

    Greg J, Maggard.

    2015-03-01

    Full Text Available En la costa norte del Perú, las tradiciones líticas más tempranas documentadas se conocen, en conjunto, como la fase El Palto (~14.200-9.600 cal a.p.). Esta fase, que abarca desde el Pleistoceno Tardío hasta el Holoceno Temprano, contiene evidencias de varias tradiciones contemporáneas o que coincid [...] en parcialmente en el tiempo, lo que incluye conjuntos unifaciales tempranos y los complejos Cola de Pescado y Paiján. Un reciente estudio de los sitios de la fase El Palto en el valle bajo de Jequetepeque se enfocó en la evaluación de los vínculos entre estos conjuntos y las poblaciones que los produjeron. Los resultados de varios estudios regionales de largo plazo se combinan con estos análisis con el objeto de proporcionar una nueva síntesis acerca de los patrones de asentamiento temprano y el cambio tecnológico en esta región de los Andes Centrales. Abstract in english On Perú's North Coast, the earliest documented lithic traditions are collectively known as the El Palto Phase (~14,200-9,600 cal BP). This phase, which spans the Late Pleistocene to Early Holocene, contains evidence for several contemporary or overlapping traditions, including early unifacial assemb [...] lages, and the Fishtail and Paiján complexes. Recent study of El Palto phase sites in the lower Jequetepeque Valley focused on evaluating the relationships between these assemblages and the populations who manu-factured them. The results from several long-term regional studies are considered with these analyses to provide a new synthesis regarding early settlement patterns and technological change in this region of the Central Andes.

  11. THE EL PALTO PHASE OF NORTHERN PERÚ: CULTURAL DIVERSITY IN THE LATE PLEISTOCENE-EARLY HOLOCENE / LA FASE EL PALTO EN EL NORTE DE PERÚ: DIVERSIDAD CULTURAL EN EL PLEISTOCENO TARDÍO-HOLOCENO TEMPRANO

    Scientific Electronic Library Online (English)

    Greg J, Maggard.

    Full Text Available En la costa norte del Perú, las tradiciones líticas más tempranas documentadas se conocen, en conjunto, como la fase El Palto (~14.200-9.600 cal a.p.). Esta fase, que abarca desde el Pleistoceno Tardío hasta el Holoceno Temprano, contiene evidencias de varias tradiciones contemporáneas o que coincid [...] en parcialmente en el tiempo, lo que incluye conjuntos unifaciales tempranos y los complejos Cola de Pescado y Paiján. Un reciente estudio de los sitios de la fase El Palto en el valle bajo de Jequetepeque se enfocó en la evaluación de los vínculos entre estos conjuntos y las poblaciones que los produjeron. Los resultados de varios estudios regionales de largo plazo se combinan con estos análisis con el objeto de proporcionar una nueva síntesis acerca de los patrones de asentamiento temprano y el cambio tecnológico en esta región de los Andes Centrales. Abstract in english On Perú's North Coast, the earliest documented lithic traditions are collectively known as the El Palto Phase (~14,200-9,600 cal BP). This phase, which spans the Late Pleistocene to Early Holocene, contains evidence for several contemporary or overlapping traditions, including early unifacial assemb [...] lages, and the Fishtail and Paiján complexes. Recent study of El Palto phase sites in the lower Jequetepeque Valley focused on evaluating the relationships between these assemblages and the populations who manu-factured them. The results from several long-term regional studies are considered with these analyses to provide a new synthesis regarding early settlement patterns and technological change in this region of the Central Andes.

  12. Late Pleistocene vertebrates from Touro Passo Creek (Touro Passo Formation), southern Brazil: a review / Vertebrados del Pleistoceno Tardío del arroyo Touro Passo (Formación Touro Passo), sur de Brasil: Una revisión

    Scientific Electronic Library Online (English)

    Leonardo, Kerber; Vanessa Gregis, Pitana; Ana Maria, Ribeiro; Annie Schmaltz, Hsiou; Edison V., Oliveira.

    Full Text Available El Arroyo Touro Passo es una de las más importantes localidades con fósiles pleistocénicos del sur de Brasil. Aunque los vertebrados colectados en esta localidad han sido estudiados desde la década de 1970, varias preguntas siguen abiertas. En este trabajo se presenta una revisión del conocimiento a [...] cumulado desde la proposición original de la Formación Touro Passo en 1976. Las asociaciones fosilíferas contienen una predominancia de fósiles de mamíferos, y entre estos, los artiodáctilos y cingulados son los más diversos. Las edades absolutas muestran que los niveles litológicos de grano fino (por lo menos) se depositaron durante condiciones más húmedas, en los estadios isotópicos 3 y 2. Los vertebrados muestran una mezcla de afinidades entre taxones de afinidad pampeana e intertropical. El largo intervalo de tiempo en que se depositaron los estratos del Arroyo Touro Passo pudo haber contribuido a esta mezcla de fauna. Abstract in english Touro Passo Creek is one of the most important fossiliferous late Pleistocene localities from southern Brazil. Although fossil vertebrates collected from this locality have been studied since the 1970s, several questions remain open. This paper provides a review of the knowledge on this subject accu [...] mulated since the original proposition of the Touro Passo Formation in 1976. The fossil assemblages of Touro Passo Creek show a predominance of mammals, and among them, artiodactyls and cingulates are the most diverse. The available absolute ages indicate that the fine-grained lithological levels (at least) were deposited during humid conditions of the Last Glacial Maximum, within oxygen isotope stages 3 and 2. The mammal assemblages contain a mixture of intertropical and pampean taxa. The large span of time that encompasses the deposition of the Touro Passo Creek beds could have contributed to this faunal mixture.

  13. The Balitx landslide (Mallorca, Spain) and its possible seismic origin: active spreading since the Late Pleistocene; El deslizamiento de Balitx (Mallorca) y su posible origen sismico. Procesos activos desde el Pleistoceno superior

    Energy Technology Data Exchange (ETDEWEB)

    Mateos, R. M.; Rodriguez-Peces, M. J.; Azanon, J. M.; Rodriguez-Fernandez, J.; Roldan, F. J.; Garcia-Moreno, I.; Galabert, B.; Garcia-Mayordomo, J.

    2013-02-01

    The Balitx landslide, located on the steep coastal side of the Tramuntana range on the island of Mallorca, is a large translational rock landslide in which the failure surface coincides with the reactivation of an earlier normal fault. The dating of calcite striae on the fault plane with U/Th techniques reveals that the last movement was over 400 kyr ago, which falls outside of the range of this method. The volume of the landslide is estimated to be over 700 million cubic metres, with a north-westward displacement of 300 m. Active extensional cracks as well as block spreads have been identified along the main scarp, together with displacement and toppling of blocks, the beginning of which coincides with oxygen isotope stage OIS 5a (Late Pleistocene = 83 kyr), a wetter and warmer period than the present. Currently active decametre-long cracks up to 50 m wide can be seen to affect the displaced materials. They reveal the rupture of the displaced block into several units at different speeds. A retrospective analysis of slope stability has been carried out, taking into account different scenarios according to three critical sea stands. All the scenarios are stable, with a safety factor of over 1.35. These results support the thesis that the Balitx landslide could have been triggered by seismicity. A study of the Balitx landslide under dynamic conditions reveals that the landslide could have been triggered by a moderate-to-high-magnitude earthquake (Mw=6.0) located close to the landslide (10-30 km) and probably related to some of the active faults identified in Majorca, such as the Palma Fault. (Author) 58 refs.

  14. Late Pleistocene Panthera leo spelaea (Goldfuss, 1810 skeletons from the Czech Republic (central Europe; their pathological cranial features and injuries resulting from intraspecific fights, conflicts with hyenas, and attacks on cave bears

    Directory of Open Access Journals (Sweden)

    Diedrich C G

    2011-11-01

    Full Text Available The world’s first mounted "skeletons" of the Late Pleistocene Panthera leo spelaea (Goldfuss, 1810 from the Sloup Cave hyena and cave bear den in the Moravian Karst (Czech Republic, central Europe are compilations that have used bones from several different individuals. These skeletons are described and compared with the most complete known skeleton in Europe from a single individual, a lioness skeleton from the hyena den site at the Srbsko Chlum-Komín Cave in the Bohemian Karst (Czech Republic. Pathological features such as rib fractures and brain-case damage in these specimens, and also in other skulls from the Zoolithen Cave (Germany that were used for comparison, are indicative of intraspecific fights, fights with Ice Age spotted hyenas, and possibly also of fights with cave bears. In contrast, other skulls from the Perick and Zoolithen caves in Germany and the Ur?ilor Cave in Romania exhibit post mortem damage in the form of bites and fractures probably caused either by hyena scavenging or by lion cannibalism. In the Srbsko Chlum-Komín Cave a young and brain-damaged lioness appears to have died (or possibly been killed by hyenas within the hyena prey-storage den. In the cave bear dominated bone-rich Sloup and Zoolithen caves of central Europe it appears that lions may have actively hunted cave bears, mainly during their hibernation. Bears may have occasionally injured or even killed predating lions, but in contrast to hyenas, the bears were herbivorous and so did not feed on the lion carcasses. The articulated lion skeletons found in cave bear dens deep within caves scattered across Europe (such as those from the Sloup, Zoolithen and Ur?ilor caves can therefore now be explained as being the result of lions being killed during predation on cave bears, either by the cave bears defending themselves or as a result of interspecific fights.

  15. Late Pliocene/Pleistocene changes in Arctic sea-ice cover: Biomarker and dinoflagellate records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)

    Science.gov (United States)

    Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens

    2014-05-01

    Sea ice is a critical component in the (global) climate system that contributes to changes in the Earth's albedo (heat reduction) and biological processes (primary productivity), as well as deep-water formation, a driving mechanism for global thermohaline circulation. Thus, understanding the processes controlling Arctic sea ice variability is of overall interest and significance. Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-ice conditions was developed and is based on the determination of a highly-branched isoprenoid with 25 carbons (IP25; Belt et al., 2007; PIP25 when combined with open-water phytoplankton biomarkers; Müller et al., 2011). Here, we present biomarker data from Ocean Drilling Program (ODP) Sites 911 and 912, recovered from the southern Yermak Plateau and representing information of sea-ice variability, changes in primary productivity and terrigenous input during the last about 3.5 Ma. As Sites 911 and 912 are close to the modern sea-ice edge, their sedimentary records seem to be optimal for studying past variability in sea-ice coverage and testing the applicability of IP25 and PIP25 in older sedimentary sequences. In general, our biomarker records correlate quite well with other climate and sea-ice proxies (e.g., dinoflagellates, IRD, etc.). The main results can be summarized as follows: (1) The novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea ice studies covering at least the last 3.5 Ma, i.e., the time interval including the onset (intensification) of major Northern Hemisphere Glaciation (NHG). (2) These data indicate that sea ice of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. (3) Elevated IP25/PIP25 values indicative for an extended spring sea-ice cover, already occurred between 3.6 and 2.9 Ma, i.e., prior to the onset of major NHG. This may suggest that sea-ice and related albedo effects might have been important for general cooling and ice-sheet build-up. (4) Maxima in sea ice occurred near 3.3, 2.7, 2.1, 1.7 and during the last 1.2 Ma whereas between about 2.6 and 2.2 Ma the sea-ice cover was surprisingly reduced. The IP25 maxima are similar to those determined for the late Holocene. (5) Both, dinoflagellate and IP25/PIP25 data indicate that also during the Late Pliocene Warming Event at least occasionally sea ice must have occurred. (6) This low-resolution pilot study motivates to carry out further detailed high-resolution sea-ice biomarker research on ODP/IODP material in order to prove or disprove these preliminary interpretations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38, 16-27. Müller, J., Wagner, A., Fahl, K., Stein, R., Prange, M., Lohmann, G., 2011. Towards quantitative sea ice reconstructions in the northern North Atlantic: A combined biomarker and numerical modelling approach. Earth Planetary Science Letters 306, 137-148.

  16. Morphology and palaeoenvironmental interpretation of deformed soft-sediment clasts: examples from within Late Pleistocene glacial outwash, Tempo Valley, Northern Ireland

    Science.gov (United States)

    Knight, Jasper

    1999-10-01

    Glacial outwash, deposited during deglaciation of the late Devensian ice sheet, is present as a flat-topped valley fill in the Tempo Valley on the southern flanks of the Fintona Hills, Northern Ireland. Sedimentologically, the outwash comprises well-sorted and interbedded rippled to massive sands which record distal deposition within a proglacial water body. Beds of ripple-drift cross-laminated sands contain deformed (folded and contorted) soft-sediment clasts which are composed mainly of silt and clay. The soft-sediment clasts were deformed prior to final deposition because clast a- b planes lie conformable to sand laminae which are undeformed. Morphological characteristics of the soft-sediment clasts, and their facies context, provide evidence for transport mechanisms, depositional environment, and processes of clast deformation. The soft-sediment clasts were transported into a proglacial water body by unidirectional water currents (˜1.5-2.5 m s -1). Sediment transport processes include sediment bypassing within the water column, a low bedload component, and grain flow activity during waning flow stages. The overall morphology of soft-sediment clasts records between 1 and 3 distinct phases of hydroplastic deformation prior to emplacement. The deformation phases are recognised on the basis of morphologically `unrolling' the superimposed folds of the soft-sediment clasts. Deformation structures (i.e. fold style) and direction of the principal stress axis relative to clast axes suggest that clasts were reoriented with respect to water flow direction following each deformation phase. Processes of deformation include folding-over of the clast along its b axis into two or more components, crumpling and abrasion of the outer margins of the b plane, and squashing of the clast c axis (some of which may be post-depositional deformation). The presence of silt- and clay-rich soft-sediment clasts within the outwash succession suggests that they were ripped-up from shallow and irregular pools on the glacier forefield, into which fine sediments accumulated after flood or meltwater events, and transported distally into a proglacial water body. These inferences based on facies evidence and styles of hydroplastic deformation impact on reconstructions of local palaeogeography, and the wider interpretation of similar soft-sediment clasts in the geological record.

  17. Late Pleistocene and Holocene Paleomagnetic Record From Lago Cardiel, Argentina: Correlation of Geomagnetic Paleointensity Records and Geomagnetic Modulation of the Radionuclide Production

    Science.gov (United States)

    Gilli, A.; Channell, J. E.; Anselmetti, F. S.; Ariztegui, D.; Markgraf, V.

    2007-12-01

    Paleomagnetic analyses of sedimentary cores provide a powerful tool for high-resolution stratigraphic correlation, however, the database of high-resolution sedimentary paleomagnetic records, including paleointensity data, for the last 10 kyr is sparse, particularly for the southern hemisphere. We have generated high-resolution records of paleomagnetic directional secular variation (PSV) and relative paleointensity (RPI) from three long piston cores from Lago Cardiel, southern Argentina (CAR 99-7P, CAR 99-9P, and CAR 99-10P) covering the last ~16 kyr. A single-component low-coercivity magnetization carried by magnetite, and homogeneity in magnetic concentration, allows the reconstruction of well-defined PSV and RPI records. Comparison with two other Argentinean lacustrine PSV records from Lake Escondido and El Trébol revealed comparable features. The Holocene RPI records from Lago Cardiel include a broad low around 7-5 ka and a high around 2 ka, followed by a decrease comparable to published archeomagnetic records from the northern hemisphere, implying that the RPI records from Lago Cardiel are strongly influenced by the main axial dipole field. Holocene geomagnetic field intensity has been implicated as a potential driver for climate (and regime) change in the Middle East and elsewhere, through the links between field intensity and cosmic ray flux, and cosmic ray flux and low cloud formation. In order to test the former linkage, the RPI records from Lago Cardiel were band-pass filtered and subsequently compared with the identically treated radiocarbon production record. The remarkable similarity between both records points towards a link between cosmogenic radionuclide production rate and geomagnetic paleointensity on millennial or even shorter timescales. With a sampling resolution of less than two years, the late Holocene RPI record of core CAR 99-10P can be directly compared with the radiocarbon production rate. Both records show similar characteristics with a dominant periodicity around the ~ 205 yr de Vries cycle. As the de Vries cycle is considered of solar origin, this implies a climatic contamination of the RPI record from this core in spite of its similarity with RPI and archaeomagnetic records from the northern hemisphere.

  18. Continental deposits and archaeological data in the Trieste Karst area (north-east Italy: evidence of sea-level changes and possible tectonic activity in the Late Pleistocene and Early Holocene

    Science.gov (United States)

    Boschian, G.

    1993-07-01

    The relationships between the land and sea in the northern Adriatic at the Pleistocene—Holocene boundary are examined by considering sea-level curves and archaeological data. Changes in the Mesolithic (Early Holocene) economy of the inhabitants can be interpreted as a result of palaeoecological variations due to glacioecustatic sea-level changes and recent tectonics. This hypothesis is also supported by evidence of older tectonic movements which may have continued until the end of the Pleistocene.

  19. Pleistocene to recent dietary shifts in California condors

    OpenAIRE

    Chamberlain, C. P.; Waldbauer, J. R.; Fox-Dobbs, K.; Newsome, S.D.; Koch, P. L.; Smith, D. R.; Church, M. E.; Chamberlain, S. D.; Sorenson, K. J.; Risebrough, R.

    2005-01-01

    We used carbon and nitrogen isotopes to investigate changes in the diet of California condors from the Pleistocene to the recent. During the Pleistocene, condors from California fed on both terrestrial megafauna and marine mammals. Early accounts reported condors feeding on the carcasses of marine mammals, but by the late 1700s, condor diets had shifted predominantly to terrestrial animals, following the commercial harvesting of marine mammals and the development of cattle ranching on land. A...

  20. Extent of Pleistocene lakes in the western Great Basin

    Science.gov (United States)

    Reheis, Marith C.

    1999-01-01

    During the Pliocene to middle Pleistocene, pluvial lakes in the western Great Basin repeatedly rose to levels much higher than those of the well-documented late Pleistocene pluvial lakes, and some presently isolated basins were connected. Sedimentologic, geomorphic, and chronologic evidence at sites shown on the map indicates that Lakes Lahontan and Columbus-Rennie were as much as 70 m higher in the early-middle Pleistocene than during their late Pleistocene high stands. Lake Lahontan at its 1400-m shoreline level would submerge present-day Reno, Carson City, and Battle Mountain, and would flood other now-dry basins. To the east, Lakes Jonathan (new name), Diamond, Newark, and Hubbs also reached high stands during the early-middle(?) Pleistocene that were 25-40 m above their late Pleistocene shorelines; at these very high levels, the lakes became temporarily or permanently tributary to the Humboldt River and hence to Lake Lahontan. Such a temporary connection could have permitted fish to migrate from the Humboldt River southward into the presently isolated Newark Valley and from Lake Lahontan into Fairview Valley. The timing of drainage integration also provides suggested maximum ages for fish to populate the basins of Lake Diamond and Lake Jonathan. Reconstructing and dating these lake levels also has important implications for paleoclimate, tectonics, and drainage evolution in the western Great Basin. For example, shorelines in several basins form a stair-step sequence downward with time from the highest levels, thought to have formed at about 650 ka, to the lowest, formed during the late Pleistocene. This descending sequence indicates progressive drying of pluvial periods, possibly caused by uplift of the Sierra Nevada and other western ranges relative to the western Great Basin. However, these effects cannot account for the extremely high lake levels during the early middle Pleistocene; rather, these high levels were probably due to a combination of increased effective moisture and changes in the size of the Lahontan drainage basin.

  1. Quaternary stratigraphy: Recent changes

    Directory of Open Access Journals (Sweden)

    Gaudenji Tivadar

    2012-01-01

    Full Text Available Corrections to the Quaternary stratigraphic division of Serbia was updated/renewed by lowering limit of the Pleistocene / Quaternary to the beginning of the Gelasian that is at approximately 2.588 million years. Rather than the officially rejected Penck & Brückner Alpine stratigraphic model, the use of oxygen isotope stages (OIS / MIS is recommended. Climatostratigraphic terms glacial and interglacial have a regional applicability and their use is recommended only in areas where there are traces of glaciation, while the terms cold and warm stage (or moderate stages should be used within the global context. Eopleistocene is a regional term for the former Soviet Union and due to its uniqueness it can hardly be applied in the stratigraphical scheme of the Quaternary depostis in Serbia. With the latest extension of the Lower Pleistocene, further use of Eopleistocene would lead to further confusion in stratigraphic correlation as such the use of the Lower / Early Pleistocene or other appropriate stratigraphic units is recommended. [Projekat Ministarstva nauke Republike Srbije, br. 47007

  2. Luminescence Chronology for the Formation of Glacial Lake Calgary, Southern Alberta, Canada: Age Constraints for the Initiation of the Late Pleistocene Retreat of the Laurentide Ice Sheet from its Western Margin

    Science.gov (United States)

    Munyikwa, K.; Rittenour, T. M.

    2014-12-01

    Glacial Lake Calgary in southern Alberta, Canada, was a Late Pleistocene proglacial lake that formed along the southwest margin of the Laurentide Ice Sheet (LIS), dammed by the retreating ice sheet margin. Attempts to constrain the age of the lake using radiocarbon methods have been hampered by the lack of datable organic material. In an effort to apply an alternative chronometer, this study uses two optically stimulated luminescence (OSL) dating approaches to date fine grained sand and silt that were deposited in the lake during its existence. OSL dating determines the depositional ages of sediments by measuring the energy from ionizing radiation that is stored in mineral grains such as quartz and feldspar. Dividing the stored energy, also referred to as the paleodose, by the rate at which the dose accumulated, allows an age to be ascertained. In one method applied in this study, the paleodose stored in the feldspar component of the sediment is determined using normalized infrared stimulated luminescence signals acquired using a portable OSL reader. In the second method, blue optically stimulated luminescence signals obtained from quartz separates from the sediment by employing a regular OSL reader and standard protocols are used to determine the paleodose. After correcting the feldspar data for anomalous fading, the age results from the two dating approaches are compared. The ages signify a time period by which the LIS had retreated from the study area and, hence, serve as constraints for the initiation of the retreat of the ice sheet from its western limit. Advantages and limitations of the dating methods are briefly discussed. Constraining the chronology of the retreat of the LIS from western Canada allows for a better understanding of the driving forces behind ice sheet retreat. Secondly, assigning a temporal scale to the postglacial evolution of the environment of the region permits a better insight into the dynamics of the physical and biological environments of the time. Thirdly, the region is at the heart of the ice-free corridor that was ostensibly used by early humans to migrate southwards to populate the Americas ca. 16 ka ago. Hence, an improved deglaciation chronology would allow a more comprehensive evaluation of this concept.

  3. Interhemispheric correlation of late pleistocene glacial events.

    Science.gov (United States)

    Lowell, T V; Heusser, C J; Andersen, B G; Moreno, P I; Hauser, A; Heusser, L E; Schlüchter, C; Marchant, D R; Denton, G H

    1995-09-15

    A radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima during the last glaciation at 13,900 to 14,890, 21,000, 23,060, 26,940, 29,600, and >/=33,500 carbon-14 years before present ((14)C yr B.P.) in a cold and wet Subantarctic Parkland environment. The last glaciation ended with massive collapse of ice lobes close to 14,000(14)C yr B.P., accompanied by an influx of North Patagonian Rain Forest species. In the Southern Alps of New Zealand, additional glacial maxima are registered at 17,720(14)C yr B.P., and at the beginning of the Younger Dryas at 11,050 (14)C yr B. P. These glacial maxima in mid-latitude mountains rimming the South Pacific were coeval with ice-rafting pulses in the North Atlantic Ocean. Furthermore, the last termination began suddenly and simultaneously in both polar hemispheres before the resumption of the modern mode of deep-water production in the Nordic Seas. Such interhemispheric coupling implies a global atmospheric signal rather than regional climatic changes caused by North Atlantic thermohaline switches or Laurentide ice surges. PMID:17789444

  4. Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae)

    Science.gov (United States)

    Boessenecker, Robert W.

    2013-04-01

    Pliocene baleen whale assemblages are characterized by a mix of early records of extant mysticetes, extinct genera within modern families, and late surviving members of the extinct family Cetotheriidae. Although Pleistocene baleen whales are poorly known, thus far they include only fossils of extant genera, indicating Late Pliocene extinctions of numerous mysticetes alongside other marine mammals. Here a new fossil of the Late Neogene cetotheriid mysticete Herpetocetus is reported from the Lower to Middle Pleistocene Falor Formation of Northern California. This find demonstrates that at least one archaic mysticete survived well into the Quaternary Period, indicating a recent loss of a unique niche and a more complex pattern of Plio-Pleistocene faunal overturn for marine mammals than has been previously acknowledged. This discovery also lends indirect support to the hypothesis that the pygmy right whale ( Caperea marginata) is an extant cetotheriid, as it documents another cetotheriid nearly surviving to modern times.

  5. Contribution to the stratigraphy of the onshore Paraíba Basin, Brazil

    Directory of Open Access Journals (Sweden)

    Dilce F. Rossetti

    2012-06-01

    Full Text Available Several publications have contributed to improve the stratigraphy of the Paraíba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono-sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraíba Basin. Except for a few outcrops of carbonatic rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraíba Basin.Várias publicações têm contribuído para melhorar a estratigrafia da Bacia Paraíba no nordeste do Brasil. Entretanto, a caracterização e distribuição das unidades sedimentares em áreas continentais desta bacia são ainda incompletas, apesar de sua importância para reconstruir a evolução tectono-sedimentar da margem passiva sulamericana. Este trabalho fornece novas informações para diferenciar entre estratos litologicamente similares que, por outro lado, não são relacionados no tempo. Esta abordagem incluiu descrições morfológica, sedimentológica e estratigráfica baseadas em dados de superfície e sub-superfície, integrada com sensoriamento remoto, datação por luminescência opticamente estimulada, datação de goetita intempérica por U+Th/He e análise de minerais pesados. Baseado neste estudo, foi possível mostrar que unidades cretáceas são restritas à parte leste da porção continental da Bacia Paraíba. Exceto por poucos afloramentos de rochas carbonáticas próximo da linha de costa atual, depósitos desta idade não são expostos à superfície na área de estudo. Ao invés disto, a cobertura sedimentar ao longo da bacia é constituída por depósitos mineralogicamente e cronologicamente distintos, inseridos na Formação Barreiras e, principalmente, nos Sedimentos Pós-Barreiras, de idade eo/mesomiocena e pleistocena tardia-holocena, respectivamente. Os dados apresentados neste trabalho suportam deformação tectônica como um fator de grande relevância na distribuição das unidades sedimentares da Bacia Paraíba.

  6. Contribution to the stratigraphy of the onshore Paraíba Basin, Brazil

    Scientific Electronic Library Online (English)

    Dilce F., Rossetti; Ana M., Góes; Francisco H.R., Bezerra; Márcio M., Valeriano; Benjamim B., Brito-Neves; Felipe L., Ochoa.

    2012-06-01

    Full Text Available Várias publicações têm contribuído para melhorar a estratigrafia da Bacia Paraíba no nordeste do Brasil. Entretanto, a caracterização e distribuição das unidades sedimentares em áreas continentais desta bacia são ainda incompletas, apesar de sua importância para reconstruir a evolução tectono-sedime [...] ntar da margem passiva sulamericana. Este trabalho fornece novas informações para diferenciar entre estratos litologicamente similares que, por outro lado, não são relacionados no tempo. Esta abordagem incluiu descrições morfológica, sedimentológica e estratigráfica baseadas em dados de superfície e sub-superfície, integrada com sensoriamento remoto, datação por luminescência opticamente estimulada, datação de goetita intempérica por U+Th/He e análise de minerais pesados. Baseado neste estudo, foi possível mostrar que unidades cretáceas são restritas à parte leste da porção continental da Bacia Paraíba. Exceto por poucos afloramentos de rochas carbonáticas próximo da linha de costa atual, depósitos desta idade não são expostos à superfície na área de estudo. Ao invés disto, a cobertura sedimentar ao longo da bacia é constituída por depósitos mineralogicamente e cronologicamente distintos, inseridos na Formação Barreiras e, principalmente, nos Sedimentos Pós-Barreiras, de idade eo/mesomiocena e pleistocena tardia-holocena, respectivamente. Os dados apresentados neste trabalho suportam deformação tectônica como um fator de grande relevância na distribuição das unidades sedimentares da Bacia Paraíba. Abstract in english Several publications have contributed to improve the stratigraphy of the Paraíba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono-sedimentar [...] y evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraíba Basin. Except for a few outcrops of carbonatic rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraíba Basin.

  7. El registro sedimentario Pleistoceno tardío-Holoceno de la Salina de Ambargasta (Argentina central): una aproximación paleolimnológica / The late Pleistocene-Holocene sedimentary record of the Salina de Ambargasta (central Argentina): a paleolimnological approach

    Scientific Electronic Library Online (English)

    Gabriela A., Zanor; Eduardo L., Piovano; Daniel, Ariztegui; Andrea I., Pasquini; Jorge O., Chiesa.

    2013-08-01

    Full Text Available La Salina de Ambargasta es un sistema playa localizado a latitudes medias de Argentina (29°S; 64°W). El estudio de dos testigos sedimentarios, AB-1 (borde este de la salina) y AB-2 (área central), efectuado mediante un enfoque de multi-indicadores ambientales, la aplicación de un modelo sedimentario [...] análogo y edades radiocarbónicas, permitió reconstruir la historia paleohidrológica de la salina de Ambargasta a partir del Pleistoceno tardío. La reconstrucción paleoambiental de los últimos ca. 45,000 años hasta el presente, indica seis estadios ambientales principales: 1) entre 44,700 y 39,600 años cal. AP, un intervalo seco está representado por el desarrollo de una planicie fangosa capilar; 2) entre 39,600 y 26,700 años cal. AP, un período más húmedo es registrado por facies lacustres con precipitación carbonática y sulfatada; 3) entre 26,700y 23,600 años cal. AP ocurre la fase más húmeda en Ambargasta, caracterizada por la sedimentación en una laguna efímera sulfatada, relativamente profunda, rica en tapices microbianos y marginada por planicies fangosas; 4) entre 23,600y 18,500 años cal. AP se presenta un cambio a condiciones más secas con pulsos húmedos intercalados, evidenciado por el desarrollo de planicies fangosas salinas que alternan con lagunas efímeras, y planicies fangosas capilares en las zonas supralitorales; 5) entre 18,500y 8,600 años cal. AP se identifica un intervalo más seco caracterizado por el dominio de planicies fangosas salinas y capilares, y 6) desde los 8,600 años cal. AP al presente se registra el balance hídrico más negativo en el sistema salino representado por una expansión de las planicies fangosas capilares. El control del balance hidrológico en la Salina de Ambargasta está vinculado con la variación del Sistema de tipo Monzónico Sudamericano, por lo cual la reconstrucción efectuada desde el Pleistoceno tardío permite aportar nuevas claves para comprender las fluctuaciones pasadas de este importante forzante del sistema climático de Sudamérica. Abstract in english Salina de Ambargasta is a playa system located at the middle latitude of Argentina (29°S; 64°W). Two sedimentary cores retrieved at the eastern border (AB-1) and the central area of the salina (AB-2) were studied using a multi-proxy approach, an actualistic sedimentary model and radiocarbon dates al [...] lowed reconstructing the paleohydrological history of the Salina de Ambargasta since the late Pleistocene. The paleoenvironmental reconstruction for the last ca. 45,000 years to the present suggests six main environmental stages: 1) between 44,700 and 39,600 cal. year BP, a dry period is represented by the development of a capillary mudflat; 2) between ca. 39,600 and 26,700 cal. year BP a more humid period is recorded by lacustrine facies with carbonate and sulfateprecipitation; 3) between ca. 26,700 and 23,600 cal. year BP occurs the most humid phase in Ambargasta, characterized by the sedimentation in an ephemeral sulfate lake, relatively deep, enriched with microbial mats and fringed by mudflats; 4) between 23,600 and 18,500 cal. year BP, a change to drier conditions with humid pulses is evidenced by the development of saline mudflats alternating with ephemeral lakes and associated with mudflats in the supralittoral areas; 5) between 18,500 and 8,600 cal. year BP a drier period is identified by the dominance of capillary and saline mudflats, and 6) since 8,600 cal. year BP to the present the most negative hydrological balance is recorded in the saline system, represented by an expansion of capillary mudflats The control of the hydrological balance in the Salina de Ambargasta is mostly associated with the variation of the South America Monsoon-like System. Thus, the record presented here allows us to provide new clues in order to decipherformerfluctuations of this important driver of the climatic system of South America since the late Pleistocene.

  8. Late Cretaceous - Cenozoic development of outer continental margin, southwestern Nova Scotia

    Energy Technology Data Exchange (ETDEWEB)

    Swift, S.A.

    1987-06-01

    The growth pattern for the outer continental margin of Nova Scotia during the Late Cretaceous and Cenozoic was studied using seismic stratigraphy and well data. Sediment accumulation was broadly controlled by temporal changes in relative sea level, but significant spatial and temporal changes in accumulation patterns were caused by changes in sediment supply rate, morphology, erosion by abyssal currents, and salt tectonics. A Jurassic-Early Cretaceous carbonate platform remained exposed until the Late Cretaceous and controlled the location and steepness of the paleoslope until the late Miocene. Local erosion of the outer shelf and slope in the late Paleocene-early Eocene produced chalky fans on the upper rise. The relationship between erosion of the shelf in the late Eocene and early Oligocene, and abyssal current erosion of the upper rise in the Oligocene, is unclear. Seaward extensions of Tertiary shelf-edge canyons are poorly defined except for the Eocene fans. In the Miocene, abyssal currents eroded a bench on the upper continental rise. Subsequently, sediments lapped onto and buried the paleoslope. The lower rise above horizon A/sup u/ (Oligocene) is composed of fans and olistostromes shed from halokinetic uplift of the upper rise. Current eroded unconformities are common in the rise sequence, but the only current deposit is a Pliocene interval (< 300 m) restricted to the lowermost rise. Pleistocene turbidity currents eroded the present canyon morphology. 15 figures, 2 tables.

  9. Obliquity and precession as pacemakers of Pleistocene deglaciations

    Science.gov (United States)

    Feng, Fabo; Bailer-Jones, C. A. L.

    2015-08-01

    The Milankovitch theory states that the orbital eccentricity, precession, and obliquity of the Earth influence our climate by modulating the summer insolation at high latitudes in the northern hemisphere. Despite considerable success of this theory in explaining climate change over the Pleistocene epoch (2.6-0.01 Myr ago), it is inconclusive with regard to which combination of orbital elements paced the 100 kyr glacial-interglacial cycles over the late Pleistocene. Here we explore the role of the orbital elements in pacing the Pleistocene deglaciations by modeling ice-volume variations in a Bayesian approach. When comparing models, this approach takes into account the uncertainties in the data as well as the different degrees of model complexity. We find that the Earth's obliquity (axial tilt) plays a dominant role in pacing the glacial cycles over the whole Pleistocene, while precession only becomes important in pacing major deglaciations after the transition of the dominant period from 41 kyr to 100 kyr (the mid-Pleistocene transition). We also find that geomagnetic field and orbital inclination variations are unlikely to have paced the Pleistocene deglaciations. We estimate that the mid-Pleistocene transition took place over a 220 kyr interval centered on a time 715 kyr ago, although the data permit a range of 600-1000 kyr. This transition, occurring within just two 100 kyr cycles, indicates a relatively rapid change in the climate response to insolation.

  10. A phase-space model for Pleistocene ice volume

    CERN Document Server

    Imbrie, John Z; Lisiecki, Lorraine E

    2011-01-01

    We present a phase-space model that simulates Pleistocene ice volume changes based on Earth's orbital parameters. Terminations in the model are triggered by a combination of ice volume and orbital forcing and agree well with age estimates for Late Pleistocene terminations. The average phase at which model terminations begin is approximately 90 +/- 90 degrees before the maxima in all three orbital cycles. The large variability in phase is likely caused by interactions between the three cycles and ice volume. Unlike previous ice volume models, this model produces an orbitally driven increase in 100-kyr power during the mid-Pleistocene transition without any change in model parameters. This supports the hypothesis that Pleistocene variations in the 100-kyr power of glacial cycles could be caused, at least in part, by changes in Earth's orbital parameters, such as amplitude modulation of the 100-kyr eccentricity cycle, rather than changes within the climate system.

  11. Pleistocene Palaeoart of Asia

    Directory of Open Access Journals (Sweden)

    Robert G. Bednarik

    2013-06-01

    Full Text Available This comprehensive overview considers the currently known Pleistocene palaeoart of Asia on a common basis, which suggests that the available data are entirely inadequate to form any cohesive synthesis about this corpus. In comparison to the attention lavished on the corresponding record available from Eurasia’s small western appendage, Europe, it is evident that Pleistocene palaeoart from the rest of the world has been severely neglected. Southern Asia, in particular, holds great promise for the study of early cognitive development of hominins, and yet this potential has remained almost entirely unexplored. Asia is suggested to be the key continent in any global synthesis of ‘art’ origins, emphasising the need for a comprehensive pan-continental research program. This is not just to counter-balance the incredible imbalance in favour of Europe, but to examine the topic of Middle Pleistocene palaeoart development effectively.

  12. Aspectos sedimentológicos de arenas eólicas del Pleistoceno tardío-Holoceno de la provincia de La Pampa / Sedimentologic aspects of eolian sands from the Late Pleistocene-Holocene of the La Pampa Province

    Scientific Electronic Library Online (English)

    Manuel, Szelagowski; Marcelo A, Zárate; Adriana M, Blasi.

    2004-12-01

    Full Text Available El objetivo general de este trabajo es analizar la procedencia, génesis y dinámica de transporte de los depósitos eólicos arenosos del centro-este de la provincia de la Pampa. Para ello, se analizaron el marco geológico-geomorfológico y los aspectos estratigráficos de tres sectores considerados como [...] sendos estudios de casos: cordón medanoso La Pastoril-Santa Isabel, cordón medanoso Toay y cordón medanoso General Acha. Estos cordones se caracterizaron sedimentológicamente (granulometría, mineralogía) a través del análisis de 20 muestras. Se identificaron dos unidades eólicas asociadas a dos ciclos de sedimentación, informalmente denominadas inferior (Pleistoceno tardío-Holoceno medio) y superior (originado por acción antrópica durante el siglo XX) relacionados con vientos del cuadrante O-NO en Santa Isabel y del S y SO en General Acha. Los resultados obtenidos sugieren que la topografía sería un factor de control importante en la distribución de los sedimentos, además de la distancia al sistema fluvial, que determinaría su tamaño de grano. Los análisis mineralógicos indicarían un aporte mixto de materiales, tanto distal (sistema fluvial del Bermejo-Desaguadero-Salado-Curacó), como local (afloramientos rocosos de la provincia). Abstract in english The main goal of this paper is to analyze the provenience of sandy eolian deposits of the central eastern part of La Pampa Province. Considering present eolian models proposed by different authors, the hypothesis tested in this paper is that eolian sediments are the result of deflation of alluvial d [...] eposits from the Bermejo-Desaguadero-Salado-Curacó fluvial system. With this purpose in mind, three case studies were selected (La Pastoril-Santa Isabel, Toay and General Acha) (Fig. 1). The analysis was made following the concept of spatial scale hierarchy which considered the geological and general environmental setting of the studied areas along with fundamental geomorphological features of the analyzed dune systems. This was complemented by the stratigraphic survey of selected sections from which 20 samples were collected for sedimentological analysis (grain-size and mineralogy). Also, due to the lack of information, three samples were collected from the present Desaguadero fluvial system for general characterization. At the regional scale two main geoforms were identified: an extensive plain and the paleovalley of the Desaguadero fluvial system. The plain grades eastward and includes several longitudinal depressions (longitudinal valleys). A sandy silt mantle is covering the plain, whereas the main dune system is located along the longitudinal depressions and the Desaguadero paleovalley (Fig. 1). In the three studied areas two eolian units, informally named lower and upper, were identified. These units, separated by a buried soil, were generated by winds from the W-NW in Santa Isabel and from the S and SW in General Acha. Wind directions coincide with present wind systems. The upper part of the lower unit is modified by the development of a buried soil showing an A-C horizon sequence. This soil is only buried in areas deeply affected by anthropic activities. Away from these impacted settings, the soil is on the present groundsurface. In Toay, fossil remains of Megatherium americanum were exhumed from the lowermost part of the sampled section which together with regional evidences indicate a late Pleistocene-Holocene age to the lower eolian unit. The upper eolian unit is also restricted to areas deeply modified by human activities, where the vegetation cover was removed and the sediments exposed to eolian reactivation. The occurrence of cultural artifacts (pieces of wire fences, plastic bags) as well as written documents suggest that this eolian reactivation occurred during the XXth century. Based on the stratigraphic results, the sedimentolo-gical analysis was focused on the lower eolian unit. In all three areas the eolian sediments are medium to fine sands with unimodal distribution, transported in saltation and modi

  13. Una sucesión de paleosuelos superpuestos del pleistoceno medio - tardio, holoceno: Zona sur de La Plata, Provincia de Buenos Aires / A succession of superposed paleosols (Middle-Late Pleistocene and Holocene) in the south area of La Plata. Argentina

    Scientific Electronic Library Online (English)

    Perla A, Imbellone; Andrea, Cumba.

    2003-07-01

    Full Text Available Se estudia una sucesión (Pleistoceno medio-tardío y Holoceno) de 11 m de exposición, ubicada en un interfluvio plano de la zona sur de la ciudad de la Plata (34º55´ 00´´S y 57º57´30´´O). El objetivo del trabajo es analizar los procesos sedimentario-pedológicos acaecidos a fin de obtener: a) nuevas e [...] videncias que permitan hacer consideraciones sobre el modelo sedimentario-pedológico propuesto por Teruggi e Imbellone (1987); b) correlacionar los eventos indicados en la descripción del perfil tipo en los diferentes frentes de exposición de la cantera, y c) correlacionar el contenido de vitroclastos con otros perfiles de la zona. En el perfil tipo se identifican 6 unidades constituidas por loess retrabajado y paleosuelos asociados con rasgos semejantes al de suelos actuales. La porción superior muestra cambios morfológicos más sutiles que la inferior hasta la base y correspondería a la Fm La Postrera y Fm Buenos Aires hasta 2,10 y 4,45 m de profundidad, respectivamente. Se identifican dos paleosuelos además del suelo actual separados por una superficie de erosión suave y discontinua, y una discontinuidad temporal insinuada p or cambios de color y características de las calcretas. A partir de 4,45 m de profundidad (Fm Ensenada) la sucesión refleja acontecimientos sedimentario-pedológicos identificables claramente en el campo y laboratorio. Se identifican tres paleosuelos superpuestos separados por superficies de erosión. Dos de ellas onduladas y acompañadas por concreciones de carbonato de calcio subparalelas a la superficie de erosión a 4,45 y 9,60 m, respectivamente, y otra totalmente planar a 7,30 m sólo interrumpida en su continuidad lateral por megacrotovinas. La variación lateral de las paleosuperficies muestra unidades de contactos concordantes, paralelos y subparalelos con escasa variación de espesores entre ellas. Los rasgos pedológicos con mayor variación entre uno y otro frente son los de carbonatación e hidromorfismo. La ciclicidad sedimentariopedológica está mejor definida en la base de la cantera. Toda la sección posee clases texturales arcillo limosas y franco limosas, y con característica de loess retrabajado. El intervalo modal es 62-31mm (limo grueso) y 62-125 mm (arena muy fina) con escasa representatividad de las subfracciones de mayor tamaño. La arena se incrementa en la mitad inferior de la sucesión por aumento de pseudopartículas. La micromorfología fue instrumental en la verificación de a) procesos pedogenéticos superpuestos de iluviación, hidromorfismo y carbonatación indicados por rasgos texturales, amorfos y cristalinos; b) presencia de biorasgos como pedotúblulos y fábrica excremental de fundamental importancia en procesos de bioturbación, y c) presencia de microestructura laminar, sedirelictos y pedorelictos que aseguran el carácter retrabajado del loess. En los paleosuelos inferiores la evidencia micromorfológica se corresponde con la observación de campo. En cambio, en los superiores los aparentes rasgos macroscópicos de iluviación pertenecerían a superficies de fricción muy finas en correspondencia con abundante fábrica plásmica poro, grano estriada y reticulada. El modelo clásico de sedimentación y pedogénesis episódica se aplicaría a los tres paleosuelos inferiores. Ellos están separados espacialmente en la columna sedimentaria, con el material originario identificable, y decapitados por una superficie de erosión. Se habrían desarrollado con aporte discontinuo de sedimentos y un período de pedogénesis suficiente para desarrollar un suelo maduro. En los paleosuelos superiores habría existido un aporte continuo o levemente discontinuo pero lento, que permitió la formación de rasgos pedológicos mientras el paisaje se elevaba acrecionalmente y se producía la superposición de pedogénesis. Abstract in english A 11-m deep pedological sedimentary succession (Middle-Late Pleistocene and Holocene) has been studied in a quarry exposure located on a flat interfluve, in the vicinity of La Plata airport, Ar

  14. Una sucesión de paleosuelos superpuestos del pleistoceno medio - tardio, holoceno: Zona sur de La Plata, Provincia de Buenos Aires A succession of superposed paleosols (Middle-Late Pleistocene and Holocene in the south area of La Plata. Argentina

    Directory of Open Access Journals (Sweden)

    Perla A Imbellone

    2003-07-01

    Full Text Available Se estudia una sucesión (Pleistoceno medio-tardío y Holoceno de 11 m de exposición, ubicada en un interfluvio plano de la zona sur de la ciudad de la Plata (34º55´ 00´´S y 57º57´30´´O. El objetivo del trabajo es analizar los procesos sedimentario-pedológicos acaecidos a fin de obtener: a nuevas evidencias que permitan hacer consideraciones sobre el modelo sedimentario-pedológico propuesto por Teruggi e Imbellone (1987; b correlacionar los eventos indicados en la descripción del perfil tipo en los diferentes frentes de exposición de la cantera, y c correlacionar el contenido de vitroclastos con otros perfiles de la zona. En el perfil tipo se identifican 6 unidades constituidas por loess retrabajado y paleosuelos asociados con rasgos semejantes al de suelos actuales. La porción superior muestra cambios morfológicos más sutiles que la inferior hasta la base y correspondería a la Fm La Postrera y Fm Buenos Aires hasta 2,10 y 4,45 m de profundidad, respectivamente. Se identifican dos paleosuelos además del suelo actual separados por una superficie de erosión suave y discontinua, y una discontinuidad temporal insinuada p or cambios de color y características de las calcretas. A partir de 4,45 m de profundidad (Fm Ensenada la sucesión refleja acontecimientos sedimentario-pedológicos identificables claramente en el campo y laboratorio. Se identifican tres paleosuelos superpuestos separados por superficies de erosión. Dos de ellas onduladas y acompañadas por concreciones de carbonato de calcio subparalelas a la superficie de erosión a 4,45 y 9,60 m, respectivamente, y otra totalmente planar a 7,30 m sólo interrumpida en su continuidad lateral por megacrotovinas. La variación lateral de las paleosuperficies muestra unidades de contactos concordantes, paralelos y subparalelos con escasa variación de espesores entre ellas. Los rasgos pedológicos con mayor variación entre uno y otro frente son los de carbonatación e hidromorfismo. La ciclicidad sedimentariopedológica está mejor definida en la base de la cantera. Toda la sección posee clases texturales arcillo limosas y franco limosas, y con característica de loess retrabajado. El intervalo modal es 62-31mm (limo grueso y 62-125 mm (arena muy fina con escasa representatividad de las subfracciones de mayor tamaño. La arena se incrementa en la mitad inferior de la sucesión por aumento de pseudopartículas. La micromorfología fue instrumental en la verificación de a procesos pedogenéticos superpuestos de iluviación, hidromorfismo y carbonatación indicados por rasgos texturales, amorfos y cristalinos; b presencia de biorasgos como pedotúblulos y fábrica excremental de fundamental importancia en procesos de bioturbación, y c presencia de microestructura laminar, sedirelictos y pedorelictos que aseguran el carácter retrabajado del loess. En los paleosuelos inferiores la evidencia micromorfológica se corresponde con la observación de campo. En cambio, en los superiores los aparentes rasgos macroscópicos de iluviación pertenecerían a superficies de fricción muy finas en correspondencia con abundante fábrica plásmica poro, grano estriada y reticulada. El modelo clásico de sedimentación y pedogénesis episódica se aplicaría a los tres paleosuelos inferiores. Ellos están separados espacialmente en la columna sedimentaria, con el material originario identificable, y decapitados por una superficie de erosión. Se habrían desarrollado con aporte discontinuo de sedimentos y un período de pedogénesis suficiente para desarrollar un suelo maduro. En los paleosuelos superiores habría existido un aporte continuo o levemente discontinuo pero lento, que permitió la formación de rasgos pedológicos mientras el paisaje se elevaba acrecionalmente y se producía la superposición de pedogénesis.A 11-m deep pedological sedimentary succession (Middle-Late Pleistocene and Holocene has been studied in a quarry exposure located on a flat interfluve, in the vicinity of La Plata airport, Argentina (34º55´00´´S y 57º57´30´´

  15. Evaluation of the structure and stratigraphy over Richton Dome, Mississippi

    International Nuclear Information System (INIS)

    The structure and stratigraphy over Richton Salt Dome, Mississippi, have been evaluated from 70 borings that were completed to various depths above the dome. Seven lithologic units have been identified and tentatively correlated with the regional Tertiary stratigraphy. Structure-contour and thickness maps of the units show the effects of dome growth from Eocene through early Pliocene time. Growth of the salt stock from late Oligocene through early Pliocene is estimated to have averaged 0.6 to 2.6 centimeters (0.2 to 1.1 inches) per 1000 years. No dome growth has occurred since the early Pliocene. The late Oligocene to early Pliocene strata over and adjacent to the dome reflect arching over the entire salt stock; some additional arching over individual centers may represent pre-Quaternary differential movement in the salt stock. The lithology and structure of the caprock at the Richton Salt Dome indicate that the caprock probably was completely formed by late Oligocene. In late Oligocene, the caprock was fractured by arching and altered by gypsum veining. Since late Oligocene, there are no indications of significant hydrologic connections through the caprock - that is, there are no indications of dissolution collapse or further anhydrite caprock accumulation. This structural and stratigraphic analysis provides insights on dome growth history, dome geometry, and neardome hydrostratigraphy that will aid in planning site characterization field activities, including an exploratory shaft, and in the conceptual design of a high-level waste (HLW) repository

  16. Pleistocene glaciation of the Biokovo Massif

    Directory of Open Access Journals (Sweden)

    Manja Žebre

    2013-12-01

    Full Text Available Biokovo massif is situated in the coastal part of the Dinaric Mountains in Croatia. Detailed morphographic and morphometric analysis of the highest parts of the massif were used to determine the extent and characteristics of Late Pleistocene glaciation. The reconstruction of glaciers and calculations of equilibrium line altitude (ELA were carried out. Our research revealed that on the north-eastern side of the highest peak Sveti Jure two cirque glaciers with an overall area of 1 km2 were formed and their ELA was 1515 m a.s.l.

  17. Stratigraphy of the Sarkisla area, Sivas basin, eastern central Anatolia

    Energy Technology Data Exchange (ETDEWEB)

    Bilgic, T.; Sumengen, M.; Terlemez, I.; Unay, E.; Gurbuz, M.; Erkan, E.

    1988-08-01

    The stratigraphy of the Sarkisla area, southeastern Central Anatolian Massif, is characterized by a succession of rock units ranging from late Paleocene to Pliocene in age. The Caldag group mostly consists of deep-water units and forms the base of the Tertiary rocks. However, its relation to the basement rocks is not observed in the area. This group is represented by late Paleocene-Lutetian-age turbiditic pyroclastics and limestones, andesitic lavas and pyroclastics topped with reefal limestones, and turbiditic limestones and pyroclastics alternating with limestone blocks. During Lutetian to early Priabonian time, shallow marine clastics were deposited along the southern margin of the basin, while continental clastics and platform limestones accumulated along the northern margin. Late Priabonian to early Oligocene time is represented by gypsiferous deposits followed by late Oligocene-age fluvial clastics. The gypsiferous deposits conformably overlie the shallow marine formations but rest on the Caldag group unconformably. During early to middle Miocene time, alternating lacustrine limestones, gypsum, and basalts formed on the fluvial clastics; to the north, basalts formed on the platform limestones. The uppermost sequence of the basin, composed of Tortonian-early Pliocene-age fluvial clastics, lacustrine limestones, and fan deposits, unconformably overlies the older formations. The stratigraphy of the study area is similar to the Ulukisla basin, southwestern Central Anatolian Massif. Therefore, this basin can be considered to be the prolongation of the Ulukisla basin offset by the Ecemis fault.

  18. OSTEOMETRÍA DE VICUGNA VICUGNA MOLINA, 1782 EN EL PLEISTOCENO FINAL DE PATAGONIA MERIDIONAL CHILENA: IMPLICANCIAS PALEOECOLÓGICAS Y BIOGEOGRÁFICAS / Osteometry of Vicugna vicugna Molina, 1782 in the late Pleistocene of southern chilean Patagonia

    Directory of Open Access Journals (Sweden)

    Rafael Labarca Encina

    2009-12-01

    Full Text Available  Se presenta un análisis osteométrico uni y multivariado con los materiales fósiles -principalmente huesos cortos y falanges- de Vicugna sp. del yacimiento Cueva Lago Sofía 4 (13500 – 11000 AP, ubicado en la provincia de Última Esperanza (Región de Magallanes, Chile. Los resultados indican que los elementos analizados poseen un tamaño compatible con los registrados para Vicugna vicugna, no superando en ningún caso a los especímenes conocidos para Vicugna gracilis del Pleistoceno de la región Pampeana. Esto confirma la información morfológica y de ADN antiguo que indicaba la presencia de Vicugna vicugna en la Patagonia meridional chilena. Se discuten los resultados en términos taxonómicos, biogeográficos y paleoecológicos sugiriendo que la presencia de este taxón fuera de su rango actual de distribución se debió a las condiciones ambientales compartidas entre la Puna y Patagonia austral durante la transición Pleistoceno-Holoceno. La extinción de V. vicugna se habría debido al impacto de los cambios climáticos ocurridos al inicio del Holoceno producto de su dieta pastadora y etología no migratoria y territorial, a lo que se habría sumado una caza por parte de depredadores humanos y no humanos.Palabras clave: género Vicugna, osteometría, Pleistoceno, Patagonia AbstractThis contribution presents the results of single and multi-variable osteometric analyses performed on a sample of short bones and phalanxes assigned to Vicugna sp. from Lago Sofía Cave 4 site (13500 – 11000 BP, Región de Magallanes, Chile. The elements analyzed show a similar size to the reference collections for Vicugna vicugna, and do not exceed the metrics for the pampean pleistocenic specimens of Vicugna gracilis. This confirms the morphological and ancient DNA data that indicated the presence of vicuña in southern Chilean Patagonia. The taxonomic, biogeographic and palaeoecologic discussion of these results, suggests that the presence of this species outside its current distribution range was due to shared environmental conditions between the Puna and Patagonia during the Pleistocene-Holocene transition. The extinction of this form is, most likely, due to the impact of climatic change during the begining of the Holocene over its pasturing diet and its territorial and non migratory habits. It is added to this, a hunting pressure by human and non-human predators.Keywords: Vicugna genus, osteometry, Pleistocene, Patagonia 

  19. Changing sedimentary environments during Pleistocene-Holocene in a core from the eastern continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Rao, Ch.M.; Mascarenhas, A.; Rao, K.M.; Reddy, N.P.C.; Das, H.C.

    Sedimentological and geochemical investigations of the sediments in a core from the eastern continental margin of India, at a water depth of 1200 m, revealed two distinct types. The Late Pleistocene sediments are greyish-black in colour and consist...

  20. The Pleistocene Gomphotheres (Proboscidea) from South America: Diversity, Habitats and Feeding Ecology

    OpenAIRE

    Prado, J. L.; Alberdi Alonso, María Teresa; Azanza, B.; Sánchez Chillón, Begoña; Frassinetti, D.

    2001-01-01

    Gomphotheres were recorded in South America from the early-middle Pleistocene (Ensenadan Land-mammal Age) to the late Pleistocene (Lujanian Land-mammal Age). They arrived in South America during the “Great American Biotic Interchange”. Only two genera are recognised: Cuvieronius, which has only one species, Cuvieronius hyodon; and Stegomastodon, which has two species, Stegomastodon waringi and Stegomastodon platensis. The small Cuvieronius utilised the Andean corridor and it was a...

  1. Stratigraphy and tectonics of a time-transgressive ophiolite obduction onto the eastern margin of the Pelagonian platform from Late Bathonian until Valanginian time, exemplified in northern Evvoia, Greece

    Science.gov (United States)

    Scherreiks, Rudolph; Meléndez, Guillermo; BouDagher-Fadel, Marcelle; Fermeli, Georgia; Bosence, Dan

    2014-11-01

    The obduction of an ophiolite sheet onto the eastern Pelagonian carbonate platform complex of the Hellenides began during the Late Bathonian and ended with the final emplacement of the ophiolite during Valanginian time. The early stages of obduction caused subaerial exposure of the platform, recorded by an unconformity of Callovian age, which is marked by laterites overlying folded and faulted, karstic substrates. The laterites have distinct ophiolitic geochemical signatures, indicating that emergent ophiolite had been undergoing lateritic weathering. This unconformity coincides with widespread western Tethyan, Callovian gaps, indicating that the obduction in the Hellenides was probably related to far-reaching plate tectonic processes. Resumed gravitational pull and rollback of the subducted, oceanic leading edge of the temporarily exposed ophiolite. Platform drowning continued into Tithonian-Valanginian time, documented initially by reefal carbonates and then by below-CCD, carbonate-free radiolarian cherts and shales. Subsequently, siliciclastic turbidites, which apparently originated from uplifted Variscan basement, were deposited together with and over the radiolarite as the ophiolite nappe sheet advanced. The nappe substrate underwent tectonic deformations of varying intensity, while polymictic mélange and syntectonic sedimentary debris accreted beneath the ophiolite and at the nappe front. The provenience of the ophiolite nappe complexes of northern Evvoia most probably has to be looked for in the Vardar ocean.

  2. Presencia de Antifer ultra Ameghino (=Antifer niemeyeri Casamiquela) (Artiodactyla, Cervidae) en el Pleistoceno tardío-Holoceno temprano de Chile central (30-35°S) / Presence of Antifer ultra Ameghino (=Antifer niemeyeri Casamiquela) in the late Pleistocene-early Holocene of Central Chile (30-35°S)

    Scientific Electronic Library Online (English)

    Rafael, Labarca E; M. Alejandra, Alcaraz.

    2011-01-01

    Full Text Available El presente trabajo discute el estatus taxonómico de la especie Antifer niemeyeri Casamiquela, 1984, definida a partir de astas completas procedentes de la laguna Taguatagua y la quebrada de Quereo (Pleistoceno tardío-Holoceno temprano), en Chile central (30-35°S). Se concluye, a partir de un estudi [...] o morfológico y morfométrico detallado, que Antifer niemeyeri debe ser considerado sinónimo de Antifer ultra Ameghino, 1889 dados los caracteres anatómicos compartidos con esta especie. Los resultados amplían la distribución geográfica del taxón, que previamente se registraba en Argentina, Uruguay y sur de Brasil, y confirman su biocrón para el Pleistoceno tardío-Holoceno temprano (edad Lu-janense), aun cuando las fechas radiocarbónicas de Chile central (ca. 9.900 años 14C AP) corresponden a las más tardías para la especie. A la luz de la evidencia paleoclimática disponible, se vincula A ultra durante el Pleistoceno de Chile central a ambientes cálidos y abiertos. Considerando estos requerimientos, se discute su posible vía de ingreso al actual territorio chileno a través de corredores ubicados hacia el sur del macizo andino, y su coexistencia con Hippocamelus bisulcus Molina, 1782. De acuerdo a la información estratigráfica y paleoambiental, se postula que ambas especies habrían sido alopátridas, por lo menos en el área de estudio. Abstract in english This paper discusses the taxonomic status of Antifer niemeyeri Casamiquela, 1984, defined from complete antlers from Taguatagua lake and Quereo canyon, both located in central Chile (30-35°S). From a detailed morphological and moiphometrical study, it is concluded that Antifer niemeyeri should be co [...] nsidered synonymous with Antifer ultra Ameghino, 1889, due to the anatomical characters shared between both forms. These results expand the geographical distribution of this taxa previously recorded in Argentina, Uruguay and southern Brazil, confirming their late Pleistocene-early Holocene biochron, in spite the fact that radiocarbon dates obtained in central Chile (ca. 9.900 14C yr BP) imply the youngest age for the species. According to the available paleoclimate evidence, A. ultra is linked to warm climate and an open landscape during the late Pleistocene of central Chile. Its possible routes of entry to central Chile through corridors located at the south of the Andean range and its coexistence with Hippocamelus bisulcus Molina, 1782, are also discussed. According to the stratigraphic and paleoenvironmental data we suggest that both species have been allopatric, at least in the study area.

  3. On the Pleistocene extinctions of Alaskan mammoths and horses

    OpenAIRE

    Solow, Andrew R; Roberts, David L.; Robbirt, Karen M.

    2006-01-01

    The fossil record has been used to shed light on the late Pleistocene megafaunal extinctions in North America and elsewhere. It is therefore important to account for variability due to the incompleteness of the fossil record and error in dating fossil remains. Here, a joint confidence region for the extinction times of horses and mammoths in Alaska is constructed. The results suggest that a prior claim that the extinction of horses preceded the arrival of humans cannot be made with confidence.

  4. Late Triassic and Early Cretaceous sedimentary sequences of the northern Isfahan Province (Central Iran): stratigraphy and paleoenvironments / Paleoecología y paleogeografía de secuencias del Triásico Superior al Cretácico Inferior en el área de Isfahan (Irán central)

    Scientific Electronic Library Online (English)

    Maryam, Mannani; Mehdi, Yazdi.

    2009-12-01

    Full Text Available Este estudio provee de un esquema general de las secuencias del Triásico Superior y Cretáceo Inferior localizadas al norte de Isfahan, en el Centro de Irán. La formación Nayband del Triásico Superior está subdividida en los miembros Gelkan, Bidestan, Howz-e-Sheikh, Howz-e-Khan y Qadir. Dos niveles d [...] e biostroma están documentados en los miembros Bidestan y Howz-e-Khan. Debido a las condiciones favorables en el Triásico tardío que incluyeron luz, oxígeno y nutrientes, fauna como: corales, esponjas, hidrozoarios, bivalvos, gasterópodos, braquiópodos, equinodermos y Dicroidium prosperaron en el agua y la flora en tierra. La presencia de Heterastridium spp. en el nivel del Miembro Bidestan es aparentemente el primer registro de este taxón el Centro de Irán. El miembro Qadir tiene varios estratos índice, uno de ellos con flora terrestre Clathropteris spp., y tres estratos índice con el bivalvo Indopecten glabra, fechados como etapa Rhaetian. Una disconformidad angular se puede trazar entre los sedimentos Rhaetian, conglomerados rojos, y areniscas provenientes de Secuencias del Cretáceo inferior en el área de Isfahan que incluye a todas las rocas del Jurásico. Esta discontinuidad puede estar relacionada con la fase tectónica Cimmeriana. Abstract in english This research gives a general outline of the Upper Triassic and Lower Cretaceous sequences cropping out north of Isfahan, Central Iran. Upper Triassic Nayband Formation subdivided into the Gelkan, Bidestan, Howz-e-Sheikh, Howz-e Khan and Qadir members. Two biostromal levels are documented in the Bid [...] estan and Howz-e-Khan members. Due to a suitable condition in Late Triassic time including light, oxygen and nutrient, fauna such as: corals, sponges, hydrozoas, bivalves, gastropods, brachiopods, echinoderms and Dicroidium were fourished in water and flora on land. The first appearance of Heterastridium spp. in level of the Bidestan Member is apparently the first occurrence of this taxon in Central Iran. Qadir Member has several key beds, one key bed with land flora Clathropteris spp., and three key beds with bivalve Indopecten glabra, dating as Rhaetian Stage. An angular unconformity can be traced between Rhaetian sediments and red conglomerates and sandstones of Lower Cretaceous Sequences in Isfahan area which encompasses all Jurassic rocks. This gap can be related to Cimmerian tectonic phase.

  5. Fragilariopsis diatom evolution in Pliocene and Pleistocene Antarctic shelf sediments

    Science.gov (United States)

    Sjunneskog, Charlotte; Riesselman, Christina; Winter, Diane; Scherer, Reed

    2012-01-01

    The late Pliocene – early Pleistocene sediment record in the AND-1B core from the McMurdo Sound, Ross Sea, Antarctica, displays a rich diversity and high abundance of diatoms, including several new morphologies within the genus Fragilariopsis. These new morphologies exhibit similarities to the extinct late Miocene/early Pliocene species Fragilariopsis aurica Gersonde and Fragilariopsis praecurta Gersonde, as well as to the modern sea ice-associated species Fragilariopsis ritscheri Hustedt and Fragilariopsis obliquecostata van Heurck. From the diverse morphologies present, we use light microscopy and scanning electron microscopy to identify and describe the characteristics of three new taxa, Fragilariopsis laqueata Riesselman, Fragilariopsis bohatyi Sjunneskog et Riesselman, and Fragilariopsis robusta Sjunneskog, which are common in the diatom-bearing intervals from ~3.2 to 1.95 Ma. Comparisons with extant and extinct species are made to assess possible environmental affinities, evolutionary relationships, and potential for future biostratigraphic utility. This complex of newmorphologies diversified as conditions cooled during the Pliocene, then went into decline as heavy sea ice conditions of the Pleistocene were established. Only the lineage of F. robusta appears to continue into the late Pleistocene, where it is interpreted to have evolved into F. obliquecostata.

  6. Late Pleistocene to Holocene river terrace deformation within the Little Salmon Fault Zone: insights to tectonic transition from Cascadia Subduction to San Andreas transform stress regimes, Van Duzen river, Northern California

    Science.gov (United States)

    Nicovich, S.; Hemphill-Haley, M. A.; Leroy, T. H.

    2014-12-01

    The southern Cascadia subduction zone (CSZ) of northwestern California exhibits northeast-directed contraction, transitioning to north-northwest directed translation within the broad San Andreas fault (SAF) transform margin to the south. The Little Salmon fault (LSF) is one of the southern-most, active thrust faults within the onshore fold and thrust belt of the CSZ, and lies proximal to the transition from compressional to dextral stress across the Mendocino Triple Junction. Thus, it is an ideal location to characterize strain associated with this complex region of transitional stress regimes. High precision topographic data (LiDAR) enabled detailed mapping of geomorphic features that would otherwise be obscured by dense vegetation of the area. A northwest trending lineament, sub-parallel and south of the main splay of the LSF is observed on LiDAR imagery. The lineament exhibits potential up-to-the-northeast offset and traverses several Van Duzen river terrace risers and treads that range from Pleistocene to potentially Holocene in age. A shallow, exploratory trench was hand-excavated across the lineament. The shallow, roughly 1.5 m-deep, 16 m-long trench exposed imbricated gravels that dip into the base of the trench in the upper end. Coring within the lower end of the trench mapped the southern extent of the gravels. The architecture of the unconsolidated, clast-supported gravel deposit displays a diffuse up-to-the-northeast step. More obvious offset may be expressed at lower depths and/or in mediums with more confining stress. The linear map expression of the lineament across relatively steep terrain suggests that the fault may be relatively steeply dipping. Conjugate deformation shear bands within Neogene bedrock nearby along the Van Duzen river provide additional information about the state of stress within this area of transition.

  7. New data on the pleistocene of Mallorca

    Science.gov (United States)

    Hearty, P. J.

    Stratigraphic, geomorphologic and isoleucine epimerization studies at 15 sites in Mallorca define four aminozones (A, C, E and F-G) of increasing age that are related to transgressive-regressive marine cycles from the Holocene to the mid Pleistocene. Calibration of aminozone E ( Glycymeris aIle/Ile mean from all sites = 0.41 ± 0.03 ( n=38)) is provided by a 129 ± 7 ka U-series coral age on Cladocora caespitosa from Son Grauet. Of the younger aminozones, A relates to the Holocene transgression and aminozone C to a mid to late isotopic stage 5 event (90 ± 15 ka) revealed only by supralittoral eolianites. Assigning an age to the older, poorly resolved aminozones F and G (called F-G in this case) is uncertain without supporting radiometric data. But an age of > 180 ka can be assigned to these aminozone (s) F-G based on a kinetic model and other examples in the Mediterranean. Several deposits, previously dated (U-series, molluscs) between 75 and > 300 ka appear to belong to the last interglacial complex (Stage 5) and aminozone E. A proposed revision of the positive sea level history of Mallorca shows multiple minor oscillations during the major last interglacial cycle (Stage 5) and two mid Pleistocene sea levels, one lower than present and the other at about 14 m a.s.l.

  8. Registros de fluctuaciones paleobatimétricas del sistema lacustre Pueyrredon-Posadas-Salitroso durante el Pleistoceno Tardío? - Holoceno Temprano, noroeste de Santa Cruz, Argentina / Register of paleobametric fluctuations of the Pueyrredon-Posadas-salitroso Lacustrine System during the Late Pleistocene? -Early holocene (Northwestern of Santa Cruz, Argentina

    Scientific Electronic Library Online (English)

    Luis R, Horta; Sergio M, Georgieff; Carlos A, Console Gonella; José, Busnelli; Carlos A, Aschero.

    2011-12-01

    Full Text Available El estudio de depósitos lacustres datados entre el Pleistoceno Tardío? - Holoceno Temprano vinculado con un modelo de elevación digital han permitido reconstruir la posición de las paleocostas del Sistema lacustre Pueyrredón - Posadas - Salitroso, demostrando la conexión entre ellos, que se verifica [...] en algunos niveles específicos de paleocotas. En este trabajo, se utilizaron como indicadores paleobatimétricos: la ubicación altitudinal relativa de depósitos glacilacustres, depósitos de arenas costeras, depósitos de abanico deltaico en la margen sur del lago Pueyrredón, dataciones absolutas (AMS y 14C), trazas fósiles y comparaciones de malacofauna fósil con la actual para las interpretaciones paleoambientales. Abstract in english The palaeocoast line positions of the lacustrine system of Pueyrredón - Posadas - Salitroso lakes were determined through the study of the lacustrine deposits, which were dated between the Late Pleistocene? - Early Holocene, together with a digital elevation model (DEM). This has demonstrated the li [...] nk among them verified on some specific palaeoheight levels. In this research, paleo-bathymetric geoindicators, as relative height of glaci-lacustrine, coastal sand and fandelta deposits onto the southern margin of Pueyrredon Lake, and absolute dating techniques (AMS & 14C), fossil trace and fossil and current malacofauna comparison were used in order to develop palaeoenvironment interpretations.

  9. Cenozoic stratigraphy of the southern Salar de Antofalla region, northwestern Argentina

    OpenAIRE

    Reno Voss

    2002-01-01

    In the region of the southern Salar de Antofalla (Catamarca Province, northwestern Argentina), Late Eocene to Pliocene/(?)Pleistocene successions are exposed with thicknesses of up to 1,600 m. They consist of fluvial, lacustrine and eolian sediments with intercalations of pyroclastic rocks and lava flows. The sedimentary deposits represent 'alluvial fan-playa-complexes' accumulated under a semi-arid to arid climate. From the Late Eocene to the Early Miocene, the sedimentation took place in br...

  10. Quaternary alluvial stratigraphy and palaeoclimatic reconstruction at the Thar margin

    DEFF Research Database (Denmark)

    Jain, M.; Tandon, S.K.

    2003-01-01

    Quaternary alluvial record at the Thar desert margin has been examined using the exposed succession along Mahudi, Sabarmati river, Western India. Different alluvial facies, their associations and granulometry have been studied for palaeoenvironmental reconstruction. Clay mineral indices smectite/chlorite and smectite/illite of the alluvial palaeosols have been used as proxy indicators of climate change. These indicate wet phases during the OIS 5 and OIS 1. The overall stratigraphic development is discussed in the framework of fluvial response to climate change during the Late Pleistocene.

  11. Obliquity and precession as pacemakers of Pleistocene deglaciations

    CERN Document Server

    Feng, Fabo

    2015-01-01

    The Milankovitch theory states that the orbital eccentricity, precession, and obliquity of the Earth influence our climate by modulating the summer insolation at high latitudes in the northern hemisphere. Despite considerable success of this theory in explaining climate change over the Pleistocene epoch (2.6 to 0.01 Myr ago), it is inconclusive with regard to which combination of orbital elements paced the 100 kyr glacial-interglacial cycles over the late Pleistocene. Here we explore the role of the orbital elements in pacing the Pleistocene deglaciations by modeling ice-volume variations in a Bayesian approach. When comparing models, this approach takes into account the uncertainties in the data as well as the different degrees of model complexity. We find that the Earth's obliquity (axial tilt) plays a dominant role in pacing the glacial cycles over the whole Pleistocene, while precession only becomes important in pacing major deglaciations after the transition of the dominant period from 41 kyr to 100 kyr ...

  12. Oxygen isotope stratigraphy in the Gulf of Alaska (IODP Exp. 341)

    Science.gov (United States)

    Asahi, H.; Mix, A. C.; Suto, I.; Belanger, C. L.; Fukumura, A.; Gupta, S.; Konno, S.; Matsuzaki, K. M.; Romero, O. E.; Gulick, S. P. S.; Jaeger, J. M.; Schneider, L. J.

    2014-12-01

    Age constrains provided by oxygen isotope stratigraphy, biostratigraphy and paleomagnetics can provide fundamental insights for interpreting other paleoceanographic reconstructions at orbital scale. In the case of the high latitude in the North Pacific, most paleoceanographic studies investigating the evolution of the North Pacific climate since the intensification of Northern Hemisphere Glaciation (iNHG) face difficulties in establishing orbital-scale age models due to the low preservation of foraminifer fossils. Most North Pacific studies targeting the Pleistocene heavily rely on alternative approaches with higher preservation potential (e.g. MS: Magnetic Susceptibility) for orbital-scale age models, and assume such data are mainly reflecting the Glacial-Interglacial (G-IG) cycle. A continuous oxygen iope record from the subarctic North Pacific is long anticipated data set to test such assumptions. Two sites (Sites U1417 and U1418) in the Gulf of Alaska (GoA) drilled during IODP Exp. 341 are expected to provide continuous sediment records back to the middle Pleistocene (U1418) and Miocene (U1417), respectively. Here we present age models at Sites U1417 and U1418 derived from refined biostratigraphy and planktic foraminiferal (PF) oxygen isotope (Neogloboquadrina pachyderma sinistral, 150-250 ?m fraction) stratigraphy (~1.2Ma at Site U1418 and ~3.0Ma at U1417, respectively). General agreement between oxygen isotope stratigraphy and other age constraints (biostratigraphy and paleomagnetism) at Site U1418 confirms the reliability of those age models. Furthermore, general trends seen in PF oxygen isotope time series roughly matches MS, suggesting that MS can be used for further age model tuning or as an alternative solution for the orbital scale age constrains in the GoA.

  13. Pleistocene Paleoart of Europe

    Directory of Open Access Journals (Sweden)

    Robert G. Bednarik

    2014-06-01

    Full Text Available As in Australia, Pleistocene rock art is relatively abundant in Europe, but it has so far received much more attention than the combined Ice Age paleoart of the rest of the world. Since archaeology initially rejected its authenticity for several decades, the cave art of France and Spain and the portable paleoart from various regions of Europe have been the subjects of thousands of studies. It is shown, however, that much of the published information is unreliable and subjective, and that fundamental trends in the evidence have been misunderstood. In particular, the data implies that the paleoart of the Early Upper Paleolithic, the work of robust humans such as Neanderthals, is considerably more sophisticated and developed that that of more recent times. Thus, the European paleoart demonstrates that the teleological model of cultural “evolution” is false, which is to be expected because evolution is purely dysteleological. This is confirmed by the extensive record of pre-Upper Paleolithic European paleoart, which is comprehensively reviewed in this paper.

  14. Cambios en lagos y circulación fluvial vinculados al calentamiento climático del Pleistoceno tardío-Holoceno temprano en Patagonia e isla 25 de mayo, islas Shetland del Sur, Antártida / Changes in lakes and fluvial circulationlinked to climate warming in Late Pleistocene - Early Holocene in Patagonia and 25 de Mayo Island, Shetland del Sur Islands, Antarctica

    Scientific Electronic Library Online (English)

    R.A., del Valle; A., Tatur; C.A., Rinaldi.

    2007-12-01

    Full Text Available El calentamiento clim ático que afectó a la Patagonia en el Pleistoceno tardío-Holoceno temprano produjo cambios en la morfología del paisaje, incluyendo la génesis, desarrollo y desintegración de grandes lagos al este de los Andes. Hasta entonces, los glaciares y sus morenas formaban diques natural [...] es que embalsaron las aguas de deshielo y mantenían alto el nivel de las aguas en los grandes paleolagos. Posteriormente, la migración hacia el sur de la mejoría climática ocasionó la progresiva fusión del campo de hielo regional, y las morenas fueron cortadas por la erosión fluvial, cuando el calentamiento climático impactó plenamente en la región. El proceso afectó a la región de norte a sur en tiempos diferentes: 1) hace c. 13.200 años en el norte, 2) durante la transición Pleistoceno/Holoceno en la parte central, y 3) finalmente, en Tierra del Fuego hace unos 7.800 años. El rápido retroceso de los glaciares produjo el desalojo de los valles andinos a ambos lados de la cordillera, lo cual abrió cauces fluviales que atraviesan la cordillera desde entonces, inaugurando el drenaje hacia el océano Pacífico de grandes lagos glaciales que existían al oriente de los Andes. Esto resultó en el rápido descenso del nivel de los paleolagos. Un proceso similar ocurrió en las islas Shetland del Sur (Antártida) hace unos 6.000 años. Abstract in english The climate warming that affected Patagonia region during late Pleistocene-early Holocene times produced changes in landscape morphology, including the formation, development, breakdown and disintegration of big lakes at the eastern side of Andes. Before these times, glaciers and their moraines form [...] ed natural dams that maintained a high water level in large paleolakes. The subsequent southward migration of climate amelioration produced the melting of the regional ice field, and moraines were cut by fluvial erosion, when climate warming strongly impacted in the region. The process occurred in the region from north to south at different times: 1) in the northern part c. 13,200 years ago, 2) in the central part during the Pleistocene/Holocene transition and 3) finally, in Tierra del Fuego c. 7,800 years ago. With the rapid retreat of glaciers from the Andean valleys during prominent regional deglaciation, outflow from the eastern side of Andes to the Pacific Ocean was formed. As a result, the water level in glacial paleolakes fell down rapidly in stages. A similar process occurred in South Shetland Islands (Antarctica) c. 6,000 years ago.

  15. Paleosuelos y niveles límnicos desarrollados en sucesiones aluviales del Pleistoceno tardío y Holoceno del Piedemonte Andino de Mendoza (33°-34° ls), Argentina / Paleosoils and limnic levels in the late Pleistocene and Holocene alluvial successions of the Andean Piedmont of Mendoza (33°-34° LS), Argentina

    Scientific Electronic Library Online (English)

    Adriana, Mehl; Marcelo, Zárate.

    2013-06-01

    Full Text Available Los depósitos aluviales del Pleistoceno tardío y Holoceno de la cuenca del Arroyo La Estacada, en el piedemonte andino mendocino, entre los 33° y 34° LS, componen tres unidades geomorfológicas conspicuas: una planicie de agradación regional (PAR, Pleistoceno tardío - Holoceno temprano), una terraza [...] de relleno aluvial (TRA, Holoceno medio y tardío) y la planicie de inundación actual (posterior a los 400 a AP). La PAR y la TRA registran procesos alternantes de agradación y pedogénesis, siendo estos últimos más frecuentes en los depósitos holocenos, caracterizados también por una mayor abundancia de niveles con contenido orgánico elevado (niveles límnicos). Este trabajo evalúa el registro de paleosuelos y niveles límnicos de la cuenca, con el objetivo de inferir sus implicancias en la dinámica paleoambiental y paleoclimática de la región centrooeste de Argentina durante el Pleistoceno tardío y Holoceno, y aportar información al marco paleoclimático del extremo sur de Sudamérica. Se muestrearon depósitos aluviales que exhiben paleosuelos y niveles límnicos en cuatro perfiles litoestratigráficos en las márgenes del Arroyo La Estacada y su tributario el Arroyo Anchayuyo; se utilizó el color como indicador de campo. Se describieron atributos en forma cualitativa (granulometría, color; consistencia, tipo y grado de estructuración de los sedimentos; forma y tipo de límites, sustancias cementantes y/o aglutinantes, rasgos redoximórficos, etc) y cuantitativa (contenido de materia orgánica y carbonato de calcio); se realizaron análisis micromorfológicos en muestras de sedimentos no disturbadas. Los resultados se presentan con un criterio cronológico decreciente basado en la calibración cronológica de los depósitos aluviales. Los paleosuelos de la PAR revelan un pobre desarrollo pedológico, con presencia de carbonato de calcio en la masa, y en forma de nódulos y concreciones. Por su parte, los paleosuelos de la TRA presentan mayor desarrollo relativo, y ausencia de carbonatos en general. Los niveles límnicos reflejan un incremento en la productividad vegetal en ambientes de la planicie de inundación saturados en agua; y quizás también un mayor transporte de MO por parte de las corrientes de agua en el valle fluvial. La mayor concentración de rasgos de carbonatación de la PAR reflejaría condiciones de mayor evaporación en los ambientes depositacionales del Pleistoceno tardío - Holoceno temprano; mientras que la abundancia de rasgos redoximórficos en los niveles de la TRA, registraría la saturación en agua de los depósitos del Holoceno medio y tardío, quizás en respuesta a frecuentes fluctuaciones del nivel freático. Las sucesiones aluviales analizadas registran los cambios paleoambientales / paleoclimáticos acaecidos en el piedemonte andino oriental entre los 33° y 34° LS, en vinculación con la transición climática del Pleistoceno tardío - Holoceno. Los paleosuelos y niveles límnicos observados resultaron herramientas útiles para la calibración geocronológica de las sucesiones aluviales estudiadas. Abstract in english The late Pleistocene and Holocene alluvial deposits of the Arroyo La Estacada basin, located in the Andean piedmont of Mendoza province between 33° and 34° SL (Fig. 1a-b), are arranged in three conspicuous geomorphological units, a regional aggradational plain (RAP, late Pleistocene - early Holocene [...] ), a fill terrace (FT, middle and late Holocene) and a present floodplain (developed ca. 400 yr BP) (A-A', B-B', Fig. 1c). The RAP (Figs. 2a, 3a) and the FT (Figs. 2b, 3b) record aggradational and pedological proccesses; the latter are more frequents in the Holocene deposits together with abundant sedimentary levels showing high organic matter content (limnic levels). High organic matter content deposits have been studied by the international scientific community, particularly in North America, where some authors discussed the paleoenvironmental and paleoclimatic implicances of the 'black mats' (Haynes, 1968; 2008; Firesto

  16. El registro más completo de un Hoplophorini (Xenarthra: Glyptodontidae para los Pisos/Edades Chapadmalalense-Marplatense (Plioceno tardío-Pleistoceno temprano The most complete record of a Hoplophorini (Xenarthra: Glyptodontidae for the Chapadmalalan-Marplatan Stages (Late Pliocene-Early Pleistocene

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    Alfredo E Zurita

    2011-06-01

    Full Text Available Los Glyptodontidae del Neógeno tardío (Pisos/Edades Chapadmalalense-Marplatense; ca. 3.9-1.8 Ma constituyen un grupo escasamente conocido, en tanto la mayoría de los registros están limitados a restos aislados de la coraza dorsal y/o caudal. Las únicas excepciones están representadas por Paraglyptodon chapalmalensis (Ameghino in Rovereto, un fósil guía para el Chapadmalalense superior, y el Plohophorini Plohophorus figuratus Ameghino. Por otro lado, los "Hoplophorinae" Hoplophorini son gliptodontes que tienen sus primeros registros durante los Pisos Huayqueriense (Mioceno tardío y "Araucanense" (Mioceno tardío-Plioceno, pero están prácticamente ausentes durante los Pisos Chapadmalalense-Marplatense (Plioceno-Pleistoceno temprano. Posteriormente, los Hoplophorini (Neosclerocalyptus Paula Couto son, junto con Glyptodon Owen, los Glyptodontidae de registro más frecuente en el Pleistoceno de América del Sur. En esta contribución damos a conocer el primer registro de un Hoplophorini de antigüedad Chapadmalalense, asignado al género Eosclerocalyptus C. Ameghino (Eosclerocalyptus cf. E. lineatus. Este nuevo material, representado por una coraza dorsal, fue exhumado de la sección superior de la Fm. Chapadmalal, Mar del Plata, provincia de Buenos Aires. Desde una perspectiva morfológica, esta coraza presenta un tamaño intermedio entre E. tapinocephalus Cabrera, E. proximus (Moreno & Mercerat y Neosclerocalyptus Paula Couto. Junto con cf. Paraglyptodon chapalmalensis y Plohophorus figuratus Ameghino, estos registros representan los Glyptodontidae Pliocenos más completos que se conocen; a su vez, completa parcialmente la distribución estratigráfica de los Glyptodontidae Hoplophorini.The late Neogene (Chapadmalalan-Marplatan Stages; ca. 3.9-1.8 Ma Glyptodontidae from southern South America are poorly known since most of the record are limited to remains of the dorsal and/or caudal armour. In this sense, the exceptions are represented by Paraglyptodon chapadmalensis (Ameghino in Rovereto, a fossil guide of the Upper Chapadmalalan Stage, and the Plohophorini Plohophorus figuratus Ameghino. On the other hand, the "Hoplophorinae" Hoplophorini are glyptodonts that have its first records during the Huayquerian (late Miocene and "Araucanian" Stages (late Miocene-early Pliocene, but they are almost absents during the Chapadmalalan-Marplatan Stages (Pliocene-early Pleistocene. Later, the Hoplophorini (Neosclerocalyptus Paula Couto are, together with Glyptodon Owen, the most common South American Pleistocene Glyptodontidae. In this contribution we report the first record of a Chapadmalalan Hoplophorini, assigned to the genus Eosclerocalyptus C. Ameghino (Eosclerocalyptus cf. E. lineatus, coming from the Mar del Plata locality, Buenos Aires province (Argentina. This new material, represented by a complete dorsal carapace, was exhumed from the upper section of the Chapadmalalan Formation. From a morphological perspective, this dorsal carapace shows an intermediate size between E. tapinocephalus Cabrera, E. proximus (Moreno & Mercerat and Neosclerocalyptus Paula Couto. Together with cf. Paraglyptodon chapadmalensis and Plohophorus figuratus Ameghino those records represents the most entire Pliocene Glyptodontidae known and, in addition, it partially complete the stratigraphical distribution of the Glyptodontidae Hoplophorini.

  17. El registro más completo de un Hoplophorini (Xenarthra: Glyptodontidae) para los Pisos/Edades Chapadmalalense-Marplatense (Plioceno tardío-Pleistoceno temprano) / The most complete record of a Hoplophorini (Xenarthra: Glyptodontidae) for the Chapadmalalan-Marplatan Stages (Late Pliocene-Early Pleistocene)

    Scientific Electronic Library Online (English)

    Alfredo E, Zurita; Cristian, Oliva; Alejandro, Dondas; Esteban, Soibelzon; Federico I, Isla.

    2011-06-01

    Full Text Available Los Glyptodontidae del Neógeno tardío (Pisos/Edades Chapadmalalense-Marplatense; ca. 3.9-1.8 Ma) constituyen un grupo escasamente conocido, en tanto la mayoría de los registros están limitados a restos aislados de la coraza dorsal y/o caudal. Las únicas excepciones están representadas por Paraglypto [...] don chapalmalensis (Ameghino in Rovereto), un fósil guía para el Chapadmalalense superior, y el Plohophorini Plohophorus figuratus Ameghino. Por otro lado, los "Hoplophorinae" Hoplophorini son gliptodontes que tienen sus primeros registros durante los Pisos Huayqueriense (Mioceno tardío) y "Araucanense" (Mioceno tardío-Plioceno), pero están prácticamente ausentes durante los Pisos Chapadmalalense-Marplatense (Plioceno-Pleistoceno temprano). Posteriormente, los Hoplophorini (Neosclerocalyptus Paula Couto) son, junto con Glyptodon Owen, los Glyptodontidae de registro más frecuente en el Pleistoceno de América del Sur. En esta contribución damos a conocer el primer registro de un Hoplophorini de antigüedad Chapadmalalense, asignado al género Eosclerocalyptus C. Ameghino (Eosclerocalyptus cf. E. lineatus). Este nuevo material, representado por una coraza dorsal, fue exhumado de la sección superior de la Fm. Chapadmalal, Mar del Plata, provincia de Buenos Aires. Desde una perspectiva morfológica, esta coraza presenta un tamaño intermedio entre E. tapinocephalus Cabrera, E. proximus (Moreno & Mercerat) y Neosclerocalyptus Paula Couto. Junto con cf. Paraglyptodon chapalmalensis y Plohophorus figuratus Ameghino, estos registros representan los Glyptodontidae Pliocenos más completos que se conocen; a su vez, completa parcialmente la distribución estratigráfica de los Glyptodontidae Hoplophorini. Abstract in english The late Neogene (Chapadmalalan-Marplatan Stages; ca. 3.9-1.8 Ma) Glyptodontidae from southern South America are poorly known since most of the record are limited to remains of the dorsal and/or caudal armour. In this sense, the exceptions are represented by Paraglyptodon chapadmalensis (Ameghino in [...] Rovereto), a fossil guide of the Upper Chapadmalalan Stage, and the Plohophorini Plohophorus figuratus Ameghino. On the other hand, the "Hoplophorinae" Hoplophorini are glyptodonts that have its first records during the Huayquerian (late Miocene) and "Araucanian" Stages (late Miocene-early Pliocene), but they are almost absents during the Chapadmalalan-Marplatan Stages (Pliocene-early Pleistocene). Later, the Hoplophorini (Neosclerocalyptus Paula Couto) are, together with Glyptodon Owen, the most common South American Pleistocene Glyptodontidae. In this contribution we report the first record of a Chapadmalalan Hoplophorini, assigned to the genus Eosclerocalyptus C. Ameghino (Eosclerocalyptus cf. E. lineatus), coming from the Mar del Plata locality, Buenos Aires province (Argentina). This new material, represented by a complete dorsal carapace, was exhumed from the upper section of the Chapadmalalan Formation. From a morphological perspective, this dorsal carapace shows an intermediate size between E. tapinocephalus Cabrera, E. proximus (Moreno & Mercerat) and Neosclerocalyptus Paula Couto. Together with cf. Paraglyptodon chapadmalensis and Plohophorus figuratus Ameghino those records represents the most entire Pliocene Glyptodontidae known and, in addition, it partially complete the stratigraphical distribution of the Glyptodontidae Hoplophorini.

  18. Sedimentología de unidades loéssicas (Pleistoceno tardío - Holoceno) del centro-sur de Santa Fe / Sedimentology of loessic units (Late Pleistocene - Holocene) of the center-south of Santa Fe

    Scientific Electronic Library Online (English)

    Daniela, Kröhling; Oscar, Orfeo.

    2002-12-01

    Full Text Available Se presenta una caracterización integral de las secuencias loess-paleosuelos aflorantes en un área típica de la Pampa Norte, basada en el análisis estratigráfico y en la variabilidad granulométrica y mineralógica. El estudio sedimentológico de detalle del loess fue practicado en dos perfiles del cen [...] tro-sur de Santa Fe (Tortugas y Carcarañá). El loess está representado por la Fm Tezanos Pinto, integrada por dos miembros separados por una discordancia intraformacional (generados durante el Ultimo Máximo Glacial y el Pleistoceno tardío-Holoceno temprano, respectivamente). Esta unidad está coronada por un suelo parcialmente erodado, desarrollado durante el Período Hypsithermal. Una formación loéssica delgada (Fm San Guillermo; Holoceno tardío) yace sobre el suelo decapitado. La fracción granulométrica dominante de la Fm Tezanos Pinto en ambos perfiles es el limo (?70%), con participación subordinada de arena muy fina y arcilla. En general, el tamaño medio corresponde a la fracción limo entre 4 y 6 ?; con una tendencia granodecreciente y un mejoramiento del coeficiente de selección desde el miembro inferior hacia el superior. Las curvas de frecuencias acumuladas evidencian una subpoblación transportada por saltación y dos subpoblaciones de partículas asociadas a transporte por suspensión. Cada una de estas dos subpoblaciones representa entre el 30 y el 50% de la distribución. La población mayoritaria de minerales livianos de la fracción modal de arenas (125- 63µm) del loess aflorante en ambos perfiles está formada por materiales volcaniclásticos andinos aportados por vía eólica (cuarzo policristalino, microaglomerados, vidrio volcánico, fragmentos líticos y plagioclasas). La fuente minoritaria integra minerales provenientes del basamento cristalino de las Sierras Pampeanas, transportados y depositados por acción fluvial (cuarzo y feldespatos potásicos). El limo (63-4µm) está compuesto por cuarzo, con menor cantidad de feldespatos; la illita es el mineral arcilloso más abundante. En la arcilla ( Abstract in english An integral characterization of the outcropping loess-paleosols sequence in a type area of North Pampa is presented, based on the stratigraphic analyses and the grain size and mineralogic variability. Two loess profiles representative of interfluve areas of southern Santa Fe province were selected f [...] or detailed sedimentological analyses (Tortugas and Carcarañá Profiles). The loessic cover is part of the quaternary aeolian sedimentary body of the Argentine plain, defined as "Pampean Aeolian System" by Iriondo (1990a) and Iriondo and Kröhling (1995). Both geomorphological and sedimentological systems compose the Pampean Aeolian System: a Sand Sea and a Peripheral Loess Belt. The Loess Belt, about 2,000 Km long and 250-300 Km wide in North Pampa, is located at the northeast of the Sand Sea. The sediments of the Pampean Aeolian System accumulated during the first stages of the last Pleistocene glaciation; later on they were partially reworked during successive dry phases and underwent pedogenesis in humid periods (Iriondo and Kröhling, 1995). The outcropping sedimentary sequence of the area is represented by fine aeolian units interbedded with buried soils. The Tezanos Pinto Fm (Iriondo, 1987) is the typical loessic unit of the North Pampa. In most places (Carcarañá Profile) it lays in erosive contact on a dissipation deposit of aeolian sand (Carcarañá Fm; Kröhling, 1999a). The loess is a loose deposit, silt with subordinated clay and very fine sand, light brown in colour. The loess thickness generally ranges from 4 to 10 m in the interfluves. The loess is a homogeneous, massive and permeable deposit. The sedimentary mass is calcareous; it contains powdery concentrations and hard concretions of CaCO3. The loess body is crossed by fine rhizoid ramified canalicula and very fine micropores of tubular forms. It is stable in steep walls, in parts altered by subcutaneous subfussion and shaped by columnar disjunction. Two members of the loe

  19. Dark humic alluvial paleosols in Central and Southern Mexico: Micromorphological indicators of Late Pleistocene megafauna habitats Paleosuelos aluviales con humus oscuro en el Centro y Sur de México: indicadores micromorfológicos de los hábitats de la megafauna del Pleistoceno tardío Paleosolos aluviais com húmus escuro no Centro e Sul do México: indicadores micromorfológicos dos habitats da megafauna do Pleistocénico tardio

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    Rosa E. Tovar

    2013-11-01

    Full Text Available During the Late Pleistocene, Mexico had a richer fauna than today with many different forms of megafauna that are now extinct. However, the ecosystems they inhabited and the particular ecological niches that they occupied are still poorly understood. Most of the findings of Pleistocene megafauna have been in alluvial deposits that present rich opportunities for paleoecological studies using paleopedological records. Floodplain paleosols commonly are poorly developed. However, micromorphological analysis provides information about the grade of development of the soil at a microscale, discriminating between genetic and sedimentary processes; thus helping in the identification of the environmental setting in which they formed. We analyzed the micromorphology of six pedogenetic units in the sequences of Santa Cruz Nuevo and Axamilpa, in the south of Puebla, and Huexoyucan, in the state of Tlaxcala. These pedosequences correspond to the second half of marine isotopic stage 3 (MIS3, MIS2 and the early Holocene. All studied units are characterized by strong pigmentation with dark humus. The micromorphological analysis of MIS3 paleosols reveals aquatic conditions with evidence of freshwater biota and microlamination as well as pedogenetic features of hydrogenic carbonate precipitation and redoximorphic processes. The dark paleosols of MIS2 and the early Holocene demonstrate signs of stronger coprogenic aggregation, weathering and fewer gleyic features. Comparison with modern soils shows that the latter were formed under better-drained, aerated conditions that exclude redoximorphic processes. We conclude that the dark colored Pleistocene paleosol units are indicative of different paleo-landscapes: wetlands in the MIS3 and moist meadows in MIS2 ? early Holocene. The swampy ecosystems could play an important role as a megafauna habitat.En el Pleistoceno Tardío, México tenía una diversidad faunística más rica que en la actualidad, con diferentes formas de megafauna, hoy extinta. Sin embargo, los ecosistemas que habitaron y determinados nichos ecológicos que ocupaban son poco conocidos. Los hallazgos más numerosos de la megafauna del Pleistoceno han sido en depósitos aluviales, los cuales son registros paleoecológicos importantes que representan una excelente oportunidad para ser estudiados. Los paleosuelos aluviales regularmente son poco desarrollados, sin embargo, el análisis micromorfológico proporciona información relevante sobre el grado de desarrollo del suelo a una microescala, permitiendo discriminar entre los procesos edafogenéticos y sedimentarios; ayudando con ello a la identificación de la configuración del medio ambiente en el que se formaron. Nosotros analizamos la micromofología de seis unidades edafogenéticas en las secuencias de Santa Cruz Nuevo y Axamilpa, en el sur de Puebla y Huexoyucan, en el estado de Tlaxcala. Estas edafosecuencias corresponden a la segunda mitad de la etapa isotópica marina 3 (MIS3, etapa isotópica marina 2 MIS2 y al Holoceno Temprano. Todas las unidades estudiadas se caracterizan por una fuerte pigmentación con humus oscuro. El análisis micromorfológico de los paleosuelos de MIS3 revela condiciones acuáticas con evidencias de biota de agua dulce, como también microlaminaciones de precipitación de carbonatos hidrogénicos y procesos redoximórficos. Los paleosuelos oscuros de MIS2 y el Holoceno Temprano muestran fuerte agregación coprogénica, intemperismo y pocos rasgos gleycos, presentando fuertes diferencias con los suelos modernos. Los suelos modernos se formaron en condiciones aireadas, con un mejor drenaje que excluyen los procesos redoximórficos. Llegamos a la conclusión de que las unidades de paleosuelos del Pleistoceno de color oscuro son indicativos de diferentes paleopaisajes: humedales pantanosos en la MIS3 y praderas húmedas desde MIS2 hasta el Holoceno Temprano. Los ecosistemas pantanosos podrían representar un importante hábitat para la megafauna del Pleistoceno.No Pleistocénico tardio, o México apresentava uma diversidade fa

  20. Mechanics of wind ripple stratigraphy.

    Science.gov (United States)

    Forrest, S B; Haff, P K

    1992-03-01

    Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The simulations show that climbing strata can be produced by impact alone; direct action of fluid shear is unnecessary. The model provides a means for evaluating the connection between mechanical processes occurring in the paleoenvironment during deposition and the resulting stratigraphy preserved in the geologic column: vertical compression of small laminae above a planar surface indicates nascent ripple growth; supercritical laminae are associated with unusually intense deposition episodes; and a plane erosion surface separating sets of well-developed laminae is consistent with continued migration of mature ripples during a hiatus in deposition. PMID:17816833

  1. Contribution of stable isotopes (C,N,S) in collagen of late Pleistocene large mammal trophic ecology and landscape use: a case study in Goyet and Scladina cave (30-40,000 years BP)

    Science.gov (United States)

    Bocherens, Hervé; Germonpré, Mietje

    2010-05-01

    Two Belgian caves yielded very rich large mammal associations dating around 30 to 40,000 years ago: Goyet and Scladina cave (layer 1A). These sites are only 5 km apart but the cave entrances open on different valleys, in a quite diverse landscape ranging between open, unprotected uplands, steep cliffs and sheltered sun-exposed gorges, with the larger Meuse valley nearby. This mosaic scenery permitted during the Last Glacial a rich diversity of fossil flora and fauna. The faunal association includes a large diversity of taxa including Aurochs Bos primigenius, steppe bison Bison priscus, reindeer Rangifer tarandus, giant deer Megaloceros giganteus, horse Equus ferus, woolly rhinoceros Coelodonta antiquitatis, woolly mammoth Mammuthus primigenius, cave bear Ursus spelaeus, brown bear Ursus arctos, wolf Canis lupus, cave lion Panthera leo spelaea, and cave hyaena Crocuta crocuta spelaea. All the 90 studied bones and teeth yielded collagen with excellent collagen preservation, allowing reliable investigations of carbon, nitrogen and sulfur isotopic biogeochemistry. The combination of three different isotopic tracers allows to deciphering the effects of food selection and landscape use by different herbivorous and carnivorous taxa. This is the first study to include sulfur isotopic signatures in the study of late Quaternary large mammal palaeobiology. This new tracer yields evidence on mobility and differences in pasture areas, as different geological bedrock may exhibit various sulfur isotopic signatures that will pass on the herbivores and further on their predators. Using this feature in addition to the trophic information provided by carbon and nitrogen isotopic signatures, it appears that for some species present in both sites, such as horse and woolly rhinoceros, the individuals found in each site probably did not use the same pasture areas. This seems to also the case for the overwhelmingly vegetarian cave bears. In addition, individuals from the same species found in one site sometimes exhibit clear isotopic differences in the three isotopic tracers that suggest different pasture grounds as well, and therefore the possibility of different herds in the vicinity of the cave site. In the case of cave hyeanas, the isotopic signatures of individuals from both caves are not significantly different and suggest that these predators obtained their prey from a large territory including the pasture grounds of herbivores from both caves. In addition, direct radiocarbon dating of some of the studied collagen allows to investigating possible chronological trends. This study shows how new isotopic tracers can provide invaluable information on late Quaternary large mammal palaeobiology.

  2. Two contemporaneous mitogenomes from terminal Pleistocene burials in eastern Beringia.

    Science.gov (United States)

    Tackney, Justin C; Potter, Ben A; Raff, Jennifer; Powers, Michael; Watkins, W Scott; Warner, Derek; Reuther, Joshua D; Irish, Joel D; O'Rourke, Dennis H

    2015-11-10

    Pleistocene residential sites with multiple contemporaneous human burials are extremely rare in the Americas. We report mitochondrial genomic variation in the first multiple mitochondrial genomes from a single prehistoric population: two infant burials (USR1 and USR2) from a common interment at the Upward Sun River Site in central Alaska dating to ?11,500 cal B.P. Using a targeted capture method and next-generation sequencing, we determined that the USR1 infant possessed variants that define mitochondrial lineage C1b, whereas the USR2 genome falls at the root of lineage B2, allowing us to refine younger coalescence age estimates for these two clades. C1b and B2 are rare to absent in modern populations of northern North America. Documentation of these lineages at this location in the Late Pleistocene provides evidence for the extent of mitochondrial diversity in early Beringian populations, which supports the expectations of the Beringian Standstill Model. PMID:26504230

  3. Macro fossils vegetable in Palmar formation (later pleistocene) in Entre Rios - Argentina

    International Nuclear Information System (INIS)

    This work is about the macro fossil knowledge preserved like wood fossils in the El Palmar Formation (Late Pleistocene) from a systematic - anatomical as well as paleoecological and paleoclimate point of view.The paleo Flora comes from various fossil located in the province of Entre Rios - Argentina

  4. Análisis fitolítico de la Formación Tezanos Pinto (Pleistoceno tardío- Holoceno temprano) en el sector noroeste de su área de distribución en la provincia de Entre Ríos (Argentina) / Phytolitic analysis of the Tezanos Pinto Formation (Late Pleistocene-early Holocene) in the northwestern sector of its distribution area, Provincia de Entre Ríos (Argentina)

    Scientific Electronic Library Online (English)

    Georgina, Erra; Alejandro Fabián, Zucol; Daniela Mariela, Kröhling.

    2011-12-01

    Full Text Available Los depósitos de loess son los componentes principales de las secuencias del Cuaternario Superior de la llanura pampeana (Sudamérica). La unidad loéssica generada durante el Ultimo Máximo Glacial a sotavento del Sistema Eólico Pampeano (Pampa Norte) representa un loess primario, indicando la expansi [...] ón de condiciones semiáridas al noreste de dicho sistema. La Formación Tezanos Pinto es la unidad loéssica típica del Pleistoceno tardío - Holoceno temprano de la Pampa Norte, caracterizada por su considerable continuidad espacial. En esta contribución se presentan los primeros resultados del análisis fitolítico del loess en el área noroeste de esta formación en la provincia de Entre Ríos. Las asociaciones fitolíticas analizadas presentaron una elevada homogeneidad con variaciones que permitieron su diferenciación cuantitativa a través de los perfiles analizados, mediante la presencia de fitolitos graminoides (de afinidad dantonioide, pooide-festucoide, chloridoide y panicoide), de palmeras, podostemáceas y ciperáceas. Estas variaciones posibilitaron reconocer la presencia de una estepa templada fría a templada con condiciones xéricas en los niveles basales, con episodios templados húmedos principalmente hacia las secciones medias y superiores. Abstract in english Loess deposits are the main component of the Late Quaternary sequences of Pampa plains (South America). The loess unit of the Last Glacial Maximum at the leeward side of the Pampean aeolian system represents primary loess, indicating the expansion of semiarid conditions to the NE of that system. The [...] Tezanos Pinto Formation is the typical loessic unit of the late Pleistocene-early Holocene of North Pampa, characterized by its considerable spatial continuity. The first result of the phytolith analysis of the Tezanos Pinto Formation at the northwestern area of this formation in the Entre Ríos province is presented in this contribution. The analyzed phytolith assemblages show a high homogeneity with several variations that allowed their quantitative differentiation across the sedimentary sections. The presences of grass phytoliths jointly with palm, podostemoid and ciperoid elements allowed to realize this characterization. The association of danthoniod, pooid-festucoid, chloridoid and panicoid grass phytolith types described the presence of a cold temperate to temperate steppe with xeric conditions in the basal levels, with temperate episodes with major moistureprincipally in their middle and top sections.

  5. Stratigraphy of a proposed wind farm site southeast of Block Island: Utilization of borehole samples, downhole logging, and seismic profiles

    Science.gov (United States)

    Sheldon, Dane P. H.

    Seismic stratigraphy, sedimentology, lithostratigraphy, downhole geophysical logging, mineralogy, and palynology were used to study and interpret the upper 70 meters of the inner continental shelf sediments within a proposed wind farm site located approximately two to three nautical miles to the southeast of Block Island, Rhode Island. Core samples and downhole logging collected from borings drilled for geotechnical purposes at proposed wind turbine sites along with seismic surveys in the surrounding area provide the data for this study. Cretaceous coastal plain sediments that consist of non-marine to marine sand, silt, and clay are found overlying bedrock at a contact depth beyond the sampling depth of this study. The upper Cretaceous sediments sampled in borings are correlated with the Magothy/Matawan formations described regionally from New Jersey to Nantucket. An unconformity formed through sub-aerial, fluvial, marine, and glacial erosion marks the upper strata of the Cretaceous sediments separating them from the overlying deposits. The majority of Quaternary deposits overlying the unconformity represent the advance, pulsing, and retreat of the Laurentide ice sheet that reached its southern terminus in the area of Block Island approximately 25,000 to 21,000 years before present. The sequence consists of a basal glacial till overlain by sediments deposited by meltwater environments ranging from deltaic to proglacial lakefloor. A late Pleistocene to early Holocene unconformity marks the top of the glacial sequence and was formed after glacial retreat through fluvial and subaerial erosion/deposition. Overlying the glacial sequence are sediments deposited during the late Pleistocene and Holocene consisting of interbedded gravel, sand, silt, and clay. Sampling of these sediments was limited and surficial reflectors in seismic profiles were masked due to a hard bottom return. However, two depositional periods are interpreted as representing fluvial and estuarine/marine environments respectively. One sample recovered at five meters contained shell fragments within a gray fine to coarse sand possibly representing a shallow estuarine to marine environment. A coarse near surface deposit described but not recovered in all borings may represent a transgressive unconformity and resulting lag deposit however due to lack of sampling and seismic resolution in the upper 5 meters, the nature of this deposit is merely speculation. In areas where depth to the glacial surface increased, sediments ranging from sand to fine-grained silt and clay were encountered in borings. In summary, the upper 70 meters of the inner continental shelf section within the study site consists of unconsolidated sediments spanning three major depositional periods. Sediments derived from glacial activity represent the bulk of samples collected. The glacial sequences represent various depositional environments, although most samples are interpreted to be the product of glacial meltwater deposition with distribution determined by source as well as highs and lows present in the antecedent topography. Finely laminated (varved) sediment to the south of Block Island indicates the presence of proglacial lakes in the area during the time of glacial retreat. Overlying sediments represent environments ranging from fluvial to marine.

  6. Marine 87Sr/86Sr ratios from the Jurassic to Pleistocene: Evidence from groundwaters in Israel

    International Nuclear Information System (INIS)

    Oceanic 87Sr/86Sr ratios during Jurassic to Pleistocene have been determined by analysing fresh waters from marine limestone and dolomite aquifers. The results are in good agreement with published data from well preserved fossil material. The 87Sr/86Sr ratios obtained are 0.7070 for Lower to Middle Jurassic, 0.7075 for Late Cretaceous, 0.7080 for Lower to Middle Eocene and 0.7087 for Pleistocene aquifer waters. The values of 87Sr/86Sr for the Eimer and Amend isotopic standard was 0.7082. (orig.)

  7. Plio-Pleistocene time evolution of the 100-ky cycle in marine paleoclimate records

    Science.gov (United States)

    Park, Jeffrey; Maasch, Kirk A.

    1992-01-01

    To constrain theories for the dynamical evolution of global ice mass through the late Neogene, it is important to determine whether major changes in the record were gradual or rapid. Of particular interest is the evolution of the near 100-ky ice age cycle in the middle Pleistocene. We have applied a new technique based on multiple taper spectrum analysis which allows us to model the time evolution of quasi-periodic signals. This technique uses both phase and amplitude information, and enables us to address the question of abrupt versus gradual onset of the 100-ky periodicity in the middle Pleistocene.

  8. Snapshots of the Greenland ice sheet configuration in the Pliocene to early Pleistocene

    DEFF Research Database (Denmark)

    Solgaard, Anne M.; Reeh, Niels; Japsen, Peter; Nielsen, Tove

    2011-01-01

    The geometry of the ice sheets during the Pliocene to early Pleistocene is not well constrained. Here we apply an ice-flow model in the study of the Greenland ice sheet (GIS) during three extreme intervals of this period constrained by geological observations and climate reconstructions. We study the extent of the GIS during the Mid-Pliocene Warmth (3.3-3.0 Ma), its advance across the continental shelf during the late Pliocene to early Pleistocene glaciations (3.0-2.4 Ma) as implied by offshore ...

  9. Pleistocene and Holocene Iberian flora: a complete picture and review

    Science.gov (United States)

    González Sampériz, Penélope

    2010-05-01

    A detailed analysis of the location and composition of Iberian vegetation types during the whole Pleistocene and Holocene periods shows a complex patched landscape with persistence of different types of ecosystems, even during glacial times. In addition, recent, high-resolution palaeoecological records are changing the traditional picture of post-glacial vegetation succession in the Iberian Peninsula. The main available charcoal and pollen sequences include, coniferous and deciduous forest, steppes, shrublands, savannahs and glacial refugia during the Pleistocene for Meso-thermophytes (phytodiversity reservoirs), in different proportions. This panorama suggests an environmental complexity that relates biotic responses to climate changes forced by Milankovitch cycles, suborbital forcings and by the latitudinal and physiographic particularities of the Iberian Peninsula. Thus, many factors are critical in the course of vegetational developments and strong regional differences are observed since the Early Pleistocene. Currently, the flora of Iberia is located in two biogeographical/climatic regions: the Eurosiberian and the Mediterranean. The first one includes northern and northwestern areas of the peninsula, where post-glacial responses of vegetation are very similar to Central Europe, although with some particularities due to its proximity to both the Atlantic Ocean and the Mediterranean region. The second one comprises the main territory of Iberia and shows more complex patterns and singularities, now and in the past. Steppe landscapes dominated extensive areas over all the territory during the cold spells of the Quaternary, especially during the Late Pleistocene up to the Last Glacial Maximum, but differences in composition of the dominant taxa (Compositae versus Artemisia) are observed since the Early Pleistocene, probably related to moisture regional gradients. Coastal shelves and intramountainous valleys, even in continental areas, are spots of floristic diversity and nuclei of population expansion during climatic ameliorations of the Pleistocene. The floristic composition, location and structure of glacial tree populations and communities may have been a primary control on these developments and on the origin and composition of Holocene scenarios. Refugial populations would have been a source, but not the only one, for the early Lateglacial oak expansions for example. From Middle to Late Holocene, inertial, resilient, and rapid responses of vegetation to climatic change are described, any time with regional and local differences. The role of fire, pastoralism, agriculture and other anthropogenic disturbances such as mining during the Copper, Bronze, Iberic, and Roman times must be also considered as an important factor of the current vegetation distribution. In fact, the Iberian Peninsula constitutes a territory where climatic, geological, biogeographical and historical conditions have converged to produce environmental heterogeneity, large biological diversity and ecosystem richness. A note of singularity: in comparison with other Mediterranean peninsulas, Iberia was, doubtless, particularly suitable for the survival and permanence of sclerophyllous elements of any kind (including Ibero-Maghrebian scrubs such as Maytenus, Periploca, Ziziphus,Withania, Lycium, and Calicotome), currently, during the Holocene, and even during glacial stages of the Pleistocene. However, no macro-remains of these taxa have been documented until Late Holocene chronologies, but the survival of other thermophilous species, such as Olea, reveals the existence of glacial refugia in the southernmost areas of Iberia. Over all, and dealing with plant species, the Iberian Peninsula is a land of survival.

  10. Eocene to Pleistocene lithostratigraphy, chronostratigraphy and tectono-sedimentary evolution of the Calama Basin, northern Chile Litoestratigrafía, cronoestratigrafía durante el Eoceno al Pleistoceno y evolución tectono-sedimentaria de la Cuenca de Calama, norte de Chile

    Directory of Open Access Journals (Sweden)

    Geoffrey May

    2005-01-01

    Full Text Available New 40Ar/39Ar radiometric, sedimentological and structural data from post-Paleocene sedimentary strata in the Calama Basin, northern Chile suggest that the established lithostratigraphy of the basin-fill requires revision. A new lithostratigraphic scheme for the Eocene-Pleistocene stratigraphy of the Calama Basin is proposed here. The key features of this scheme are that the existing Calama Formation is retained although the age of the formation is redefined as (?Lower Eocene to (?Lower Miocene. The El Loa Formation is elevated to group status and redefined as Lower Miocene to Upper Pliocene in age. The El Loa Group includes four newly defined formations: the Jalquinche, Opache, Lasana and Chiquinaputo formations. The existing definition of the uppermost unit within the Calama Basin, the Upper Pliocene to Pleistocene Chiu-Chiu Formation, is retained. The tectono-sedimentary evolution of the Calama Basin-fill reveals three distinct unconformity-bounded phases of sedimentation: Eocene-Oligocene, early Miocene to late mid-Miocene and late Miocene to late Pliocene. Sedimentation commenced in the Eocene with deposition of alluvial braidplain deposits (Calama Formation. This style of sedimentation occurred across northern Chile throughout the Oligocene following the Incaic Orogeny. From 22 Ma to 10 Ma ephemeral fluvial sediments were developed along the Calama Basin flanks (Lasana Formation, playa sandflat and mudflat deposits (Jalquinche Formation in the basin centre. Equivalently-aged sediments in both the Salar de Atacama and Pampa del Tamarugal basins also indicate deposition in endorheic basins. Late Miocene sedimentation occurred diachronously across the north Chilean forearc. The Pampa del Tamarugal and Calama Basin areas were linked around 6 Ma following tectonic activity. Regional palustrine carbonate sedimentation occurred in the Calama Basin centre (Opache Formation with fluvial sedimentation along the eastern basin margin (Chiquinaputo Formation. The change in depositional style is attributed to increased rainfall in drainage basins. At about 3 Ma the Calama Basin was subject to gentle folding, followed by entrenchment of the Río Loa and Río San Salvador through Miocene to Pliocene strata to reach a new base-level caused by breaching of the Coastal Cordillera by the Río Loa to reach the Pacific. Localised diatomite and evaporite (anhydrite deposition took place in depressions created by either folding of older strata or geomorphic features (Chiu-Chiu Formation. Up to 5 unconformities are present in the Calama Basin-fill and occur across either the whole of the basin or localised areas of the basin. They are not present in adjacent basins which suggests they were generated by movement on the Precordilleran/West Fissure Fault Systems. Facies analysis of the Eocene to Pleistocene succession suggests that sedimentation took place under an arid/semi-arid climate throughout this time period. Occasional fluctuations in climate suggesting increased runoff are indicated by the development of diatomites together with lacustrine and palustrine limestones. However, it is unlikely that the climate was never more humid than semi-arid. Similar facies developments in the Pampa del Tamarugal and Salar de Atacama basins during the Oligocene to Pleistocene suggest that climate changes affected the whole of the forearc and were not restricted to individual basinsLos resultados obtenidos de estudios estructurales, sedimentológicos y dataciones radiométricas de las secuencias sedimentarias post Eoceno de la Cuenca de Calama, sugieren que la litoestratigrafía establecida para su relleno sedimentario, requiere una revisión. En este trabajo, se propone un nuevo esquema litoestratigráfico pos-Paleoceno para esta cuenca. Las características claves de este esquema son que la Formación Calama se mantiene aunque su edad es considerada como Eoceno Inferior (? a Mioceno Inferior (?. La Formación El Loa es redefinida como Grupo y asignada al Mioceno Inferior-Plioceno Superior. Este Grupo incluiría la definición de

  11. Early Pleistocene sea level and millennial-scale climate fluctuations: a view from the tropical Pacific

    Science.gov (United States)

    Alix Jakob, Kim; Friedrich, Oliver; Pross, Jörg

    2015-04-01

    This project aims at deciphering the rate of sea level variability and its effect on millennial-scale climate fluctuations during the final phase of the intensification of northern hemisphere glaciation (NHG). Millennial-scale climate fluctuations appear to have changed significantly at glacial-interglacial time scales during the late Pliocene and Pleistocene. Thereby, millennial-scale climate fluctuations under a warmer climate during late Pliocene and early Pleistocene show markedly lower ampitudes compared to the fluctuations of the late Pleistocene. Numerous Pleistocene proxy records (e.g. McManus et al., 1999) suggest that this difference can be explained by an ice-volume/sea-level threshold that amplifies millennial-scale climate fluctuations and was not reached prior to the Mid-Pleistocene Transition (MPT). However, new records question the existence of this threshold (Bolton et al., 2010) and indicate that either the amplification of millennial-scale climate fluctuations before the MPT required a higher ice-volume threshold than in the late Pleistocene, that ice-volume had no significant effect on the amplitude of climate fluctuations, and/or the available sea level estimates for the early Pleistocene are inaccurate. For identifying the mechanisms underlying the dynamics of early Pleistocene ice sheets, material from the tropical Pacific Ocean (ODP Site 849) is studied over a time interval from 2.6 to 2.4 Ma (marine isotope stages 104 to 96). In summary, the main deliverables are (1) the establishment of a precise ?18O chemostratigraphy using the benthic foraminifera Cibicidoides wuellerstorfi by tuning the ?18O dataset to the LR04 benthic isotope stack (Lisiecki & Raymo, 2005), and (2) providing high-resolution (˜700 years) Mg/Ca and ?18O datasets using the benthic foraminifera Oridorsalis umbonatus and the planktonic foraminifera Globigerinoides ruber. This combined geochemical approach will be used to address the following research questions: (1) Quantification of sea level change from 2.6 to 2.4 Ma; (2) Critically assess the hypothesis of an ice-volume threshold for millennial-scale climate amplification during the early Pleistocene (and if it exists, what its value was); (3) Detailed comparison with late Pleistocene glacials; (4) Model-data comparison to assess the fidelity of model-based sea level estimates; and (5) reconstruction of sea surface temperature fluctuations of the tropical Pacific. References Bolton, C.T., Wilson, P.A., Bailey, I., Friedrich, O., Beer, C.J., Becker, J., Baranwal, S., Schiebel, R. (2010): Millennial-scale climate variability in the subpolar North Atlantic Ocean during the late Pliocene. Paleoceanography 25, doi:10.1029/2010PA001951. Lisiecki, L.E. & Raymo, M.E. (2005): A Pliocene-Pleistocene stack of 57 globally distributed benthic ?18O records. Paleoceanography 20, doi:10.1029/2004PA 001071. McManus, J., Oppo, D.W., Cullen, J.L. (1999): A 0.5-Million-Year Record of Millenial-Scale Climate Variability in the North Atlantic. Science 283, 971-975.

  12. La dieta y el hábitat del mamut y los caballos del Pleistoceno tardío de El Cedral con base en isótopos estables (?13C, ?18O) / Diet and habitat of the late Pleistocene mamut and horses from El Cedral based on stable isotopes (?13C, ?18O)

    Scientific Electronic Library Online (English)

    Víctor Adrián, Pérez-Crespo; Begoña, Sánchez-Chillón; Joaquín, Arroyo-Cabrales; María Teresa, Alberdi; Óscar J., Polaco; Antonio, Santos-Moreno; Mouloud, Benammi; Pedro, Morales-Puente; Edith, Cienfuegos-Alvarado.

    2009-08-01

    Full Text Available La dieta y el hábitat de Mammuthus columbi y de tres especies de Equus procedentes de El Cedral (San Luis Potosí, México) son inferidos a partir del análisis de isótopos estables de ?13C y ?18O en el apatito del esmalte dental. En el mamut, los valores de ?13C reflejan una dieta mixta C3/C4, mientra [...] s que los équidos tienen un intervalo que va desde individuos con una dieta mixta C3/C4 a aquéllos que sólo se alimentan de plantas C4. Las comparaciones realizadas entre los valores obtenidos de las muestras mexicanas con las publicadas para los mismos grupos de Florida, Nuevo México y Texas, señala que las preferencias alimentarias en ambos grupos eran parecidas. Asimismo, la comparación efectuada de los valores de ?13C junto con los de ?18O, para las especies de El Cedral con los valores de jabalíes, mastodontes, tapires y venados cola blanca del Pleistoceno tardío de Florida, revela que los caballos y el mamut de El Cedral habitaban en una zona abierta, como pastizales o sabanas, lo que concuerda con el estudio palinológico de la localidad. Abstract in english The diet and habitat for Mammuthus columbi and three species of Equus from El Cedral (San Luis Potosí, Mexico) were inferred from the analysis of stable isotopes, ?13C and ?18O, present in dental enamel apatite. For the mammoth, ?13C values indicate a mix C3/C4 diet, while the equids have a range of [...] values from individuals feeding only a mix C3/C4 diet to those that ate exclusively C4 plants. Comparisons between values obtained for Mexican samples with those published for the same groups from Florida, New Mexico, and Texas, point out to similar food habits in both groups. Also, comparisons of ?13C and ?18O values of the El Cedral species with those for javelinas, mastodonts, tapirs, and white-tailed deer from the Floridan late Pleistocene, showed that horses and mammoth from El Cedral lived in open spaces, with grasslands savanna, in accordance with the pollen studies for the locality.

  13. Climate variability of the tropical Andes since the late Pleistocene

    Directory of Open Access Journals (Sweden)

    A. Bräuning

    2009-10-01

    Full Text Available Available proxy records witnessing palaeoclimate of the tropical Andes are comparably scarce. Major implications of palaeoclimate development in the humid and arid parts of the Andes are briefly summarized. The long-term behaviour of ENSO has general significance for the climatic history of the Andes due to its impact on regional circulation patterns and precipitation regimes, therefore ENSO history derived from non-Andean palaeo-records is highlighted. Methodological constraints of the chronological precision and the palaeoclimatic interpretation of records derived from different natural archives, such as glacier sediments and ice cores, lake sediments and palaeo-wetlands, pollen profiles and tree rings are addressed and complementary results concerning former climatic conditions are discussed in terms of possible implications of former atmospheric circulation patterns and main climatic forcing factors. During the last years, increasing tree-ring information is getting available from the tropical Andes, providing high-resolution climate-sensitive records covering the past centuries for the study of climate variability.

  14. Assessing Holocene and late Pleistocene geomagnetic dipole field variability

    OpenAIRE

    Nilsson, Andreas

    2011-01-01

    Palaeomagnetic studies of continuous geological archives and archaeological artefacts are required to reconstruct geomagnetic field changes beyond the range of historical observations. In this thesis I assess the reliability of sedimentary palaeomagnetic data and Holocene dipole field reconstructions. New palaeomagnetic records are presented from a maar crater lake in New Zealand and a post-glacial lake in Sweden. The fidelity of the data is evaluated through comparisons with sediment paramet...

  15. Preliminary Cosmogenic Nuclide Chronology of Late Pleistocene Missoula Floods

    Science.gov (United States)

    Balbas, A.; Clark, J.; Clark, P. U.; Caffey, M. W.; Woodruff, T. E.; Baker, V. R.

    2014-12-01

    The Missoula floods had the largest known peak flood discharges of fresh water known from the geologic record. Multiple floods are believed to have originated from the failure of the Purcell trench ice lobe, which dammed glacial Lake Missoula. The flood waters traveled westward creating the Channeled Scabland region, a spectacular complex of anastomosing channels, coulees, cataracts, loess islands, rock basins, broad gravel deposits, and immense gravel bars in east-central Washington State. Several important questions about the Missoula floods and the formation of the Channeled Scabland remain, primarily due to the few geochronological constraints on their timing. Attempts to date the duration of the multiple floods have produced a wide range of ages (13-19 ka from land deposits and 13-31 ka from marine cores), but few of these directly constrain the age of the major flood landscape elements. Here we present 14 new in situ cosmogenic 10Be ages from quartz-bearing boulders deposited at four sites in eastern Washington. Wallula Gap is a narrow constriction along the Columbia River between Oregon and Washington. Hydraulic damming of floodwater at Wallula Gap created glacial Lake Lewis. Surface exposure ages on large boulders found at over 300 m elevation above the river at this site will date the largest flood events. The Wenatchee region represents the most northwestern area influenced by flooding. Dates from this area will determine when flooding occurred after the retreat of the Okanogan lobe. We sampled boulders from the lower Pangborn Bar, ice-rafted boulders north of Wenatchee, and boulders from a flood bar on the Columbia River north of Wenatchee. A boulder from the Mattawa Fan was sampled to assess the last time a megaflood came through the Sentinel Gap. Finally, in order to constrain the last debris dam failure at the southern end of the Upper Grand Coulee, we sampled flood boulders deposited on the Ephrata Fan.

  16. Rupicapra rupicapra (Mammalia) in the Late Pleistocene of Portugal

    OpenAIRE

    Cardoso, J. L.; Antunes, M. T.

    2010-01-01

    A presença do género Rupicapra é demonstrada pela primeira vez em Portugal, com base em restos, dentários e do esqueleto, provenientes do Plistocénico superior (Solutrense) da gruta das Salemas. O material fóssil pode ser atribuído a subespécie Rupicapra rupicapra pyrenaica.

  17. Ecological consequences of early Late Pleistocene megadroughts in tropical Africa

    OpenAIRE

    Andrew S. Cohen; Stone, Jeffery R.; Kristina R.M. Beuning; Park, Lisa E.; Reinthal, Peter N.; Dettman, David; Christopher A. Scholz; Thomas C. Johnson; King, John W.; Talbot, Michael R; Brown, Erik T.; Ivory, Sarah J.

    2007-01-01

    Extremely arid conditions in tropical Africa occurred in several discrete episodes between 135 and 90 ka, as demonstrated by lake core and seismic records from multiple basins [Scholz CA, Johnson TC, Cohen AS, King JW, Peck J, Overpeck JT, Talbot MR, Brown ET, Kalindekafe L, Amoako PYO, et al. (2007) Proc Natl Acad Sci USA 104:16416–16421]. This resulted in extraordinarily low lake levels, even in Africa's deepest lakes. On the basis of well dated paleoecological records from Lake Malawi, whi...

  18. Two metagenomes from late pleistocene northeast siberian permafrost.

    Science.gov (United States)

    Krivushin, Kirill; Kondrashov, Fyodor; Shmakova, Lyubov; Tutukina, Mariya; Petrovskaya, Lada; Rivkina, Elizaveta

    2015-01-01

    The present study reports metagenomic shotgun sequencing of microbial communities of two ancient permafrost horizons of the Russian Arctic. Results demonstrate a significant difference in microbial community structure of the analyzed samples in general and microorganisms of the methane cycle in particular. PMID:25555741

  19. Climate variability of the tropical Andes since the late Pleistocene

    OpenAIRE

    Bräuning, A.

    2009-01-01

    Available proxy records witnessing palaeoclimate of the tropical Andes are comparably scarce. Major implications of palaeoclimate development in the humid and arid parts of the Andes are briefly summarized. The long-term behaviour of ENSO has general significance for the climatic history of the Andes due to its impact on regional circulation patterns and precipitation regimes, therefore ENSO history derived from non-Andean palaeo-records is highlighted. Methodological constraints of the chron...

  20. Importance of active tectonics during karst formation. A Middle Eocene to Pleistocene example of the Lina Moutains (Irian Jaya, Indonesia)

    Science.gov (United States)

    Thery, J.-M.; Pubellier, M.; Thery, B.; Butterlin, J.; Blondeau, A.; Adams, C. G.

    1999-05-01

    The Lina Moutains show a typical example of karst formation associated to recent and active tectonics. The limestone samples were collected from giant potholes present beneath the heavy rainforest, during speleological expeditions to the Bird's Head of Irian-Jaya. Micropalaeontological data allow us to give a Middle Pleistocene age for the most recent karst formation. A detailed stratigraphy between the Upper Lutetian and the Middle Pleistocene was recorded, with tectonic events during the Oligocene and Pleistocene. The edge of the resurgence layer was also dated. We also conclude the probable existence of a subterraneous network downhill of the karst within the most recent levels of the Kais Limestone formation. We replace this formation within the tectonic evolution of this area between the Eocene and the Middle Pleistocene, in conjunction with the oblique convergence of the Pacific plate carrying volcanic arc fragments and the Australian margin, which resulted in folding, normal faulting associated with local extension, and wrench motion, which are settings capable of creating uplift of the carbonated platform.

  1. Stratigraphy and dissolution of the Rustler Formation

    International Nuclear Information System (INIS)

    This report describes the physical stratigraphy of the Rustler Formation, because the Waste Isolation Pilot Plant will be constructed in salt beds that underlie this formation. Described are subdivisions of the formations, the major karst features, and a proposed method for the formation of Nash Draw. 2 refs., 2 figs

  2. Dietary resource partitioning in the Late Pleistocene horses from Cedral, north-central Mexico: evidence from the study of dental wear / Partición de recursos dietéticos en los caballos del Pleistoceno Tardío de Cedral, centro-norte de México: evidencia del estudio de desgaste dental

    Scientific Electronic Library Online (English)

    Christian R., Barrón-Ortiz; Jessica M., Theodor; Joaquín, Arroyo-Cabrales.

    Full Text Available Los sedimentos del Pleistoceno Tardío (etapa glacial del Wisconsiniano tardío) del sitio arqueológico-paleontológico de Cedral, centro-norte de México, han producido abundantes restos fósiles de tres especies de équidos, los cuales han sido identificados como Equus mexicanus, E. conversidens y E. sp [...] . Estos caballos al parecer fueron simpátricos, no solamente en esta localidad, sino también en diferentes sitios de México y el suroeste de Estados Unidos, lo que plantea la posibilidad de que presentaban una partición de los recursos alimenticios disponibles para coexistir. En el presente estudio, se investigaron los hábitos alimenticios de los caballos de Cedral a través del análisis del desgaste dental. Se emplearon los métodos de mesodesgaste y microdesgaste de baja magnificación para inferir la paleodieta de cada especie de caballo. El análisis de mesodesgate muestra diferencias significativas en la forma de las cúspides de los molares entre E. mexicanus y las otras dos especies, ya que E. mexicanus presenta un mayor porcentaje de cúspides redondeadas y menores porcentajes de cúspides aguzadas y romas. Estas diferencias son consistentes con los resultados reportados en un estudio reciente de isótopos estables. Por otra parte, el análisis de microdesgaste dental indica diferencias significativas en el patrón de microdesgaste de los tres équidos. Los resultados del análisis de microdesgaste sugieren que cada especie tendía a ingerir materiales con diferentes propiedades físicas, lo cual apoya la hipótesis de que presentaban una partición de recursos alimenticios. Integrando los resultados derivados del estudio de mesodesgaste y microdesgaste con aquéllos reportados en un estudio de isótopos estables, se sugiere que E. conversidens y E. sp. presentaban una dieta predominantemente pacedora y posiblemente se alimentaban a diferentes alturas del suelo y/o en diferentes microhábitats. Equus mexicanus parece también haber incorporado en su dieta una gran proporción de pastos, pero con un hábito alimenticio más generalista que los otros dos équidos. Abstract in english The Late Pleistocene (late Wisconsinan glacial stage) deposits of the archeological-paleontological site of Cedral, north-central Mexico, have yielded abundant fossil remains of three horse species: Equus mexicanus, E. conversidens, and E. sp. These horses appear to have been sympatric, not only at [...] this locality but in different sites in Mexico and the southwestern United States, posing the possibility that they partitioned available food resources in order to coexist. In this study, we investigated the feeding ecology of the Cedral horses through the analysis of dental wear (i.e., mesowear and microwear). The extended mesowear and low magnification microwear methods were used to infer the paleodiet of each species. The analysis of mesowear reveals significant differences in cusp shape between E. mexicanus and the other two equid species, with the former showing a higher percentage of rounded cusps and lower percentages of sharp and blunt cusps. These differences are consistent with those reported in a recent study of stable isotopes. Furthermore, the analysis of dental microwear indicates significant differences between the microwear patterns of the three equids. The results of the microwear analysis suggest that each species tended to feed on different foodstuffs with varying physical properties, supporting the hypothesis of dietary resource partitioning. Integrating the results derived from the examination of mesowear and microwear, as well as those gathered from the study of stable isotopes, it is suggested that E. conversidens and E. sp. were predominantly grazers, which may have fed at different feeding heights and/or in different microhabitats. Equus mexicanus also appears to have grazed to a large extent, but possibly with a more generalist dietary behavior.

  3. Carboniferous-Permian sedimentology and stratigraphy of the Nordfjorden High and Loppa Spur, Arctic Norway

    DEFF Research Database (Denmark)

    Ahlborn, Morten

    2014-01-01

    Abstract (shortened) Facies analysis of Late Paleozoic warm-water carbonates, were conducted in order to investigate the depositional evolution, cyclicity, internal architecture and sequence stratigraphy of the upper Gipsdalen Group carbonate platform on the Nordfjorden High in central Spitsbergen. In addition a 3D seismic analysis of the offshore northeastern Loppa High was carried out to investigate a hitherto undescribed Late Paleozoic carbonate-dominated succession in the southwestern Barents Sea Shelf. The Late Paleozoic carbonates of the Gipsdalen Group have previously been studied in great detail in central Spitsbergen and offshore in the Barents Sea using well data and seismic analysis. These studies have mainly focused on the tectonic development, depositional evolution and the sedimentary facies of the Late Paleozoic succession and have greatly improved the overall perception of the evolution of the Northern Pangean margin. In this study, the emphasis has been to understand the warm-water carbonate deposition, cyclicity, sequence stratigraphy and subaerial exposure events in high resolution across a structural high, all problems not fully understood so far in the Barents Sea. This Ph.D. study increase the knowledge on these topics and furthermore contribute with the first detailed outcrop analogue of a carbonate ramp on a structural high in the area - useful for the ongoing exploration studies of the Gipsdalen Group on offshore structural highs in the Barents Sea (e.g. Loppa High and Norsel High).

  4. Thermoluminescence dating of pleistocene sediments

    International Nuclear Information System (INIS)

    After a short introduction on recent trends in quaternary geochronology, this article focuses on the thermoluminescence dating of sediments, whose principles and present limits and prospects are discussed. Results are presented for the TL behaviour of sands from various geological contexts in Brazil. They show that the coarse (approx. 100-200?m) quartz fraction of coastal and intra continental, eolian and fluvial-type deposits, might be datable by TL from the upper Holocene to at least the basis of the upper Pleistocene, with a precision of + - 10-15%. (Author)

  5. Thermoluminescence dating of pleistocene sediments

    International Nuclear Information System (INIS)

    After a short introduction on recent trends in quaternary geochronology, this article focuses on the thermoluminescence (TL) dating of sediments, whose principles, present limits and prospects are discussed. Results are presented for TL behavior of sands from various geological contexts in Brazil. They show that the coarse (approx. 100-200 ?m) quartz fraction of coastal and intracontinental, eolian and fluvial - type deposits, might be datable by TL from the upper Holocene to at least the base of the upper Pleistocene, with a precision of +- 10-15%. (Author)

  6. Eocene to Pleistocene lithostratigraphy, chronostratigraphy and tectono-sedimentary evolution of the Calama Basin, northern Chile Litoestratigrafía, cronoestratigrafía durante el Eoceno al Pleistoceno y evolución tectono-sedimentaria de la Cuenca de Calama, norte de Chile

    OpenAIRE

    Geoffrey May; Adrian J Hartley; Guillermo Chong; Fin Stuart; Peter Turner; Stephanie J Kape

    2005-01-01

    New 40Ar/39Ar radiometric, sedimentological and structural data from post-Paleocene sedimentary strata in the Calama Basin, northern Chile suggest that the established lithostratigraphy of the basin-fill requires revision. A new lithostratigraphic scheme for the Eocene-Pleistocene stratigraphy of the Calama Basin is proposed here. The key features of this scheme are that the existing Calama Formation is retained although the age of the formation is redefined as (?Lower) Eocene to (?)Lower Mio...

  7. Snapshots of the Greenland ice sheet configuration in the Pliocene to early Pleistocene

    DEFF Research Database (Denmark)

    Solgaard, Anne M.; Reeh, Niels

    2011-01-01

    The geometry of the ice sheets during the Pliocene to early Pleistocene is not well constrained. Here we apply an ice-flow model in the study of the Greenland ice sheet (GIS) during three extreme intervals of this period constrained by geological observations and climate reconstructions. We study the extent of the GIS during the Mid-Pliocene Warmth (3.3-3.0 Ma), its advance across the continental shelf during the late Pliocene to early Pleistocene glaciations (3.0-2.4 Ma) as implied by offshore geological studies, and the transition from glacial to interglacial conditions around 2.4 Ma as deduced from the deposits of the Kap Kobenhavn Formation, North Greenland. Our experiments show that no coherent ice sheet is likely to have existed in Greenland during the Mid-Pliocene Warmth and that only local ice caps may have been present in the coastal mountains of East Greenland. Our results illustrate the variability of the GIS during the Pliocene to early Pleistocene and underline the importance of including independent estimates of the GIS in studies of climate during this period. We conclude that the GIS did not exist throughout the Pliocene to early Pleistocene, and that it melted during interglacials even during the late Pliocene climate deterioration.

  8. New carbon dates link climatic change with human colonization and Pleistocene extinctions.

    Science.gov (United States)

    Guthrie, R Dale

    2006-05-11

    Drastic ecological restructuring, species redistribution and extinctions mark the Pleistocene-Holocene transition, but an insufficiency of numbers of well-dated large mammal fossils from this transition have impeded progress in understanding the various causative links. Here I add many new radiocarbon dates to those already published on late Pleistocene fossils from Alaska and the Yukon Territory (AK-YT) and show previously unrecognized patterns. Species that survived the Pleistocene, for example, bison (Bison priscus, which evolved into Bison bison), wapiti (Cervus canadensis) and, to a smaller degree, moose (Alces alces), began to increase in numbers and continued to do so before and during human colonization and before the regional extinction of horse (Equus ferus) and mammoth (Mammuthus primigenius). These patterns allow us to reject, at least in AK-YT, some hypotheses of late Pleistocene extinction: 'Blitzkrieg' version of simultaneous human overkill, 'keystone' removal, and 'palaeo-disease'. Hypotheses of a subtler human impact and/or ecological replacement or displacement are more consistent with the data. The new patterns of dates indicate a radical ecological sorting during a uniquely forage-rich transitional period, affecting all large mammals, including humans. PMID:16688174

  9. Patterns in fish radiation are compatible with Pleistocene desiccation of Lake Victoria and 14,600 year history for its cichlid species flock.

    OpenAIRE

    Seehausen, Ole

    2002-01-01

    Geophysical data are currently being interpreted as evidence for a late Pleistocene desiccation of Lake Victoria and its refilling 14,600 years ago. This implies that between 500 and 1000 endemic cichlid fish species must have evolved in 14,600 years, the fastest large-scale species radiation known. A recent review concludes that biological evidence clearly rejects the postulated Pleistocene desiccation of the lake: a 14,600 year history would imply exceptionally high speciation rates across ...

  10. The sedimentology and stratigraphy of the Early Tertiary, Cusiana field, Colombia

    International Nuclear Information System (INIS)

    The cusiana field (BP, Ecopetrol, Total and Triton is located in the llanos foothills of Eastern Colombia. There are three key reservoirs in the Cusiana field; the late Eocene to Early Oligocene Mirador Formation, the late Paleocene Barco Formation and the Santonian to Late Campanian Guadalupe Formation. The Mirador Formation contains over 50% of the original oil in place. Production for 1995 is planned at 130.000 barrels of oil per day (bopd; daily average), principally for the Mirador Formation with some production from the Guadalupe Formation. The mirador formation has therefore been the focus of a detailed reservoir description study aimed at understanding reservoir performance and putting a foundation in place for long-term reservoir management. The Mirador Formation comprises sandy (>60%), high frequency sequences dominated by the deposits of incised valleys. This paper describes the sedimentology and stratigraphy of the Mirador and the methodology chosen to construct a reservoir model fit for reservoir simulation

  11. High-latitude steppe vegetation and the mineral nutrition of Pleistocene herbivores

    Science.gov (United States)

    Davydov, S. P.; Davydova, A.; Makarevich, R.; Loranty, M. M.; Boeskorov, G.

    2014-12-01

    High-latitude steppes were widespread and zonal in the Late Pleistocene and formed a landscape basis for the Mammoth Biome. Now the patches of these steppes survived on steep slopes under southern aspects. These steppes serve as unique information sources about the Late Pleistocene "Mammoth" steppe. Numerous data obtained by palynological, carpological, and DNA analysis of plant remains from feces and stomach contents of Pleistocene herbivore mummies, as well as from buried soils and enclosing deposits show that they are similar to modern steppe plant assemblage in taxa composition. Plant's nutrient concentrations are of fundamental importance across Pleistocene grass-rich ecosystems because of their role in the support of large herbivores. The average weight of an adult mammoth skeleton (about 0.5 tons) and of a woolly rhinoceros (about 0.2 tons) clearly suggests this. Detailed studies on fossil bone remains showed mineral deficiency in large Pleistocene herbivores. A three-year study of ash and mineral contents of two types of relict steppe vegetation at the Kolyma Lowland, Arctic Siberia has been carried out. Nowadays refugia of similar vegetation are located not far (1 - 15km) from the Yedoma permafrost outcrops were abundant fossil remains are found. Dominant species of the steppe vegetation were sampled. Preliminary studies indicate that the ash-content varied 1.5-2 times in speceies of steppe herbs. The Ca, P, Mg, K element contents was higher for most steppe species than in the local herbaceous vegetation, especially in Ca and P. One of the most important elements of the mineral nutrition, the phosphorus, was always found in higher concentrations in the steppe vegetation than in plants of recently dominant landscapes of the study area. It should be noted that the mineral nutrient content of the modern steppe vegetation of Siberian Arctic is comparable to that of the recent zonal steppe of Transbaikal Region. This study supports the hypothesis that aboveground mineral concentrations of late Pleistocene grass-rich ecosystem were consistently higher than that of the recent common species of Siberian Arctic grassland. The source of mineral nutrients in the Pleistocene high-latitude steppe vegetation served as one of the reasons for the existence and survival of large herbivores in the Mammoth Biome.

  12. Parallels between playbacks and Pleistocene tar seeps suggest sociality in an extinct sabretooth cat, Smilodon

    OpenAIRE

    Carbone, Chris; Maddox, Tom; Funston, Paul J.; Michael G.L. Mills; Grether, Gregory F.; Van Valkenburgh, Blaire

    2008-01-01

    Inferences concerning the lives of extinct animals are difficult to obtain from the fossil record. Here we present a novel approach to the study of extinct carnivores, using a comparison between fossil records (n=3324) found in Late Pleistocene tar seeps at Rancho La Brea in North America and counts (n=4491) from playback experiments used to estimate carnivore abundance in Africa. Playbacks and tar seep deposits represent competitive, potentially dangerous encounters where multiple predators ...

  13. Anthropogenic Origin of Siliceous Scoria Droplets from Pleistocene and Holocene Archeaological Sites in Northern Syria

    DEFF Research Database (Denmark)

    Thy, Peter; Willcox, George; Barfod, Gry; Fueller, Dorian

    2015-01-01

    Siliceous scoria droplets, measuring from 1 to 10 mm, from one late Pleistocene and four early Holocene archaeological sites in northern Syria are compared to similar droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas global cooling event. The !ndings demonstrate that the presence of siliceous scoria droplets are independent of age and thus are not speci!c to the beginning of the Younger Dryas. Occurrences have not been reported from natural depos...

  14. Extinction implications of a chenopod browse diet for a giant Pleistocene kangaroo

    OpenAIRE

    Gavin J. Prideaux; Ayliffe, Linda K.; DeSantis, Larisa R. G.; Schubert, Blaine W.; Murray, Peter F.; Gagan, Michael K.; Cerling, Thure E.

    2009-01-01

    Kangaroos are the world's most diverse group of herbivorous marsupials. Following late-Miocene intensification of aridity and seasonality, they radiated across Australia, becoming the continent's ecological equivalents of the artiodactyl ungulates elsewhere. Their diversity peaked during the Pleistocene, but by approximately 45,000 years ago, 90% of larger kangaroos were extinct, along with a range of other giant species. Resolving whether climate change or human arrival was the principal ext...

  15. Upper Cretaceous to Pleistocene melilitic volcanic rocks of the Bohemian Massif: petrology and mineral chemistry

    Directory of Open Access Journals (Sweden)

    Skála Roman

    2015-06-01

    Full Text Available Upper Cretaceous to Pleistocene volcanic rocks of the Bohemian Massif represent the easternmost part of the Central European Volcanic Province. These alkaline volcanic series include rare melilitic rocks occurring as dykes, sills, scoria cones and flows. They occur in three volcanic periods: (i the Late Cretaceous to Paleocene period (80–59 Ma in northern Bohemia including adjacent territories of Saxony and Lusatia, (ii the Mid Eocene to Late Miocene (32.3–5.9 Ma period disseminated in the Oh?e Rift, the Cheb–Domažlice Graben, Vogtland, and Silesia and (iii the Early to Late Pleistocene period (1.0–0.26 Ma in western Bohemia. Melilitic magmas of the Eocene to Miocene and Pleistocene periods show a primitive mantle source [(143Nd/144Ndt=0.51280–0.51287; (87Sr/86Srt=0.7034–0.7038] while those of the Upper Cretaceous to Paleocene period display a broad scatter of Sr–Nd ratios. The (143Nd/144Ndt ratios (0.51272–0.51282 of the Upper Cretaceous to Paleocene rocks suggest a partly heterogeneous mantle source, and their (87Sr/86Srt ratios (0.7033–0.7049 point to an additional late- to post-magmatic hydrothermal contribution. Major rock-forming minerals include forsterite, diopside, melilite, nepheline, sodalite group minerals, phlogopite, Cr- and Ti-bearing spinels. Crystallization pressures and temperatures of clinopyroxene vary widely between ~1 to 2 GPa and between 1000 to 1200 °C, respectively. Nepheline crystallized at about 500 to 770 °C. Geochemical and isotopic similarities of these rocks occurring from the Upper Cretaceous to Pleistocene suggest that they had similar mantle sources and similar processes of magma development by partial melting of a heterogeneous carbonatized mantle source.

  16. Effects of Pleistocene environmental changes on the distribution and community structure of the mammalian fauna of Mexico

    Science.gov (United States)

    Ceballos, Gerardo; Arroyo-Cabrales, Joaquín; Ponce, Eduardo

    2010-05-01

    Biological communities in Mexico experienced profound changes in species composition and structure as a consequence of the environmental fluctuations during the Pleistocene. Based on the recent and fossil Mexican mammal checklists, we determine the distribution, composition, diversity, and community structure of late Pleistocene mammalian faunas, and analyze extinction patterns and response of individual species to environmental changes. We conclude that (1) differential extinctions occurred at family, genus, and species level, with a major impact on species heavier than 100 kg, including the extinction all proboscideans and several ruminants; (2) Pleistocene mammal communities in Mexico were more diverse than recent ones; and (3) the current assemblages of species are relatively young. Furthermore, Pleistocene relicts support the presence of biogeographic corridors; important refugia existed as well as centers of speciation in isolated regions. We identified seven corridors: eastern USA-Sierra Madre Oriental corridor, Rocky Mountains-Sierra Madre Occidental corridor, Central United States-Northern Mexico corridor, Transvolcanic Belt-Sierra Madre del Sur corridor, western USA-Baja California corridor, Tamaulipas-Central America gulf lowlands corridor, and Sonora-Central America Pacific lowlands corridor. Our study suggests that present mammalian assemblages are very different than the ones in the late Pleistocene.

  17. A Pleistocene lacustrine episode in southeastern Libya

    International Nuclear Information System (INIS)

    Results of an investigation of the Th/U dating and isotopic (stable carbon and oxygen) palaeohydrology of the fossiliferous lacustrine deposits of middle Pleistocene age found in Central Fezzan (Libya) are reported. (U.K.)

  18. Pliocene-Pleistocene coastal events and history along the western margin of Australia

    Science.gov (United States)

    Kendrick, G.W.; Wyrwoll, K.-H.; Szabo, B. J.

    1991-01-01

    Coastal deposits along the western coastal margin of Australia, a region of relative tectonic stability, record Plio-Pleistocene events and processes affecting the inner shelf and adjacent hinterland. Tectonic deformation of these deposits is more apparent in the Carnarvon Basin, and rather less so in the Perth Basin. The most complete record comes from the Perth Basin, where units of Pliocene and Pleistocene ages are well represented. In the Perth Basin, the predominantly siliciclastic Yoganup Formation, Ascot Formation and Bassendean Sand represent a complex of shoreline, inner shelf and regressive-dune facies equivalents, the deposition of which began at an undetermined stage of the Pliocene, through to the Early Pleistocene. The deposition of this sequence closed with a major regression and significant faunal extinction. Bioclastic carbonates characterize the Middle and Late Pleistocene of the Perth and Carnarvon basins. Fossil assemblages include a distinct subtropical element, unknown from the Ascot Formation and suggesting a strengthening of the Leeuwin Current. The estuarine arcoid bivalve Anadara trapezia characterizes assemblages of Oxygen Isotope Stages 5 and 7 in the Perth and Carnarvon basins, where it is now extinct. Deposits of Substage 5e (Perth Basin) also record a southerly expansion of warm-water corals and other fauna consistent with shelf temperatures warmer than present. New uranium-series ages on corals from marine sequences of the Tantabiddi Member, of the Bundera Calcarenite of the western Cape Range are consistent with the 'double peak' hypothesis for levels of Substage 5e but the evidence remains less than conclusive. Initial uranium-series dates from the Bibra and Dampier formations of Shark Bay indicate that both derive from the Late Pleistocene. These numerical ages contradict previous interpretations of relative ages obtained from field studies. The age relationship of the units requires further investigation. ?? 1991.

  19. Oxygen and carbon stable isotope studies on Globorotalia menardii from Pleistocene DSDP cores in northern Indian ocean and their paleoclimatic and paleoceanographic implications

    International Nuclear Information System (INIS)

    Stable isotope ratios of oxygen (?18O) and carbon (?13C) in tests of Globorotalia menardii from samples at 25 cm intervals of top 900 cm cores, representing different thicknesses of the Pleistocene, from DSDP(deep sea drilling project) Sites 219, 220 and 241 in the northern Indian Ocean have been measured. Isotopic ages could be assigned to the different levels of these core sections based on the correlation of ? 18O record from these sites with the SPECMAP record. Changes in sediment accumulation rates at different levels of the Pleistocene have been worked out on the basis of changes in oxygen isotopic ratio. Oscillations in ?13C stratigraphy at site 241 indicated southwest monsoon induced increase in upwelling and productivity during warmer periods. At sites 219 and 220, variations in the ?13C record were due to the mixing of bottom water. (author). 34 refs., 2 tabs., 4 figs

  20. Stratigraphy and palaeoenvironmental evolution of the mid- to upper Palaeozoic succession in Northwest Peninsular Malaysia

    Science.gov (United States)

    Amir Hassan, Meor H.; Aung, Aye-Ko; Becker, R. T.; Abdul Rahman, Noor Atirah; Ng, Tham Fatt; Ghani, Azman A.; Shuib, Mustaffa Kamal

    2014-04-01

    The stratigraphy of the Devonian to Permian succession in Northwest Peninsular Malaysia is revised. The Timah Tasoh Formation consists of black mudstone containing graptolites and tentaculitids indicating a Pragian or earliest Emsian age. The Sanai Limestone overlies the Timah Tasoh Formation at Sanai Hill B and contains conodonts indicating a Late Devonian (Frasnian to possibly early Famennian) age. In other places, Late Tournaisian chert of the Telaga Jatoh Formation overlies the Timah Tasoh Formation. The overlying Kubang Pasu Formation is predominantly composed of mudstone and sandstone, and can be divided into 3 subunits, from oldest to youngest: (1) Chepor Member; (2) Undifferentiated Kubang Pasu Formation; (3) Uppermost Kubang Pasu Formation. The ammonoid Praedaraelites tuntungensis sp. nov. is reported and described from the Chepor Member of Bukit Tuntung, Pauh. The genus indicates a Late Viséan age for part of the subunit. Dropstones and diamictites from the Chepor Member indicate a glacial marine depositional environment. The Carbo-Permian, undifferentiated Kubang Pasu Formation consists of similar interbedded mudstone and sandstone. The uppermost Kubang Pasu Formation of Kungurian age consists of coarsening upward cycles of clastics, representing a shallow marine, wave- and storm-influenced shoreline. The Permian Chuping Limestone also represents shallow marine, wave- and storm-influenced deposits. A Mid-Palaeozoic Unconformity separating Early-Late Devonian rocks from overlying Late Devonian-Carboniferous deposits probably marks initiation of rifting on Sibumasu, which eventually led to the separation of Sibumasu from Australian Gondwana during the late Sakmarian (Early Permian).

  1. Seismic stratigraphy of western Colombian basin, Caribbean Sea

    Energy Technology Data Exchange (ETDEWEB)

    Bowland, C.

    1984-04-01

    Multichannel seismic reflection profiles disclose the regional stratigraphy of the western Colombian basin. The basement complex is the seismic unit below the deepest, continuous reflection horizon that can be traced throughout the basin. The basement complex reflection signature on the flanks of the Mono Rise and adjacent areas is smooth, continuous, and characterized by local occurrences of internal reflectors, and is equivalent to the Late Cretaceous Horizon B in the Venezuelan basin. In the central basin, the reflection signature is rough with abundant diffractions typical of normal oceanic crust. The sediment overlying the basement complex is subdivided into five mapping units. Unit CB5, which directly overlies the basement complex, is thickest on the Mono Rise and thins down the flanks of the rise. This unit is equivalent to the Upper Cretaceous to the Middle Eocene pelagic unit bounded by seismic horizons A'' and B'' in the Venezuelan basin. Unit CB4, characterized by pervasive, small offset faulting, is restricted to the crest of the Mono Rise. Units CB3 and CB2 contain subparallel, variable amplitude, continuous reflectors that fill the regional basement complex relief. They are Middle Tertiary terrigenous distal turbidites and hemipelagic deposits. Unit CB1 thickens toward southern Central America and shows complicated reflection patterns typical of a deep-sea fan complex. A jump correlation to Deep Sea Drilling Project Site 154 is used to assign a Late Miocene to Quaternary age to unit CB1. Development of unit CB1 was concurrent with the uplift of and magmatic activity in southern Central America.

  2. Pliocene-Pleistocene Surface and Intermediate Water Hydrography of the South Pacific Ocean

    Science.gov (United States)

    Elmore, A.; McClymont, E.; Elderfield, H.; Kender, S.

    2014-12-01

    The reconstruction of past sea surface (SST) and intermediate water temperatures (IWT) is critical for understanding feedbacks within the ocean-climate system. Pliocene Southern Ocean dynamics are largely ambiguous, especially at intermediate water depths. However, the intermediate water reconstructions are particularly important since intermediate waters, including Antarctic Intermediate Water (AAIW), may be an important driver in high-low latitude teleconnections. Herein, we present the first Pliocene SST and IWT records from a sediment core in the Southwest Pacific (DSDP 593; 1068m water depth), in the core of modern AAIW. Benthic paleotemperature proxies have caveats, including the 'Carbonate Ion Effect' on the magnesium to calcium ratio (Mg/Ca) of benthic foraminifera. However, recent studies demonstrated that the infaunal species, Uvigerina peregrina, is carbonate ion independent, affording the use of Mg/CaU.peregrina as a paleotemperature proxy (Elderfield et al., 2010). Our results suggest that Southern Ocean IWT was warmer during the Pliocene than during the Mid- to Late-Pleistocene. The range of IWT values during the Pliocene is nearly as large as the glacial-interglacial-scale IWT changes during the Pleistocene, despite smaller ice volume oscillations suggested by benthic ?18O time series (Lisiecki & Raymo, 2005). Alkenone-derived UK37' data show Pliocene SSTs are also, on average, warmer than those estimated for the Mid- to Late-Pleistocene. Orbital-scale SST changes are evident through the Pliocene, although the range is smaller than during the late Pleistocene. Our data are consistent with modeled SST and IWT reconstructions by Dowsett et al. (2009), but raise questions about the stability or dynamism of Pliocene climate relative to the modern. References:Dowsett et al. (2009) www.clim-past.net/5/769/2009. Elderfield et al. (2010) doi:10.1594/PANGAEA.817473. Lisiecki & Raymo (2005) doi:10.1029/2004PA001071.

  3. Changing depositional environments during the Late Quatrnary along the western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Thamban, M.

    variations on a shallow core off Cochin, suggests that the average sedimentation rates were very high (~6 13.2 cm/kyr) and varied widely during the Holocene and the late Pleistocene. Grain size measurements reveal that the clay content varied with the Late...

  4. Understanding Late Quaternary change at the land-ocean interface: a synthesis of the evolution of the Wilderness coastline, South Africa

    Science.gov (United States)

    Cawthra, Hayley C.; Bateman, Mark D.; Carr, Andrew S.; Compton, John S.; Holmes, Peter J.

    2014-09-01

    Coastal barrier systems have been widely used to understand the responses of coastal margins to fluctuating Pleistocene sea levels. What has become apparent, particularly with the development of robust chronological frameworks, is that gaps in terrestrial barrier sedimentary records are not uncommon and that they most likely reflect phases of barrier construction on the now submerged continental shelf. Thus, understanding the land-ocean interface through time is critical to fully appreciate the Quaternary archives contained within the barriers and their associated back-barrier deposits. This study uses offshore and lakefloor (back-barrier) seismic profiling from the South African south coast at Wilderness to link the sub-aerially exposed barrier stratigraphy to the currently submerged geological and sedimentological record. A total of eight separate submerged aeolian units are identified at water depths of up to 130 m below mean sea level. Their approximate ages are constrained with reference to the eustatic sea-level record and the deepest units are consistent with the estimated magnitude of sea-level lowering during the Last Glacial Maximum (LGM) on the South African coastline. As previously assumed, aeolian sedimentation tracked the shoreline onto the continental shelf during the Late Pleistocene. During sea-level regressions, both the incision of fluvial channels and the deposition of back-barrier systems occurred across the continental shelf. During late low stand/early transgression periods, landward shoreface migration occurred, pre-existing channel incisions were infilled and pre-existing barriers were truncated. Rapid transgression, however, allowed the preservation of some back-barrier deposits, possibly aided by protection from antecedent topography. As sea level neared the present-day elevation, erosion of the mid-shelf sediments resulted in the development of a Holocene sediment wedge, which was augmented by Holocene fluvial sediment supply. The Holocene sand wedge is preserved in the back-barrier lakes and was deposited during the Holocene highstand inundation. Overlying middle to late Holocene terrestrial muds reflect the deposition of river-borne mud onto the shelf. These results clearly demonstrate that within transgressive-regressive sea-level cycles, accommodation space for barriers is controlled by antecedent drainage systems and gradients on the adjacent inner continental shelf.

  5. Gulf coastal plain evolution in West Louisiana: Heavy mineral provenance and Pleistocene alluvial chronology

    Science.gov (United States)

    Mange, Maria A.; Otvos, Ervin G.

    2005-12-01

    High Resolution Heavy Mineral Analysis (HRHMA) of late Pleistocene terrace samples, their Tertiary source rocks, and modern river sediments provided an effective tool for reconstructing sediment provenance and mapping heavy mineral provinces in southwest Louisiana. Each province, linked to a discrete source region, represents Pleistocene fluvial channel belts within which depositional activity was controlled by periods of climate, sediment supply, and sea level changes. Four coastal heavy mineral provinces have been identified. The Northern Province (NP), drained by the lower reaches of the Sabine and Calcasieu Rivers underlies level mid- and late Pleistocene coastal terrace surfaces and is distinguished by high-grade metamorphic assemblages (kyanite, staurolite, sillimanite) and abundant zircon, probably of Ouachita Mts. derivation. Transporting eroded Cretaceous, Tertiary, and Pleistocene coastal plain deposits, the modern Calcasieu and Sabine River sands in west-central and southwest Louisiana and east Texas, display identical heavy mineral composition to that of the NP. Level Late Pleistocene coastal terrace areas in the east represent the Red River Province (RRP) with dominant epidote, tourmaline, garnet, and zircon. Its mineralogy is influenced significantly by Paleozoic-Mesozoic sedimentary units that frame the drainage basin upstream. Modern Red River sands differ in their spectra both from Red River Pleistocene coastal terrace and valley terrace deposits, interpreted by temporal fluctuations in sediment supply initiating a variable contribution of detritus from different sources. Tributaries that drain formations with high concentrations of high-grade metamorphic minerals also affected Red River valley Pleistocene terrace deposits in west-central Louisiana, enriching them in kyanite and staurolite. The Mississippi Province (MP) occupies the eastern-southeastern area of the low, flat, gently seaward-sloping Prairie coastal terrace. Whereas modern Mississippi alluvium is dominated by hornblende, pyroxenes, and epidote, as the result of post-depositional dissolution, pyroxenes are rare in the MP. The Mixed Suite Province (MSP) reflects MP, RRP, and to a lesser degree, NP signatures and forms the Prairie fluvial coastal plain surface closer to the Texas state line. Raw data of the principal heavy minerals were used for statistical analysis. Statistical parameters proved consistent with mineralogy-derived reconstruction of sediment provenance and provinciality of heavy mineral suites, thus providing an independent and objective support to data interpretation. Optical and thermal luminescence dating at other Gulf locations [Otvos, E.G. (2005). Numerical chronology of Pleistocene coastal plain and valley development; extensive aggradation during glacial low sea levels. Quaternary Internat., 135 91-113.] supports the pre-Sangamon ages of the Intermediate Pleistocene terraces in the NP area. Sangamon (135-116 ka), Eowisconsin (114-76 ka), and Wisconsin (74-36 ka) dates characterize the four provinces in the low, level northern Gulf Prairie coastal plain. Refuting earlier assumptions that coastal plain aggradation occurred only during marine highstand phases, thermal and optical luminescence dates indicated that, despite the low Eowisconsin and Wisconsin eustatic sea levels of several preglacial and glacial stages and substages, coastal plain alluviation, paradoxically, recurred between 106 and 35 ka BP. An interesting outcome of our heavy mineral study is the recognition and dating of a previously undocumented, rare ash-fall event that originated in Caribbean andesitic volcanoes. It was identified by the presence of a volcanogenic heavy mineral suite, composed of pristine euhedral clinopyroxene, sphene, zircon, apatite, and hexagonal biotite. Unaffected by fluvial reworking, this suite was recovered from a MP sample, dated ca. 86 ka BP.

  6. Orbital forcing of continental climate during the Pleistocene: a complete astronomically tuned climatic record from Lake Baikal, SE Siberia

    Science.gov (United States)

    Prokopenko, Alexander A.; Hinnov, Linda A.; Williams, Douglas F.; Kuzmin, Mikhail I.

    2006-12-01

    A new composite BDP-96 biogenic silica record over the entire Pleistocene was generated by splicing BDP-96-1 and BDP-96-2 drill cores from Lake Baikal, crosschecked against a similar record from a nearby BDP-98 drill core. A new astronomically tuned age model is proposed based on correlating peak biogenic silica responses with the timing of September perihelia. This target is derived from analysis of regional climate proxy responses during the Holocene, the last interglacial and around paleomagnetic reversals. By resolving virtually every precessional cycle during the Pleistocene, the new age model represents a major improvement compared with previously reported Lake Baikal timescales. The astronomically tuned ages of the Pleistocene paleomagnetic reversals are consistent with published dates. The minimal tuning approach we used (precession only) has also aligned high signal power in a narrow obliquity band, confirming the strong presence of orbital forcing. There are also strong ca 100-ka scale cycles, but these are not aligned with the orbital eccentricity. Despite the location of Lake Baikal in a continental interior that is highly sensitive to insolation forcing, the tuned biogenic silica record reveals a consistent phase difference of -32° (ca 4 ka) relative to insolation in the obliquity band. An inherent lag embedded in a continental proxy record, not driven by global ice volume, is an intriguing finding. Another new observation is that long-term changes in sedimentation rates in Lake Baikal appear to be related to the amplitude of orbital forcing; both amplitudes and sedimentation rates undergo significant changes during MIS 24-MIS 19 interval corresponding to the Middle Pleistocene Transition. With potential for linking continental and marine climato-stratigraphies, the new Baikal record serves a new benchmark correlation target in continental Eurasia, as an alternative to June 65°N insolation and ODP-correlated timescales.

  7. Changes of 2H and 18O enrichment of meteoric water and Pleistocene glaciation

    International Nuclear Information System (INIS)

    Isotopic data on fluid inclusions and host speleothems are presented which support the hypothesis that the deltaD-delta18O relationship for modern meteoric waters may have changed during the Pleistocene glacial periods in response to increased ocean surface air humidity. Palaeotemperatures for five areas of east-central North America and Bermuda, calculated assuming the present deltaDdelta18O meteoric water relationship for fluid inclusion waters, are observed to be too low during late Pleistocene glacial periods (in some instances falling below O0C) while interglacial palaeotemperatures are largely equivalent to those in the areas at present. As speleothem deposition cannot occur at subzero temperatures, a possible solution to this dilemma is a shift in the intercept of the meteoric water relationship. (U.K.)

  8. Plio-Pleistocene time evolution of the 100-kyr cycle in marine paleoclimate records

    Science.gov (United States)

    Park, Jeffrey; Maasch, Kirk A.

    1993-01-01

    A new time-series analysis technique (called envelope inversion), which is based on multiple taper spectral analysis, is used to