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

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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.

Miidel, Avo

2007-03-01

2

Late Pleistocene-Holocene seismic stratigraphy of the Southeast Vietnam Shelf  

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The Late Pleistocene-Holocene sedimentary architecture of the Southeast (SE) Vietnam Shelf was investigated using high-resolution seismic profiles and core samples. Three systems tracts and a prominent seismic reflection surface at the base of the sequence were revealed. This surface (SB1) is interpreted as a sequence boundary formed by subaerial processes during the Late Pleistocene sea-level fall and subsequent marine reworking during transgression. A surface map of the lowstand surface, compiled from seismic profiles and sediment cores, revealed the W-E to N-S oriented incised-valley system of the paleo-Mekong River. The incised valleys show a clear change in morphology from the north to the south in the study area. The northern incised-valley system off Vung Tau appears as a narrow and deep V-shape in cross-section (Vietnam Shelf is a variation on the theoretical model of Vail (1987). The thick highstand wedge on the SE Vietnam Shelf is confined to the inner shelf due to the broad and low-gradient shelf morphology and the strong local hydrodynamic conditions driven by the monsoon system. Except for the one deposited within the incised-valley system, the TST deposits on the SE Vietnam Shelf tend to disperse over the shelf instead of forming a thick backstepping unit. The accommodation space was probably created faster than the sediment supply during the rapid transgression.

Dung, Bui Viet; Stattegger, Karl; Unverricht, Daniel; Phach, Phung Van; Thanh, Nguyen Trung

2013-11-01

3

Late Pleistocene sea-level history  

International Nuclear Information System (INIS)

The development of the U-series techniques for dating fossil corals is traced and case studies where dating and stratigraphy have provided a consistent picture of a region are presented. Finally a global curve of eustatic sea-level will be developed for the late Pleistocene and the implications of this curve for current theories of glaciations will be discussed. (author)

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Late Pleistocene stratigraphy of IODP Site U1396 and compiled chronology offshore of south and south west Montserrat, Lesser Antilles  

Science.gov (United States)

sediments around volcanic islands contain an archive of volcaniclastic deposits, which can be used to reconstruct the volcanic history of an area. Such records hold many advantages over often incomplete terrestrial data sets. This includes the potential for precise and continuous dating of intervening sediment packages, which allow a correlatable and temporally constrained stratigraphic framework to be constructed across multiple marine sediment cores. Here we discuss a marine record of eruptive and mass-wasting events spanning ˜250 ka offshore of Montserrat, using new data from IODP Expedition 340, as well as previously collected cores. By using a combination of high-resolution oxygen isotope stratigraphy, AMS radiocarbon dating, biostratigraphy of foraminifera and calcareous nannofossils, and clast componentry, we identify five major events at Soufriere Hills volcano since 250 ka. Lateral correlations of these events across sediment cores collected offshore of the south and south west of Montserrat have improved our understanding of the timing, extent and associations between events in this area. Correlations reveal that powerful and potentially erosive density-currents traveled at least 33 km offshore and demonstrate that marine deposits, produced by eruption-fed and mass-wasting events on volcanic islands, are heterogeneous in their spatial distribution. Thus, multiple drilling/coring sites are needed to reconstruct the full chronostratigraphy of volcanic islands. This multidisciplinary study will be vital to interpreting the chaotic records of submarine landslides at other sites drilled during Expedition 340 and provides a framework that can be applied to the stratigraphic analysis of sediments surrounding other volcanic islands.

Wall-Palmer, Deborah; Coussens, Maya; Talling, Peter J.; Jutzeler, Martin; Cassidy, Michael; Marchant, Isabelle; Palmer, Martin R.; Watt, Sebastian F. L.; Smart, Christopher W.; Fisher, Jodie K.; Hart, Malcolm B.; Fraass, Andrew; Trofimovs, Jessica; Le Friant, Anne; Ishizuka, Osamu; Adachi, Tatsuya; Aljahdali, Mohammed; Boudon, Georges; Breitkreuz, Christoph; Endo, Daisuke; Fujinawa, Akihiko; Hatfield, Robert; Hornbach, Matthew J.; Kataoka, Kyoko; Lafuerza, Sara; Maeno, Fukashi; Manga, Michael; Martinez-Colon, Michael; McCanta, Molly; Morgan, Sally; Saito, Takeshi; Slagle, Angela L.; Stinton, Adam J.; Subramanyam, K. S. V.; Tamura, Yoshihiko; Villemant, Benoit; Wang, Fei

2014-07-01

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Late Pleistocene human remains from Wezmeh Cave, western Iran.  

Science.gov (United States)

Paleontological analysis of remains from Wezmeh Cave in western Iran have yielded a Holocene Chalcolithic archeological assemblage, a rich Late Pleistocene carnivore faunal assemblage, and an isolated unerupted human maxillary premolar (P(3) or possibly P(4)). Species representation and U-series dating of faunal teeth place the carnivore assemblage during oxygen isotope stages (OIS) 3 and 2, and noninvasive gamma spectrometry dating of the human premolar places it at least as old as early OIS 2. The human premolar crown morphology is not diagnostic of late archaic versus early modern human affinities, but its buccolingual diameter places it at the upper limits of Late Pleistocene human P(3) and P(4) dimensions and separate from a terminal Pleistocene regional sample. Wezmeh Cave therefore provides additional Paleolithic human remains from the Zagros Mountains and further documents Late Pleistocene human association with otherwise carnivore-dominated cave assemblages. PMID:18000894

Trinkaus, Erik; Biglari, Fereidoun; Mashkour, Marjan; Monchot, Hervé; Reyss, Jean-Louis; Rougier, Hélène; Heydari, Saman; Abdi, Kamyar

2008-04-01

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Late Cenzoic stratigraphy of the central Scotian Slope, eastern Canada  

Energy Technology Data Exchange (ETDEWEB)

High-resolution multichannel seismic profiles have been used to define the Quaternary seismic stratigraphy for the Scotian Slope in the area of the Acadia K-62 and Shubenacadie H-100 wells southwest of Sable Island Bank. Seven key reflectors are identified and correlated through much of the study area. The wells provide biostratigraphic control for this seismic stratigraphy. During the Neogene, sediments accumulated slowly and uniformly on the slope; these now give continuous, parallel acoustic reflectors. A broad, shallow, ancestral valley on the site of the present Verrill and Dawson canyons was cut during the earliest part of the Late Pliocene, reflecting a low stand of sea level. The valley was then filled by fine grained sediment. Subsequently, in the Late Pliocene, a further lowering of the sea level resulted in gully and canyon cutting and an increase in sedimentation rates of about 0.2 m/ka. In the Quaternary, continued canyon cutting led to much sediment bypassing of the continental slope and lower sedimentation rates (0.1 m/ka). High rates of sedimentation (0.4 m/ka) are found only in some intercanyon areas on levee-like accumulations and close to ice margin tills deposited on the upper slope. Implications of these findings for hydrocarbon development are briefly discussed. 25 refs., 8 figs., 1 tab.

Piper, D.J.W.; Normark, W.R.; Sparkes, R.

1987-03-01

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BISON ANTIQUUS OCCURRENCE AND PLEISTOCENE-HOLOCENE STRATIGRAPHY, CANADA DEL BUEY, PAJARITO PLATEAU, NEW MEXICO  

Energy Technology Data Exchange (ETDEWEB)

A Bison. (probable Bison antiguus) distal humerus fragment was found within a Pleistocene colluvial deposit on a hillslope above Canada del Buey near White Rock, New Mexico. The Bison fossil is preserved within a buried soil with an inferred age of ca. 50-100 ka, based on soil properties and on stratigraphic position below a deposit of ca. 50-60 ka EI Cajete pumice. This represents the second oldest dated Bison in New Mexico, and one of the few occurrences of this genus in the northern mountains of the state. It is also only the second record of a Pleistocene vertebrate from Los Alamos County, and is a rare occurrence of a pre-25 ka Bison fossil in good stratigraphic context. Hillslopes in the study area are underlain by a sequence of truncated Pleistocene and Holocene soils that are inferred to represent colluvial deposition and soil formation followed by erosion in the mid Pleistocene (buried soil 'b3'), the late Pleistocene (buried soil 'b2'), and the mid-to-late Holocene (buried soil 'b1'). The surface soil is developed in depOSits that overlie 600-800 year-old Ancestral Puebloan sites. Colluvium is dominated by relatively fine-grained (fine to very fine sand) slopewash colluvium deposited by overland flow, but also includes rocky colluvium on hillslopes below mesas. The fine-grained colluvium is likely derived mainly from reworking of eolian deposits. Episodic colluvial deposition appears to, at least in part, accompany and follow episodic eolian events, with intervening periods dominated by erosion and the development of truncated soils.

RENEAU, STEVEN L. [Los Alamos National Laboratory; DRAKOS, PAUL G. [Los Alamos National Laboratory; MORGAN, GARY S. [Los Alamos National Laboratory

2007-02-12

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Stratigraphy, sedimentology, paleontology, and paleomagnetism of Pliocene-early Pleistocene lacustrine deposits in two cores from western Utah  

Science.gov (United States)

The paleoclimatic history of western Utah is being investigated as part of the USGS Global Change and Climate History Program studies of long-term climatic changes in the western United States. The initial objective of the study is to document the environmental conditions during the mid-Pliocene period of warmer-than-modern global climates (the focus of the USGS Pliocene Research, Interpretation, and Synoptic Mapping [PRISM] project). The investigation also seeks to determine how and when these conditions gave way to the late Quaternary pattern of climatic variations (in which short periods of very moist climates have been separated by long periods of arid conditions). This is a collaborative project involving specialists from the USGS, Kansas State University, and the University of California-Davis in paleontology (Thompson, Buchner, Forester, Bradbury), stratigraphy and sedimentology (Oviatt, Kelsey, Bracht), and paleomagnetism and environmental magnetism (Roberts). The data presented herein represent preliminary findings of the analyses of two cores of Pliocene and early Pleistocene sediments from the eastern Great Basin.

Thompson, R. S.; Oviatt, C. G.; Roberts, A. P.; Buchner, J.; Kelsey, R.; Bracht, C. J.; Forester, R. M.; Bradbury, J. P.

1995-01-01

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

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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.

Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

2014-05-01

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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

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Constraining Late Pleistocene Pluvial Lake Chronologies in Northeastern Nevada  

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The presence of lakes in closed basins of the northern Great Basin during pluvial episodes of the Pleistocene has been recognized for over a century. Some of these lakes, such as Bonneville in western Utah and Lahontan in western Nevada, were large, and their histories are well constrained by field mapping, stratigraphic investigations, and geochronology. Dozens of other lakes with smaller dimensions are known to have existed, however with few exceptions their histories are virtually unknown. This situation is unfortunate because smaller, hydrologically closed lakes should be particularly sensitive to climatic changes that shifted the balance of precipitation and evaporation. Records of their fluctuations, therefore, could provide important information about atmospheric reorganization during the last glacial-interglacial transition. Ongoing work in northeastern Nevada is aimed at developing these records through detailed mapping, investigation of natural exposures and artificial excavations, and radiocarbon dating. Gastropod shells recovered from two sites along a beach ridge in the northeast Independence Valley indicate that Lake Clover reached its late Pleistocene highstand between 14,400 and 14,200 14C years BP (~17.5 cal. ka BP). Similarly, radiocarbon dating of gastropod shells from a beach ridge in the Ruby Valley indicates that Lake Franklin was near its late Pleistocene highstand at 13,400 14C years BP (~16.4 cal. ka BP). These ages are essentially synchronous with the highstands of Lakes Newark and Jakes ~150 km to the south, overlap with the hydrologic maximum of Lake Bonneville, and appear to predate the highstand of Lake Lahontan. Additional radiocarbon dating will refine these age relationships and attempt to constrain the timing of stillstands during the overall regression of these lakes in the latest Pleistocene.

Munroe, J. S.; Laabs, B. J.

2011-12-01

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Late Pleistocene and Holocene hydrological change in central Indonesia from Lake Towuti, Sulawesi  

Science.gov (United States)

The tropical Pacific plays a fundamentally important role in global climate change due to the interaction between the El Niño Southern Oscillation (ENSO), the Intertropical Convergence Zone (ITCZ), and the Asian monsoons. Indonesia sits at the heart of the tropical western Pacific, yet we have very few terrestrial paleoclimate records from Indonesia to evaluate hydrological changes in the tropical western Pacific during the last 21,000 years. Here we present new sediment piston core and seismic reflection data from Lake Towuti, a large tectonic lake in central Sulawesi, that document the region’s late Pleistocene to Holocene climate evolution. Lithologic and magnetic susceptibility variations in ten piston cores from the lake can be clearly correlated to acoustic reflectors in our seismic stratigraphy and document substantial, basin-wide variations in precipitation and surface runoff through time. Our provisional age model suggests wetter conditions than present in central Indonesia during the latest Pleistocene and early to mid-Holocene. This behavior is generally in phase with the northern hemisphere tropics, despite the near-equatorial (2.7 degrees South) location of our site, suggesting that early Holocene intensification of the Asian monsoon and northward migration of the tropical rain belt did not result in drier conditions at the equator. Multiproxy analyses of our new cores, including compound-specific stable isotope data, will further elucidate centennial- to millennial-scale climate variations in the region.

Russell, J. M.; Bijaksana, S.; Wattrus, N. J.; Noren, A. J.; Konecky, B.; Wicaksono, S. A.

2010-12-01

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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)

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Paleohydrology of late pleistocene superflooding, altay mountains, siberia.  

Science.gov (United States)

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 x 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. PMID:17832349

Baker, V R; Benito, G; Rudoy, A N

1993-01-15

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Pleistocene calcretes from eastern Tunisia: The stratigraphy, the microstructure and the environmental significance  

Science.gov (United States)

This paper is meant to study the stratigraphy, the mineralogy, the microstructure and the geochemistry of Pleistocene calcretes from eastern Tunisia in order to infer the environmental factors intervening in their formation. Samples of eight profiles of Pleistocene calcretes from eastern Tunisia were examined on the basis of a variety of techniques including Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), chemical analysis and Atomic Absorption Spectrophotometer (AAS) techniques. Then, the obtained data underwent a statistical analysis on the basis of Factor Analysis (FA) and Principal Component Analysis (PCA). On the basis of field missions, five different horizons have been differentiated from bottom to top of all profiles: nodular, powdery, massive Brecciated and laminar horizon. The mineralogical study shows two minerals categories inversely proportional: calcite and (quartz and the clay). It shows also shows that Palygorskite is the dominant clay mineral. The escarpment edge is capped by a limestone containing fibrous palygorskite. Finally, superficial calcrete are described: a brecciated horizon which occurs in pockets on the plateau surface. This study about eastern Tunisia revealed the occurrence of successive cycles of calcretisation. Pedogenesis, water table oscillation, sedimentogenesis and stromatogenesis are the intervening factors in the calcretisation process. During the Pleistocene, they interfered with each other according to the climatic pulsations. From the studied case, it may be noticed that the formation of each calcrete horizon is the result of a dominating process that takes place during a distinguishable stage. In the first stage, the pedogenic process is developed by palygorskite formation including authigenic replacement or formation from a precursor mineral, neoformation from the breakdown products of such minerals or neoformation from suitable solutions. In the second stage, the powdery horizon is formed in the slope of the distal zone which presents a drained environment. In the third stage, several diagenetic processes (cementing, compaction, dissolution...) contribute to the formation of the laminar and massive horizon. Since it is exposed to dryness for a long period, the massive horizon is harder and more compact. In the fourth stage, the banding of light-dark in the laminar horizons reflects a dry-wet season alternation seasons. Dark beds are formed by the stromatolitic cover were developed during the wet season, whereas light beds were developed in an extremely arid climate argued by the presence of the detrital grains. In the fifth stage, the brecciated horizon, which occupies the channels, is formed by well rolled concretions, which present a dismantling material of Early and Middle Pleistocene calcretes after the Post-Villafranchian compressive phase. Thus, calcretisation seems to have been controlled by periods of uplift and stability of the slope, given that calcrete formation might be inhibited by the activation of the sedimentation of colluvial materials as a consequence of the tectonic activity. We also suggest that groundwater and biological activity may play a significant role in the development of pedogenic, sedimentological and polygenetic calcrete cycles within the same sedimentary basin. The alternation of dry and wet climatic periods may be responsible for the calcrete genesis.

Gallala, Wissem; Gaied, Mohamed Essghaïer; Essefi, Elhoucine; Montacer, Mabrouk

2010-10-01

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Late Pleistocene and Holocene mammal extinctions on continental Africa  

Science.gov (United States)

Understanding the cause of late Quaternary mammal extinctions is the subject of intense debate spanning the fields of archeology and paleontology. In the global context, the losses on continental Africa have received little attention and are poorly understood. This study aims to inspire new discussion of African extinctions through a review of the extinct species and the chronology and possible causes of those extinctions. There are at least 24 large mammal (> 5 kg) species known to have disappeared from continental Africa during the late Pleistocene or Holocene, indicating a much greater taxonomic breadth than previously recognized. Among the better sampled taxa, these losses are restricted to the terminal Pleistocene and early Holocene, between 13,000 and 6000 yrs ago. The African extinctions preferentially affected species that are grazers or prefer grasslands. Where good terrestrial paleoenvironmental records are present, extinctions are associated with changes in the availability, productivity, or structure of grassland habitats, suggesting that environmental changes played a decisive role in the losses. In the broader evolutionary context, these extinctions represent recent examples of selective taxonomic winnowing characterized by the loss of grassland specialists and the establishment of large mammal communities composed of more ecologically flexible taxa over the last million years. There is little reason to believe that humans played an important role in African extinctions.

Faith, J. Tyler

2014-01-01

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Late Pleistocene-Holocene cataclysmic eruptions at Nevado de Toluca and Jocotitlan volcanoes, central Mexico  

Science.gov (United States)

This field guide describes a five day trip to examine deposits of Late Pleistocene-Holocene cataclysmic eruptions at Nevado de Toluca and Jocotitlan volcanoes in central Mexico. We will discuss the stratigraphy, petrology, and sedimentological characteristics of these deposits which provide insights into the eruptive history, type of volcanic activity, and transport and emplacement mechanisms of pyroclastic materials. These parameters will allow us to discuss the kinds of hazards and the risk that they pose to populations around these volcanoes. The area to be visited is tectonically complex thus we will also discuss the location of the volcanoes with respect to the tectonic environment. The first four days of the field trip will be dedicated to Nevado de Toluca Volcano (19 degrees 09'N; 99 degrees 45'W) located at 23 km. southwest of the City of Toluca, and is the fourth highest peak in the country, reaching an elevation of 4,680 meters above sea level (m.a.s.l.). Nevado de Toluca is an andesitic-dacitic stratovolcano, composed of a central vent excavated upon the remains of older craters destroyed by former events. Bloomfield and Valastro, (1974, 1977) concluded that the last cycle of activity occurred nearly equal 11,600 yr. ago. For this reason Nevado de Toluca has been considered an extinct volcano. Our studies, however, indicate that Nevado de Toluca has had at least two episodes of cone destruction by sector collapse as well as several explosive episodes including plinian eruptions and dome-destruction events. These eruptions occurred during the Pleistocene but a very young eruption characterized by surge and ash flows occurred ca. 3,300 yr. BP. This new knowledge of the volcano's eruptive history makes the evaluation of its present state of activity and the geological hazards necessary. This is important because the area is densely populated and large cities such as Toluca and Mexico are located in its proximity.

Macias, J.L.; Garcia, P.A.; Arce, J.L.; Siebe, C.; Espindola, J.M.; Komorowski, J.C.; Scott, K.

1997-01-01

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A formal mammalian biostratigraphy for the Late Pleistocene of Britain  

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A series of distinctive mammalian assemblages spanning much of the British Late Pleistocene is defined on the basis of type localities and a formal biozonation proposed. The Joint Mitnor Cave mammal assemblage-zone includes the famous "Hippopotamus fauna" of the early part of the Last Interglacial complex (Oxygen Isotope Substage 5e). This is succeeded by the Bacon Hole mammal assemblage-zone in which hippopotamus is no longer present and species like mammoth, roe deer and northern vole re-enter the British region. This assemblage-zone appears to represent the later substages of OIS 5. A faunal grouping dominated by bison and reindeer is named the Banwell Bone Cave mammal assemblage-zone and is believed to correlate closely with the Early Devensian (OIS 4). The Pin Hole mammal assemblage-zone includes the familiar mammoth-steppe faunas of the Middle Devensian (OIS 3) dominated by horse, woolly rhinoceros and mammoth. The Lateglacial Interstadial is characterized by the Gough's Cave mammal assemblage-zone in which horse, red deer and humans are well represented (part of OIS 2). No definitive evidence for human activity can be found for a period spanning the Last Interglacial complex (OIS 5) and the Early Devensian (OIS 4). Human populations return to Britain with the Pin Hole mammal assemblage-zone fauna during the Middle Devensian (OIS 3) and reappear after the Dimlington Stadial during the Late Devensian (OIS 2) but in a different faunal association.

Currant, Andrew; Jacobi, Roger

2001-10-01

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Paleosol architecture of a late Quaternary basin-margin sequence and its implications for high-resolution, non-marine sequence stratigraphy  

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Paleosol stratigraphy, a technique commonly applied in basin-margin settings to depict cyclic alluvial architecture on time scales of 10-100 ky, can be consistent with regional accommodation trends at even higher temporal resolution (1-10 ky), having strong implications for the sequence stratigraphy of late Quaternary, non-marine deposits. Three closely-spaced late Pleistocene paleosols (P1-P3), dating back approximately to 42-39, 35-31, and 29-26 cal kyr BP, respectively, form prominent stratigraphic markers across a lithologically homogeneous interfluve succession in the subsurface of Bologna, close to the Apenninic foothills. These paleosols are weakly developed (Inceptisols) and can be tracked continuously for 6 km across the triangle-shaped interchannel zone between two gravel/sand-filled channel systems (Reno and Savena rivers). In particular, the thickest paleosol (P3) is a distinctive stiff horizon that can be traced into laterally extensive, erosional-based fluvial bodies. We infer the correlation between (P3) soil development (and channel downcutting) and the final stage of the stepwise Late Pleistocene sea-level fall that culminated at the marine isotope stage 3/2 transition around 29 cal kyr BP (low accommodation systems tract). A fourth laterally extensive Inceptisol, encompassing the Pleistocene-Holocene boundary (PH), represents the major phase of soil development since the Last Glacial Maximum and is inferred to be related to channel entrenchment at the onset of the Younger Dryas. With the exception of the Iron Age-Roman paleosol, which reflects a predominantly anthropogenic control, the Holocene paleosols are laterally discontinuous and invariably more immature (Entisols) than their Pleistocene counterparts. This trend of decreasing paleosol development (and correlatability) upsection is interpreted to reflect increasing (transgressive-equivalent) accommodation during sea-level rise, thus confirming the possible extension of models used to interpret the ancient rock record to short-term depositional cycles.

Amorosi, Alessandro; Bruno, Luigi; Rossi, Veronica; Severi, Paolo; Hajdas, Irka

2014-01-01

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

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

 
 
 
 
21

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

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

2014-04-01

22

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

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

2014-06-01

23

Late Pleistocene voles (Arvicolinae, Rodentia) from the Baranica Cave (Serbia)  

Science.gov (United States)

Baranica is a cave system situated in the south-eastern part of Serbia, four kilometers south to Knjaževac, on the right bank of the Trgovi\\vski Timok. The investigations in Baranica were conducted from 1994 to 1997 by the Faculty of Philosophy from Belgrade and the National Museum of Knjaževac. Four geological layers of Quaternary age were recovered. The abundance of remains of both large and small mammals was noticed in the early phase of the research. In this paper, the remains of eight vole species are described: Arvicola terrestris (Linnaeus, 1758), Chionomys nivalis (Martins, 1842), Microtus (Microtus) arvalis (Pallas, 1778) and Microtus (Microtus) agrestis (Linnaeus, 1761), Microtus (Stenocranius) gregalis (Pallas, 1779), Microtus (Terricola) subterraneus (de Sélys-Longchamps, 1836), Clethrionomys glareolus (Schreber, 1780) and Lagurus lagurus (Pallas, 1773). Among them, steppe and open area inhabitants prevail. Based on the evolutionary level and dimensions of the Arvicola terrestris molars, as well as the overall characteristics of the fauna, it was concluded that the deposits were formed in the last glacial period of the Late Pleistocene. These conclusions are rather consistent with the absolute dating of large mammal bones (23.520 ± 110 B.P. for Layer 2 and 35.780 ± 320 B.P. for Layer 4).

Bogi?evi?, Katarina; Nenadi?, Draženko; Mihailovi?, Dušan

2012-02-01

24

Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska  

Science.gov (United States)

The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode. ?? 1981.

Weber, F. R.; Hamilton, T. D.; Hopkins, D. M.; Repenning, C. A.; Haas, H.

1981-01-01

25

Late Pleistocene and Holocene Fire History of the California Islands  

Science.gov (United States)

Charcoal has been recovered from a range of late Pleistocene and Holocene sites on Santa Cruz Island and Santa Rosa Island, both islands part of California's Northern Channel Islands, U.S.A. Sediments have been dated using radiocarbon measurements based on wood charcoal, fungal sclerotia, glassy carbon and fecal pellets and are given as calendar years BP. This charcoal has been used to interpret the fire history of the Islands. Charcoal assemblages from samples dating from 24,690 to 12,900 years are dominated by coniferous wood charcoal. Little angiosperm charcoal was recovered in any of the samples. Fungal sclerotia are frequent in a number of samples from a range of ages both on Santa Cruz and Santa Rosa. Fecal pellets are common in most samples and abundant in others. Some of the fecal pellets have hexagonal sides and are likely to represent termite frass. The sediments are fluvial in origin and the distribution of charcoal is irregular making interpretation of fire return intervals and fire frequency difficult. The charcoal indicates a significant record of fire before the earliest documented human arrival on the islands. Charcoal reflectance data shows the occurrence of predominantly low temperature charcoals suggesting common surface fires in the coniferous forest. Soledad Pond sediments from Santa Rosa Island (Anderson et al., 2010) dating from 11,800 cal years BP show a distinctively different vegetation dominated by angiosperms and showing a very different fire history. Pinus stands, coastal sage scrub dominated by Baccharis sp. and grassland replaced the conifer forest as the climate warmed. The early Holocene became increasingly drier, particularly after ca. 9150 cal yr BP. By ca. 6900 cal yr BP grasslands recovered. Introduction of non-native species by ranchers occurred subsequent to AD 1850. Charcoal influx is high early in the Soledad Pond record, but declines during the early Holocene when minimal biomass suggests extended drought. A general increase occurs after ca. 7000 cal yr BP, and especially after ca. 4500 cal yr BP. The Holocene pattern closely resembles population levels constructed from the archaeological record, and suggests a potential influence by humans on the fire regime of the islands, particularly during the late Holocene. Reference: ANDERSON, R.S., STARRATT, S., JASS, R.M.B.,PINTER, N., 2010. Fire and vegetation history on Santa Rosa Island, Channel Islands, and long-term environmental change in southern California. Journal of Quaternary Science 25, 782-797.

Scott, A. C.; Hardiman, M.; Pinter, N.; Anderson, R.

2013-12-01

26

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

DEFF Research Database (Denmark)

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.

Kuneš, Petr; Odgaard, Bent Vad

27

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Neogi, Sayantani

2010-01-01

28

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

Directory of Open Access Journals (Sweden)

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.

Giulia Aimola

2014-09-01

29

Late Pleistocene human skull from Hofmeyr, South Africa, and modern human origins.  

Science.gov (United States)

The lack of Late Pleistocene human fossils from sub-Saharan Africa has limited paleontological testing of competing models of recent human evolution. We have dated a skull from Hofmeyr, South Africa, to 36.2 +/- 3.3 thousand years ago through a combination of optically stimulated luminescence and uranium-series dating methods. The skull is morphologically modern overall but displays some archaic features. Its strongest morphometric affinities are with Upper Paleolithic (UP) Eurasians rather than recent, geographically proximate people. The Hofmeyr cranium is consistent with the hypothesis that UP Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene. PMID:17218524

Grine, F E; Bailey, R M; Harvati, K; Nathan, R P; Morris, A G; Henderson, G M; Ribot, I; Pike, A W G

2007-01-12

30

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

Science.gov (United States)

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

Stojanowski, Christopher M

2014-10-01

31

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  

Directory of Open Access Journals (Sweden)

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 radiocarbónicas 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.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.

Marcelo Z?rate

2008-09-01

32

New records of temperate mollusks in two Late Pleistocene terrestrial localities from northeastern Oaxaca, Southern Mexico  

Science.gov (United States)

The Mixteca Alta Oaxaqueña is in the state of Oaxaca, southern Mexico. This region is characterized by numerous Pleistocene fossiliferous localities. The objective of this study is to describe a diverse assemblage of Late Pleistocene freshwater and terrestrial mollusks in two localities from northeastern Oaxaca, Coixtlahuaca District. We identified 10 taxa of gastropods and one of bivalves. By the sedimentological characteristics and the mollusks assemblage, it is possible to relate the first locality with meandriform river deposits, without vegetation. The second locality was associated with a floodplain with short-lived associated vegetation. Five identified species constitute the most austral records of these taxa in Neartic Realm. In all the taxa, the Late Pleistocene occurrences constitute the last records of the identified mollusks in the study zone.

Guerrero-Arenas, Rosalía; Jiménez-Hidalgo, Eduardo; García-Barrera, Pedro

2013-11-01

33

Underground temperatures - evidence of Late Pleistocene-Holocene orbital forcing  

Science.gov (United States)

An analysis of temperature-depth profiles measured in deep boreholes (more than 1 km) allows determining ground surface temperature (GST) and surface heat flux (SHF) histories in the period of global climate change at the border of Pleistocene and Holocene. We reconstructed past 40 kyr GST and SHF histories using data obtained from two deep boreholes in Russia (Middle Urals and Karelia). GST histories reveal 12-20 degrees of warming during the Pleistocene-Holocene transition 20-10 kyr BP and much smaller changes during Holocene. SHF changes precede the surface temperature changes by 1-2 kyr. The heat flux started to raise 22 kyr BP, reached its maximum value of 0.09-0.12 watts per square meter 15-10 kyr BP and then began to decrease. A comparison of SHF histories with mean annual variations of insolation at a latitude of 60° N (I), which is determined by changes in the Earth's orbital parameters, shows that all three curves are very similar. The synchronous changes of the heat flux and insolation indicate that ground surface temperature changes were mainly governed by external radiative forcing. While the amplitude ratio SHF/I is approximately 1 per cent. A comparison of the reconstructed GST and SHF with the atmospheric carbon dioxide changes (from the Antarctic ice cores) leads to another important conclusion. Carbon dioxide changes by its shape and chronology are much closer to temperature changes than they are to heat flux changes. The heat flux increase occurred faster, and then 12 kyr ago it began to fall, while the increase in carbon dioxide continues to the present. On the assumption that the reconstructed SHF generally reproduces changes in radiative forcing, one can challenge the hypothesis of the primary role of carbon dioxide and the greenhouse effect in Pleistocene-Holocene transition.

Demezhko, Dmitry; Gornostaeva, Anastasia

2014-05-01

34

Origin of late pleistocene formation water in Mexican oil reservoirs  

Energy Technology Data Exchange (ETDEWEB)

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 ({sup 2}H, {sup 13}C, {sup 14}C, {sup 18}O {sup 36}Cl, {sup 37}Cl, {sup 87}Sr, {sup 129}I, 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 CO{sub 2}-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 N{sub 2}-gas for the collection and phase separation of the pressurized gas-water-crude oil mixture. No differences in {sup 14}C-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 {sup 14}C-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 (TDS{sub max} = 0.5 g/l) to hyper-saline composition (TDS{sub max} = 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 {sup 18}O 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 {sup 18}O 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 densit

Birkle, P. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

2004-07-01

35

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

36

Late Cenozoic structure and stratigraphy of south-central Washington  

Energy Technology Data Exchange (ETDEWEB)

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.

Reidel, S.P. [Westinghouse Hanford Co., Richland, WA (United States)]|[Washington State Univ., Pullman, WA (United States). Dept. of Geology; Campbell, N.P. [Yakima Valley Coll., WA (United States); Fecht, K.R.; Lindsey, K.A. [Westinghouse Hanford Co., Richland, WA (United States)

1993-09-01

37

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

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Full Text Available 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 steppe fauna was able to colonize this region during a period of rapid environmental change. The radiocarbon evidence fits well into the known colonization pattern of the mammoth steppe and shows a continuous distribution in the Late Weichselian grassland areas of East Central Europe.

Kovács J

2012-02-01

38

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

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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.

E. Vallejo Gómez

2006-05-01

39

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 aare 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

40

The late Middle Pleistocene hominin fossil record of eastern Asia: synthesis and review.  

Science.gov (United States)

Traditionally, Middle Pleistocene hominin fossils that cannot be allocated to Homo erectus sensu lato or modern H. sapiens have been assigned to different specific taxa. For example, in eastern Asia, these hominin fossils have been classified as archaic, early, or premodern H. sapiens. An increasing number of Middle Pleistocene hominin fossils are currently being assigned to H. heidelbergensis. This is particularly the case for the African and European Middle Pleistocene hominin fossil record. There have been suggestions that perhaps the eastern Asian late Middle Pleistocene hominins can also be allocated to the H. heidelbergensis hypodigm. In this article, I review the current state of the late Middle Pleistocene hominin fossil record from eastern Asia and examine the various arguments for assigning these hominins to the different specific taxa. The two primary conclusions drawn from this review are as follows: 1) little evidence currently exists in the eastern Asian Middle Pleistocene hominin fossil record to support their assignment to H. heidelbergensis; and 2) rather than add to the growing list of hominin fossil taxa by using taxonomic names like H. daliensis for northeast Asian fossils and H. mabaensis for Southeast Asian fossils, it is better to err on the side of caution and continue to use the term archaic H. sapiens to represent all of these hominin fossils. What should be evident from this review is the need for an increase in the quality and quantity of the eastern Asian hominin fossil data set. Fortunately, with the increasing number of large-scale multidisciplinary paleoanthropological field and laboratory research projects in eastern Asia, the record is quickly becoming better understood. PMID:21086528

Bae, Christopher J

2010-01-01

 
 
 
 
41

New insights into mid-late Pleistocene fossil hominin paranasal sinus morphology.  

Science.gov (United States)

Mid-late Pleistocene fossil hominins such as Homo neanderthalensis and H. heidelbergensis are often described as having extensively pneumatized crania compared with modern humans. However, the significance of pneumatization in recognizing patterns of phyletic diversification and/or functional specialization has remained controversial. Here, we test the null hypothesis that the paranasal sinuses of fossil and extant humans and great apes can be understood as biological spandrels, i.e., their morphology reflects evolutionary, developmental, and functional constraints imposed onto the surrounding bones. Morphological description of well-preserved mid-late Pleistocene hominin specimens are contrasted with our comparative sample of modern humans and great apes. Results from a geometric morphometric analysis of the correlation between paranasal sinus and cranial dimensions show that the spandrel hypothesis cannot be refuted. However, visualizing specific features of the paranasal sinus system with methods of biomedical imaging and computer graphics reveals new aspects of patterns of growth and development of fossil hominins. PMID:18951483

Zollikofer, Christoph P E; Ponce De León, Marcia S; Schmitz, Ralf W; Stringer, Christopher B

2008-11-01

42

A re-evaluation of the late Pliocene - Pleistocene behavior of the Scoresby Sund sector of the Greenland Ice Sheet  

Science.gov (United States)

A major conclusion of Ocean Drilling Program Leg 162, drilling the western Svalbard and eastern Greenland continental margins, was that the Svalbard - Barents Sea Ice Sheet reached the shelf edge during peak glaciations much more frequently than the Greenland Ice Sheet during the late Pliocene - Pleistocene period. Both areas have a continental margin dominated by large, across-shelf oriented troughs terminating at the shelf edge. In front of these troughs, large depocenters of glacigenic sediments, Trough-Mouth-Fans (TMFs), are located. Ice streams drained the ice sheets through these troughs during glacials, eroding and transporting large quantities of sediments to the shelf edge from where they subsequently were remobilized as glacigenic debris flows. The deposits of the latter have a characteristic lens-formed morphology in cross-section. In order to tie the stratigraphy of ODP Site 987, located on the very distal part of the Scoresby Sund TMF on the east Greenland continental margin, to the more proximal parts where most of the glacigenic sediments have been deposited, a regional seismic line was acquired. The seismic line reveals that lithological unit IIA of site 987, interpreted to be debris flow deposits, corresponds to an acoustically transparent unit. The overlying lithological unit I, found to be dominated by hemipelagic sediments comprising varying amounts of ice-rafted debris, is acoustically laminated. Tracing this unit south-westwards shows a transition from an acoustically laminated facies to stacked sub-units of transparent lenses of glacigenic debris flows, very similar to the signature of other TMFs. This shows that ODP Site 987 was located too distal to sample the glacigenic debris-flow deposits that dominate the deposits of the last ~2.58Ma on the more proximal part of the fan. From this we conclude that at least the Scoresby Sund sector of the East Greenland Ice Sheet had a much more dynamic behavior during the late Pleiocene - Pleistocene period than previously realized. These fluctuations were most likely responses to the pronounced climatic fluctuations characterizing this period. The new observations have important implications for assessing the behavior of the Greenland Ice Sheet to future climate.

Laberg, J. S.; Forwick, M.; Husum, K.

2012-04-01

43

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

Science.gov (United States)

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.

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

44

Environmental changes at the Holocene-Late Pleistocene transition: Sedimentation on Akademicheskii Ridge (Lake Baikal, Russia)  

Science.gov (United States)

Akademicheskii Ridge of Lake Baikal represents a 300 m deep underwater rise, which separates the Central Basin (1647 m water depth) and the North Basin (970 m water depth) of 640 km long lake. The large distance to the turbid load of particle-carrying tributaries and coastal areas as well as the absence of slide induced turbidites are responsible for low sedimentation rates. A large number of short cores (approx. 120 cm) was used to study in detail the Holocene-Late Pleistocene transition, using lithological composition, magnetic susceptibility, microfossils, pollen and spores, chemistry, grain size and mineral composition. Holocene sediments show sedimentation rates from 0.015 to 0.25 mm y-1 and are mainly composed of biogenic material with rare admixtures of aeolian and ice-rafted terrigenous particles [1]. The sediments are characterized by abundant microfossils, such as diatoms, spicules of sponges, chrysophyte cysts, pollen and spores. Holocene diatom assemblages are representated by Aulacoseira baicalensis, A. skvortzowii, Cyclotella minuta, C. baicalensis, Synedra acus var.radians, Stephanodiscus meyerii, Crateriportula inconspicuus and Cyclostephanos dubius [2]. Concentrations of Corg.,Ntot.,and Sibiog.indicate clearly higher productivity of the lake during the Holocene [1]. Late Pleistocene sediments are composed of clastic, fine-grained, clayey material, mainly of terrigenous origin. This includes also aeolian particles and rare ice-transported sandy material and rock debris. A peak of the diatom species Stephanodiscus flabellatus, observed within the upper part of clayey sediments, defines the Late Pleistocene-Holocene transition [2]. Very low contents of microfossils (diatoms, spicules of sponges, chrysophyte cysts etc.) within Late Pleistocene deposits indicate lower productivity of Lake Baikal. Glacial melt-water dominated the sediment transport processes within the lake during this time. The main minerals of the sand fraction are quartz, feldspars and mica. The heavy mineral assemblage contains amphiboles, pyroxenes, epidote, sphene, magnetite, garnet and chloritoide. Within the Holocene, contents of chloritoide are low (0.6-1.2 %), but they are distinctly higher within the Late Pleistocene sediments (3.2-14.6 %) [1]. An increase of chloritoide in sediments points towards an intensification of aeolian transport by stronger winds and longer-lasting periods of ice cover during the Late Pleistocene [3]. Results of pollen analyses support these findings. They indicate that mountain slopes of the catchment of Lake Baikal were mostly uncovered by vegetation. A polymineral composition is characteristic for the clay fraction of Late Pleistocene deposits: hydro-mica, kaolinite, smectite and chlorite. This is caused by extensive glaciation of the catchment of the lake during this time [4], generating increased transport of terrigenous material to the lake by glacial melt water [5]. References [1] Vologina, E.G. and Sturm, M. 2009. Types of Holocene deposits and regional pattern of sedimentation in Lake Baikal. Russian Geology and Geophysics 50, 1-6. [2] Bradbury, J.P., Bezrukova, Ye.V., Chernyaeva, G.P. et al. 1994. A synthesis of post-glacial diatom records from Lake Baikal. J. Paleolimnol. 10, 213-252.

Vologina, Elena G.; Sturm, Michael

2010-05-01

45

Late Pleistocene glaciolacustrine sedimentation and paleogeography of southeastern Michigan, USA  

Science.gov (United States)

The geomorphic, stratigraphic and sedimentological characteristics of glaciolacustrine sediments in the metropolitan Detroit, Michigan area were studied to determine environments of deposition and make paleogeographic reconstructions. Nine lithofacies were identified and paleoenvironments interpreted based on their morphostratigraphic relationships with relict landforms. The sediments studied are found southeast of the Defiance and Birmingham moraines lying beneath a lowland characterized by a low morainal swell (Detroit moraine) and a series of lacustrine terraces that descend progressively in elevation southeastward. The glaciolacustrine sediments were deposited approximately 14.3-12.4 kA BP during the Port Bruce and Port Huron glacial phases of late Wisconsinan time, and are related to proglacial paleolakes Maumee, Arkona, Whittlesey, Warren, Wayne, Grassmere, Lundy and Rouge. The glaciolacustrine section is typically 2-4 m thick and consists of a basal unit of wavy-bedded clayey diamicton overlain by a surficial deposit of stratified and cross-stratified sand and gravel. The basal unit is comprised of subaqueous debris flow deposits that accumulated as subaqueous moraine in paleolake Maumee along the retreating front of the Huron lobe. The surficial deposits of sand and gravel were formed by traction, resulting from lacustrine wave activity and fluvial processes, in lakebed plain, beach ridge and deltaic depositional settings. Much of the lake-margin sand and gravel was derived from clayey diamicton by lacustrine wave action and winnowing, and that associated with paleolakes of the Port Huron phase is largely reworked Port Bruce sediment. Paleogeographic reconstructions show that the Defiance, Birmingham and Detroit moraines, Defiance and Rochester channels, and the Rochester delta, were deposited penecontemporaneously as paleolake Maumee expanded northward across the map area. A unique type of wavy bedform is characteristic of clayey diamicton deposited by subaqueous mass flow in the study area that is useful for differentiating sediment: 1) deposited by mass flow in subaqueous vs. subaerial settings, and 2) deposited by subaqueous mass flow vs. basal till. These bedforms are a useful tool for identifying subglacial meltwater deposits, and facilitate the mapping and correlation of glacial sediments based on till sheets. The map area provides a continental record of ice sheet dynamics along the southern margin of the Laurentide ice sheet during Heinrich event H-1. The record reveals rapid glacial retreat (˜ 0.8 km/yr) contemporaneous with the discharge of a large volume of meltwater. Evidence in the study area for subglacial meltwater is problematic, but indications that periglacial conditions persisted in the map area until ˜ 12.7 kA BP, and extended for 200 km or more south of the ice front suggest that a frozen substrate may have contributed to instability of the LIS.

Howard, Jeffrey L.

2010-01-01

46

Late Wisconsinan glacial, lacustrine and marine stratigraphy in the Champlain Valley, New York and Vermont  

Energy Technology Data Exchange (ETDEWEB)

The stratigraphy of late-glacial, and postglacial deposits and landforms in the Champlain Lowland is interpreted from high-resolution (3.5 khz transducer) acoustical profiling and piston core analysis of sediments beneath Lake Champlain in conjunction with detailed morphologic sequence mapping of surficial deposits. The sediments of Lake Champlain have been grouped by acoustic, lithologic, and biostratigraphic criteria into three stratigraphic units that were deposited successively into Lake Vermont, the Champlain Sea, and Lake Champlain. The maximum thickness of unconsolidated sediment is known to exceed 200 meters locally. Biostratigraphic subdivision of these units using pollen, diatoms, ostracodes, and foraminifera provides further definition of late-glacial and postglacial events in the region and indicates that transitional environments occurred as conditions changed from proglacial lake to marine estuary to freshwater lake. The stratigraphy of surficial deposits records proglacial lake sequences in the Champlain Valley and its tributaries. Interbasinal correlation of the tributary proglacial lake sequences and reconstructed ice marginal positions, is consistent with a model of generally synchronous, northward recession controlled primarily by backwasting of active continental ice lobes. Minor asynchroneity of retreat rates may be attributed to local differences in subglacial topography and changes in proglacial lake level, both of which may affect calving rates. Northward ice recession of the Champlain Lobe allowed successive inundation of tributary valleys by Lake Vermont. Elevations of deltaic sandplains reveal at least three distinct lake levels in the northwestern Champlain Valley. The highest level corresponds to the Coveville Stage while the lower two represent levels of the Fort Ann Stage.

Franzi, D.A. (Stat Univ. of New York, Plattsburgh, NY (United States). Center for Earth and Environmental Science); Hunt, A.S. (Univ. of Vermont, Burlington, VT (United States). Dept. of Geology)

1993-03-01

47

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

DEFF Research Database (Denmark)

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.

Foote, Andrew D; Kaschner, Kristin

2013-01-01

48

The Ob?azowa 1 early modern human pollical phalanx and Late Pleistocene distal thumb proportions.  

Science.gov (United States)

The human distal thumb phalanx from the earlier Upper Paleolithic of Ob?azowa Cave, southern Poland, exhibits features of its palmar surface that align it morphologically principally with early modern humans. These aspects include the configurations of the proximal palmar fossa, the flexor pollicis longus tendon insertion, the proximal margin of the palmar apical tuft, and especially its low ulnar deviation angle. If it is assumed that it possessed the pollical phalangeal length proportions of an early modern human, it would exhibit modest base and tuft breadths. However, given Late Pleistocene archaic-modern contrasts in relative pollical phalanx lengths, the isolated nature of the phalanx prevents secure assessment of its radioulnar interphalangeal articular and apicaltuft hypertrophy. Similar constraints apply to the assessment of other Pleistocene Homo pollical phalanges. PMID:24616929

Trinkaus, E; Haduch, E; Valde-Nowak, P W; Wojtal, P

2014-02-01

49

Response of methanogenic archaea to Late Pleistocene and Holocene climate changes in the Siberian Arctic  

Science.gov (United States)

order to investigate the link between the methane dynamics in permafrost deposits and climate changes in the past, we studied the abundance, composition, and methane production of methanogenic communities in Late Pleistocene and Holocene sediments of the Siberian Arctic. We detected intervals of increased methane concentrations in Late Pleistocene and Holocene deposits along a 42 ka old permafrost sequence from Kurungnakh Island in the Lena Delta (northeast Siberia). Increased amounts of archaeal life markers (intact phospholipid ethers) and a high variety in genetic fingerprints detected by 16S ribosomal ribonucleic acid gene analyses of methanogenic archaea suggest presently living and presumably active methanogenic archaea in distinct layers predominantly in Holocene deposits, but also in deep frozen ground at 17 m depth. Potential methanogenic activity was confirmed by incubation experiments. By comparing methane concentrations, microbial incubation experiments, gene analysis of methanogens, and microbial life markers (intact phospholipid esters and ethers) to already partly degraded membrane lipids, such as archaeol and isoprenoid glycerol dialkyl glycerol tetraethers, we demonstrated that archaeol likely represents a signal of past methanogenic archaea. The archaeol signal was used to reconstruct the response of methanogenic communities to past temperature changes in the Siberian Arctic, and the data suggest higher methane emissions occurred during warm periods, particularly during an interval in the Late Pleistocene and during the Holocene. This new data on present and past methanogenic communities in the Siberian terrestrial permafrost imply that these microorganisms will respond to the predicted future temperature rise in the Arctic with increasing methane production, as demonstrated in previous warmer periods.

Bischoff, Juliane; Mangelsdorf, Kai; Gattinger, Andreas; Schloter, Michael; Kurchatova, Anna N.; Herzschuh, Ulrike; Wagner, Dirk

2013-04-01

50

Size Analysis of the Late Pliocene-Early Pleistocene Upper Siwalik Sediments, Northwestern Himalaya, India  

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Full Text Available Size analysis of the Late Pliocene-Early Pleistocene Upper Siwalik sediments comprising the Pinjor Formation in the type area and adjoining regions reveals that the sediments are bimodal to polymodal in nature, medium to fine grained and are moderately sorted. The inclusive graphic standard deviation and moment standard deviation values suggest the deposition of sediments in shallow to moderately deep fluvial agitated water. The log probability plots reveal that saltation mode is the dominant mode of transportation of detritus. The sediments are continental in character and are derived from crystalline, metamorphic and sedimentary rocks of the Himalaya exposed to the North of the type area Pinjor.

Mahavir Singh

2013-10-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Vallejo Go?mez, E.; Sedov, S.; Cienfuegos Alvarado, E.; Cabadas Ba?ez, H. V.; Morales Puente, P.; Lounejeva Baturina, E.; Solleiro Rebolledo, E.

2006-01-01

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The first radiation dates of syngenetic Late Pleistocene ice-wedges  

International Nuclear Information System (INIS)

Direct radiocarbon dating of organic mater extracted directly from ice wedges of the Late Pleistocene wedges of Siberia using the accelerating mass spectrometry was carried out. It is shown that the ice wedges opened in the cross section base at a height from 0 to +1 m started their formation about 21 thousand years ago. The rate of the wedges vertical growth in the course of 21-14.7 thousand of years. Subhorizontal age stratification of the ice-wedges formed by consecutive penetration of thawing ice water along with accumulation of precipitate on the surface, was confirmed

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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)

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Cryostratigraphy of late Pleistocene syngenetic permafrost (yedoma) in northern Alaska, Itkillik River exposure  

Science.gov (United States)

Extremely ice-rich syngenetic permafrost, or yedoma, developed extensively under the cold climate of the Pleistocene in unglaciated regions of Eurasia and North America. In Alaska, yedoma occurs in the Arctic Foothills, the northern part of the Seward Peninsula, and in interior Alaska. A remarkable 33-m-high exposure along the lower Itkillik River in northern Alaska opened an opportunity to study the unmodified yedoma, including stratigraphy, particle-size distribution, soil carbon contents, morphology and quantity of segregated, wedge, and thermokarst-cave ice. The exposed permafrost sequence comprised seven cryostratigraphic units, which formed over a period from > 48,000 to 5,000 14C yr BP, including: 1) active layer; 2) intermediate layer of the upper permafrost; 3-4) two yedoma silt units with different thicknesses of syngenetic ice wedges; 5) buried peat layer; 6) buried intermediate layer beneath the peat; and 7) silt layer with short ice wedges. This exposure is comparable to the well known Mus-Khaya and Duvanny Yar yedoma exposures in Russia. Based on our field observations, literature sources, and interpretation of satellite images and aerial photography, we have developed a preliminary map of yedoma distribution in Alaska.

Kanevskiy, M.; Shur, Y.; Fortier, D.; Jorgenson, M. T.; Stephani, E.

2011-05-01

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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.

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

2012-08-01

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

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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.

Li Shouhsien

2009-06-01

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

Science.gov (United States)

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. PMID:19558699

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

2009-01-01

58

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

DEFF Research Database (Denmark)

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.

Döhler, Susanne; Damm, Bodo

2014-01-01

59

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

Science.gov (United States)

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.

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

2007-01-01

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

DEFF Research Database (Denmark)

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.

Buylaert, Jan-Pieter; Jain, Mayank

2012-01-01

 
 
 
 
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A Pathological Late Pleistocene canid from San Sidero (Italy): implications for social- and feeding-behaviour  

Science.gov (United States)

Evidence of diseases on vertebrate fossil bones can provide detailed information on many aspects of extinct animals. This study focused on pathological craniodental remains (left maxilla and dentary) referred to the canid Cuon alpinus unearthed from a Late Pleistocene karst filling deposit at San Sidero (Apulia, southern Italy). These fossils show clear evidence of a chronic periodontitis that caused the animal's death. Clinical diagnosis of the disease and the timing of its development have been defined on the basis of a veterinary odontostomatology approach, in addition to radiographic and tomographic techniques. From the initiation of the infection until death, a time span of at least 6 months occurred, and three main steps have been defined: (1) the bacterial infections of the buccal cavity turning into severe periodontitis, (2) the fracture of the lower carnassial and (3) the loss of teeth due to the worsening infection that deformed and/or eroded maxillary and mandibular bones and enlarged alveoli. The analysis of the palaeopathology also provides information about the biomechanics of the bite, on the feeding behaviour and on the relationships of injured members in a pack of Late Pleistocene canids.

Iurino, Dawid Adam; Fico, Rosario; Petrucci, Mauro; Sardella, Raffaele

2013-03-01

62

Late Pleistocene Holocene landscape evolution in Fossa Bradanica, Basilicata (southern Italy)  

Science.gov (United States)

Studies in the middle Basento river basin supported by reliable chronological data (tephra layers and a number of absolute datings) have allowed the reconstruction of Late Pleistocene-Holocene geomorphological evolution of the middle to low Fossa Bradanica area (Basilicata, southern Italy). The original Upper Pleistocene hillslope has been dissected by deep gullies leaving relict slope pediments. Holocene filling of the Basento river valley and gullies occurred as a succession of downcut and fill episodes. A first phase of accumulation occurred in the Late Neolithic, which was followed by a downcutting between 4500 and 3700 cal. yr BP. A second deposition phase took place in the Greek-Roman period between 2800 and 1620 cal. yr BP, which was interrupted at around 2500 cal. yr BP. Another downcutting phase took place between 1620 and 1500 cal. yr BP, followed by a deposition phase between 1440 and 1000 cal. yr BP. After 1000 cal. yr BP a deep downcutting took place. Evidence collected with this study, coupled with climate data recorded in other Italian and European locations, suggests that filling and downcutting episodes in Fossa Bradanica were predominantly climate-driven. Anthropogenic impact only intensified or weakened these processes.

Boenzi, F.; Caldara, M.; Capolongo, D.; Dellino, P.; Piccarreta, M.; Simone, O.

2008-12-01

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Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths  

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Full Text Available The number of cervical vertebrae in mammals is highly conserved at seven. We have shown that changes of this number are selected against due to a coupling with major congenital abnormalities (pleiotropic effects. Here we show that the incidence of abnormal cervical vertebral numbers in Late Pleistocene mammoths from the North Sea is high (33.3% and approximately 10 times higher than that of extant elephants (3.6%. Abnormal numbers were due to the presence of large cervical ribs on the seventh vertebra, which we deduced from the presence of rib articulation facets on sixth (posterior side and seventh (anterior side cervical vertebrae. The incidence of abnormal cervical vertebral numbers in mammoths appears to be much higher than in other mammalian species, apart from exceptional sloths, manatees and dugongs and indicates a vulnerable condition. We argue that the increased incidence of cervical ribs in mammoths is probably caused by inbreeding and adverse conditions that impact early pregnancies in declining populations close to extinction in the Late Pleistocene.

Jelle W.F. Reumer

2014-03-01

64

Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths.  

Science.gov (United States)

The number of cervical vertebrae in mammals is highly conserved at seven. We have shown that changes of this number are selected against due to a coupling with major congenital abnormalities (pleiotropic effects). Here we show that the incidence of abnormal cervical vertebral numbers in Late Pleistocene mammoths from the North Sea is high (33.3%) and approximately 10 times higher than that of extant elephants (3.6%). Abnormal numbers were due to the presence of large cervical ribs on the seventh vertebra, which we deduced from the presence of rib articulation facets on sixth (posterior side) and seventh (anterior side) cervical vertebrae. The incidence of abnormal cervical vertebral numbers in mammoths appears to be much higher than in other mammalian species, apart from exceptional sloths, manatees and dugongs and indicates a vulnerable condition. We argue that the increased incidence of cervical ribs in mammoths is probably caused by inbreeding and adverse conditions that impact early pregnancies in declining populations close to extinction in the Late Pleistocene. PMID:24711969

Reumer, Jelle W F; Ten Broek, Clara M A; Galis, Frietson

2014-01-01

65

Isotopically-depleted late Pleistocene groundwater in Columbia River Basalt aquifers: Evidence for recharge of glacial Lake Missoula floodwaters?  

Science.gov (United States)

Late Pleistocene outburst flooding of ice-dammed glacial Lake Missoula, and possible discharge from the Cordilleran Ice Sheet (CIS), catastrophically altered the northwestern United States landscape, yet little is known about potential infiltration of flood waters into the subsurface. This study provides compelling evidence for the presence of late Pleistocene CIS-related recharge waters in the Columbia River Basalt Aquifers (CRBAs) in central Washington. CRBA groundwaters with corrected 14C ages from 15.7 and 33.3 k yrs BP (during periods of flood events) have anomalously low ?18O values (-18.9 to -17.6‰), compared to late Pleistocene soil waters (-16.1 to -13.4‰) and modern precipitation in the region (average -15.9‰), consistent with CIS-related meltwater recharge. These results have implications for our understanding of megaflood phenomena on earth and Mars.

Brown, Kyle B.; McIntosh, Jennifer C.; Baker, Victor R.; Gosch, Damian

2010-11-01

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Late Pleistocene oxygen isotope records of biogenic silica from the Atlantic sector of the Southern Ocean  

Science.gov (United States)

We determined the isotopic composition of oxygen in marine diatoms in eight deep-sea cores recovered from the Atlantic sector of the Southern Ocean. The analytical reproducibility and core-to-core consistency of the isotopic signal suggests that diatom ?18O can be used as a new paleocenographic tool to reconstruct past variations in surface water characteristics and to generate 18O -isotope-based stratigraphy for the Southern Ocean. The data indicate that diatom ?18O reflects sea surface temperature and seawater isotopic composition and that diatoms retain their isotopic signal on timescales of a least 430 ka. The ?18O analyses of different diatom assemblages reveal that the isotopic signal is free of species effects and that the common Antarctic species have the same water-opal fractionation. The transition from the last glacial maximum (LGM) to the Holocene is fully recorded in high sedimentation rate cores. An 18O enrichment during the LGM, a post-LGM meltwater spike and an input of meltwater during the late Holocene are the main isotopic features observed in down core records. The origin of this meltwater was very likely melting icebergs and/or continental ice or by melting sea ice that had accumulated snow. The most pronounced meltwater effects are recorded in cores that are associated with the Weddel gyre. Our results provide the basis for extending isotope studies to oceanic regions devoid of carbonate; further, isotopic stratigraphies may be constructed for records and regions where they were previously not possible.

Shemesh, A.; Burckle, L. H.; Hays, J. D.

1995-04-01

67

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

68

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

Science.gov (United States)

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.

Mewis, H.; Kiessling, W.

2013-03-01

69

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

Energy Technology Data Exchange (ETDEWEB)

We discuss the {sup 14}C 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 {sup 14}C 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 {sup 14}C dates yield for the first time a timescale (in {sup 14}C years) for paleoclimatic indicators (oxygen and hydrogen isotope ratios from the ice)

Vasil' chuk, Yurij K. E-mail: vasilch@orc.ru; Plicht, Johannes van der; Jungner, Hoegne; Vasil' chuk, Alla C

2000-10-01

70

Middle Pleistocene palaeoenvironments and the late Lower-Middle Palaeolithic of the Hrazdan valley, central Armenia  

Science.gov (United States)

The palaeogeographic importance of the southern Caucasus in the Pleistocene as a region of population expansion and contraction between Africa, the Levant and Eurasia is well established as a result of recent archaeological works in the Republics of Armenia and Georgia. Not only does the area have a unique Palaeolithic record, but the presence of volcanic layers in association with archaeological sites and off site sequences means that there is the potential for both high precision dating and correlation. The Hrazdan valley, central Armenia is a case in point. Late Lower to late Middle Palaeolithic sites found as a result of systematic survey and then explored in excavations in 2008-2011 are associated with various volcanogenic strata. 40K/40Ar and 40Ar/39Ar dating in the 1970-2000s demonstrates the onset of volcanism in the adjacent Gegham range in the period 700-500ky BP, while recent 40Ar/39Ar dates on the latest lava from the Gutanasar volcano shows the latest effusive eruption to have occurred at c. 200 ky BP. Nine Middle Pleistocene lavas from the intervening period have been mapped in the Hrazdan valley in a 15km-long study area 12km north-east of Yerevan. Several of the basalts seal terrestrial strata, and thereby bury and 'fossilize' earlier landscapes. The most significant of these is sandwiched between basalts dating to 200 and 440ky BP, where a 135m-long exposure contains a palaeosol developing in floodplain alluvium and in situ archaeological material (Nor Geghi 1). Morphological and micromorphological examination of site strata suggest that hominin activity took place during a temperate episode, which 40Ar/39Ar dating of interbedded crypotephra suggests was MIS 9e. However, strata at other locales buried beneath the same 200ky BP basalt suggest that the landscape occupied by these hominids was a mosaic of river channels, floodplains and lakes. The fossilized MIS 9 landscape is not unique as further lacustrine deposits are buried beneath earlier Middle Pleistocene basalts, although earlier archaeological sites have yet to be found.

Wilkinson, Keith; Adler, Daniel; Nahapetyan, Samvel; Smith, Victoria; Mark, Darren; Mallol, Carolina; Blockley, Simon; Gasparian, Boris

2014-05-01

71

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)

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.

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

2014-05-01

72

Middle-Late Pleistocene polycyclic evolution of a stable coastal area (southern Apulia, Italy)  

Science.gov (United States)

The Otranto-Leuca coastal tract is marked by the presence of numerous sea caves placed close to present sea level. They are located generally at the back of a shore platform covered by a sequence of breccia deposits, marine sediments and speleothems. At Grotta di Masseria dell'Orte, marine cemented sands rest on a narrow shore platform at about 6.2 m above mean sea level and are covered by speleothems older than 185 ka. At Grotta del Diavolo, which is mostly filled by breccia deposits, three beach levels have been detected at about 3.0, 3.5 and 5.9 m above msl. They are either covered by or overlie speleothems that yield an U/Th age of 340, 78 ka and between 170.3 and 146.5, respectively. Geomorphological evidence and radiometric ages indicate that the area after a period of uplift has been tectonically stable since the last part of the Middle Pleistocene so that marine landforms close to the present shoreline underwent a polycyclic evolution. The sedimentary fills of sea caves formed during Middle-Late Pleistocene glacial stages, when arid or semiarid conditions promoted the removal of regolith and the development of thick breccia deposits. During Marine Isotope Stages (MIS) 9.3, 5.5 and 5.1, cave sediments were partially eroded whereas beach layers and related speleothems developed. These are, in fact, the only marine isotope stages marked by a sea level position which in this Mediterranean region was either close to, or slightly higher than, the present one.

Mastronuzzi, Giuseppe; Quinif, Yves; Sansò, Paolo; Selleri, Gianluca

2007-05-01

73

The Late Pleistocene distribution of vicuñas (Vicugna vicugna) and the “extinction” of the gracile llama (“Lama gracilis”): New molecular data  

Science.gov (United States)

We present the results of a palaeogenetic analysis of two Late Pleistocene camelids originating in southern Chile. Our analysis of two mitochondrial DNA fragments (control region and cytochrome b gene) reveals that these specimens do not belong to an extinct taxon, but rather to extant vicuña ( Vicugna vicugna), whose modern distribution is restricted to the extreme elevations of the Andes, more than 3500 km to the north of where these specimens originated. Our results also suggest fossil specimens from Patagonia that are currently assigned to the extinct taxon Lama gracilis, may actually belong to V. vicugna, implying a continuous distribution of the latter from the southern tip of South America to the Andes during the Final Pleistocene. The haplotypes of both specimens are not present in modern populations, suggesting a loss of genetic diversity concomitant with the contraction of the vicuña geographical distribution during the Final Pleistocene or early Holocene.

Weinstock, Jaco; Shapiro, Beth; Prieto, Alfredo; Marín, Juan Carlos; González, Benito A.; Gilbert, M. Thomas P.; Willerslev, Eske

2009-07-01

74

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

Science.gov (United States)

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.

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

2014-05-01

75

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

Science.gov (United States)

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.

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

76

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

DEFF Research Database (Denmark)

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.

Campos, Paula F; Willerslev, Eske

2010-01-01

77

Synchronization of late-glacial vegetation changes at Crystal Lake, Illinois, USA with the North Atlantic Event Stratigraphy  

Science.gov (United States)

Late-glacial (17-11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300-400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures.

Gonzales, Leila M.; Grimm, Eric C.

2009-09-01

78

Stratigraphy and U-series geochronology of Late Quaternary megatsunami deposits in Hawaii  

Science.gov (United States)

Our previous work on Kohala, Hawaii, established that the elevated marine basalt boulder conglomerates found there represent at least one, and probably two megatsunami events in the late Pleistocene. Together with the evidence for giant submarine landslides off western Hawaii island from contemporaneous flank failures of Mauna Loa volcano and identical sequences of submarine terraces off the NW coasts of the islands of Hawaii and Lanai, our hydrodynamic modeling indicates that all islands in the Hawaiian chain must have been affected by these giant waves. We present new dating of these deposits on Hawaii, Lanai and Maui islands together with stratigraphic interpretations of their impacts and origins. We used uranium-series dating of in situ coral clasts to constrain the age of the marine conglomerates, using multiple ion counting- inductively coupled plasma-mass spectrometry techniques, and used 87Sr/86Sr ratios of carbonates to help delineate their origins where marine fossils were absent. Southern Lanai records at least four megatsunami events: at 110 ka, 135 ka, 200 ka, and 240 ka, that likely correspond to the Alika phase 2, Alika phase 1, and two stages of the older South Kona giant submarine landslides. These event dates also correspond to O- isotopic stages 5d, 5e, 7a and 7b, and are in agreement with a changing-climate trigger mechanism for volcanic flank collapse proposed in previous work by ourselves and others. On southern Lanai, there is evidence for two megatsunami deposits in stratigraphic succession in the vicinity of Manele Bay, as well as higher-elevation deposits there containing reworked coral-bearing debris from two older megatsunami events. Coral clasts have been dated from all four events within the high-elevation gullies within Kaluakapo Crater on southern Lanai in this study and Moore and Moore (1988), indicating enormous runups to more than 626 m and wave heights of more than 240 m there that are in agreement with the latest hydrodynamic modeling. There is presently evidence for the 110 ka event on Hawaii, Lanai and West Maui, and for the 200 ka and 240 ka events on the islands of Lanai, Molokai and probably Hawaii. The 135 ka event has so far only been recorded on southern Lanai, but will likely turn up in future work elsewhere.

McMurtry, G. M.; Fryer, G. J.; Tappin, D. R.; Fietzke, J.

2008-12-01

79

California condor associated with spruce-jack pine woodland in the late Pleistocene of New York  

Science.gov (United States)

A humerus, coracoid, and pedal phalanx of the California Condor, Gymnogyps californianus, were recovered from the Hiscock Site in western New York, in an inorganic stratum containing wood that is 11,000 radiocarbon years old. Associated vertebrates include mastodont, wapiti, and caribou. Pollen and plant macrofossils from the sediments indicate a spruce-jack pine woodland and a local, herb-dominated wetland community. Historic records (all from western North America) and previous late Pleistocene fossils of the California Condor are associated mainly with warm-temperate climates and floras. The New York fossils show that this bird was able to live in a colder climate and in a boreal, coniferous setting at a time when appropriate food (large mammal carrion) was available. The California Condor, which survives only in captivity, has suffered a greater reduction in geographical range than previously suspected. Much of this reduction in range probably occurred ca. 11,000 yr B.P. when the extinction many North American large mammals resulted in severely reduced availability of food for the California Condor and other large scavenging birds.

Steadman, David W.; Miller, Norton G.

1987-11-01

80

A model of late Pleistocene ice sheet growth with realistic geography and simplified cryodynamics and geodynamics  

Science.gov (United States)

A global two-dimensional one-level seasonal energy-balance model is asynchronously coupled to vertically integrated ice-flow models (which depend both on latitude and longitude) to study the response of the atmosphere-ocean-cryosphere-lithosphere system to solar forcing for the last ice age cycle of the late Pleistocene. The model simulates the position of the North American and European ice sheet complexes at the last glacial maximum satisfactorily. Both the geographic distributions of the ice volumes delivered by the model and their masses are a reasonable approximation to those inferred on the basis of relative sea level data (Tushingham and Peltier 1990). The sensitivity of the coupled model over the last glacial-interglacial cycle to solar forcing is nevertheless low, which suggests that further physical mechanisms will have to be added to the model (such as explicit basal sliding and ice shelves which would respond to sea-level variations and therefore permit marine incursions), if it is to adequately simulate the terminations that control the 105 year ice age cycle. One should also incorporate long-term variations of the greenhouse gases (Manabe et al. 1985b).

Deblonde, G.; Peltier, W. R.

1990-12-01

 
 
 
 
81

The view from the Lincoln Cave: mid- to late Pleistocene fossil deposits from Sterkfontein hominid site, South Africa.  

Science.gov (United States)

The Lincoln-Fault cave system lies adjacent to the Sterkfontein Cave system in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Lincoln Cave contains a mid- to late Pleistocene fossiliferous deposit which has been dated using uranium series methods to between 252,600+/-35,600 and 115,300+/-7,700 years old. Although speleologists presumed that there was no connection between the Lincoln Cave and Sterkfontein Cave systems, results of excavations conducted in 1997 suggest a link between the deposits. Detailed comparisons of artifacts, fauna, hominid material, and a statistical correspondence analysis (CA) of the macromammalian fauna in the deposits strongly support this hypothesis. The recovery of Early Acheulean-type artifacts from the Lincoln Cave suggests that older artifacts eroded out of Sterkfontein Member 5 West and were redeposited into the younger Lincoln Cave deposits. The close physical proximity of these deposits, and the nature of the material recovered from them, indicates that the material was probably redeposited via a link between the two cave systems. Although faunal mixing is present, it is possible to say that large carnivorans become more scarce at Sterkfontein during the mid- to late Pleistocene, while small canids and felids appear to become more abundant, indicating that large and small carnivorans probably varied their use of the site through time. This may also reflect an increasing presence of humans in the Sterkfontein area during the mid- to late Pleistocene. PMID:17624409

Reynolds, S C; Clarke, R J; Kuman, K A

2007-09-01

82

Provenance of Palouse Loess and Relation to Late Pleistocene Glacial Outburst Flooding, Washington State  

Science.gov (United States)

The eolian system of the Pacific Northwest is a product of long-term deflation of expansive sedimentary units by prevailing winds throughout the Quaternary. The Palouse loess is a deposit of wind-blown silt that covers approximately 10,000 sqare km up to 75 m thick. Late Quaternary units of the loess become finer texturally and thinner to the northeast, suggesting that they were derived from sedimentary basins south and west. The source of the loess has been inferred and hypothesized but never directly determined. A geochemical study of the late-Pleistocene to Holocene L1 unit of the Palouse loess and its possible sources was conducted to determine its provenance. There are two sedimentary units that lie upwind of the loess that may have contributed sediment via eolian deflation: 1) sand- and silt-rich slackwater sediment derived from late-Pleistocene outburst flooding of glacial Lake Missoula, and 2) sand- and silt-rich sediment from the Miocene-Pliocene Ringold Formation. Both are very similar in mineral composition, being derived from plutonic, metamorphic, and volcanic rocks of the western United States and southern British Columbia. Major and trace element data determined by x-ray fluorescence (XRF) of silt to very fine sand from loess and potential source sediments was used to pinpoint the exact source of the loess. A one-to-one relationship of major and trace elements exists between eolian and flood sediments, whereas Ringold Formation sediments have elevated Ti, P, Mg, and Ca oxides and lower K oxide values as well as scattered trace element values relative to Palouse loess. These trends may be due to the presence of basalt lithic grains in flood sediment that have been broken down and distributed throughout the loess. The Ringold Formation lacks appreciable amounts of basalt. The geochemical data from this study demonstrates that flood sediment is the dominant source of eolian material for the Palouse loess. The spatial distribution of the possible source sediments also suggests that flood slackwater sediment is the dominant source. Slackwater flood sediments rest in basins upwind of loess, where deflation is documented today. The Ringold Formation has limited exposure near the present day Columbia River and was eroded by outburst floods or covered by slackwater sediments. Its limited extent and exposure makes the Ringold Formation an less likely candidate for a source of the L1 loess. Study of the oldest units of Palouse loess will show whether or not the Ringold contributed a larger proportion of eolian material prior to the onset of glacial outburst flooding. This new provenance data will allow estimates to be made of the volume of dust ejected into the atmosphere from the Palouse eolian system since the last glacial maximum, which is essential to modeling of atmospheric dust fluxes that force climate fluctuations.

Sweeney, M. R.; Busacca, A. J.; Gaylord, D. R.; Zender, C. S.

2002-12-01

83

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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 Holoce

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

2006-06-01

84

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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 Holoce

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

85

Morpho-Sedimentary Impacts By The Late-Pleistocene - Holocene Jökulhlaups In The Þjórsá-Tungnaá Fluvio-Glacial System  

Science.gov (United States)

In Iceland, jökulhlaups correspond to glacial outburst floods that are generally related to sublagial volcanic and hydrothermal activities. They affect the main fluvial outwash plains around the ice caps. They result of the sudden outflow of a large volume of melt water with variable sediment charges drained from a (sub)glacial or an ice-dammed marginal lake that feeds short (hours to days) cataclysmic floods with peak discharges (103 to 107 m3.s-1), up to 10-100 times the magnitude of classical hydrometeorological fluvial floods. Despite their short duration, and because of large peak discharges, they have important erosive and sediment transport capacities. Consequently, repeated events have a strong morpho-sedimentary impact on the inundated areas. The connected watersheds of the Þjórsá and Tungnaá rivers (200 km long; ˜5000 km2, South Island), west of Vatnajökull, correspond to the largest periglacial fluvial system in Iceland. It has drained numerous jökulhlaup floods during the Late Pleistocene deglaciation and the Holocene during periods of increase of the volcanic activity and heat flow. Jökulhlaups were emitted from at least two outlets along the western edge of Vatnajökull that fed the Kaldakvísl and Tungnaá rivers. The subglacial depressions (calderas) of the Bárðarbunga-Hamarinn volcanic system are favorable to the storage of large volumes of water that can feed major jökulhlaups. The Þjórsá-Tungnaá jökulhlaup system can be subdivided into three parts: (1) the source located at the outlets of the subglacial hydraulic network, (2) a proximal transit zone along which erosional processes are dominant (erosively incised rocky substratum - scablands, abraded scoria cones, scour structures, residual buttes of the sedimentary cover) with minor lateral slackwater deposits, flood overflow ponded lakes, and hydraulic dunes along constrictions of the fluvial network, and (3) a distal depositional zone that corresponds to the coastal sandur, the area of main sedimentation before possible floods entrance into the sea as hyperpycnal plumes. Erosion and sedimentation along the system are controlled by the geometry of the fluvial network. Main erosional processes occur along steep slopes and constrictions, and in areas of fluvial channels confluences. These erosional and depositional structures were mapped along the system and summarized on a DEM. Preliminary 2D and 3D hydraulic simple modeling of the floods has been conducted for the Kaldakvísl-Þjórsá jökulhlaup sub-system with an outlet located in the present-day lake Hágöngulón area. The modeling is based on the solutions of Saint-Venant equations obtained by both eulerian (VF2D; IRSTEA) and lagrangian (TELLUS, CSIRO) approaches. Results provide theoretical velocity fields and flood heights along the flooded area. The preliminary results of this modeling were compared to the location of the field structures along the system, and significant correlations between the structures into the field and the velocity fields have been identified. In conclusion, a large jökulhlaup system is mainly erosive, with limited sedimentation located on its edges and on the coastal plain. Works in progress on the Þjórsá-Tungnaá jökulhlaup system deal with the stratigraphy of past large-scale outburst events, their modeling and the estimate of their recurrence. These are some of the main objectives of the JOKER project submitted to the French Research Agency.

Schneider, Jean Luc; van Vliet-Lanoe, Brigitte; Naaim, Mohamed; Salles, Tristan; Bjornsson, Helgi; Palsson, Finnur

2013-04-01

86

Quantifying late Pleistocene lithospheric flexure and fault movements in the Mississippi Delta  

Science.gov (United States)

It is well known that a significant portion of the Mississippi Delta (MD) land surface is subsiding at rates on the order of a centimeter per year. Several recent studies have argued that lithospheric flexure due to sediment loading in the MD and fault movements in southeast Louisiana induce as much as ~6 mm/yr of subsidence, and therefore would be major driving forces of land-surface subsidence in the MD. However, geological rates of lithospheric flexure and fault movements have rarely been quantified. In this study, we quantify geological rates of these two processes in and near the MD by means of quartz optically-stimulated luminescence (OSL) dating of late Pleistocene sediments. Lithospheric flexure is quantified by studying long profiles of the Lower Mississippi River (LMR). Recent OSL dating of the Prairie Complex strata in the Lower Mississippi Valley (LMV) and MD identified segments of ~80 ka (MIS 5a) old LMR remnants. Comparing the reconstructed MIS 5a LMR long profile with the present-day long profile demonstrates that the former has been deformed due to lithospheric flexure associated with MD sediment loading, featuring uplift in the southern LMV and down-warping in the MD. Using the present-day long profile as a proxy for deformation of the MIS 5a long profile, the bulge in the southern LMV exhibits an average uplift rate of subsided subsidence rates due to lithospheric flexure may be up to 1 to 2 mm/yr. The half-wavelength of the flexural bulge in the LMV suggests a minimum elastic thickness of the lithosphere for this region of ~60 km. Fault movements were quantified at four locations along the Baton Rouge fault zone (BRFZ) in southeast Louisiana. Geomorphic and stratigraphic studies were used to identify fault-displaced strata that were subsequently OSL dated. Time-averaged fault slip rates are ~0.04 mm/yr, irrespective of strata age (ranging from 30 to 130 ka), suggesting that the fault slip rates exhibited little change over late Pleistocene time. Hillslope morphology along the surface expression of the BRFZ is consistent along-strike and from segment to segment; this observation, plus the consistency of slip rates temporally and spatially, suggests a creeping fault interpretation. Our new findings indicate that fault slip in the BRFZ is geologically slow (by several orders of magnitude) relative to the rapid land-surface subsidence in the MD. Furthermore, the MIS 5a long profile shows no abrupt slope change in the MD as would be expected if tectonic movements were driven by faulting. The combined effect of fault movement and lithospheric flexure, while geologically highly significant, is not a major cause of present-day land-surface subsidence on a regional scale in the MD.

Shen, Z.; Tornqvist, T. E.; Dawers, N. H.; Gasparini, N. M.; Milne, G. A.; Mauz, B.

2011-12-01

87

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

DEFF Research Database (Denmark)

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.

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

2012-01-01

88

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

Science.gov (United States)

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 exceptionally thick, rich, and high-resolution archaeological sequence that dates to ?58 ka, which has recently been proposed as type assemblage for the “Sibudan”. This study presents a detailed analysis of the six uppermost lithic assemblages from these deposits (BM-BSP) that we excavated from 2011–2013. We define the key elements of the lithic technology and compare our findings to other assemblages post-dating the HP. The six lithic assemblages provide a distinct and robust cultural signal, closely resembling each other in various technological, techno-functional, techno-economic, and typological characteristics. These results refute assertions that modern humans living after the HP possessed an unstructured and unsophisticated MSA lithic technology. While we observed several parallels with other contemporaneous MSA sites, particularly in the eastern part of southern Africa, the lithic assemblages at Sibudu demonstrate a distinct and so far unique combination of techno-typological traits. Our findings support the use of the Sibudan to help structuring this part of the southern African MSA and emphasize the need for further research to identify the spatial and temporal extent of this proposed cultural unit. PMID:24878544

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

2014-01-01

89

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

Science.gov (United States)

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.

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

2002-11-01

90

Atmospheric circulation patterns during late Pleistocene climate changes at Lake Malawi, Africa  

Science.gov (United States)

The climate of tropical Africa transitioned from an interval of pronounced, orbitally-paced megadroughts to more humid and stable conditions approximately 70,000 years ago (Scholz et al., 2007). The regional atmospheric circulation patterns that accompanied these climatic changes, however, are unclear due to a paucity of continental paleoclimate records from tropical Africa extending into the last interglacial. We present a new 140-kyr record of the deuterium/hydrogen isotopic ratio of terrestrial leaf waxes (?D wax) from drill cores from Lake Malawi, southeast Africa, that spans this important climatic transition. ?D wax shifts from highly variable and relatively D-depleted to more stable and D-enriched around 56 ka, contemporary with the onset of more humid conditions in the region. Moisture source and transport history dominate the ?D wax signal at Lake Malawi, with local rainfall amount playing a secondary role for much of the paleorecord. Analysis of modern moisture sources for Lake Malawi suggests that D-depletion of waxes during the megadroughts may have been caused by an enhanced contribution of the drier, D-depleted air mass currently located in central southern Africa to the Lake Malawi catchment. This D-depleted air mass is associated with the descending limb of the Hadley cell, which implies significant changes in the Hadley circulation during the megadroughts and related changes in the position of the Intertropical Convergence Zone over Africa. These findings demonstrate the ability of ?D wax to serve as an atmospheric tracer when used in conjunction with additional proxy records for moisture balance, and elucidate potential mechanisms for pronounced hydrological change in southeast Africa during the late Pleistocene.

Konecky, Bronwen L.; Russell, James M.; Johnson, Thomas C.; Brown, Erik T.; Berke, Melissa A.; Werne, Josef P.; Huang, Yongsong

2011-12-01

91

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.

92

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

Science.gov (United States)

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.

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

2009-01-01

93

Origin and stratigraphy of phreatomagmatic deposits at the Pleistocene Sinker Butte Volcano, Western Snake River Plain, Idaho  

Science.gov (United States)

Sinker Butte is the erosional remnant of a very large basaltic tuff cone of middle Pleistocene age located at the southern edge of the western Snake River Plain. Phreatomagmatic tephras are exposed in complete sections up to 100 m thick in the walls of the Snake River Canyon, creating an unusual opportunity to study the deposits produced by this volcano through its entire sequence of explosive eruptions. The main objectives of the study were to determine the overall evolution of the Sinker Butte volcano while focusing particularly on the tephras produced by its phreatomagmatic eruptions. Toward this end, twenty-three detailed stratigraphic sections ranging from 20 to 100 m thick were examined and measured in canyon walls exposing tephras deposited around 180° of the circumference of the volcano. Three main rock units are recognized in canyon walls at Sinker Butte: a lower sequence composed of numerous thin basaltic lava flows, an intermediate sequence of phreatomagmatic tephras, and a capping sequence of welded basaltic spatter and more lava flows. We subdivide the phreatomagmatic deposits into two main parts, a series of reworked, mostly subaqueously deposited tephras and a more voluminous sequence of overlying subaerial surge and fall deposits. Most of the reworked deposits are gray in color and exhibit features such as channel scour and fill, planar-stratification, high and low angle cross-stratification, trough cross-stratification, and Bouma-turbidite sequences consistent with their being deposited in shallow standing water or in braided streams. The overlying subaerial deposits are commonly brown or orange in color due to palagonitization. They display a wide variety of bedding types and sedimentary structures consistent with deposition by base surges, wet to dry pyroclastic fall events, and water saturated debris flows. Proximal sections through the subaerial tephras exhibit large regressive cross-strata, planar bedding, and bomb sags suggesting deposition by wet base surges and tephra fallout. Medial and distal deposits consist of a thick sequence of well-bedded tephras; however, the cross-stratified base-surge deposits are thinner and interbedded within the fallout deposits. The average wavelength and amplitude of the cross strata continue to decrease with distance from the vent. These bedded surge and fall deposits grade upward into dominantly fall deposits containing 75-95% juvenile vesiculated clasts and localized layers of welded spatter, indicating a greatly reduced water-melt ratio. Overlying these "dryer" deposits are massive tuff breccias that were probably deposited as water saturated debris flows (lahars). The first appearance of rounded river gravels in these massive tuff breccias indicates downward coring of the diatreme and entrainment of country rock from lower in the stratigraphic section. The "wetter" nature of these deposits suggests a renewed source of external water. The massive deposits grade upward into wet fallout tephras and the phreatomagmatic sequence ends with a dry scoria fall deposit overlain by welded spatter and lava flows. Field observations and two new 40Ar- 39Ar incremental heating dates suggest the succession of lavas and tephra deposits exposed in this part of the Snake River canyon may all have been erupted from a closely related complex of vents at Sinker Butte. We propose that initial eruptions of lava flows built a small shield edifice that dammed or disrupted the flow of the ancestral Snake River. The shift from effusive to explosive eruptions occurred when the surface water or rising ground water gained access to the vent. As the river cut a new channel around the lava dam, water levels dropped and the volcano returned to an effusive style of eruption.

Brand, Brittany D.; White, Craig M.

2007-02-01

94

Late Pleistocene Slip Rates Along the Panamint Valley Fault Zone, Eastern California  

Science.gov (United States)

In an effort to assess the rate of shear across eastern California during the Late Pleistocne, we present new slip rate estimates from the central and southern Panamint Valley fault zone (PVFZ). We utilize displaced alluvial deposits at two localities along the southern portion of the fault system and reconstruct fault slip from field surveys and airborne LiDAR topography. Chronologic control is provided by radiocarbon dating of lacustrine tufa associated with shoreline deposits, soil development, and terrestrial cosmogenic nuclide (10Be) dating of alluvial fan surfaces. Together, these provide the first radiometric control for slip-rate estimates along this major fault system. The PVFZ is characterized by dextral, oblique-normal displacement along a moderately to shallowly-dipping range front fault. Along the range front, high-angle faults offset late Pleistocene alluvial and lacustrine surfaces. In southern Panamint Valley, near Manly Canyon, oblique-slip appears to be partitioned into fault strands with primarily right lateral and normal slip. The same fan surface is displaced by ~10m along the normal fault and debris-flow levees are right-laterally offset by ~26m. 10Be surface exposure ages from unweathered boulders suggest a maximum surface age of 14 ka, consistent with soil characteristics and cross-cutting relationships with shoreline features. Our results suggest a minimum slip rate ~ 1.75-2 mm/yr at Manly Canyon. Near Happy Canyon, a releasing step in the fault zone forms a 2-3 km long embayment where displacement on NE-trending faults is dip-slip, affording an opportunity to constrain fault displacement directly from the vertical offset of varying fan surfaces. Cosmogenic 10Be surface clast dating of the oldest fan suggests a surface age of 30-35 ka, whereas the youngest inset surface appears to have been deposited synchronously with a shallow MIS stage 2 lake (~15-25 ka). We are working to refine this estimate with additional dating from multiple depth profiles, radiocarbon from tufa samples, and soil characterization, but our preliminary estimates suggest a minimum oblique- slip rate of 1.5-2 mm/yr at Happy Canyon. Although our results confirm that the PVFZ accommodates a significant component of right-lateral shear in eastern California, it remains difficult to reconcile geologic slip rates along structures north of the Garlock fault with the total rate of shear observed geodetically.

Hoffman, W.; Kirby, E.; McDonald, E.; Walker, J. D.; Gosse, J.

2009-12-01

95

Late cenozoic fluvial stratigraphy of the New Jersey piedmont: A record of glacioeustasy, planation, and incision on a low-relief passive margin  

Science.gov (United States)

Late Cenozoic fluvial deposits and erosional landforms in the New Jersey Piedmont record two episodes of valley incision, one in the Late Miocene and one in the Early Pleistocene, separated by periods of planation and fluvial deposition. The upland erosion surface and a fluvial gravel are the remnants of a low-relief Late Miocene landscape. Late Miocene incision was followed by deposition of a fluvial plain and cutting of straths in the Pliocene. Early Pleistocene incision produced the present valleys, which contain Middle to Late Pleistocene fluvial deposits. The two incisions correspond to permanent glacioeustatic lowering during expansion of the Antarctic ice sheet in the Middle to Late Miocene and development of Northern Hemisphere ice sheets in the Late Pliocene. Bordering Coastal Plain marine deposits indicate that the upland erosion surface was formed during a rising sea-level trend between the Late Oligocene and Middle Miocene. The Pliocene plain and straths formed during a period of rising sea level in the Early Pliocene. The stratigraphic record indicates that the oldest preserved landforms are no older than Late Miocene, that landscape planation in coastal regions of low-relief passive margins can be achieved in <20 m.yr., and that these surfaces can be incised and dissected in <5 m.yr.

Stanford, S.D.; Ashley, G.M.; Brenner, G.J.

2001-01-01

96

Late Miocene to Pleistocene potassic volcanism in the Republic of Macedonia  

Science.gov (United States)

The potassic (K) to ultrapotassic (UK) volcanic rocks cropping out in the Vardar Zone of Macedonia and southern Serbia span in age from Late Miocene (6.57 ??) to Pleistocene (1.47 ??). The main identified outcrops are in the Kumanovo, Sveti Nikole, Shtip and Demir Kapia areas; the southernmost occurrences of these volcanic rocks are located in the large Kozuf Massif (Voras Massif in Greece) at the Macedonia Greek border. Three distinct groups may be distinguished. The first group has a shoshonitic affinity and occurs in the Kozuf Massif (LMg-K group); it includes shoshonites to rare rhyolites, with latites and trachytes being the most widespread products. The second group consists of potassic rocks (HMg-K group, K2O/Na2O between 1.0 and 1.8) occurring in both southern Serbia (Cer and Slavujevci) and Macedonia (Djuristhe, near Sveti Nikole). The third group, present only in Macedonia, consists of ultrapotassic rocks (UK group, K2O/Na2O >1.8, Mg# >71) classified as UK shoshonites, UK latites and UK phonotephrites; overall, they show a “Roman Province type” affinity (Group III of Foley, Venturelli, Green, Toscani, Earth Sci Rev 24:81 134, 1987). Geochemically, the studied rocks exhibit strong enrichment in LILE, Th and Pb, as well as relative depletion in Ta Nb and Hf; such signatures are typical of magmas generated in convergent geotectonic settings. In the HMg-K and UK rocks, Sr and Nd isotopic ratios vary from 0.70768 to 0.71040, and 0.51243 to 0.512149, respectively. The rocks of the LMg-K group show relatively limited Sr and Nd isotope variations (0.7087 0.7093 and 0.51233 0.51229), which correlate with a decrease in MgO and increase in SiO2 contents. The geochemical features of the LMg-K volcanic rocks indicate that their evolution was mainly driven by fractional crystallization coupled with contamination by feldspar-rich crustal materials. In contrast, the HMg-K and UK rocks have not been significantly modified by crustal contamination, and their geochemical features are considered to reflect lithospheric mantle heterogeneity acquired during the subduction of the Western Vardar Ocean and the Apulian plate. The metasomatizing agent was apparently more enriched in Zr, Th, Ta and Ce than in fluid-mobile elements, such as Pb and Cs, suggesting that it was characterized by a high melt/fluid ratio. The potassic and ultrapotassic magmatic activity developed in response to the Pliocene Pleistocene extension in the Vardar Zone, in turn related to the opposite propagation of extension in the Aegean and Pannonian basins (respectively SW and NE).

Yanev, Yotzo; Boev, Blazo; Doglioni, Carlo; Innocenti, Fabrizio; Manetti, Piero; Pecskay, Zoltan; Tonarini, Sonia; D'Orazio, Massimo

2008-09-01

97

A review and synthesis of late Pleistocene extinction modeling: progress delayed by mismatches between ecological realism, interpretation, and methodological transparency.  

Science.gov (United States)

Late Pleistocene extinctions occurred globally over a period of about 50,000 years, primarily affecting mammals of > or = 44 kg body mass (i.e., megafauna) first in Australia, continuing in Eurasia and, finally, in the Americas. Polarized debate about the cause(s) of the extinctions centers on the role of climate change and anthropogenic factors (especially hunting). Since the late 1960s, investigators have developed mathematical models to simulate the ecological interactions that might have contributed to the extinctions. Here, we provide an overview of the various methodologies used and conclusions reached in the modeling literature, addressing both the strengths and weaknesses of modeling as an explanatory tool. Although late Pleistocene extinction models now provide a solid foundation for viable future work, we conclude, first, that single models offer less compelling support for their respective explanatory hypotheses than many realize; second, that disparities in methodology (both in terms of model parameterization and design) prevent meaningful comparison between models and, more generally, progress from model to model in increasing our understanding of these extinctions; and third, that recent models have been presented and possibly developed without sufficient regard for the transparency of design that facilitates scientific progress. PMID:24984323

Yule, Jeffrey V; Fournier, Robert J; Jensen, Christopher X J; Yang, Jinyan

2014-06-01

98

Carbon and oxygen stable isotope compositions of late Pleistocene mammal teeth from dolines of Ajoie (Northwestern Switzerland)  

Science.gov (United States)

Fossils of megaherbivores from eight late Pleistocene 14C- and OSL-dated doline infillings of Ajoie (NW Switzerland) were discovered along the Transjurane highway in the Swiss Jura. Carbon and oxygen analyses of enamel were performed on forty-six teeth of large mammals (Equus germanicus, Mammuthus primigenius, Coelodonta antiquitatis, and Bison priscus), coming from one doline in Boncourt (~ 80 ka, marine oxygen isotope stage MIS5a) and seven in Courtedoux (51-27 ka, late MIS3), in order to reconstruct the paleoclimatic and paleoenvironmental conditions of the region. Similar enamel ?13C values for both periods, ranging from - 14.5 to - 9.2‰, indicate that the megaherbivores lived in a C3 plant-dominated environment. Enamel ?18OPO4 values range from 10.9 to 16.3‰ with a mean of 13.5 ± 1.0‰ (n = 46). Mean air temperatures (MATs) were inferred using species-specific ?18OPO4-?18OH2O-calibrations for modern mammals and a present-day precipitation ?18OH2O-MAT relation for Switzerland. Similar average MATs of 6.6 ± 3.6°C for the deposits dated to ~ 80 ka and 6.5 ± 3.3°C for those dated to the interval 51-27 ka were estimated. This suggests that these mammals in the Ajoie area lived in mild periods of the late Pleistocene with MATs only about 2.5°C lower than modern-day temperatures.

Scherler, Laureline; Tütken, Thomas; Becker, Damien

2014-09-01

99

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

Science.gov (United States)

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.

Storer, John E.

2003-07-01

100

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

Science.gov (United States)

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.

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

2002-01-01

 
 
 
 
101

Earthquake recurrences since late Pleistocene in Nankai Trough off Kumano: A preliminary result on Site C0006, IODP Exp.316  

Science.gov (United States)

The Nankai Trough has a 1,300-year record of generating large earthquakes (Mw>8) with a recurrence time of ~100-200 yr, but unfortunately, we haven’t known the frequency of earthquakes before that. Results from recent expeditions of NanTroSEIZE Stage 1 IODP 314/315/316 recovered many cycles of turbidites since late Pleistocene, which are triggered during past earthquake shaking. Site C0006 is near to deep Nankai Trough so that most of earthquake-triggered deposits have been drilled into in this site. Our purpose is to investigate the history of earthquakes since late Pleistocene via these earthquake-triggered event deposits, including turbidites, debris, slope failures and so on. Due to unique backgrounds, they are suggested little other triggers except for earthquakes. After integrating core-log-seismic data and any other available data, e.g. biostratigraphy, the correlations among all of holes were done so that we acquired the records of earthquakes as whole as possible. In details, stratum and fault reflections in 3D seismic data are illuminated for the interpretation of lithostratigraphy, structural patterns, and the integration between core and LWD data. Some of these reflections become key boundaries. The integration of cores with LWD data has been referenced to seismic profiles relying primarily on comparison between NGR, P-wave velocity logs from multi-sensor core logger for whole round cores (MSCL-W) and Gamma ray, Sonic logs from LWD datasets. The depth transfer functions were defined by linear regression between correlated peaks. Finally, the LWD data from Hole C0006B have been used to create synthetic LWD logs for the locations of Holes C0006D and C0006E to patch the gap of sedimentary sequence due to core recovery. In order to dating those gravity sediments, considering of the possibility of little microfossils at somewhere, the exact location of event-beds and applicable ranges of dating methods, we detected luminescence dating for sandstones in them to supplement and reinforce the high resolution age profile. Combined with paleontologic and paleomagnetic data, high-resolution and continuous age profile since late Pleistocene was obtained. In results, we can know the earthquake recurrences since late Pleistocene in Nankai Trough, which should be useful to statistic earthquake prediction. This work is supported by J-DESC (Japan Drilling Earth Science Consortium) and the National Natural Science Foundations of China (No. 40806019 and 40876022).

Jiang, T.; Li, S.; Li, C.; Xie, X.; Su, X.; Ren, J.

2009-12-01

102

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

Energy Technology Data Exchange (ETDEWEB)

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). {sup 1}4C 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.

Calmel-Avila, M.; Silva, P. G.; Bardaji, T.; Goy, J. L.; Zazo, C.

2009-07-01

103

Strontium and carbon isotope stratigraphy of the Late Jurassic shallow marine limestone in western Palaeo-Pacific, northwest Borneo  

Science.gov (United States)

Strontium and carbon isotope stratigraphy was applied to a 202 m-thick shallow marine carbonate section within the Late Jurassic Bau Limestone at the SSF quarry in northwest Borneo, Malaysia, which was deposited in the western Palaeo-Pacific. Strontium isotopic ratios of rudist specimens suggest that the SSF section was formed between the latest Oxfordian (155.95 Ma) and the Late Kimmeridgian (152.70 Ma), which is consistent with previous biostratigraphy. The ?13Ccarb values of bulk carbonate range from -0.10 to +2.28‰ and generally show an increasing upward trend in the lower part of the section and a decreasing upward trend in the upper part of the section. A comparable pattern is preserved in the ?13Corg isotope record. Limestone samples of the SSF section mainly preserve the initial ?13Ccarb values, except for the interval 84-92 m, where an apparent negative anomaly likely developed as a result of meteoric diagenesis. Comparing with the Tethyan ?13Ccarb profile, a negative anomaly in the lower SSF section can be correlated with the lowered ?13C values around the Oxfordian/Kimmeridgian boundary. In addition, ?13Ccarb values of the Bau Limestone are generally ?1‰ lower than the Tethyan values, but comparable with the values reported from Scotland and Russia, located in Boreal realm during the Late Jurassic. This suggests that either the Tethyan record or the other records have been affected by the ?13C values of regionally variable dissolved inorganic carbon (DIC). The Late Jurassic ?13CDIC values are thought to have been regionally variable as a result of their palaeoceanographic settings. This study shows that ?13C chemostratigraphy of the Palaeo-Pacific region contributes to an improved understanding of global carbon cycling and oceanography during this time period.

Kakizaki, Yoshihiro; Weissert, Helmut; Hasegawa, Takashi; Ishikawa, Tsuyoshi; Matsuoka, Jun; Kano, Akihiro

2013-09-01

104

Multi-proxy evidence for Late Pleistocene-Holocene climatic and environmental changes in Lop-Nur, Xinjiang, Northwest China  

Science.gov (United States)

A 10.35-m-long sediment core from the Luobei depression in Lop-Nur, Xinjiang, Northwest China, provides detailed information about environmental changes during the Late Pleistocene. The samples taken every 5 cm of the core were analyzed for 10 environmental proxies, including magnetic susceptibility, granularity, chroma, carbonate and loss on ignition (LOI), and pH value. The chronology data are provided by the uranium/thorium disequilibrium dates. The sediments of the section were deposited during the last 32000 years. The results of analysis of 10 proxies were examined using multivariate statistical analysis, and the principal components were calculated. According to the results, the Late Pleistocene sequence contains four climatic and environmental stages appearing in the cycles of cold-wet and warm-dry changes. During 10-9 ka BP, it was the earliest warm episode in the Holocene. Environmental changes in this district were restricted by global change, as suggested by the analysis of glacial-interglacial cycles. But it was different from the mutative trend of a monsoon region in East China because of its own characteristics, which was the situation of cold-wet and warm-dry climate-environment change. The candidate reason may be the uplift of the Tibet Plateau and the westerly wind circulation. ?? Science Press, Institute of Geochemistry, CAS and Springer-Verlag GmbH 2008.

Luo, C.; Yang, D.; Peng, Z.; Zhang, Z.; Weiguo, L.; He, J.; Zhou, C.

2008-01-01

105

Late Neogene stratigraphy and tectonic control on facies evolution in the Laguna Salada Basin, northern Baja California, Mexico  

Science.gov (United States)

The Laguna Salada Basin (LSB) in northeastern Baja California records late-Neogene marine incursions in the Salton Trough and progradation of the Colorado River delta. Early subsidence and subsequent tectonic erosion are related to evolution of the Sierra El Mayor detachment fault during late Miocene time (Laguna Salada Basin and from three exploratory wells allows reconstruction of the main sedimentary and tectonic events. Marine mudstone and sandstone, and subordinate conglomerate of the Imperial Formation tectonically overlie metamorphic and granitic basement. Microfossils, lithology, and sedimentary structures in the Imperial Formation define Upper Miocene (Laguna Salada fault and rapid uplift of Sierra Cucapa and Sierra El Mayor. Up to 2 km of Quaternary alluvial-fan and lacustrine deposits accumulated along the eastern margin of LSB, whereas lower subsidence rates produced a thinner sedimentary wedge over a ramp-like crystalline basement along the western margin. In early Pleistocene time (˜2-1 Ma), the Laguna Salada became progressively isolated from the Colorado River delta complex, and the Salton Trough by activity on the Elsinore and Laguna Salada fault zones.

Martín-Barajas, A.; Vázquez-Hernández, S.; Carreño, A. L.; Helenes, J.; Suárez-Vidal, F.; Alvarez-Rosales, J.

2001-10-01

106

Quaternary Stratigraphy, Drainage-Basin Development, and Geomorphology of the Lake Manix Basin, Mojave Desert: Guidebook for Fall Field Trip, Friends of the Pleistocene, Pacific Cell, October 4-7, 2007  

Science.gov (United States)

The 2007 field trip of the Pacific Cell, Friends of the Pleistocene, visited features of the Quaternary geology and geomorphology of the Lake Manix basin in the Mojave Desert. This report is the guidebook for this trip and includes some discussion of relations observable along the road and at various field trip stops. The Mojave River originates in the San Bernardino Mountains and in high-water years flows north and east to its terminus in Silver Lake playa north of Baker, Calif. Along this course, the river passes through or near several basins that were internally drained prior to integration by the Mojave River, including the Victorville, Harper, Manix, and Soda Lake basins. Sediments in the Lake Manix basin record Mojave River discharge and lake fluctuations that began during the middle Pleistocene and continued through most of the late Pleistocene.

Reheis, Marith C.; Miller, David M.; Redwine, Joanna L.

2007-01-01

107

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

Science.gov (United States)

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.

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

2014-05-01

108

Dynamics of the late Plio-Pleistocene West Antarctic Ice Sheet documented in subglacial diamictites, AND-1B drill core  

Science.gov (United States)

Geologic studies of sediment deposited by glaciers can provide crucial insights into the subglacial environment. We studied muddy diamictites in the ANtarctic geological DRILLing (ANDRILL) AND-1B drill core, acquired from beneath the Ross Ice Shelf in McMurdo Sound, with the aim of identifying paleo-ice stream activity in the Plio-Pleistocene. Glacial advances were identified from glacial surfaces of erosion (GSEs) and subglacial diamictites within three complete sequences were investigated using lithofacies associations, micromorphology, and quartz sand grain microtextures. Whereas conditions in the Late Pliocene resemble the modern Greenland Ice Sheet where fast flowing glaciers lubricated by surface meltwater terminate directly in the sea (interval 201-212 mbsl) conditions in the Late Pleistocene are similar to modern West Antarctic Ice Sheet (WAIS) ice streams (38-49 mbsl). We identify the latter from ductile deformation and high pore-water pressure, which resulted in pervasive rotation and formation of till pellets and low relief, rounded sand grains dominated by abrasion. In the transitional period during the Mid-Pleistocene (55-68 mbsf), a slow moving inland ice sheet deposited tills with brittle deformation, producing lineations and bi-masepic and unistrial plasma fabric, along with high relief, conchoidally fractured quartz grains. Changes in the provenance of gravel to cobble-size clasts support a distant source area of Byrd Glacier for fast-flowing paleo-ice streams and a proximal area between Darwin and Skelton Glaciers for the slow-moving inland ice sheet. This difference in till provenance documents a shift in direction of glacial flow at the core site, which indirectly reflects changes in the size and thickness of the WAIS. Hence, we found that fast ice streaming motion is a consequence of a thicker WAIS pushing flow lines to the west and introducing clasts from the Byrd Glacier source area to the drill site. The detailed analysis of diamictites in AND-1B demonstrates that Pliocene glacial intervals were warmer than in the Pleistocene when polar ice sheets grew from local inland ice to regional ice streams.

Cowan, Ellen A.; Christoffersen, Poul; Powell, Ross D.; Talarico, Franco M.

2014-08-01

109

Stratigraphy and fission track ages of late Cretaceous to Paleogene tertiary volcanic rocks  

International Nuclear Information System (INIS)

Downstream of riber Hime correspond to the northern-most of Itoigawa-Shizuoka tectonic line (ISTL). On the west side of ISTL, late Cretaceous to Neogene formations are distributed and they are divided into five formations, namely Akahageyama sandstone, Ipponmatsuyama sandstone, Ishizaka rhyolite, Yamato and Imai. The distribution of igneous rocks of those formations are scattered by elevation of base rock followed by erosion, and Neogene deposition. Additionally, fossils are very rare. Consequently, the time correlation of formation which has important meaning for the formation process of Fossa Magna, was impossible. Fission track age determination of late Cretaceous to Paleogene igneous rocks were carried out using ''external detection method''. The results were 94.2 ± 5.9 Ma for Akahageyama formation; 66.4 ± 2.4 Ma for Ipponmatsuyama formation; 54.7 ± 1.9 Ma for Ishizaka formation; 74.8 ± 2.9 Ma for Azakiri; 55.7 ± 2.3 Ma for Sasagawa tuff formation; 92.7 ± 5.9 Ma for Omi granite and 62.2 ± 3.5 Ma for garnet porphylite. From obtained ages along with stratigraphical studies of the region, the late Cretaceous to Neogene igneous activities in the northern area along ISTL were found to be devided into 4 periods: 1) plutonic activity in early Cretaceous, Omi granite, 2) local andestic volcanism from the end of late Cretaceous to early Paleocene characterized by Ipponmatsuyama formation, 3) wide acidic volcanism from late Paleocene to early Eocene, characterized by Ishizaka rhyolite and 4) middle Miocene volcanism, so-called ''Green tuff'' movement. (Ishimitsu, A.)

110

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

Science.gov (United States)

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).

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

2013-12-01

111

The late Pleistocene environment of the Eastern West Beringia based on the principal section at the Main River, Chukotka  

DEFF Research Database (Denmark)

Chukotka is a key region for understanding both Quaternary environmental history and transcontinental migrations of flora and fauna during the Pleistocene as it lies at the far eastern edge of Asia bordering the Bering Sea. The now submerged land bridge is the least understood region of Beringia yet the most critical to understanding migrations between the Old and New Worlds. The insect fauna of the Main River Ledovy Obryv (Ice Bluff) section, which is late Pleistocene in age (MIS 3-2), is markedly different from coeval faunas of areas further to the west, as it is characterized by very few thermophilous steppe elements. From the fauna we reconstruct a steppe-tundra environment and relatively cold conditions; the reconstructed environment was moister than that of typical steppe-tundra described from further west. The data from this locality, if typical of the Chukotka Peninsula as a whole, may indicate that a barrier associated with the environments of the land bridge restricted trans-Beringian migrations, particularly the more thermophilous and xeric-adapted elements of the Beringian biota, supporting the hypothesis of a cool but moist land-bridge filter inferred from evidence from several other studies.

Kuzmina, Svetlana A.; Sher, Andrei V.

2011-01-01

112

Stratigraphy and complex fluvial geomorphology in a Middle and Late Pleistocene endmoraine setting of the European Alpine Foreland  

Science.gov (United States)

The Alpine Foreland was repeatedly covered by massive Piedmont glaciers during Quaternary peak glacial periods. Glacial and associated glaciofluvial landforms are especially well preserved in the area of the former Salzach Piedmont glacier (Austria/Germany), where remnants of at least 4 glacial maxima, minor anthropogenic overprint and comprehensive geological and topographic data provide a unique opportunity to study glacial and glaciofluvial sediment/landform associations. In this presentation we focus on a local setting containing deposits from the last ("Würm"; MIS 2) and penultimate ("Riß"; MIS 6) glacial maximum. Foreland glacier area, typically representing sediment/landform associations at the glacial lobe terminus. Specifically, we investigate the transition from the endmoraine system to the glaciofluvial outwash in order to make statements on the internal built up, the timing and the subsequent degradation associated with glaciofluvial reorganization during deglaciation. Investigations were carried out using outcrop information, drillcore logs, near-surface geophysics (ground penetrating radar and seismic refraction), as well as luminescence dating of selected sand-sized samples. The geometry and lateral extension of remnants of a thick interglacial paleosol were investigated using core log information and terrestrial lascerscan data. Detailed topographical information benefitted from high resolution airborne laserscan imagery. We identify two main glaciofluvial depositional systems for the LGM: (i) sheet flow dominated landforms (i.e. alluvial fans) broadly attached to the end moraine system and (ii) braided river deposits from meltwater streams initiating at distinct meltwater outlets. Our first results point to a very short period of active deposition. With the onset of deglaciation and ice meltdown back into the tongue basin, partial degradation of deposits started, leading to multiple terrace level formation along the meltwater pathways. Where sheet flow of the LGM dominates, it overlies MIS6-deposits almost without any unconformity well preserving thick and laterally extensive paleosol deposits.

Salcher, Bernhard; Joachim, Götz; Reinhard, Starnberger

2014-05-01

113

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

Science.gov (United States)

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.

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

2014-07-01

114

Assessing the impact of late Pleistocene megafaunal extinctions on global vegetation and climate  

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Full Text Available The end of the Pleistocene was a turning point for the Earth system as climate gradually emerged from millennia of severe glaciation in the Northern Hemisphere. The deglacial climate change coincided with an unprecedented decline in many species of Pleistocene megafauna, including the near-total eradication of the woolly mammoth. Due to an herbivorous diet that presumably involved large-scale tree grazing, the mammoth extinction has been associated with the rapid expansion of dwarf deciduous trees in Siberia and Beringia, thus potentially contributing to the changing climate of the period. In this study, we use the University of Victoria Earth System Climate Model (UVic ESCM to simulate the possible effects of these extinctions on climate during the latest deglacial period. We have explored various hypothetical scenarios of forest expansion in the northern high latitudes, quantifying the biogeophysical effects in terms of changes in surface albedo and air temperature. These scenarios include a Maximum Impact Scenario (MIS which simulates the greatest possible post-extinction reforestation in the model, and sensitivity tests which investigate the timing of extinction, the fraction of trees grazed by mammoths, and the southern extent of mammoth habitats. We also show the results of a simulation with free atmospheric CO2-carbon cycle interactions. For the MIS, we obtained a surface albedo increase and global warming of 0.006 and 0.175 °C, respectively. Less extreme scenarios produced smaller global mean temperature changes, though local warming in some locations exceeded 0.3 °C even in the more realistic extinction scenarios. In the free CO2 simulation, the biogeophysical-induced warming was amplified by a biogeochemical effect, whereby the replacement of high-latitude tundra with shrub forest led to a release of soil carbon to the atmosphere and a small atmospheric CO2 increase. Overall, our results suggest the potential for a small, though non-trivial, effect of megafaunal extinctions on Pleistocene climate.

M.-O. Brault

2013-08-01

115

Late Holocene Soil Stratigraphy and Geochronology of Alluvial Sedimentation in the Sonoran Desert, Arizona  

Science.gov (United States)

The integration of soil stratigraphic investigations and radiocarbon dating at two sites in combination with geomorphic mapping at scales of 1:50k and 1:5k offer insight to the timing and magnitude of alluvial sedimentation during the late Holocene within the Sonoran Desert near Yuma, Arizona. Mapping at 1:50k was performed over an area of 3400 km2 and alluvial landforms were labeled Qf1 to Qf5, from oldest to youngest, using 1- and 5-meter resolution satellite imagery within the U.S. Army Yuma Proving Ground (YPG). Approximately 70% of the identified landforms within YPG are Quaternary alluvial fans, alluvial plains, and active washes, whereas the other 30% consist of mountain highlands, pediments, and badlands. In the southwest portion of YPG near Muggins Mountains, alluvial fan terraces (Qf4) positioned 0.5 m above active washes are characterized as having moderate bar-and-swale microtopography, moderately developed desert pavement, and a Av/ Bw/ Cky/ Cky1/ Cky2/ Cky3 gravelly soil profile. A large piece of charcoalized Ironwood ( Olneya tesota) was recovered from a depth of 0.75 m and yielded three AMS 14C dates that range from 3330 to 2860 cal yr B.P. Geomorphic mapping at a scale of 1:5k indicates that in an area of 25 km2 at the site, the distribution of late Holocene alluvial fan terraces comprise 17% of the surrounding Quaternary alluvium. Similar aged alluvial features were observed about 70 km to the north near South Trigo Peak at YPG. Terraces of a broad and flat alluvial plain positioned 0.5 m above active channels are characterized as having moderate bar- and-swale microtopography, poorly developed desert pavement, and a AC/ C/ Bwkb1/ Bwk1b2/ Bwk2b2/ BCkb2/ Bwkb3 sandy soil profile. A terrestrial gastropod shell ( Lymnea sp.) fragment was recovered from a depth of 0.5 m and yielded an AMS 14C date of 2360-2310 cal yr B.P. Additional geomorphic mapping at 1:5k shows that in an area of 30 km2, the distribution of late Holocene alluvial plain terraces and equivalent alluvial fans include 35% of the surrounding Quaternary alluvium. Of the total Quaternary alluvium identified at 1:50k, 10% of the landforms consist of gravelly alluvial fans and sandy alluvial plains deposited between 3330 and 2310 cal yr B.P. The numerical ages and associated soil development provide evidence of regional alluvial sedimentation near Yuma, Arizona, and provides well constrained geomorphic data for paleoclimatic modeling in the Sonoran Desert during the late Holocene.

Bacon, S. N.; McDonald, E. V.; Dalldorf, G. K.; Caldwell, T. G.

2007-12-01

116

Discovery of Homo sp. tooth associated with a mammalian cave fauna of Late Middle Pleistocene age, northern Thailand.  

Science.gov (United States)

In the context of a Thai-French paleontological project, a single human tooth, a right upper fourth premolar, has been discovered in Northern Thailand among mammalian fossil remains excavated from the "Thum Wiman Nakin" cave. Based on the fauna associated with the human tooth and the Uranium/Thorium datings from the overlying calcite beds, we attribute this site to the Late Middle Pleistocene. The human tooth was compared with teeth of Chinese and Javanese Homo erectus, Homo sapiens neanderthalensis and Homo sapiens sapiens as well as teeth of apes (Orang-utan). The tooth has archaic features of the crown which are similar to Homo erectus. It also has derived features of the root which makes it aligns with Neanderthals and modern humans. Consequently, it has been tentatively attributed to Homo sp. Homo remains have not been previously reported from Thailand, and the specimen described here is therefore the first and oldest fossil human remain from this country. PMID:9680466

Tougard, C; Jaeger, J J

1998-07-01

117

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

Directory of Open Access Journals (Sweden)

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.

Esther Jacobson-Tepfer

2013-09-01

118

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1999-10-01

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

Science.gov (United States)

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) < Pedon 2 < Pedon 1, reflected e. g. in increasing Fed/Fet ratios, decreasing molar ratios of (Ca+K+Na)/Al, and decreasing pH. However, it needs to be considered that lapilli are more readily weatherable than gneiss fragments. The profile morphology of the paleosol, characterized by reddish-brown color (7.5YR), strong angular blocky structure and well-expressed illuvial clay coatings, rather indicates that it developed over a longer time-span and/or warmer climate than the two yellowish-brown surface soils. Since the morphology of the paleosol clearly reflects interglacial climatic conditions and 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.

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

2014-05-01

120

Sedimentology and sequence stratigraphy of the Lopingian (Late Permian) coal measures in southwestern China  

Energy Technology Data Exchange (ETDEWEB)

The Lopingian coal measures of southwestern China were deposited within a range of facies associations spanning a spectrum of settings from fluvial to marine carbonate platform. The transitional to terrestrial coal measures are dominated by siliciclastics, but they also contain fifteen laterally extensive marine bands (limestone beds and mudstone). These bands act as marker horizons that enable correlation between fully marine and terrestrial facies. Examination of this range of facies and their sedimentology has enabled the development of a high-resolution sequence stratigraphic framework. Set against the established backdrop of second-order Lopingian transgression, sixteen fourth-order sequences and three composite sequences (third-order) are recognized. Results show that, in the composite sequences, peat accumulation in the seaward parts of the study area predominantly correlates with early transgressive sequence sets (TSS), while in more landward areas it correlates with the middle TSS to late highstand sequence sets (HSS). Differences in peat-accumulation regimes within the sequence stratigraphic framework are attributed to variations in subsidence and background siliciclastic input rates in different depositional settings, with these combining to produce differences in the rate of accommodation change. The preservation of coal resources in the middle to late HSS in this area was most likely related to the rise of the regional base level throughout the Lopingian. (author)

Wang, Hao [School of Geosciences and Surveying Engineering, China University of Mining and Technology, Beijing (China); School of Earth and Environment, University of Leeds (United Kingdom); Shao, Longyi; Hao, Liming; Zhang, Pengfei [School of Geosciences and Surveying Engineering, China University of Mining and Technology, Beijing (China); Glasspool, Ian J. [Department of Geology, Field Museum of Natural History, Chicago, Illinois (United States); Wheeley, James R.; Hilton, Jason [School of Geography, Earth and Environmental Sciences, University of Birmingham (United Kingdom); Wignall, Paul B. [School of Earth and Environment, University of Leeds (United Kingdom); Yi, Tongsheng [Guizhou Bureau of Coal Geological Exploration, Guiyang, Guizhou (China); Zhang, Mingquan [Coal Geology and Prospecting Institute of Yunnan Province, Kunming, Yunnan (China)

2011-01-01

 
 
 
 
121

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

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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.

Tiiu Koff

2011-06-01

122

Stratigraphy and facies development of the marine Late Devonian near the Boulongour Reservoir, northwest Xinjiang, China  

Science.gov (United States)

Late Devonian to Early Carboniferous stratigraphic units within the 'Zhulumute' Formation, Hongguleleng Formation (stratotype), 'Hebukehe' Formation and the Heishantou Formation near the Boulongour Reservoir in northwestern Xinjiang are fossil-rich. The Hongguleleng and 'Hebukehe' formations are biostratigraphically well constrained by microfossils from the latest Frasnian linguiformis to mid-Famennian trachytera conodont biozones. The Hongguleleng Formation (96.8 m) is characterized by bioclastic argillaceous limestones and marls (the dominant facies) intercalated with green spiculitic calcareous shales. It yields abundant and highly diverse faunas of bryozoans, brachiopods and crinoids with subordinate solitary rugose corals, ostracods, trilobites, conodonts and other fish teeth. The succeeding 'Hebukehe' Formation (95.7 m) consists of siltstones, mudstones, arenites and intervals of bioclastic limestone (e.g. 'Blastoid Hill') and cherts with radiolarians. A diverse ichnofauna, phacopid trilobites, echinoderms (crinoids and blastoids) together with brachiopods, ostracods, bryozoans and rare cephalopods have been collected from this interval. Analysis of geochemical data, microfacies and especially the distribution of marine organisms, which are not described in detail here, but used for facies analysis, indicate a deepening of the depositional environment at the Boulongour Reservoir section. Results presented here concern mainly the sedimentological and stratigraphical context of the investigated section. Additionally, one Late Devonian palaeo-oceanic and biotic event, the Upper Kellwasser Event is recognized near the section base.

Suttner, Thomas J.; Kido, Erika; Chen, Xiuqin; Mawson, Ruth; Waters, Johnny A.; Frýda, Ji?í; Mathieson, David; Molloy, Peter D.; Pickett, John; Webster, Gary D.; Frýdová, Barbora

2014-02-01

123

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1989-03-01

124

Rock-magnetic study of Late Pleistocene-Holocene sediments from the Babícora lacustrine basin, Chihuahua, northern Mexico  

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Full Text Available Rock-magnetic and sedimentological studies of the Quaternary sequence of lake Babícora (29.4°N, 107.7°W; 2,100 m a.s.l. from Late Wisconsin to Holocene are reported. Two vertical profiles have been studied. Magnetic susceptibilities and natural remanence (NRM and isothermal remanence (IRM intensities correlate with sand, silt and clay contents in the sediments, suggesting that magnetic minerals are allogenic. IRM acquisition curves and alternating field coercivity spectra document the occurrence of Ti-poor titanomagnetites, hematites and iron-hydroxides. The fluctuations in the input of sedi¬ment correlate with changes in erosional processes, climate and tectonics in the catchment basin. Five radiocarbon dates ranging from 4,346 to 16,343 yr B.P. were obtained. The southern profile covers a longer time span than the western pro¬file, which spans from 11,000 to 6,000 yr B.P., when the lake extended over a larger area. Two major periods of increased rainfall and high lake levels in Late Pleistocene and Early Holocene are recognized. The Late Wisconsin wet period was fol¬lowed by gradual drying up to around 6,000 yr B.P. Between 11,000 and 8,000 yr B.P. there was another wet period, related to increased summer rainfall. The dry period between 3,000 and 2,000 yr B.P. was followed by widespread erosion.

R. Cruz-Gatica

1997-01-01

125

Reconstructing late Pliocene to middle Pleistocene Death Valley lakes and river systems as a test of pupfish (Cyprinodontidae) dispersal hypotheses  

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During glacial (pluvial) climatic periods, Death Valley is hypothesized to have episodically been the terminus for the Amargosa, Owens, and Mojave Rivers. Geological and biological studies have tended to support this hypothesis and a hydrological link that included the Colorado River, allowing dispersal of pupfish throughout southeastern California and western Nevada. Recent mitochondrial deoxyribonucleic acid (mtDNA) studies show a common pupfish (Cyprinodontidae) ancestry in this region with divergence beginning 3-2 Ma. We present tephrochronologic and paleomagnetic data in the context of testing the paleohydrologic connections with respect to the common collection point of the Amargosa, Owens, and Mojave Rivers in Death during successive time periods: (1) the late Pliocene to early Pleistocene (3-2 Ma), (2) early to middle Pleistocene (1.2-0.5 Ma), and (3) middle to late Pleistocene (<0.70.03 Ma; paleolakes Manly and Mojave). Using the 3.35 Ma Zabriskie Wash tuff and 3.28 Ma Nomlaki Tuff Member of the Tuscan and Tehama Formations, which are prominent marker beds in the region, we conclude that at 3-2 Ma, a narrow lake occupied the ancient Furnace Creek Basin and that Death Valley was not hydrologically connected with the Amargosa or Mojave Rivers. A paucity of data for Panamint Valley does not allow us to evaluate an Owens River connection to Death Valley ca. 3-2 Ma. Studies by others have shown that Death Valley was not hydrologically linked to the Amargosa, Owens, or Mojave Rivers from 1.2 to 0.5 Ma. We found no evidence that Lake Manly flooded back up the Mojave River to pluvial Lake Mojave between 0.18 and 0.12 Ma, although surface water flowed from the Amargosa and Owens Rivers to Death Valley at this time. There is also no evidence for a connection of the Owens, Amargosa, or Mojave Rivers to the Colorado River in the last 3-2 m.y. Therefore, the hypothesis that pupfish dispersed or were isolated in basins throughout southeastern California and western Nevada by such a connection is not supported. Beyond the biologically predicted time frame, however, sparse and disputed data suggest that a fluvial system connected Panamint (Owens River), Death, and Amargosa Valleys, which could account for the dispersal and isolation before 3 Ma. ?? 2008 The Geological Society of America.

Knott, J.R.; Machette, M.N.; Klinger, R.E.; Sarna-Wojcicki, A. M.; Liddicoat, J.C.; Tinsley, J. C., III; David, B.T.; Ebbs, V.M.

2008-01-01

126

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

International Nuclear Information System (INIS)

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

127

Assessing the impact of late Pleistocene megafaunal extinctions on global vegetation and climate  

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Full Text Available The end of the Pleistocene marked a turning point for the Earth system as climate gradually emerged from millennia of severe glaciation in the Northern Hemisphere. It is widely acknowledged that the deglacial climate change coincided with an unprecedented decline in many species of large terrestrial mammals, including the near-total eradication of the woolly mammoth. Due to an herbivorous diet that presumably involved large-scale tree grazing, the mammoth expansion would have accelerated the expansion of dwarf deciduous trees in Siberia and Beringia, thus contributing to the changing climate of the period. In this study, we use the University of Victoria Earth System Climate Model (UVic ESCM to simulate the possible effects of megafaunal extinctions on Pleistocene climate change. We have explored various hypothetical scenarios of forest expansion in the Northern Continents, quantifying the regional and global biogeophysical effects in terms of changes in surface albedo and air temperature. In particular, we focus our attention on a Maximum Impact Scenario (MIS which simulates the greatest possible post-extinction reforestation in the model. More realistic experiments include sensitivity tests based on the timing of extinction, the fraction of trees grazed by mammoths, and the size of mammoth habitats. We also show the results of a simulation with free (non-prescribed atmospheric CO2. For the MIS, we obtained a surface albedo increase of 0.006, which resulted in a global warming of 0.175 °C. Less extreme scenarios produced smaller global mean temperature changes, though local warming in some locations exceeded 0.3 °C even in the more realistic extinction scenarios. In the free CO2 simulation, the biogeophysical-induced warming was amplified by a biogeochemical effect whereby the replacement of high-latitude tundra with shrub forest led to a release of soil carbon to the atmosphere and a small atmospheric CO2 increase. Overall, our results suggest the potential for a small, though non-trivial, effect of megafaunal extinctions on Pleistocene climate change.

M.-O. Brault

2013-01-01

128

The Late Holocene Stratigraphy of an Inlet-Dominated Barrier Island, Pea Island, North Carolina.  

Science.gov (United States)

Sedimentological, foraminiferal, geochemical, and geophysical data sets as well as aerial photographs have been used to investigate the natural processes (inlet dynamics, ocean/estuarine washover, and sea-level change) responsible for the late Holocene units preserved in the barrier island subsurface at Pea Island National Wildlife Refuge. Historic nautical charts indicate that three inlets characterized Pea Island between early European exploration (1590) and the late 19th century; aerial photographs show New Inlet open in 1932 and 1940. Vibracores (up to 5.5 m) collected along three transects across Pea Island extend our knowledge of the geological evolution of this region to pre-historic times. The section in the longest core (PI01S6) consists of four fining-upwards depositional sequences. The basal unit of each sequence is a bedded, medium to fine, clean quartz sand with increasing concentrations of organic matter (3-4 % detrital and 5-7 % in situ Spartina alterniflora roots) or irregular mud clasts (2-5 cm) to spherical mud balls (1-2 cm) up core. The clean sand units have so far proven to be barren of foraminifera except for a shelly unit at ca. 220 cm below MSL. The foraminiferal assemblage in this unit is of open shelf character (Elphidium excavatum, Hanzawaia strattoni, and Buccella inusitata). A 14C age on a disarticulated Chione cancellata valve from this unit is cal. 930+/-60 BP. The sand grades into a gray, tight mud in the first two sequences and into an inter-laminated mud and in situ peat in the third sequence. The peat contains leaf fragments and rhizomes of the marsh plants Juncus roemarianus, Spartina cynosuroides, and/or Phragmites spp. The peat and muddy sand units contain marsh foraminifera (Trochammina spp., Miliammina fusca, Arenoparrella mexicana), which are also found in modern marsh deposits. A peat sample from the third fining upward sequence (the only one to grade into a true peat) has a 14C age of cal. 395+/-35 BP, cal. 295+/-35 BP, or cal 180+/-40 BP. The four fining-upwards sequences have sharp erosional basal contacts. These deposits appear to reflect back-barrier processes including sequential deposition of flood-tide delta sands and/or sound sands adjacent to marshes. The shelly sands, containing open shelf foraminiferal assemblages, represent oceanic overwash, inlet deposits, or open embayment sands deposited behind a laterally extensive breach in the barrier island. The sequences are capped by the deposits of modern environments that include algal flats, tidal creeks, high and low marshes, back-barrier berms, overwash fans, and aeolian dunes. Several of the modern environments became covered with marsh vegetation after the construction of barrier dune ridges in the late 1930?s.

Smith, C. G.; Ames, D.; Corbett, D. R.; Culver, S.; Mallinson, D.; Riggs, S. R.; Vance, D.

2002-12-01

129

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

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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.

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

2014-10-01

130

Stable Isotope Stratigraphy of a Late Last Interglacial Speleothem from Rana, Northern Norway  

Science.gov (United States)

A stalagmite from Rana, northern Norway, dated by the TIMS uranium-series technique, yields records of stable oxygen and carbon isotopes covering the period from late marine oxygen isotope substages (MIS) 5e to 5a, that is, 123,350 to 73,300 yr ago. Rapid growth (?46 ?m/yr) between 123,350 and 119,500 yr ago reflects climatic conditions favorable for speleothem growth. This period is characterized by century- to millennial-scale oscillations in both stable isotope records, where both the absolute values and the isotope ranges are similar to Holocene and older samples from the region. From 119,500 to 107,700 yr ago, speleothem growth was slow (?0.7 ?m/yr), and between 107,700 and 73,300 yr ago growth is barely noticeable (0.07 ?m/yr). During the period of slow growth the stable isotope records show an overall enrichment trend. The transition between rapid and slow growth rate occurring sometime between 119,500 and 107,700 yr ago is believed to reflect the termination of interglacial climate in this region. The absence of detritus and corrosion features in the slowly deposited calcite suggests that the valley outside the cave remained sufficiently ice free for speleothem growth to occur until at least 73,300 yr ago.

Linge, Henriette; Lauritzen, Stein-Erik; Lundberg, Joyce

2001-09-01

131

Geothermal evidence of the Late Pleistocene-Holocene orbital forcing (example from the Urals, Russia)  

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We use early obtained in the Middle Urals geothermal reconstruction of the ground surface temperature (GST) history 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 time scale 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 (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 changes amplitude. The increase of carbon dioxide concentrations lagged by 2-3 kyr from the SHF increase and occurred synchronously with GST changes.

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

2014-08-01

132

A critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for Late Cretaceous global correlation  

Science.gov (United States)

Climate variability is driven by a complex interplay of global-scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter-regional correlation, which in most cases cannot be obtained with biostratigraphic methods alone. Chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high-resolution correlation over large distances, but complications arise from a multitude of possible influences from local differences in biological, diagenetic and physico-chemical factors on individual ?13C records that can mask the global signal. To better assess the global versus local contribution in a ?13C record it is necessary to compare numerous isotopic records on a global scale. As a contribution to this objective, this paper reviews bulk sediment ?13Ccarb records from the Late Cretaceous in order to identify differences and similarities in secular ?13C trends that help establish a global reference ?13C record for this period. The study presents a global-scale comparison of twenty ?13C records from sections representing various palaeo-latitudes in both hemispheres and different oceanic settings from the Boreal, Tethys, Western Interior, Indian Ocean and Pacific Ocean, and with various diagenetic overprinting. The isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute ?13C values and variation in amplitude between the sites. These differences reflect the varying local influences e.g. from depositional settings, bottom water age and diagenetic history, whereas the concordant patterns in ?13C shifts might represent ?13C fluctuations in the global seawater dissolved inorganic carbon. The latter is modulated by variations in organic matter burial relative to re-mineralization, in the global-scale formation of authigenic carbonate, and in partitioning of carbon between organic carbon and carbonate sinks. These variations are mainly controlled by changes in climate and eustasy. Additionally, some globally synchronous shifts in the bulk ?13Ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment. Formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and, thus, can be globally synchronized by fluctuations in eustasy, atmospheric and oceanic oxygen levels or in large-scale oceanic circulation. Because the influence of early diagenetic cements on the bulk ?13Ccarb signal can, but need not be synchronized, chemostratigraphy should not be used as a stand-alone method for trans-continental correlation, and especially minor isotopic shifts have to be interpreted with utmost care. Nevertheless, the observed consistency of the ?13C correlations confirms global scale applicability of bulk sediment ?13C chemostratigraphy for the Late Cretaceous, including sediments that underwent lithification and burial diagenesis such as the sediments from the Himalayan and Alpine sections. Limitations arise from increased uncertainties (1) in sediments with very low carbonate content, (2) from larger ?13C variability in sediments from very shallow marine environments, (3) from unrecognized hiatuses or strong changes in sedimentation rates, and (4) in sections with short stratigraphic coverage or with few biostratigraphic marker horizons.

Wendler, Ines

2013-11-01

133

New Insights on Late Pleistocene Sedimentation at the New Jersey Margin Based on Chirp Sonar Profiles and Vibracores  

Science.gov (United States)

Chirp sonar profiling and vibracoring at the New Jersey margin during cruise 370 of R/V Endeavor (May, 2002) sheds new light on late Pleistocene sedimentation beneath the outer shelf and upper continental slope. The sonar transmitted 40msec, 1 to 4 kHz pulses, and generated profiles with a vertical resolution of 20 cm and subsurface penetration on the order of 30-50 m. Here we discuss new observations concerning the youngest of five Pleistocene sequence boundaries, a prominent offlap surface informally termed pp0 that corresponds approximately with the Last Glacial Maximum. This surface is characterized in places by closely spaced channels typically ~75 m wide and ~10 m deep. Most of the channels are thought to have developed as a result of subaerial exposure. Some may relate to progradation or to subsequent marine transgression. Three offlapping stratigraphic units below pp0 are characterized by an upward transition from acoustically stratified to structureless facies, consistent with our vibracoring evidence of upward coarsening from silty clay to sand. We interpret these units as parasequences representing progradational pulses and sea-level changes at sub-100 ky timescales. Offlap continues seaward to a present-day water depth >150 m, which is significantly deeper than the LGM low stand 120 m below present sea level, and is consistent with emerging evidence that offlap should not be interpreted as an unequivocal indicator of subaerial exposure ("forced regression"). Surface R, a high-amplitude reflection of much-debated significance, is a downlap surface older than pp0. In different places, it merges with underlying sequence boundary pp1 and with pp0, but is itself not a sequence boundary. Broad erosional features in R, up to several meters deep and hundreds of meters across, are interpreted to relate to transgression following the development of pp1. Core evidence for abrupt upward fining from sand to clay across R is not consistent with regressive ravinement (cf. Duncan et al., 2000, Mar. Geol. 170, 395-421). One of our goals was to survey canyon heads to learn their influence on Pleistocene sedimentation. We found that the Hudson shelf valley is underlain by a complex of nested fluvial channels that have occupied approximately the same location through at least several sea-level cycles, perhaps as a result of incomplete filling between successive sea-level falls. During the late Pleistocene, the Hudson Canyon eroded headward into the shelf valley despite overall progradation of the margin. However, the head of the canyon is nearly filled by tens of meters of offlapping acoustically stratified sediment of uncertain age, but apparently older than pp0. Overlying the pp0 canyon-cutting unconformity in the same area is canyon at ~2-3°, pinches out up canyon ~130 m below present sea level, and is interpreted as a lowstand delta. Flooding of the shelf since 20 ka has resulted in levees adjacent to the distal Hudson shelf valley, backstepping nearshore deposits <10 m thick, and lenticular accumulations of sand that may represent fossil shoreface-attached ridges. This assemblage of features, which extends seaward to a depth perhaps as great as 120 m below present sea level, was interpreted by Uchupi et al. (2001, Mar. Geol. 172, 117-145) as sediment lobes related to catastrophic drainage of glacial lakes.

Christie-Blick, N.; Mountain, G. S.; Ghosh, A.; McHugh, C. M.; Pekar, S. F.; Schock, S. G.

2002-12-01

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

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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.

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

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

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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

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

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Amplicon pyrosequencing late Pleistocene permafrost: the removal of putative contaminant sequences and small-scale reproducibility.  

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DNA sequencing of ancient permafrost samples can be used to reconstruct past plant, animal and bacterial communities. In this study, we assess the small-scale reproducibility of taxonomic composition obtained from sequencing four molecular markers (mitochondrial 12S ribosomal DNA (rDNA), prokaryote 16S rDNA, mitochondrial cox1 and chloroplast trnL intron) from two soil cores sampled 10 cm apart. In addition, sequenced control reactions were used to produce a contaminant library that was used to filter similar sequences from sample libraries. Contaminant filtering resulted in the removal of 1% of reads or 0.3% of operational taxonomic units. We found similar richness, overlap, abundance and taxonomic diversity from the 12S, 16S and trnL markers from each soil core. Jaccard dissimilarity across the two soil cores was highest for metazoan taxa detected by the 12S and cox1 markers. Taxonomic community distances were similar for each marker across the two soil cores when the chi-squared metric was used; however, the 12S and cox1 markers did not cluster well when the Goodall similarity metric was used. A comparison of plant macrofossil vs. read abundance corroborates previous work that suggests eastern Beringia was dominated by grasses and forbs during cold stages of the Pleistocene, a habitat that is restricted to isolated sites in the present-day Yukon. PMID:23694692

Porter, Teresita M; Golding, G Brian; King, Christine; Froese, Duane; Zazula, Grant; Poinar, Hendrik N

2013-09-01

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A warm thermal enclave in the late Pleistocene of the south-eastern United States.  

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Physical and biological evidence supports the probable existence of an enclave of relatively warm climate located between the Southern Appalachian Mountains and the Atlantic Ocean in the United States during the Last Glacial Maximum. The region supported a mosaic of forest and prairie habitats inhabited by a "Floridian" ice-age biota. Plant and vertebrate remains suggest an ecological gradient towards Cape Hatteras (35 degreesN) wherein forests tended to replace prairies, and browsing proboscideans tended to replace grazing proboscideans. Beyond 35 degreesN, warm waters of the Gulf Stream were deflected towards the central Atlantic, and a cold-facies biota replaced "Floridian" biota on the Atlantic coastal plain. Because of niche diversity and relatively benign climate, biodiversity may have been greater in the south-eastern thermal enclave than in other unglaciated areas of North America. However, the impact of terminal Pleistocene megafaunal extinctions may also have been shorter and more severe in the enclave than further north. A comparison with biotic changes that occurred in North America approximately 55 million years (ma) ago at the Paleocene-Eocene Thermal Maximum suggests that similar processes of change took place under both ice-house and greenhouse climates. PMID:19391200

Russell, Dale A; Rich, Fredrick J; Schneider, Vincent; Lynch-Stieglitz, Jean

2009-05-01

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Seasonality of the late Pleistocene Dawson tephra and exceptional preservation of a buried riparian surface in central Yukon Territory, Canada  

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The late Pleistocene Dawson tephra was deposited by one of the largest Quaternary eruptions in northwestern North America. Its distribution is known sparsely from sites near the source area in southwestern Alaska and central Yukon Territory, where more than 20 occurrences are documented in the Klondike region. Dawson tephra erupted about 25,300C yr BP, near the onset of the last glaciation, and provides a stratigraphic marker across Eastern Beringia. We report radiocarbon ages, paleobotanical data, and cryostratigraphic observations from a new Dawson tephra locale at Goldbottom Creek, in the Klondike region of Yukon Territory, which collectively indicate that the eruption occurred in the late winter or early spring. Multiple, fining-upward tephra-rich ice beds are interpreted as remnants of surface icings, which presently are common in the region during spring. A buried in situ riparian meadow, preserved below the icing and tephra, consists of abundant tufted hair grass ( Deschampsia caespitosa), with interspersed horsetails ( Equisetum cf. palustre) and mosses. Detrital plant remains and preserved in situ grass inflorescences entombed in the icing had expelled their fruits, consistent with a late season surface when the icing was active. The extraordinary thickness of Dawson tephra in central Yukon likely reflects reworking of a winter-deposited tephra by snow melt in the spring following the eruption, indicating that the primary thickness may be overestimated at valley-bottom sites. Winter deposition of the tephra may have, in part, minimized the terrestrial ecological impacts of the eruption on zonal "steppe-tundra" vegetation through the retransportation of tephra from hillslopes to the riparian areas, where the tephra became incorporated into local fluvial systems.

Froese, Duane G.; Zazula, Grant D.; Reyes, Alberto V.

2006-07-01

139

Stratigraphie relations of australites in the Port Campbell Embayment, Victoria  

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In the Port Campbell Embayment of Victoria, australites have been found in situ in channel deposits of the Hanson Plain Sand of Pliocene and Pleistocene age. The large majority of the australites, however, occur as a lag deposit at the basal contact of the Sturgess Sand of late Pleistocene and Holocene age and are spatially correlated with ferruginous sandstone clasts that are derived from the Hanson Plain Sand. Some of the tektites are imbedded in or bonded to the ferruginous sandstone clasts, but most are found as individual tektite fragments. A few percent of the tektites have nearly perfectly preserved, complete aerodynamically shaped forms. The sandstone clasts and associated tektites have been reworked from the much older underlying Hanson Plain and have been locally concentrated in the lag deposit. Some tektites also occur at higher levels in the Sturgess Sand, almost invariably in association with stone flakes, exotic stones transported by the aborigines and, locally, with middens of mollusc shells. Circumstantial evidence indicates that the aborigines transported the tektites found in the upper part of the Sturgess, particularly at Stanhope Bay. As Port Campbell australites unequivocally occur in strata much older than the late Pleistocene and Holocene Sturgess, there is no longer any conflict between the apparent stratigraphie age of the tektites and the middle Pleistocene ages obtained by various Chronometrie methods. ?? Meteoritical Society, 1999.

Shoemakeri, E. M.; Ralph, Uhlherr, H.

1999-01-01

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Late Pleistocene glaciation of the Mt Giluwe volcano, Papua New Guinea  

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The Mt Giluwe shield volcano was the largest area glaciated in Papua New Guinea during the Pleistocene. Despite minimal cooling of the sea surface during the last glacial maximum, glaciers reached elevations as low as 3200 m. To investigate changes in the extent of ice through time we have re-mapped evidence for glaciation on the southwest flank of Mt Giluwe. We find that an ice cap has formed on the flanks of the mountain on at least three, and probably four, separate occasions. To constrain the ages of these glaciations we present 39 new cosmogenic 36Cl exposure ages complemented by new radiocarbon dates. Direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought. In conjunction with existing potassium/argon and radiocarbon dating, we recognise four distinct glacial periods between 293-306 ka (Gogon Glaciation), 136-158 ka (Mengane Glaciation), centred at 62 ka (Komia Glaciation) and from >20.3-11.5 ka (Tongo Glaciation). The temperature difference relative to the present during the Tongo Glaciation is likely to be of the order of at least 5 ??C which is a minimum difference for the previous glaciations. During the Tongo Glaciation, ice was briefly at its maximum for less than 1000 years, but stayed near maximum levels for nearly 4000 years, until about 15.4 ka. Over the next 4000 years there was more rapid retreat with ice free conditions by the early Holocene. ?? 2011 Elsevier Ltd.

Barrows, T. T.; Hope, G. S.; Prentice, M. L.; Fifield, L. K.; Tims, S. G.

2011-01-01

 
 
 
 
141

Assessing the impact of late Pleistocene megafaunal extinctions on global vegetation and climate  

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The end of the Pleistocene marked a turning point for the Earth system, as climate gradually emerged from millennia of severe glaciation in the Northern Hemisphere. It is widely known that the deglacial climate change then was accompanied by an unprecedented decline in many species of large terrestrial mammals, featuring among others the near-total eradication of the woolly mammoth. Due to a herbivorous diet that involved the grazing of a large number of trees, their extinction is thought to have contributed to the rapid and well-documented expansion of dwarf deciduous trees in Siberia and Beringia, which in turn would have resulted in a significant reduction in surface albedo, leading to an increase in global temperature. In this study, we use the UVic Earth System Climate Model (an EMIC) to simulate various scenarios of the megafaunal extinctions, ranging from the catastrophic to more realistic cases, in order to quantify their potential impact on the climate system, and investigate the associated biogeophysical feedbacks between the growing vegetation and rising temperatures. The more realistic experiments include sensitivity tests based on the timing of extinction, tree clearance ration, and size of habitat, as well as a gradual extinction and a simulation involving free (non-prescribed) atmospheric CO2. Overall, most of the paleoclimate simulations and the sensitivity tests yield results that correspond well with our intuition. For the maximum impact scenario, we obtain a surface albedo increase of 0.006, which translates into a global warming of 0.175°C; these numbers are comparable in magnitude to those in similar studies.

Brault, M.; Mysak, L. A.; Matthews, D.; Simmons, C. T.

2012-12-01

142

Late Pleistocene zircon ages for intracaldera domes at Gölcük (Isparta, Turkey)  

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Pleistocene to Quaternary volcanism in the Isparta region (SW Anatolia, Turkey) comprises potassic lavas and pyroclastic deposits, which are largely centered around Gölcük caldera. Trachytic intracaldera lava domes represent the latest eruptive event at Gölcük, and their eruption age is crucial for defining a minimum age for the preceding caldera-forming explosive eruption. Here, we present combined U-Th and (U-Th)/He zircon geochronological data for two intracaldera lava domes constraining their crystallization and eruption ages, respectively. U-Th zircon crystallization ages peak between ca. 15 and 25 ka. In rare instances U-Th zircon crystallization ages date back to ca. 59 and 136 ka. U-Th zircon crystallization ages also permit (U-Th)/He eruption ages from the same crystals to be individually corrected for uranium series decay chain disequilibrium, which is mainly due to the deficit of the intermediate daughter 230Th in zircon. Average disequilibrium-corrected (U-Th)/He zircon ages are 14.1 ± 0.5 and 12.9 ± 0.4 ka (1?). These ages are indistinguishable within analytical uncertainties suggesting that both lavas erupted quasi simultaneously. This contradicts published K-Ar ages that suggest an extended hiatus from ca. 52 to 24 ka between intracaldera dome eruptions. Evidence for protracted zircon crystallization over several thousands of years prior to eruption indicates the presence of a long-lived magma reservoir underneath Gölcük caldera. Implications of the revised eruptive geochronology presented here include younger ages for the latest effusive eruptions at Gölcük, and potentially also a more recent explosive eruption than previously assumed.

Schmitt, Axel K.; Danišík, Martin; Siebel, Wolfgang; Elitok, Ömer; Chang, Yu-Wei; Shen, Chuan-Chou

2014-10-01

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Late Pleistocene and Holocene Fire History of the Swiftcurrent Lake basin, eastern Glacier National Park, Montana  

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High altitude alpine landscapes of the northern U.S. Rocky Mountains are geomorphically dynamic and sensitive to climate change. Understanding the timing and magnitude of past changes in temperature, aridity, and other factors such as seasonality and storminess are key in constraining natural climate variability in these sensitive environments. Fire frequency can provide strong insight into past climate regimes, with increased periodicity and/or intensity of fires reflecting episodes of warming and/or aridity. Lacustrine climate records in the Rockies are most abundant either further south of northern Montana at lower elevations, or in the Canadian Rockies further north. Here we examine a ˜12,900 year long lake sediment record from the northeastern basin of Swiftcurrent Lake in eastern Glacier National Park, MT to document fire frequency as a proxy for aridity in the region. Swiftcurrent Lake is fed mainly by melt from Grinnell Glacier, and thus reflects glacial, geomorphic, and climatic processes throughout the Holocene. Existing data, such as mineralogy, percent organic carbon, C/N, and grain size will be paired with the fire frequency record over the Holocene and latest Pleistocene to develop a comprehensive environmental history of the Swiftcurrent Lake Basin and greater Grinnell Glacier Valley. A clear understanding of fire history in the basin is important for future fire management decisions in Glacier National Park. Charcoal particles were tallied at contiguous 0.5 cm intervals over the first half meter of the core, and at 1 cm intervals over the remaining ~6.0 m, then converted to charcoal abundance and accumulation rates. Based age controls from radiocarbon analyses and ash fingerprinting the sampling interval represents between 5 and 20 years. A core collected in July 2010 will be analyzed for lead-210, providing additional age control for the past few centuries. Preliminary results show low charcoal counts overall with some clear peaks. High charcoal abundance and accumulation rates appear to be tied to increased fire activity in basin. We anticipate correlation with climatic anomalies such as the Medieval Warm Period. Charcoal morphotypes, also identified and tallied in conducted charcoal counts, will be used to indicate the nature of the basin vegetation. These data will be compared to pollen data to consider changing vegetation regimes. The focus on the last few centuries will provide insight into the extent of anthropogenic effects on burn periodicity. This study will also be paired with other similar fire frequency records in the greater northern Rockies region. Finally, comparisons with total organic carbon in the core, which is tied to solar forcing over the last 7500 years, will further illuminate the environmental history of the basin over the Holocene.

Kutvirt, J. C.; MacGregor, K. R.; Riihimaki, C. A.; Myrbo, A.

2010-12-01

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Assessing the strength of the monsoon during the late Pleistocene in southwestern United States  

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Improved predictions of drought require an understanding of natural and human-induced climate variability. Long-term records across glacial-interglacial cycles provide the natural component of variability, however few such records exist for the southwestern United States (US) and quantitative or semi-quantitative records of precipitation are absent. Here we use the hydrogen isotope (?D) value of C28n-alkanoic acid in lacustrine sediments of Pleistocene age to reconstruct ?D values of precipitation in northern New Mexico over two glacial-interglacial cycles (?550,000-360,000 years before present) and obtain a record of monsoon strength. Overall, reconstructed ?D values range from -53.8‰ to -94.4‰, with a mean value of -77.5 ± 8‰. Remarkably, this variation falls within the measured present-day summer monsoonal and winter weighted means (-50.3 ± 3‰ and -106.4 ± 20‰ respectively), suggesting that processes similar to those of present time also controlled precipitation during Marine Isotope Stage (MIS) 13 to 10. Using the ?D summer monsoonal and winter mean values as end-members, we interpret our reconstructed ?D record of precipitation as a direct, and semi-quantitative, indicator of monsoon strength during MIS 13 to 10. Interglacial periods were characterized by greater monsoon strength but also greater variability compared to glacial periods. Pronounced cycles in the strength of the monsoon occurred during interglacial periods and in general were positively correlated with maximum mean annual temperatures. Our estimates of monsoon strength are supported by independent proxies of ecosystem productivity, namely, TOC, ?13C of TOC and Si/Ti ratio and warm pollen taxa Juniperus and Quercus. Interglacial variability in the strength of the monsoon resembles a response to the land-sea surface temperature contrast (LSTC) except for the early part of MIS 11. During this period, LSTC would have remained relatively strong while monsoonal strength decreased to a minimum. This minimum occurred following the warmest interval of MIS 11, suggesting a more complex driving of monsoon strength during warm periods. In addition, this period of monsoon minimum coincided with a core section of mud-cracked sediments that suggest low monsoonal precipitation was an important factor in the onset of drought. Our estimates of monsoon strength represent a record of natural variability in the region that is relevant to present time, in particular the variability during interglacial MIS 11, which is considered an analog for the current interglacial. Our results suggest that natural variability can cause significant reductions in monsoonal precipitation with the implication of a potentially adverse effect from sustained warming.

Cisneros-Dozal, Luz M.; Huang, Yongsong; Heikoop, Jeffrey M.; Fawcett, Peter J.; Fessenden, Julianna; Anderson, R. Scott; Meyers, Philip A.; Larson, Toti; Perkins, George; Toney, Jaime; Werne, Josef P.; Goff, Fraser; WoldeGabriel, Giday; Allen, Craig D.; Berke, Melissa A.

2014-11-01

145

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

Science.gov (United States)

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.

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

2009-12-01

146

New stratigraphic and taphonomic data from the late Pleistocene deposits of the San Teodoro Cave (North-Eastern Sicily, Italy  

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Full Text Available In previous excavations at the San Teodoro Cave (North-Eastern Sicily the Authors distinguished an upper Late Glacial sedimentary unit (Unit A and a lower sedimentary unit (Unit B containing Upper Pleistocene endemic mammal remains. New data collected during 2002 and 2003 excavations come from a trench located on the eastern side of the cave at a distance of 30-34 m from the entrance. In the new trench the composition and taphonomic characters of the faunal assemblage of the Unit B deposits are similar to those recognized in 1998 in a trench located on the eastern side of the cave at a distance of 9-13 m from the entrance. The Unit B contains a highly diversified assemblage of vertebrates, invertebrates and vegetal remains. Damages on bones and abundant coprolites testify to intense hyena activity. Complete and undamaged remains of elephant and deer are actually a novelty from a taphonomic point of view. A new sterile sedimentary unit (Unit C has been brought to light. The characters of the new sedimentary Unit C suggest a correlation with the older lacustrine deposits located at the base of the vertical cliffs where the San Teodoro cave is located.

Gabriella Mangano

2005-10-01

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A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic ?13C gradient  

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Full Text Available The fact that the deep-ocean benthic ?13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific or a decrease in Southern Ocean overturning. This study re-evaluates the implications of changes in benthic ?13C gradients by comparing Pacific Deep Water (PDW ?13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The ?13C compositions of PDW, Northern Component Water (NCW and Southern Component Water (SCW are estimated from regional benthic ?13C stacks of 3–6 sites. Changes in PDW ?13C and PDW-SCW ?13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific remineralization offset of ?0.5‰. Thus, a change in PDW ventilation cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic ?13C gradient.

L. E. Lisiecki

2010-05-01

148

A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic ?13C gradient  

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Full Text Available The fact that the deep-ocean benthic ?13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific. This study re-evaluates the implications of changes in benthic ?13C gradients by comparing Pacific Deep Water (PDW ?13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The ?13C compositions of PDW, Northern Component Water (NCW and Southern Component Water (SCW are estimated from regional benthic ?13C stacks of 3–6 sites. Changes in PDW ?13C and PDW-SCW ?13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific "age" offset of ?0.5‰. Thus, an additional ventilation source for glacial PDW (e.g., in the North Pacific cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic ?13C gradient.

L. E. Lisiecki

2009-12-01

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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

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The three-quarter power scaling of extinction risk in Late Pleistocene mammals, and a new theory of the size selectivity of extinction  

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Questions: What is the pattern of body mass versus extinction risk in the Late Pleistocene extinctions of mammals, both qualitatively and quantitatively? Are there patterns that relate extinction risk to the well-known allometries of body mass with population density or population growth rate? Theory: A simple theory to predict both qualitative pattern and quantitative parameters of the size-selectivity of extinction. First, I assume that external pressures (e.g. human impact and climate chan...

Polishchuk, L.

2010-01-01

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Hydrological Variability in the Indo-Pacific Warm Pool: Late Pleistocene and Holocene Records from Lake Matano, Indonesia  

Science.gov (United States)

Lake Matano (2°29.1'S 121°20'E) in South Sulawesi, Indonesia at the western edge of the Indo-Pacific Warm Pool (IPWP) contains well-stratified sediment which provides an excellent opportunity to understand the mechanisms controlling long-term variations in IPWP convection/rainfall and the interactions between the IPWP hydrology and changes in the Asian Monsoon system during the Late Pleistocene and Holocene. This study reports a millennial-scale multi-proxy hydrological reconstruction from Lake Matano, spanning MIS 3 to present, based on lithostratigraphic and geochemical analyses. Changes in magnetic susceptibility, carbon isotope of organic matter, total inorganic carbon, and elemental data from core-scanning XRF jointly record dry/wet transitions. We interpret periods of high magnetic susceptibility, enriched ?13C, and elevated inorganic carbon to indicate dry climates. Two major dry intervals are recorded in our data: 1) 37 - 32 kyr BP, and 2) 26 - 15 kyr BP. The latter corresponds with an ~10 % enrichment in ?13C, suggesting C4 expansion and rainforest contraction during the Late Glacial Maximum. The Holocene in Sulawesi was marked by an early dry period, with wetter conditions toward the present-day. Our records suggest temporally variable relationships between the IPWP convection and the orbital-scale, insolation-driven East Asian Summer Monsoon strength variations. They also indicate the influences of: 1) synoptic shifts in the Intertropical Convergence Zone, and 2) landmass changes in the region, in controlling the long-term variability of the IPWP hydrology.

Wicaksono, S. A.; Russell, J. M.; Bijaksana, S.; Tamuntuan, G. H.; Noren, A. J.; Wattrus, N. J.; Vogel, H.

2011-12-01

152

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

Science.gov (United States)

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.

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

2014-05-01

153

Late Pleistocene pollen flora with Larix from till-covered esker at Hietamäki, Ostrobothnia, western Finland  

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Full Text Available A till-covered layer of clay, fine sand and organic-bearing silt was found at Hietamäki near Haapajärvi, Ostrobothnia (Pohjanmaa, western Finland. The organic-bearing silt layer is an infill sediment in a dead ice hollow within a glaciofluvial formation interpreted as an esker. The esker is covered by till, at the base of which is a layer or lense of clay 1.5 m thick. On the basis of pollen content, the layers of clay and organic-bearing silt were deposited during the Eemian interglacial stage. Pinus-Picea-Larix forests mixed with Betula and Alnus possibly represent aregressive phase of the late Eemian vegetational development, when thermophile trees had already withdrawn from the area.

Eriksson, B.

1994-12-01

154

Holocene-Late pleistocene climatic ice core records for Qinghai-Tibetan plateau  

Energy Technology Data Exchange (ETDEWEB)

Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Wuerm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative {delta}{sup 18}O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly {approximately} 10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.

Thompson, L.G.; Mosley-Thompson, E.; Davis, M.E.; Bolzan, J.F.; Dai, J.; Klien, L. (Ohio State Univ., Columbus (USA)); Yao, T.; Wu, X.; Xie, Z. (Lanzhou Institute of Glaciology and Geocryology (China)); Gundestrup, N. (Univ. of Copenhagen (Denmark))

1989-10-27

155

Late pleistocene-holocene ostracod assemblages of the Northern Caspian Sea shelf  

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Analysis of the ostracod assemblages and the distribution of benthic foraminifera Ammonia beccarii in the core section GS 194-08-1 recovered at a depth of 7.5 m near the Volga delta front showed changes in environmental conditions in response to sea-level fluctuations. The pre-Novocaspian ostracod assemblage reflects the conditions that were dominant during the Late Khvalynian transgression, with a depth of about 20-30 m, and a salinity range of 12-13‰. The Early Novocaspian sediments contain an ostracod assemblage that represents a deeper water environment compared to the present, with an inferred depth of 12-16 m. The faunas from the younger Novocaspian sediments with abundant monospecific populations of Cyprideis torosa and co-occurring benthic foraminifera Ammonia beccarii represent modern-like environmental conditions.

Chekhovskaya, M. P.; Stepanova, A. Yu.; Khusid, T. A.; Matul, A. S.; Rakowski, A. Z.

2014-03-01

156

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

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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.

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

2008-01-01

157

Integrated stratigraphy and paleoenvironmental reconstruction for the Late Cretaceous Danish chalk based on the Stevns-2 core  

DEFF Research Database (Denmark)

An integrated stratigraphy of the Stevns-2 core located in eastern Denmark is hereby presented based on calcareous nannofossil biostratigraphy and carbon isotope stratigraphy. Carbon and oxygen isotope have been performed on 419 bulk samples. Calcareous nannofossil biostratigraphy has been applied, based on the analysis of 57 samples. Original gamma-ray data from the well-log analysis are also presented. The calcareous nannofossil data span the upper Campanian (UC16a) to the lower Danian (NNT1). These new stratigraphic data are compared and correlated to other Boreal, Tethyan and Tropical sites in order to provide an age-model for Stevns-2. While using this age-model, differences in the sedimentation rates of Stevns-1 and Stevns-2 borehole are nicely expressed, although the two sites are only 8 km apart from each other. The mechanisms responsible for these changes are under investigation, but are probably related to a combination of variations in paleoproductivity, paleocurrents, geodynamics and paleotopography.

Boussaha, Myriam; Thibault, Nicolas Rudolph

158

Unexpected technological heterogeneity in northern Arabia indicates complex Late Pleistocene demography at the gateway to Asia.  

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The role and significance of the Arabian Peninsula in modern human dispersals out of Africa is currently contentious. While qualitative observations of similarities between Arabian Middle Palaeolithic and African Middle Stone Age (MSA) assemblages have been made, these inferences remain untested and often situated within overly broad dichotomies (e.g., 'Africa' versus the 'Levant'), which distort concepts of geographic scale and subsume local variability. Here, we quantitatively test the hypothesis that assemblages from Jubbah, in the Nefud Desert of northern Saudi Arabia are similar to MSA industries from northeast Africa. Based on the quantitative analysis of a suite of metric and morphological data describing lithic reduction sequences, our results show that early and late core reduction at Jubbah is distinct from equivalent northeast African strategies, perhaps as a result of raw material factors. However, specific techniques of core shaping, preparation and preferential flake production at Jubbah draw from a number of methods also present in the northeast African MSA. While two Jubbah lithic assemblages (JKF-1 and JKF-12) display both similarities and differences with the northeast African assemblages, a third locality (JSM-1) was significantly different to both the other Arabian and African assemblages, indicating an unexpected diversity of assemblages in the Jubbah basin during Marine Isotope Stage 5 (MIS 5, ?125-70,000 years ago, or ka). Along with evidence from southern Arabia and the Levant, our results add quantitative support to arguments that MIS 5 hominin demography at the interface between Africa and Asia was complex. PMID:25110207

Scerri, Eleanor M L; Groucutt, Huw S; Jennings, Richard P; Petraglia, Michael D

2014-10-01

159

Late Pleistocene and Holocene large magnitude earthquakes along Himalayan Frontal Thrust in the Central Seismic Gap in NW Himalaya, Kala Amb, India  

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The Himalayan Frontal Thrust (HFT) forms the southernmost active tectonic mountain front of the Himalaya. To understand the ongoing tectonics further, paleoseismological study has been carried out in the vicinity of the HFT system along the Himalayan Front near Kala Amb, India. The trench excavation survey conducted across an explicit surface exposure of the HFT exhibits two distinct faults considered to be associated with the reactivation of the HFT where the Middle Siwalik rocks (Late Miocene) have repeatedly thrust over the Late Pleistocene and Holocene sediments. Presence of large-sized coseismically induced sand-injection feature and its disposition recognized in the trench also suggest occurrence of large magnitude earthquakes in this region. An uplifted and upwarped strath terrace, 3 to 5 m thick alluvium, resting over the 15 m high Middle Siwaliks, abruptly truncated by the HFT indicates its latest activity. Optically Stimulated Luminescence dating techniques were employed to constrain the chronology of events. The long term slip rate of the abandoned terraces due to the activity of the HFT is estimated to be 3.4 mm/yr or greater since Late Holocene. The paleoseismological investigations have provided unambiguous evidences of at least two large magnitude earthquakes occurred in this region where an earthquake with 12 m or larger surface displacement and magnitude 7.5 or greater hit this region in the period between 29.3 ka and 17 ka in the Late Pleistocene and another great earthquake recurred with 20-22 m or more surface displacement and magnitude of 7.7 or greater between 5.8 ka and 2 ka in the Holocene. The present study is the first time report of multiple large magnitude paleoearthquakes in the northwestern part of the Frontal Himalaya during Late Pleistocene and Holocene. The repeated reactivation of HFT substantiates high seismic potential of the Frontal Himalaya and calls for more extensive study of paleoearthquakes of this vastly populous mountainous region.

Philip, G.; Bhakuni, S. S.; Suresh, N.

2012-12-01

160

Analysis of vegetation and climate change during Late Pleistocene from Ziro Valley, Arunachal Pradesh, Eastern Himalaya region  

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Vegetation and climate during later part of Late Pleistocene have been reconstructed from Ziro valley, Arunachal Pradesh, Eastern Himalaya based on pollen data along with carbon isotope and magnetic susceptibility data The study reveals that the area and the vicinity is occupied by mixed broad leaved - conifer forest and pine grass savanah at variable densities at least since 66,000yr BP. The phases of expansions and declines of Oaks with decline and increase of Pines and grasses probably occurred under increase (warm-moist) and decrease (cool-dry) of S.W. monsoon precipitation respectively. The increasing trend of S.W. monsoon and temperature is recorded during ˜44,000 to 34,000 cal yr BP synchronizing with the peat development, and which peaked at around 35,000 cal yr BP. This may link to the interstadial phase during the last major glacial cycle in the Himalayan region. It is also reflected in the decline of ?13C value indicating dominance of C-3 type of vegetation. The increased values of ?FD%, and lower values ?LF magnetic susceptibility, recorded during the phase of the peat deposit, further advocate's higher monsoon intensity. Impact of expansion of glacier felt with peak (LGM) around 20,000 cal yr BP is perceived. Tree line had moved to lower altitudes due to increased aridity and low temperature. During this time existence of savannah type of vegetation is also evident by the increase of C4 taxa. Decreased FD% and increased ?LF susceptibility also indicate reduced S.W. monsoon intensity.

Bhattacharyya, Amalava; Mehrotra, Nivedita; Shah, Santosh K.; Basavaiah, Nathani; Chaudhary, Vandana; Singh, Indra Bir

2014-10-01

 
 
 
 
161

Chronology of late Pleistocene and Holocene volcanics, Long Valley and Mono Basin geothermal areas, eastern California  

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Hydration-rind ages based on hydration-rind thicknesses of obsidian and an assumed hydration rate of 5 microns /1000 yrs have been determined for the 26 exposed Mono domes and coulees. Hydration-rind thickness data give good estimates of relative age differences between the domes, but determination of absolute ages will depend upon calibration to radiometric ages. The first extrusion of highly differentiated, sparsely porphyritic rhyolite occurred an estimated 32,000 to 40,000 yrs ago and consists of a small dome at the northwest end of the contiguous chain. The next major extrusive event occurred about 24,000 yrs ago and is represented by two domes and a major tephra. About 10,000 yrs ago the frequency of eruptive activity increases and rhyolite lave was extruded at an average rate of 0.2 km3/1000 yrs; periods of dormancy ranging in length from 300 to 2000 yrs. About 2000 to 3000 yrs ago the rate of extrusion increased dramatically to 0.8 km3/1000 yrs beginning with the eruption of the South Coulee and its associated tephra. At the same time, the nature of erupted magma changed from sparsely porphyritic (3 to 10 per cent sanidine) to aphyric rhyolite. All eruptions since 2000 radiocarbon yrs BP have produced magma that is aphyric but is of the same chemical composition as the earlier porphyritic magma. Volumes of porphyritic and aphyric extrusives, each of which includes volumes of lava and volumes of pumiceous pyroclastics reduced for porosity, are nearly equal and together total about 4 km3. Projecting the recent rate of extrusion over the time since the last major eruption, 1185 radiocarbon yrs ago suggests that a future eruption in the Mono Chain could release as much as 1 km 3 of magma. The recent increase in extrusion rate and the contemporaneous change in the nature of the magma are attributed to an event in the magma chamber that allowed the release of hotter, more fluid, crystal-free magma. The young age for the beginning of rhyolite volcanism from the mono magma chamber suggests that rhyolite magma may have been emplaced in the shallow crust as recently as 32,000 to 40,000 yrs ago. Calculations by Lachenbruch et al. (1976, Jour. Geophys. Research, v. 81, p. 769-784) that a thermal disturbance at this age would have propagated upward by solid conduction only 4 km and offer an explanation for the lack of a heat-flow anomaly and surface indications of hydrothermal activity over the Mono magma chamber and its associated ring-fracture system. This report also contains new information on the age and chemistry of volcanics on the Mono Lake island, the Inyo domes, and tephras within the Long Valley Caldera. A newly discovered rhyolite tuff ring of late Quaternary age in the Toowa volcanic field of the southern Sierra Nevada is briefly described for it represents a new area that should be examined for potential as a geothermal area.

Wood, S.H.

1983-01-01

162

The Late Pleistocene and Holocene palaeoenvironmental context of Wonderwerk Cave in the southern Kalahari, South Africa  

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Wonderwerk Cave, located in the arid southern Kalahari in South Africa, is an exceptional site, since it preserves a two million year long record of human occupation. While research on older levels in various excavation sections of the cave deposits is ongoing, we focus here on the younger levels that span the last 35,000 years. We present the results of past and recent work on zooarchaeology, macrobotany, palynology, phytoliths, stable isotopes, micromorphology and speleothem growth, which track marked diachronic environmental fluctuations. Except for a hiatus of ~33-23 ka, growth and isotope data for a speleothem near the cave entrance suggests moist conditions from ~35-33, and ~22-14 ka with brief, dry episodes at ~34, ~22 and ~15 ka. Temperatures were cool except for an increase ~16-14 ka after which cold conditions equivalent to the Younger Dryas event occurred. In Stratum 5 (>12.5 ka in Excavation 1), relatively low carbon isotope (?13C) values, pollen in the speleothem, and pollen in dung deposits indicate that the vegetation included a large C3 component during this phase. While the climate experienced sharp fluctuations in moisture when stalagmite growth was interrupted, more severe drying occurred by ~12 ka as indicated by dung pollen. Pollen in Stratum 4d (undifferentiated by stratum sub-phases) suggest that warmer grassy conditions developed before 11 ka, which is supported by ?13C values in OES that suggest a greater C4plant component in Stratum 4dII associated with the Oakhurst-like archaeological industry. Undifferentiated Stratum 4d indicates moderate moisture availability (pollen) but sub-phase 4dII suggest drying (OES ?18O). C3-presence (OES ?13C) in the vegetation became stronger again in Stratum 4dI (Oakhurst) and Stratum 4cII (Wilton). This is supported by Asteraceae pollen especially ~8.5 ka. Except for a fluctuation in OES ?18O values in Stratum 4cII, ?18O and pollen and micromammal composition suggest progressive aridity until ~6 ka (Stratum 4bII). ?18O values on OES indicate a marked shift to a moister episode in the mid-Holocene between 5.9 and 4.9 ka while pollen, phytoliths and microfauna indicate that more grassy vegetation with woodland developed ~5.5-4.4 ka (Strata 4bI-4aLH, Wilton). A trend towards more arid conditions culminated ~2.8-1.2 ka (Strata 3a-2b, the Ceramic Later Stone Age) as suggested by oxygen and carbon isotopes in OES, and is consistent with pollen and phytolith data indicating vegetation with C4 grasses. The macrofaunal data corroborate this picture, with grassland environments increasing through the Holocene as reflected in an increase in grazers; frequencies of springbok (Antidorcas marsupialis), a species that suggests aridity, rises from 0% in the early Holocene, to 10% in the mid-Holocene, and further to 16% in the Late Holocene. The general arid trend has continued until a slight increase in moisture availability ~0.8 ka leading up to modern semi-arid conditions in the uppermost disturbed strata.

Scott, Louis; Avery, Margaret; Bamford, Marion; Berna, Francesco; Brink, James; Brook, George; Chazan, Michael; Ecker, Michaela; Fernandez-Jalvo, Yolanda; Goldberg, Paul; Lee-Thorp, Julia; Rossouw, Lloyd; Thackeray, Francis; Horwitz, Liora

2014-05-01

163

Composition and provenance of Late Pleistocene-Holocene alluvial sediments of the eastern Andean piedmont between 33 and 34° S (Mendoza Province, Argentina)  

Science.gov (United States)

The Andean cordillera, and its piedmont in the central western Argentina, has been long considered as one of the main source areas of detritus for the Chaco-Pampean plain sand dune fields and loess/loess-like deposits of central Argentina. The main goal of this study is to evaluate the composition of the late Pleistocene-Holocene alluvial deposits of the Andes cordillera piedmont, from 33° to 34° S. The results are interpreted in the context of the regional geology, tectonic setting of the study area and its implications in the continent-wide perspective of modern alluvial sands proposed by Potter (1994). Sampling was conducted at the alluvial stratigraphic sequences of four study sites along three Andean piedmont arroyos; modal mineralogy in the very fine sand fraction (3 phi to 4 phi) was determined using standard petrographic microscope methods. Q:F:LF average compositions indicate that the Late Pleistocene-Holocene very fine-grained alluvial sands of the Cordillera Frontal piedmont reflects the modern lithic arenites of the Argentine Association reported by Potter (1994). The results show two geologically distinct sources in the catchment areas, volcaniclastic and metamorphic rocks. High concentrations of mica and volcanic glass are likely related to particle morphologies and to the deposition sedimentary environment recorded in the alluvial sequences—floodplains. The overabundance of micas over the volcanic glass in the mid-late Holocene alluvial sequence indicates the drainage of a metamorphic area at the expense of other lithological sources. Source areas are located mainly in the Frontal cordillera, and to a lesser extent, in the piedmont Tertiary deposits, another likely source for the analyzed Quaternary alluvial sediments. The mineralogical signature of the late Pleistocene and Holocene alluvial sequences is in agreement with the composition of the southern Pampean sand mantles, loess and loess-like deposits mainly formed by a volcanic mineral assemblage with source areas placed at the headwaters of the main Andean rivers.

Mehl, A.; Blasi, A.; Zárate, M.

2012-12-01

164

Applied Stratigraphy  

Science.gov (United States)

Stratigraphy is a cornerstone of the Earth sciences. The study of layered rocks, especially their age determination and correlation, which are integral parts of stratigraphy, are key to fields as diverse as geoarchaeology and tectonics. In the Anglophile history of geology, in the early 1800s, the untutored English surveyor William Smith was the first practical stratigrapher, constructing a geological map of England based on his own applied stratigraphy. Smith has, thus, been seen as the first “industrial stratigrapher,” and practical applications of stratigraphy have since been essential to most of the extractive industries from mining to petroleum. Indeed, gasoline is in your automobile because of a tremendous use of applied stratigraphy in oil exploration, especially during the latter half of the twentieth century. Applied stratigraphy, thus, is a subject of broad interest to Earth scientists.

Lucas, Spencer G.

165

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 reqment 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

166

Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to Late Pliocene/Early Pleistocene climate cooling  

Science.gov (United States)

The global Late Pliocene/Early Pleistocene cooling (~3.0-2.0 million years ago - Ma) concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela upwelling system (BUS), off Namibia, where it is known as the Matuyama Diatom Maximum (MDM). Our study focuses on a new diatom silicon isotope (?30Si) record covering the MDM in the BUS. Unexpectedly, the variations in ?30Si signal follow biogenic opal content, whereby the highest ?30Si values correspond to the highest biogenic opal content. We interpret the higher ?30Si values during the MDM as a result of a stronger degree of silicate utilisation in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Late Pliocene/Early Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0-2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California) during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to Late Pliocene/Early Pleistocene cooling.

Etourneau, J.; Ehlert, C.; Frank, M.; Martinez, P.; Schneider, R.

2012-09-01

167

Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to Late Pliocene/Early Pleistocene climate cooling  

Directory of Open Access Journals (Sweden)

Full Text Available The global Late Pliocene/Early Pleistocene cooling (~3.0–2.0 million years ago – Ma concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela upwelling system (BUS, off Namibia, where it is known as the Matuyama Diatom Maximum (MDM. Our study focuses on a new diatom silicon isotope (?30Si record covering the MDM in the BUS. Unexpectedly, the variations in ?30Si signal follow biogenic opal content, whereby the highest ?30Si values correspond to the highest biogenic opal content. We interpret the higher ?30Si values during the MDM as a result of a stronger degree of silicate utilisation in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Late Pliocene/Early Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to Late Pliocene/Early Pleistocene cooling.

J. Etourneau

2012-09-01

168

Multi-component Magnetization Of The Late Pliocene Pyroclastic Flow Deposit In Central Japan, Indicating Early Early Pleistocene Fault Activity  

Science.gov (United States)

The Late Pliocene Ichiuda Welded Tuff Bed in central Japan acquired three magnetization components. All of primary reverse intermediate temperature component, and secondary normal low and high temperature components show positive fold tests, indicating that fault-related folding structure postdated the Olduvai normal subchron. The northern segment of Itoigawa-Shizuoka Tectonic Line that bounds the North American and Eurasian Plates in central Japan, comprises the geological Otari-Nakayama and active Kamishiro faults. The Ichiuda Welded Tuff Bed intruded by the 2.1 Ma Taro-yama Andesite is subjected to the NE-SW trending folding structure adjacent to the Otari-Nakayama fault. PAFD and PThD were performed to the drilled samples of Taro-yama Andesite and the Ichiuda Welded Tuff Bed at three and five sites on both limbs of the syncline, respectively. Positive fold test for the tilt-corrected site-mean directions of the andesite indicates prefolding magnetization. The fresh welded tuff bed at one site yields similar reverse direction. Whereas the greenly altered beds at four sites shows normal tilt-corrected site-mean directions by PAFD, and following three temperature-dependent directional components by PThD: normal below 350 degree, reverse from 350 to 530 degree, and normal above 530 degree, all which show positive fold test. IRM acquisition, thermal demagnetization of three orthogonal IRM, thermomagnetic analysis with VSM, and low temperature magnetization measurements with MPMS indicate that the Ichiuda Welded Tuff Bed with single and three magnetization components contains titanomagnetites, and both titanomagnetites and magnetite, respectively. Magnetization of the Taro-yama Andesite is dominated by titanomagnetites under high temperature oxidation state and minor proportion of titanomaghemites. The Taro-yama Andesite and the Ichiuda Welded Tuff Bed exhibit primary reverse magnetism corresponding to the Matsuyama Chron. The Ichiuda Welded Tuff Bed additionally acquired normal magnetization components by hydrothermal alternation in the Olduvai Subchron; low and high temperature components are secondary TRM by re-heating for titanomagnetites and CRM by formation of magnetite, respectively. Positive fold test for secondary magnetization of the welded tuff bed would introduce the early Early Pleistocene activity of the Otari-Nakayama fault.

Ueki, T.; Yamazaki, T.; Funaki, M.; Hoshi, H.

2003-12-01

169

Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa  

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New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ˜14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific ?D of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific ?13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ˜10-9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The ?13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the interhemispheric contrast gradient minima. We interpret a shift in conditions at the Younger Dryas to indicate a limited switch in insolation-dominated control on climate of the Lake Victoria region, to remote teleconnections with the coupled Atlantic and Pacific climate system.

Berke, Melissa A.; Johnson, Thomas C.; Werne, Josef P.; Grice, Kliti; Schouten, Stefan; Sinninghe Damsté, Jaap S.

2012-11-01

170

Late Pleistocene Terraces in River Valleys of the Central Russian Plain: Morphology, Structure and History of Development  

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Morphology and sedimentary composition of low terraces of the Seim (the middle Dnieper catchment) and Khoper (the middle Don catchment) rivers were studied in the field (DGPS topographic profiling, hand and mechanical coring, examination of natural exposures) and in laboratory (grain size analysis, spore-pollen composition, 14C and OSL dating, microscopic study of quartz grains). Archaeological data have also been taken into account. It was found that Late Pleistocene river terraces were subject to complex reworking after the alluvial sedimentation had finished. Terraces may therefore contain sediments of different origin and terrace levels may vary according to the post-alluvial reworking. To establish terrace sedimentation mechanisms we supplemented lithological data collected in the field with quartz grains morphoscopy technique - microscopic study of quartz grains surfaces. The results exhibit wide participation of aeolian and slope wash sediments in terrace deposits, deep aeolian reworking of terrace alluvium during LGM that could be possible due to ground water lowering because of deep pre-LGM incision of rivers. The main difficulty in interpretation of morphoscopic results is that aeolian signals are sometimes not clear due to short duration of wind action over alluvial sands. River incision was detected within the interval since 50-60 to 25-30 ka BP (cal). High runoff increase is proposed as the reason of this incision, which is illustrated by formation of "big meanders" (macromeanders) in river valleys. There were probably several time spans of high runoff divided by low runoff intervals. By the time of LGM rivers had already been incised down to the modern river levels or deeper. The cryoaridic LGM time (20-23 ka BP cal) makes the most pronounced low runoff interval. After LGM, the last high runoff epoch started, which is dated to 13-18(19) ka BP (cal). Numerous now relict macromeanders were formed in river valleys at that time and considerable portions of modern floodplains were established. So the morphology of river valleys indicates contrasting runoff variations being the characteristic feature of the Valdai (Weichselian) cold stage.

Matlakhova, Ekaterina; Panin, Andrey

2014-05-01

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Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to late Pliocene/early Pleistocene climate cooling  

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Full Text Available The global late Pliocene/early Pleistocene cooling (~3.0–2.0 million years ago, Ma concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela Upwelling System (BUS, off Namibia, where it is known as the Matuyama Diatom Maximum (MDM. Our study focuses on a new diatom silicon isotope (?30Si record covering the MDM in the BUS. Unexpectedly, the variations in ?30Si signal follow biogenic opal content, whereby the highest ?30Si values correspond to the highest biogenic opal content. We interpret the higher ?30Si values during the MDM as a result of a stronger degree of silicate utilization in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Plio/Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to late Pliocene/early Pleistocene cooling.

J. Etourneau

2012-03-01

172

Contemporaneous trace and body fossils from a late Pleistocene Lakebed in Victoria, Australia, allow assessment of bias in the fossil record.  

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The co-occurrence of vertebrate trace and body fossils within a single geological formation is rare and the probability of these parallel records being contemporaneous (i.e. on or near the same bedding plane) is extremely low. We report here a late Pleistocene locality from the Victorian Volcanic Plains in south-eastern Australia in which demonstrably contemporaneous, but independently accumulated vertebrate trace and body fossils occur. Bite marks from a variety of taxa are also present on the bones. This site provides a unique opportunity to examine the biases of these divergent fossil records (skeletal, footprints and bite marks) that sampled a single fauna. The skeletal record produced the most complete fauna, with the footprint record indicating a markedly different faunal composition with less diversity and the feeding traces suggesting the presence, amongst others, of a predator not represented by either the skeletal or footprint records. We found that the large extinct marsupial predator Thylacoleo was the only taxon apparently represented by all three records, suggesting that the behavioral characteristics of large carnivores may increase the likelihood of their presence being detected within a fossil fauna. In contrast, Diprotodon (the largest-ever marsupial) was represented only by trace fossils at this site and was absent from the site's skeletal record, despite its being a common and easily detected presence in late Pleistocene skeletal fossil faunas elsewhere in Australia. Small mammals absent from the footprint record for the site were represented by skeletal fossils and bite marks on bones. PMID:23301008

Camens, Aaron Bruce; Carey, Stephen Paul

2013-01-01

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Lake-level rise in the late Pleistocene and active subaquatic volcanism since the Holocene in Lake Kivu, East African Rift  

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The history of Lake Kivu is strongly linked to the activity of the Virunga volcanoes. Subaerial and subaquatic volcanoes, in addition to lake-level changes, shape the subaquatic morphologic and structural features in Lake Kivu's Main Basin. Previous studies revealed that volcanic eruptions blocked the former outlet of the lake to the north in the late Pleistocene, leading to a substantial rise in the lake level and subsequently the present-day thermohaline stratification. Additional studies have speculated that volcanic and seismic activities threaten to trigger a catastrophic release of the large amount of gases dissolved in the lake. The current study presents a bathymetric mapping and seismic profiling survey that covers the volcanically active area of the Main Basin at a resolution that is unprecedented for Lake Kivu. New geomorphologic features identified on the lake floor can accurately describe related lake-floor processes for the first time. The late Pleistocene lowstand is observed at 425 m depth, and volcanic cones, tuff rings, and lava flows observed above this level indicate both subaerial and subaquatic volcanic activities during the Holocene. The geomorphologic analysis yields new implications on the geologic processes that have shaped Lake Kivu's basin, and the presence of young volcanic features can be linked to the possibility of a lake overturn.

Ross, Kelly Ann; Smets, Benoît; De Batist, Marc; Hilbe, Michael; Schmid, Martin; Anselmetti, Flavio S.

2014-09-01

174

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

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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. All structures were studied in a natural trench created as a result of erosion by a tributary of the Acequión River, called El Mono Creek. They form part of a large-scale slump system. Two slumps occur in the western portion of the trench and must have moved towards the ENE (70°), where the depocentre of the Boca del Acequión area is situated. Considering the spatial relationship with Quaternary faults, the slumps are interpreted as being due to a seismic event. The thickest dikes in the El Mono Creek trench occur in the eastern portion of the trench, indicating that the responsible earthquake was located to the east of the study area, probably at the Cerro Salinas fault system zone. The slumps, sand dikes and other soft-sediment deformation features are interpreted as having been triggered by earthquakes, thus providing a preliminary palaeoseismic record of the Cerro Salinas fault system and extending the record of moderate-to high-magnitude earthquakes in central western Argentina to the Late Pleistocene.

Perucca, Laura P.; Godoy, Enrique; Pantano, Ana

2014-07-01

175

Pacific neogene stratigraphy  

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The Fourth International Congress of Pacific Neogene Stratigraphy, was held July 29-31, 1987, at the University of California, Berkeley. This very successful congress was organized by the Regional Committee on Pacific Neogene Stratigraphy (RCPNS) of the International Union of Geological Sciences (IUGS) and the International Geological Correlation Program (IGCP) Project 246 “Pacific Neogene Events in Time and Space.” The meeting was attended by 180 scientists from 16 different countries, and more than 90 presentations were made, on topics ranging from paleoclimatology, biostratigraphy, regional stratigraphy and geologic history, new techniques in stratigraphy, evolutionary studies, and modern biofacies and sediment relationships.A. R. Edwards of the New Zealand Geological Survey (Lower Hutt, New Zealand) spoke on climatic events that he recognizes in the late Neogene strata of New Zealand. The carbon isotope shift during chron 6 (6.3-6.5 Ma) is identified in the sequence at Blind River (Marlborough, New Zealand). The extinction of ˜25% of New Zealand molluscan genera during the latest Micoene (Kapitean Stage) accompanied the greatly accelerated diversification of planktonic foraminifera lineages at this time. The New Zealand events are also coeval with the Messinian “salinity crisis” in the Mediterranean. A series of events (extinctions of Mollusca, appearance of glacial rock types, foraminifera speciation, and nannofossil appearances) in New Zealand late Pliocene rocks reflect the climatic deterioration. One type of sub-Antarctic molluscan fauna abruptly appeared in central North Island at 2.4 m.y., coeval with the onset of major Northern Hemisphere glaciation.

Barron, John; Beu, Alan; Blueford, Joyce R.; Chinzei, Kiyotaka; Hornibrook, Norcutt; Ingle, James; Steininger, Fritz; Tsuchi, Ryuichi

176

Stratigraphy, age and correlation of middle Pleistocene silicic tephras in the Auckland region, New Zealand : a prolific distal record of Taupo Volcanic Zone volcanism  

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Coastal sections in the Auckland region reveal highly carbonaceous and/or highly weathered clay-dominated cover-bed successions with numerous discrete distal volcanic ash (tephra) layers, fluvially reworked siliciclastic (tephric) deposits, and two widely distributed pyroclastic density current (PDC) deposits generated from explosive silicic volcanism within the Taupo Volcanic Zone (TVZ). The younger of the two PDC deposits (informally named Waiuku tephra) is glass-isothermal plateau fission-track (ITPFT) dated at 1.00 ± 0.03 Ma and occurs in a normal polarity interval interpreted as the Jaramillo Subchron. Waiuku tephra is correlated with Unit E sourced from the Mangakino Volcanic Centre of the TVZ. Waiuku tephra can be subdivided into two distinctive units enabling unequivocal field correlation: a lower stratified unit (dominantly pyroclastic surge with fall component) and an upper massive to weakly stratified unit (pyroclastic flow). At many sites in south Auckland, Waiuku tephra retains basal 'surge-like' beds (<1.4 m thickness). This provides clear evidence for primary emplacement and is an exceptional feature considering the c. 200 km this PDC has travelled from its TVZ source area. However, at many other Auckland sites, Waiuku tephra displays transitional sedimentary characteristics indicating lateral transformation from hot, gas-supported flow/surge into water-supported mass flow and hyperconcentrated flow (HCF) deposits. The older PDC deposit is dated at 1.21 ± 0.09 Ma, is enveloped by tephras that are ITPFT-dated at 1.14 ± 0.06 Ma (above) and 1.21 ± 0.06 Ma (below), respectively, and occurs below a short normal polarity interval (Cobb Mountain Subchron) at c. 1.19 Ma. This PDC deposit, correlated with Ongatiti Ignimbrite sourced from the Mangakino Volcanic Centre of TVZ, has laterally transformed from a gas-supported, fine-grained pyroclastic flow deposit at Oruarangi, Port Waikato, into a water-supported volcaniclastic mass flow deposit farther north at Glenbrook Beach. The occurrence of Ongatiti Ignimbrite in Auckland significantly extends its northward distribution. Large numbers of post- and pre-Ongatiti rhyolitic tephra layers, ranging in age from c. 1.31 to 0.53 Ma, are also recognised in the region, with some up to 0.5 m in compacted fallout thickness. Although some tephras can be attributed to known TVZ eruptions (e.g., Ahuroa/Unit D), many have yet to be identified in proximal source areas and remain uncorrelated. However, some can be reliably correlated to tephra layers occurring in marine to nearshore sequences of Wanganui Basin and deep-sea cores retrieved east of North Island. The identification of previously unrecognised mid-Pleistocene TVZ-sourced tephra deposits in the Auckland region, and their correlation to the offshore marine record, represent an advance in the construction of a higher resolution history for the TVZ where, close to eruptive source, the record is fragmentary and obscured by deep burial, or erosion, or both. (author). 65 refs., 22 figs., 3 tabs

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Acoustic stratigraphy of Bear Lake, Utah-Idaho - Late Quaternary sedimentation patterns in a simple half-graben  

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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. ?? 2005 Elsevier B.V. All rights reserved.

Colman, S. M.

2006-01-01

178

Geophysics and tentative late cenozoic seismic stratigraphy of the Banda Arc-Australian continent collision zone along three transects  

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Three marine geophysical transects across the Banda Arc-Australian continent collision zone, east of Timor, north of Tanimbar and southeast of Seram show a variety of deformation patterns produced by the convergence. Seismic sequences observed in troughs and basins along these transects are tentatively correlated with the latest Cenozoic cycle chart. The sequences tentatively constrain the ages of the basins from Pliocene to Recent. In the troughs near the deformation front, Pliocene (5.5 Ma) to Recent undisturbed sediments are being accreted along the Timor and the Seram Transect. The forearc of both these transects shows deformed sediments. The Tanimbar Transect shows six basins on the Tanimbar structural high and deformation associated with strike slip and diapirism is observed. The deformation front on this transect consists of very closely spaced faults. The Weber Deep formed just prior to 5.5 Ma based on the tentative seismic sequence stratigraphy. A structural break in all 3 transects at a distance of about 45 km from the deformation front is postulated to relate to overriding of the base of the Australian continental slope.

Jongsma, D.; Woodside, J. M.; Huson, W.; Suparka, S.; Kadarisman, D.

179

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

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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.

Tsanko Tzankov

2012-12-01

180

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  

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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 lujanenses 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.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 archeological 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.

M.J. Toledo

2005-06-01

 
 
 
 
181

The Corte Blanco garnetiferous tuff: A distinctive late Miocene marker bed in northwestern Argentina applied to magnetic polarity stratigraphy in the Rio Yacones, Salta Province  

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We introduce the Corte Blanco Tuff, a white garnetiferous air fall unit, as a distinctive Neogene marker bed. Three whole-rock K/Ar ages from rocks at the source of this unit indicate that it was erupted 8.73 +/- 0.25 Ma from the La Pava-Ramadas Caldera on the Argentine Puna. Ash spread eastward across the foreland provinces of the Eastern Cordillera and Sierras Subandinas. Recognition of this dated marker unit in these provinces provides the first, easily identified, late Miocene time line in the vast, densely vegetated region to the east of the Puna. We encountered the unit in seven localities from all three morphostructural provinces in NW Argentina. A depositional gap in the air fall material is present between 20 and 150 km to the east of the caldera. Recognition of the Corte Blanco Tuff in the Rio Yacones, near Salta, allowed an interpretation to be made of a magnetic polarity stratigraphy section erected in marginally suitable Neogene detrital strata of the Rio Guanaco Formation. We interpret the strata we examined to have been deposited between 10.5 and 6.4 Ma and report a 10 deg clockwise rotation since the strata were deposited. This is the first numerically dated section in the Rio Guanaco Formation of NW Argentina. These results reveal that uplift of the Eastern Cordillera was in progress at this time.

Viramonte, Jose G.; Reynolds, James H.; del Papa, Cecilia; Disalvo, Alfredo

1994-02-01

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Studying travertines for neotectonics investigations: Middle-Late Pleistocene syn-tectonic travertine deposition at Serre di Rapolano (Northern Apennines, Italy)  

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Middle-Late Pleistocene tectonic activity has been inferred through studies on travertine deposits exposed in a tract of the hinterland Northern Apennines. A detailed study on the relationships between tectonics and travertine deposition coupled with 230Th/234U age determination of travertines at Cava Oliviera quarry, located close to Serre di Rapolano village (southern Tuscany, Northern Apennines), allowed us to recognise Pleistocene faults, whose activity has been referred to 157-24 ka, at least. Travertine deposition was tectonically controlled by WSW-ENE striking, oblique and normal faults, associated to a main fault (named as the Violante Fault). This structure dissected a regional normal fault (known as the Rapolano Fault) Early-Middle Pliocene in age, which bounded the eastern side of the Pliocene Siena Basin, and gave rise to space accommodation for clayey and sandy marine sediments. Hydrothermal circulation (and related travertine deposition) was favoured by the damaging enhancement due to the fault-fault intersection. Tectonic activity has been also documented by deformation recorded by travertines, which suggest a main tectonic event between 64 ± 5 and 40 ± 5 ka. The tectonic activity described for the study area agrees with the Quaternary tectonic evolution documented in the surrounding areas (e.g. Mt. Amiata and Mt. Vulsini), as well as the Tyrrhenian margin of the Central Apennines, indicating that a widespread tectonic activity affected the inner part of the Apennines until the latest Quaternary.

Brogi, Andrea; Capezzuoli, Enrico; Aqué, Riccardo; Branca, Marilì; Voltaggio, Mario

2010-09-01

183

Middle to Late Pleistocene loess record in eastern Nebraska, USA, and implications for the unique nature of Oxygen Isotope Stage 2  

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New subsurface data reveal a nearly continuous stratigraphic record of Middle to Late Pleistocene loess sedimentation preserved beneath upland summits in eastern Nebraska, USA. Thickness and grain size trends, as well as pedologic evidence, indicate significant changes in loess sources, accumulation rates, and depositional environments. The newly defined Kennard Formation accumulated in the Middle Pleistocene, and may represent multiple thin increments of distal loess from nonglacial sources on the Great Plains. The overlying Loveland Loess, up to 18 m thick and deposited during Oxygen Isotope Stage 6 (OIS 6) (Illinoian glaciation), probably records the emergence of the Missouri River valley as a major glaciogenic loess source. The prominent Sangamon Geosol formed through long-term pedogenic alteration of the upper Loveland Loess during OIS 5 and 4. Thin loess of the Gilman Canyon Formation records slow loess accumulation and pedogenic alteration in OIS 3. The Peoria Loess (OIS 2) is similar in thickness to Loveland Loess, but may have accumulated more rapidly in an environment less favorable to bioturbation. More importantly, comparison of Peoria and Loveland loess thickness trends indicates much greater influx of nonglaciogenic loess from the Great Plains during OIS 2 than in OIS 6, suggesting colder and/or drier conditions in the Midcontinent during OIS 2 than in earlier glacial stages.

Mason, J. A.; Joeckel, R. M.; Bettis, E. A.

2007-03-01

184

Evidence of late Gelasian dispersal of African fauna at Coste San Giacomo (Anagni Basin, central Italy): Early Pleistocene environments and the background of early human occupation in Europe  

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Since the late 70s, the Early Pleistocene (Gelasian) site of Coste San Giacomo (Anagni Basin, central Italy) has been known amongst palaeontologists for its diverse vertebrate fauna. During the last 5 years, new excavations and the drilling of a 46-m-deep core have provided novel pieces of information. Palaeomagnetic data, pollen and small vertebrates analyses are presented here for the first time and combined with the updated list of the large vertebrates and ostracod analysis in a multidisciplinary perspective. Large and small mammals, pollen and ostracod analyses have allowed an integrated palaeoenvironmental reconstruction of the sedimentary sequence, depicting the evolution of the alluvial plain in the surrounding landscape. Moreover, magnetostratigraphy, pollen and small mammal biochronological data have confirmed the position of the Coste San Giacomo Faunal Unit, focusing the possible age of the mammal assemblage around 2.1 Ma, in a reversed phase before the base of the Olduvai chron. In particular, the occurrence of the large vole Mimomys pliocaenicus has important biochronological significance. The Coste San Giacomo site offers a unique opportunity to investigate the faunal and environmental changes that occurred in Mediterranean Europe during the Early Pleistocene, coinciding with major climatic changes at a global scale. The occurrence of taxa such as Hippopotamus sp. in the assemblage provides evidence of early dispersal events of African taxa prior to the early Homo diffusion into Europe.

Bellucci, L.; Bona, F.; Corrado, P.; Magri, D.; Mazzini, I.; Parenti, F.; Scardia, G.; Sardella, R.

2014-07-01

185

The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel  

Science.gov (United States)

The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The ? 18O and ? 13C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.

Sivan, Dorit; Greenbaum, Noam; Cohen-Seffer, Ronit; Sisma-Ventura, Guy; Almogi-Labin, Ahuva

186

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

Science.gov (United States)

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.

Vergara, Luis S.

1997-03-01

187

Late Pleistocene environmental changes lead to unstable demography and population divergence of Anopheles albimanus in the northern Neotropics.  

Science.gov (United States)

We investigated the historical demography of Anopheles albimanus using mosquitoes from five countries and three different DNA regions, the mitochondrial cytochrome oxidase subunit I gene (COI), the single copy nuclear white gene and the ribosomal internal transcribed spacer two (ITS2). All the molecular markers supported the taxonomic status of a single species of An. albimanus. Furthermore, agreement between the COI and the white genes suggested a scenario of Pleistocene geographic fragmentation (i.e., population contraction) and subsequent range expansion across southern Central America. PMID:20888924

Loaiza, Jose R; Scott, Marilyn E; Bermingham, Eldredge; Sanjur, Oris I; Wilkerson, Richard; Rovira, Jose; Gutiérrez, Lina A; Correa, Margarita M; Grijalva, Mario J; Birnberg, Lotty; Bickersmith, Sara; Conn, Jan E

2010-12-01

188

A Record of Late Pleistocene and Holocene Surface-rupturing Earthquakes Along the Lake Isabella Section of the Kern Canyon Fault, California  

Science.gov (United States)

The Kern Canyon fault is a major N-S striking crustal structure that has accommodated extensional deformation within the southern Sierra Nevada range via dominantly east-down faulting since at least the middle Pleistocene. A 34-km-long portion of this fault, the Lake Isabella section, strikes N10°W between the towns of Kernville and Havilah and is characterized along much of its length by linear, east-facing bedrock scarps that impound Holocene and late Pleistocene alluvial and colluvial deposits in the Hot Spring and Havilah Valleys. The southern boundary of this fault section is a 3 km right step-over to the Breckenridge fault in Walker Basin. The northern boundary with the South Kern Canyon section of the Kern Canyon fault is a 3 to 4 km right step-over corresponding with a prominent change in strike (35°) and a distinct disruption in the continuity of fault-related geomorphic features. Detailed geomorphic mapping along the Lake Isabella section documents clear evidence for the occurrence of multiple late Quaternary surface-rupturing earthquakes, and paleoseismic and radiometric age data from one site in Havilah Valley and two sites in Hot Spring Valley indicate at least two and as many as three Holocene surface-rupturing earthquakes that faulted colluvial and alluvial deposits. Faulted colluvial deposits at the Havilah Valley site provide evidence for at least two Holocene surface ruptures and one Late Pleistocene surface rupture and a minimum vertical slip rate of 0.1 to 0.3 mm/yr since 15 to 20 ka. Faulted and warped alluvial deposits near the south end of Hot Spring Valley (Bernie/Silicz site) indicate at least two and possibly three Holocene surface ruptures and a vertical slip rate of 0.2 to 0.4 mm/yr since 25 to 30 ka. Faulted and warped colluvial deposits near the north end of Hot Spring Valley (at the Isabella Project Auxiliary Dam) show evidence for two to three Holocene to possibly late Pleistocene surface ruptures and a vertical slip rate of 0.1 to 0.3 mm/yr since about 20 ka. A paleoearthquake chronology for the Lake Isabella section of the Kern Canyon fault was developed by correlating paleoseismic data among these three sites. The most-recent surface-rupturing earthquake occurred at about 3.6 ka and the penultimate earthquake occurred between about 5.5 and 4.4 ka. Comparison of this event chronology with the South Kern Canyon section of the Kern Canyon fault indicates that these two fault sections ruptured independently during their most recent surface ruptures and may have ruptured together during their penultimate surface rupture. Trench evidence shows that the two Holocene ruptures along the Lake Isabella section produced average vertical displacements of about 0.9 to 1.1 m. A statistical analysis of these displacement data with respect to world-wide earthquake rupture data sets and consideration of possible earthquake scenarios for the Kern Canyon fault indicates that the expected upper limit of the 84th percent confidence interval for future displacements is about 1.5 m, which corresponds to an earthquake magnitude of M7.0.

Lutz, A.; Kozaci, O.; Kelson, K. I.; Simpson, D.; Baldwin, J. N.; Amos, C. B.; Turner, R.; Rose, R.

2010-12-01

189

Constancy in the vegetation of the Amazon Basin during the late Pleistocene: Evidence from the organic matter composition of Amazon deep sea fan sediments  

Science.gov (United States)

Analyses of more than 60 sediment samples from the Amazon deep sea fan show remarkably constant terrigenous biomarkers (lignin phenols and cutin acids) and stable carbon isotopic compositions of organic matter (?13COM) deposited from 10 to 70 ka. Sediments from the nine Amazon deep sea fan channel-levee systems investigated in this study yielded relatively narrow ranges for diagnostic parameters such as organic carbon (OC) normalized total lignin yields (? = 3.1 ± 1.1 mg/100 mg OC), syringyl:vanillyl phenol ratios (S/V = 0.84 ± 0.06), cinnamyl:vanillyl phenol ratios (C/V = 0.08 ± 0.02), isomeric abundances of cutin-derived dihydroxyhexadecanoic acid (f10,16-OH = 0.65 ± 0.02), and ?13COM (-27.6% ± 0.6 ‰). Our measurements support the hypothesis that the vegetation of the Amazon Basin did not change significantly during the late Pleistocene, even during the Last Glacial Maximum. Moreover, the compositions obtained from the Amazon deep sea fan are similar to those of modern Amazon River suspended sediments. Such results strongly indicate that the current tropical rainforest vegetation has been a permanent and dominant feature of the Amazon River watershed over the past 70 k.y. Specifically, we found no evidence for the development of large savannas that had been previously postulated as indicators of increased glacial aridity in Amazonia. Climate models need to be modified to account for the uninterrupted input of moisture to the tropical Amazon region over the late Pleistocene Holocene period.

Kastner, Thomas P.; Goñi, Miguel A.

2003-04-01

190

Phylogeographic heterogeneity of the brown macroalga Sargassum horneri (Fucaceae) in the northwestern Pacific in relation to late Pleistocene glaciation and tectonic configurations.  

Science.gov (United States)

Pleistocene glacial oscillations and associated tectonic processes are believed to have influenced the historical abundances and distribution of organisms in the Asia Northwest Pacific (ANP). Accumulating evidence indicates that factors shaping tempospatial population dynamics and distribution patterns of marine taxa vary with biogeographical latitude, pelagic behaviour and oceanographic regimes. To detect what kinds of historical and contemporary factors affected genetic connectivity, phylogeographic profiles of littoral macroalga Sargassum horneri in the ANP were analysed based on mitochondrial (Cox3) and chloroplast (rbcL) data sets. Five distinct clades were recovered. A strong signature of biogeographical structure was revealed (?(CT) = 0.487, P remarkable differentiation in clade distribution, as clade I is restricted to Chinese marginal seas (Yellow-Bohai Sea, East China Sea and South China Sea), whereas clades II-V are discontinuously scattered around the main Islands of Japan. Furthermore, two secondary contact regions were identified along the south Japan-Pacific coastline. This significant differentiation between the two basins may reflect historical glacial isolation in the northwestern Pacific, which is congruent with the estimates of clade divergence and demographic expansion during the late Quaternary low sea levels. Analysis of molecular variance and the population-pair statistic F(ST) also revealed significant genetic structural differences between Chinese marginal seas and the Japanese basin. This exceptional phylogeographic architecture in S. horneri, initially shaped by historical geographic isolation during the late Pleistocene ice age and physical biogeographical barriers, can be complicated by oceanographic regimes (ocean surface currents) and relocating behaviour such as oceanic drifting. PMID:21851438

Hu, Zi-Min; Uwai, Shinya; Yu, Shen-Hui; Komatsu, Teruhisa; Ajisaka, Tetsuro; Duan, De-Lin

2011-09-01

191

Invertebrate Paleontology of the Wilson Grove Formation (Late Miocene to Late Pliocene), Sonoma and Marin Counties, California, with some Observations on Its Stratigraphy, Thickness, and Structure  

Science.gov (United States)

The Wilson Grove Formation is exposed from Petaluma north to northern Santa Rosa, and from Bennett Valley west to Bodega Bay. A fauna of at least 107 invertebrate taxa consisting of two brachiopods, 95 mollusks (48 bivalves and 46 gastropods), at least eight arthropods, and at least two echinoids have been collected, ranging in age from late Miocene to late Pliocene. Rocks and fossils from the southwest part of the outcrop area, along the Estero de San Antonio, were deposited in a deep-water marine environment. At Meacham Hill, near the Stony Point Rock Quarry, and along the northern margin of the outcrop area at River Road and Wilson Grove, the Wilson Grove Formation was deposited in shallow marine to continental environments. At Meacham Hill, these shallow water deposits represent a brackish bay to continental environment, whereas at River Road and Wilson Grove, fossils suggest normal, euhaline (normal marine salinity) conditions. A few taxa from the River Road area suggest water temperatures slightly warmer than along the adjacent coast today because their modern ranges do not extend as far north in latitude as River Road. In addition, fossil collections from along River Road contain the bivalve mollusks Macoma addicotti (Nikas) and Nuttallia jamesii Roth and Naidu, both of which are restricted to the late Pliocene. The late Miocene Roblar tuff of Sarna-Wojcicki (1992) also crops out northeast of the River Road area and underlies the late Pliocene section at Wilson Grove by almost 300 m. Outcrops in the central part of the region are older than those to the northeast, and presumably younger than deposits to the southwest. The Roblar tuff of Sarna-Wojcicki (1992) occurs at Steinbeck Ranch in the central portion of the outcrop area. At Spring Hill, also in the central part of the outcrop area, the sanddollar Scutellaster sp., cf. S. oregonensis (Clark) has been recently collected. This species, questionably identified here, is restricted to the late Miocene from central California through Oregon. Outcrops at Salmon Creek, northeast of Steinbeck Ranch and also in the central part of the outcrop area, contain Aulacofusus? recurva (Gabb) and Turcica brevis Stewart, which are both restricted to the Pliocene, as well as Lirabuccinum portolaensis (Arnold) known from the early Pliocene of central and northern California and into the late Pliocene in southern California. These data suggest an overall pattern of older rocks and deeper water to the south and west, and younger rocks and shallower water to the east and north. Outcrops to the southwest, south of the Bloomfield fault, are not well dated but presumably are older than the late Miocene Roblar tuff of Sarna-Wojcicki (1992). Fossils in this part of the section are rare and are not useful in determining a precise age or environment of deposition for the lower part of the Wilson Grove Formation. However, sedimentary sequences and structures in the rocks here are useful and suggest probable outer shelf and slope water depths. Lituyapecten turneri (Arnold) which occurs in this part of the section has previously been restricted to the Pliocene, but its occurrence below the Roblar tuff of Sarna-Wojcicki (1992) indicates a revised late Miocene age for this taxon. Three possibly new gastropods (Mollusca) are reported here: Calyptraea (Trochita) n. sp. and Nucella sp., aff. N. lamellosa (Gmelin), both from the Bloomfield Quarry area, and Acanthinucella? n. sp. from the River Road area. These species are not described here because this venue is deemed insufficient for the description of new taxa.

Powell, Charles L.; Allen, James R.; Holland, Peter J.

2004-01-01

192

Tectono-stratigraphy of the Çankiri Basin: Late Cretaceous to early Miocene evolution of the Neotethyan Suture Zone in Turkey  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Çank?r? Basin straddles the ?zmir–Ankara–Erzincan Suture Zone which demarcates the former position of the northern branch of the Neotethys. It includes more than 3 km of pre-Middle Miocene in-fill related to late Cretaceous to pre-Middle Miocene evolution of the region. The basin has developed on the upper Cretaceous subduction complex and arc related basins of the Neotethys Ocean. The basin fill includes an upper Cretaceous forearc sequence overlain by Paleocene with a local unco...

Kaymakc?i, N.; O?zc?elik, Y.; White, S. H.; Dijk, P. M.

2009-01-01

193

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

Science.gov (United States)

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.

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

2013-08-01

194

Late Quaternary stratigraphy of an alluvial valley along an active convergence front: Interactions of fluvial processes, tectonic channel steering, and sea level in the eastern Ganges-Brahmaputra-Meghna River delta  

Science.gov (United States)

Insights into how tectonics, alluvial channels, and sediment interact to build the stratigraphy in a tectonically active depositional basin can be discovered by studying the sediment record and the current geomorphology of a system. Tectonics is an influence on basins that often gets overlooked due to overriding controls such as sea level, climate, and sediment load. The area for this study is in the Ganges Brahmaputra Meghna Delta (GBMD) in close proximity to an active convergent thrust front. To investigate the stratigraphy, we drilled 48 cores along two approximately longitudinal transects, 25-60 km apart, each spanning ~100 km. The boreholes were drilled every 3-4 km to a maximum depth of 100 m. The transects are situated across an alluvial valley and are bounded to the west by a Pleistocene terrace (Madhupur Terrace) and to the east by a fold belt (Indo-Burman Fold Belt) that continues to deform due to active tectonics at the thrust front. A seismic cruise using a mini-GI gun was conducted in conjunction with this study along the current river channel and has shown evidence of folded sediment at depth, and field studies in the area have found outcropping anticlines thus aiding in the determination of transect location. Through analysis of aerial imagery and digital elevation models (DEMs) of the transects, abandoned channels once occupied by the alluvial channel are evidence of migration and avulsion occurring recently enough to be recorded on the land surface. Initial analysis of the sediment cores shows a dramatic contrast in the stratigraphy between the two transects despite lying along the same morphological reach of the GBMD. The northern transect is dominated by fine to medium sands throughout indicating a strong fluvial influence, while the southern transect is dominated by muds and finer sands at depth indicating a tidal estuarine influence. The stratigraphy and land surface are a consequence of the controls on the system and reflect channel behavior over time. The establishment of channel behavior, including avulsions, migration, and overbank processes, is the key to investigating how rivers and tectonics interact to shape the landscape and build stratigraphy, which will be discussed in detail based on these transect and seismic datasets.

Williams, L.; Goodbred, S. L.; Steckler, M. S.; Seeber, L.; Spiess, V.; Schwenk, T.; Palamenghi, L.; Akhter, S. H.; Mondal, D.; Hossain, S.

2012-12-01

195

The granite tors of Dartmoor, Southwest England: rapid and recent emergence revealed by Late Pleistocene cosmogenic apparent exposure ages  

Science.gov (United States)

Dartmoor, in SW England, is a classic periglaciated granite upland adorned with a population of over 150 tors. The origin of the tors has been controversial, but their emergence by differentiation after stripping of regolith during Pleistocene cold phases is accepted. However, their actual age has been unknown, with possible scenarios ranging from preservation since the early Middle Pleistocene to relatively short-lived landforms in a maritime climate with high denudation rates. The latter is now supported by 32 cosmogenic surface exposure dates from 28 tors across the whole upland. The distribution of apparent 10Be ages peaks strongly in the Middle Devensian (36-50 ka), which with corrections for weathering and limited ice shielding could be interpreted as Early Devensian. These ages are much younger than those found for three glacially unmodified Cairngorms tors, and somewhat younger even than glacially modified Cairngorms tors. The dates show little spatial variation. Although an ice cap has now been modelled in the heart of northern Dartmoor, tors here are of median age, suggesting that ice cover sufficient to shield tors from incoming radiation was of short duration. The few younger tor ages support the idea of continuing landform instability across the landscape, with weathering flakes redeveloping soon after inferred loss of top pillows by gelifraction or gravitational toppling. The few older tor ages have no systematic explanation, and may indicate inheritance from an earlier cycle of bedrock near-exposure. Since most tors are modest in height (typically 2-5 m), volumetrically insignificant, and often in advanced stages of disintegration, the general impression is that they are evanescent features, which emerge and quickly disappear during every Pleistocene climatic downturn. Tor populations may thus flicker across the landscape rather randomly over the Quaternary. The remarkably consistent age of the present tor population could be associated with a stripping event at the start of the Devensian, but fuller analysis must await closer controls on tor denudation rates in different climatic phases, and on ice cover extent and duration. These results only date extant tor surfaces, not the landscape, but as the best available erosion pins they have evident value in exploring theories of the evolution of Dartmoor during the Quaternary.

Gunnell, Yanni; Jarman, David; Braucher, Régis; Calvet, Marc; Delmas, Magali; Leanni, Laetitia; Bourlès, Didier; Arnold, Maurice; Aumaître, Georges; Keddaouche, Karim

2013-02-01

196

A 50,000-year record of late Pleistocene tropical vegetation and human impact in lowland Borneo  

Science.gov (United States)

There has been considerable uncertainty about the nature of Pleistocene environments colonised by the first modern humans in Island SE Asia, and about the vegetation of the Last Glacial Maximum (LGM) in the region. Here, the palynology from a series of exposures in the Great Cave of Niah, Sarawak, Malaysian Borneo, spanning a period from ca. 52,000 to 5000 BP is described. Vegetation during this period was climate-driven and often highly unstable. Interstadials are marked by lowland forest, sometimes rather dry and at times by mangroves. Stadials are indicated by taxa characteristic of open environments or, as at the LGM, by highly disturbed rather open forest. Stadials are also characterised by taxa now restricted to 1000-1600 m above sea level, suggesting temperature declines of ca 7-9 °C relative to present, by comparison with modern lapse rates. The practice of biomass burning appears associated with the earliest human activity in the cave.

Hunt, Chris O.; Gilbertson, David D.; Rushworth, Garry

2012-03-01

197

First mtDNA sequencing of Volga and Ob basin taimen Hucho taimen: European populations stem from a late Pleistocene expansion of H. taimen out of western Siberia and are not intermediate to Hucho hucho.  

Science.gov (United States)

New concatenated mtDNA sequences (three genes; n = 22) of Siberian taimen Hucho taimen primarily from west Siberian and European regions of the species' range were added to 12 previously published sequences to provide a phylogeographic overview of the species. European samples show only very minor divergence from west Siberian populations, supporting a late Pleistocene expansion from Siberia into the Urals, with no particular relation to the Danube River basin huchen Hucho hucho as once hypothesized. The disjunct distribution of the genus is most likely based on an early Pleistocene vicariant event. PMID:24906052

Mari?, S; Alekseyev, S; Snoj, A; Askeyev, O; Askeyev, I; Weiss, S

2014-08-01

198

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)

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.

BjØrk, Anders Anker; Björck, Svante

2011-01-01

199

Characterization of relict Late Pleistocene and Early Holocene paleosols buried in wedge-shaped structures on the southern coast of the Finnish Gulf  

Science.gov (United States)

The physical and physicochemical properties and morphogenetic characteristics of the buried soddy gleyic and gleyed paleosols developed from the glaciolacustrine loamy sediments on the southern coast of the Finnish Gulf in the Late Pleistocene and Early Holocene (12-9 ka, calibrated) are considered. It is shown that the morphology and properties of these paleosols sharply differ from those of the enclosing gravelly sands deposited in the ancient basins. The latter substrates serve as the major type of soil-forming materials for the modern surface soils. The studied paleosols fill wedge-shaped structures dissecting the gravelly sediments. Their profiles are well preserved, though their normal horizontal orientation is disturbed; large soil blocks were displaced into the open wedges. The presence of these soils attests to the fact that the initial soil cover in the studied region was formed in the Late Glacial epoch soon after the retreat of the glacial sheet. The good degree of preservation of the paleopedogenic information recorded in the profiles of these paleosols is of great value for the paleoenvironmental reconstructions.

Rusakov, A. V.; Nikonov, A. A.

2010-07-01

200

Steppe lion remains imported by Ice Age spotted hyenas into the Late Pleistocene Perick Caves hyena den in northern Germany  

Science.gov (United States)

Upper Pleistocene remains of the Ice Age steppe lion Panthera leo spelaea (Goldfuss, 1810) have been found in the Perick Caves, Sauerland Karst, NW Germany. Bones from many hyenas and their imported prey dating from the Lower to Middle Weichselian have also been recovered from the Perick Cave hyena den. These are commonly cracked or exhibit deep chew marks. The absence of lion cub bones, in contrast to hyena and cave bear cub remains in the Perick Caves, and other caves of northern Germany, excludes the possibility that P. leo spelaea used the cave for raising cubs. Only in the Wilhelms Cave was a single skeleton of a cub found in a hyena den. Evidence of the chewing, nibbling and cracking of lion bones and crania must have resulted from the importation and destruction of lion carcasses (4% of the prey fauna). Similar evidence was preserved at other hyena den caves and open air sites in Germany. The bone material from the Perick and other Central European caves points to antagonistic hyena and lion conflicts, similar to clashes of their modern African relatives.

Diedrich, Cajus G.

2009-05-01

 
 
 
 
201

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

Science.gov (United States)

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.

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

2010-01-01

202

230Th/234U dates of late Pleistocene corals from Kita- and Minami-Diato Island, Okinawa, Japan  

International Nuclear Information System (INIS)

Alpha spectrometric Th-230/U-234 dating was applied to 50 Pleistocene corals from Kita- and Minami-Daito Islands, both have been well known as the noteworthy representatives of raised atolls. The Th-230/U-234 dates ranged from 113±6 to 133±6 ka (123±1 ka on average) in the autochthonous corals from Kita-, and from 111±5 to 159±10 ka (123±1 ka on average) in those from Minami-Daito Island, intimating that the fringing reefs have been developed during the high sea level stand of the last interglacial maximum. These dates are correlative to the oxygen isotope stage 5e. The upper limit of occurrence of the dated autochthonous corals was 8.1 m in Kita- and 11 m in Minami-Daito Island. Besides, the somewhat younger dates corresponding to OIS-5a or 5c were obtained from some allochthonous corals in a detrital limestone unit in Kita-Daito Island. However, hermatypic corals were alive, forming small scale reefs in shallow sea around Kita-Daito Island. The former shoreline was proved by the presence of raised surf bench at some localities, where the dated autochthonous corals were collected. (K.I.)

203

sup 230 Th/ sup 234 U dates of late Pleistocene corals from Kita- and Minami-Diato Island, Okinawa, Japan  

Energy Technology Data Exchange (ETDEWEB)

Alpha spectrometric Th-230/U-234 dating was applied to 50 Pleistocene corals from Kita- and Minami-Daito Islands, both have been well known as the noteworthy representatives of raised atolls. The Th-230/U-234 dates ranged from 113{+-}6 to 133{+-}6 ka (123{+-}1 ka on average) in the autochthonous corals from Kita-, and from 111{+-}5 to 159{+-}10 ka (123{+-}1 ka on average) in those from Minami-Daito Island, intimating that the fringing reefs have been developed during the high sea level stand of the last interglacial maximum. These dates are correlative to the oxygen isotope stage 5e. The upper limit of occurrence of the dated autochthonous corals was 8.1 m in Kita- and 11 m in Minami-Daito Island. Besides, the somewhat younger dates corresponding to OIS-5a or 5c were obtained from some allochthonous corals in a detrital limestone unit in Kita-Daito Island. However, hermatypic corals were alive, forming small scale reefs in shallow sea around Kita-Daito Island. The former shoreline was proved by the presence of raised surf bench at some localities, where the dated autochthonous corals were collected. (K.I.).

Omura, Akio; Iwata, Hideki (Kanazawa Univ. (Japan). Faculty of Science); Ota, Yoko; Koba, Motoharu; Kawana, Toshio

1991-06-01

204

Spectral stratigraphy  

Science.gov (United States)

Stratigraphic and structural studies of the Wind River and Bighorn basins, Wyoming, and the Guerrero-Morelos basin, Mexico, have resulted in development of ''spectral stratigraphy.'' This approach to stratigraphic analysis uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. This paper reviews selected published examples that illustrate this new stratigraphic procedure. Visible to thermal infrared laboratory, spectral measurements of sedimentary rocks are the physical basis for spectral stratigraphy. Results show that laboratory, field, and remote spectroscopy can augment conventional laboratory and field methods for petrologic analysis, stratigraphic correlation, interpretation of depositional environments, and construction of facies models. Landsat thematic mapper data are used to map strata and construct stratigraphic columns and structural cross sections at 1:24,000 scale or less. Experimental multispectral thermal infrared aircraft data facilitate lithofacies/biofacies analyses. Visible short-wavelength infrared imaging spectrometer data allow remote determination of the stratigraphic distribution of iron oxides, quartz, calcite, dolomite, gypsum, specific clay species, and other minerals diagnostic of environments of deposition. Development of a desk-top, computer-based, geologic analysis system that provides for automated application of these approaches to coregistered digital image and topographic data portends major expansion in the use of spectral stratigraphy for purely scientific (lithospheric research) or practical (resource exploration) objectives.

Lang, Harold R.

1991-09-01

205

Cosmogenic Be-10 ages of Angel Lake and Lamoille moraines and late Pleistocene slip rate of the rangefront normal fault, Ruby Mountains, Basin and Range, Nevada  

Science.gov (United States)

We use Be-10 cosmogenic radionuclide (CRN) exposure dating to quantify the timing of late Pleistocene glacial advances and to estimate the rangefront normal fault slip rate along the Ruby Mountains in the Basin and Range, Nevada. Ten Be-10 CRN exposure ages from the Angel Lake terminal moraine in Hennen Canyon limit deposition to between 15.4-23.1 ka (average = 18.2 ka; SD = 2.5 ka), an interval that overlaps with the Tioga glacial advances in the Sierra Nevada and Pinedale advances in the Rocky Mountains during MIS-2. The termination of the Angel Lake glaciation at ~15.4 ka is nearly synchronous with the final highstand and subsequent rapid desiccation of Lake Lahontan. Previous relative age dating studies in the Ruby Mountains have inferred deposition of Lamoille moraines during MIS-4 (~59-74 ka) or MIS-6 (~130-190 ka). However, fifteen Be-10 CRN exposure dates obtained from a Lamoille lateral moraine in Hennen Canyon (average = 30.7 ka; SD = 11.5; range = 19.3-66.5 ka) do not support these assignments and instead suggest that the moraine may have been deposited during MIS-3. Assuming the average Be-10 model age from the Lamoille surface represents a minimum age constraint, we obtain a maximum fault slip rate of 0.40-0.60 mm/year for a 60° dipping fault and 11-16 m of vertical separation across faulted Lamoille moraines. Accommodation of 0.4-0.6 mm/year of slip by the Ruby Mountains fault zone implies an average 0.2-0.3 mm/year of horizontal strain accumulation across the fault during the last ~31 ka, and thus characterization of the central Basin and Range as a geodetic microplate may be at odds with late Pleistocene horizontal displacement rates along the Ruby Mountains fault zone. If correct, the observed disparity between the CRN exposure dates and geologic correlations underscores the importance of quantitative age constraints for climate reconstruction, landscape evolution, and tectonic geomorphology.

Briggs, R. W.; Wesnousky, S. G.; Ryerson, F. J.; Finkel, R. C.; Meriaux, A.

2004-12-01

206

Dynamics of the Barents-Kara ice sheet as revealed by quartz sand grain microtextures of the late Pleistocene Arctic Ocean sediments  

Science.gov (United States)

During the entire Quaternary, ice sheets advanced and retreated across the circum-Arctic margins in a series of climate related glacial-interglacial cycles. It is critical to obtain evaluation of the nature of initiated glaciers at the Arctic margins after the pronounced interglacial periods. In this study this will be done by inferring from glacially generated quartz sand grain surface microtextures and related sedimentology extracted from the central Arctic Ocean sediments. These microtextures can be correlated with the generation and fluctuations in the extent of the late Pleistocene Eurasian Ice Sheet i.e. Barents-Kara Ice Sheet. The central Arctic Ocean sediments in the Lomonosov Ridge, having been deposited after the late Pleistocene interglaciations and having had no internal hiatuses, provide an excellent time window for usage of quartz sand grain surface textures for evaluating possible evolving glaciers and continental ice sheets. This is based on the fact that iceberg and sea-ice transported quartz sand grains and their mechanically formed surface textures, created under high cryostatic stress, are diagnostic for glacier thickness and dynamics having been existed in sediment source areas. Sand-sized quartz grains in deep marine sediments favour iceberg or sea-ice transportation with characteristic content of microtextures formed prior this transportation. The sand grain surface microtextures and their frequencies of the selected submarine Lomonosov Ridge sediments during Marine Isotope Stage (MIS) 5 to MIS 3 are analysed using a scanning electron microscope (SEM). Coring during the Arctic Ocean 96 expedition (core 96/12-1pc) provided alternating clay to silty clay sediments which are characterised by prominent silt to sand-size containing intervals. The specific glacial crushing and high cryostatic stress generated features, such as high angularity, conchoidal fractures, steps and sub-parallel linear fractures, were observed from quartz sand grain surfaces. Continental ice generation and extent are evident soon after the Eemian interglaciation and the following MIS 4 stage shows the highest frequencies of glacigenic microtextures. The microtexture generation under high cryostatic pressure underneath ice more than 1 km thick, can be taken as concurrent signal of the temporal expansion of the northernmost continental ice sheets, which could easily have reached the shelf break of the Barents, Kara and western Laptev seas during that time.

Strand, Kari; Immonen, Ninna

2010-12-01

207

Soft-sediment deformation structures in Late Pleistocene alluvial-aeolian sediments caused by GIA induced seismicity along the Osning Thrust (northern Germany)  

Science.gov (United States)

Historic sources report that northern Germany was affected by significant earthquakes during the last 500 years (Leydecker 2009), but the only modern study so far on earthquake related soft-sediment deformation structures was carried out by Hoffmann and Reicherter (2012) for the Baltic Sea coast area of northeastern Germany. We present new data on seismically triggered soft-sediment deformation structures in Pleniglacial to Late Glacial alluvial fan and aeolian sand-sheet deposits of the upper Senne (Münsterland Embayment) and link this soft-sediment deformation directly to Late Glacial earthquakes generated along the Osning Thrust, which is one of the major fault systems in Central Europe. The reactivation of the Mesozoic Osning Thrust was an effect of glacial isostatic adjustment during the Pleniglacial to Late Glacial (Brandes et al., 2012). Young tectonic activity in this area is indicated by the 1612 Bielefeld earthquake (Vogt & Grünthal 1994). The analysed soft-sediment deformation structures are exposed in two sand pits in the vicinity of the Osning Thrust and include a complex fault and fold pattern, clastic dykes, sand volcanoes, sills, irregular intrusive sedimentary bodies, flower- to antler-like dewatering structures, flame structures, and ball-and-pillow structures. There is a distinct variation of the soft-sediment deformation style parallel to the trend of the Osning Thrust. In the northwestern part of the study area, close to Oerlinghausen there is a wide range of structures developed that is mainly related to fluidization processes. In contrast, in the southeast only flower- to antler-like dewatering structures and normal fault-arrays occur. This might indicate that the epicentre of the Late Pleniglacial to Late Glacial seismic event was close to Oerlinghausen. It is the first time in northern Germany, that fluidization and liquefaction features can be directly related to a fault. The occurrence of seismicity in the Late Pleniglacial to Late Glacial together with the 17th century seismicity indicates ongoing crustal movements along the Osning Thrust and sheds new light on the seismic activity of northern Germany. The association of soft-sediment deformation structures implies that the Late Glacial earthquake had a Richter magnitude of at least 5. References Brandes C, Winsemann J, Roskosch J, Meinsen J, Tanner DC, Frechen M, Steffen H, Wu P (2012). Activity of the Osning thrust during the late Weichselian: ice-sheet and lithosphere interactions. Quat Sci Rev 38:49-62 Hoffmann G, Reicherter K (2012) Soft-sediment deformation of Late Pleistocene sediments along the southwestern coast of the Baltic Sea (NE Germany). Int J Earth Sci 101:351-363 Leydecker G (2009) Erdbebenkatalog für die Bundesrepublik Deutschland mit Randgebieten für die Jahre 800 - 2007. Datenfile www.bgr.de/quakecat, Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover. Vogt J, Grünthal G (1994) Die Erdbebenfolge vom Herbst 1612 im Raum Bielefeld. Geowissenschaften 12:236-240

Brandes, Christian; Winsemann, Jutta

2013-04-01

208

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

209

Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)  

Science.gov (United States)

Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ˜120-110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ˜70-60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ˜55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today's alpine timberline. The Unterangerberg record ended at ˜45 ka and/or was truncated by ice during the Last Glacial Maximum.

Starnberger, Reinhard; Drescher-Schneider, Ruth; Reitner, Jürgen M.; Rodnight, Helena; Reimer, Paula J.; Spötl, Christoph

2013-05-01

210

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)

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.

Diedrich, Cajus G.

2013-09-01

211

Stratigraphy and the depositional environments of the Plio-Quaternary deposits of the Eastern Marmara Region, NW Turkey  

Science.gov (United States)

The study area is located along the western part of the North Anatolian Fault zone between the Gulf of Izmit and Adapazari and is represented by an east-west trending narrow depression. The depression is filled by Late Pliocene and younger deposits. Stratigraphy and depositional characteristics of this sedimentary fill shed light onto the geological evolution of North Anatolian Fault in the region. The sediments filling the Gulf of Izmit were examined mainly by seismic profiles and some borehole data. Seismic data were obtained by Sismik-1 vessel of General Directorate of Mineral Research and Exploration. Within the Gulf of Izmit; anoxic, brackish marine, brackish marine-deltaic and marine sediments have been deposited during the Late Pliocene, Early-Middle Pleistocene, Late Pleistocene and Late Pleistocene-Holocene periods respectively. In the onshore part to the east, Izmit-Adapazari depression, thick alluvial fan sediments (~400 m) have been deposited at the same time. These sediments consist of fluvial and alluvial fan deposits, mainly fed from the southern areas. Alluvial fan deposits can be separated into proximal, medial and distal parts from south to north. Coarse grained fanglomerates in the proximal parts and fine grained mudstones and local swamp and flood-plain deposits in the distal parts can be recognized. Fossils from the lower parts of these sediments indicate a late Pliocene-Pleistocene age. Palaeocurrent measurements and facies distribution of the fan deposits indicate that the depression started to form under the control of NE-SW and NW-SE trending faults having dominantly normal component since Late Pliocene. This period is characterized by the development of series of pull-apart basins. Recents sediments are still depositing in the Gulf of Izmit and the Izmit- Adapazari depression and cut by E-W trending active branches of the North Anatolian Fault.

Erturac, M. K.; Tari, U.; Tuysuz, O.; Kurt, H.; Demirbag, E.

2003-04-01

212

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 234}U/{sup 238}U activity ratios (AR) of shells support the hypothesis of closure of the geochemical system with respect to this element. It is remarkable that {sup 234}U/{sup 238}U 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 {sup 234}U/{sup 238}U AR values comparable to those observed for shells. {sup 14}C 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 {delta}{sup 13}C and {delta}{sup 18}O 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.

Causse, Christiane; Ghaleb, Bassam; Chkir, Najiba; Zouari, Kamel; Ben Ouezdou, Hedi; Mamou, A

2003-11-01

213

Diapiric uplift of an MIS 3 marine deposit in SW Spain: Implications for Late Pleistocene sea level reconstruction and palaeogeography of the Strait of Gibraltar  

Science.gov (United States)

In the Bay of Cádiz (SW Spain) an Upper Pleistocene beach deposit (31.5 ka BP) has been recognised at about 1-3 m above m.s.l. The deposit is affected by a set of joints and fractures filled by calcretes and other subaerial sediments, dated at 19.9 ka BP. Deformation and uplift of this level is related to the moderate activity of a diapiric structure. The resulting uplift produced local emersion of the deposit and a transition from marine to continental conditions during the Late Quaternary. The deformational style and tectonic location of the deposit argue against strong vertical motion. Regional comparisons between this diapir and other similar and coeval structures near the zone suggest a vertical uplift of about 25 m. Therefore, between 30 and 20 ka BP the sea level can be supposed to have been placed near to its present-day position, probably less than 30 m below. These results confirm other regional data indicating that during MIS 3 several relative sea level rises took place, reaching heights of only several tens of metres below the present m.s.l. The palaeogeographical implications of these results include the existing controversy about the possible crossing of the Strait of Gibraltar by Neanderthals between ca 40 and 30 ka. The palaeogeographical reconstruction of the Strait for this period suggests that its width and depth were very similar to the present ones.

Gracia, F. J.; Rodríguez-Vidal, J.; Cáceres, L. M.; Belluomini, G.; Benavente, J.; Alonso, C.

2008-11-01

214

A draft de novo genome assembly for the northern bobwhite (Colinus virginianus) reveals evidence for a rapid decline in effective population size beginning in the Late Pleistocene.  

Science.gov (United States)

Wild populations of northern bobwhites (Colinus virginianus; hereafter bobwhite) have declined across nearly all of their U.S. range, and despite their importance as an experimental wildlife model for ecotoxicology studies, no bobwhite draft genome assembly currently exists. Herein, we present a bobwhite draft de novo genome assembly with annotation, comparative analyses including genome-wide analyses of divergence with the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata) genomes, and coalescent modeling to reconstruct the demographic history of the bobwhite for comparison to other birds currently in decline (i.e., scarlet macaw; Ara macao). More than 90% of the assembled bobwhite genome was captured within 14,000 unique genes and proteins. Bobwhite analyses of divergence with the chicken and zebra finch genomes revealed many extremely conserved gene sequences, and evidence for lineage-specific divergence of noncoding regions. Coalescent models for reconstructing the demographic history of the bobwhite and the scarlet macaw provided evidence for population bottlenecks which were temporally coincident with human colonization of the New World, the late Pleistocene collapse of the megafauna, and the last glacial maximum. Demographic trends predicted for the bobwhite and the scarlet macaw also were concordant with how opposing natural selection strategies (i.e., skewness in the r-/K-selection continuum) would be expected to shape genome diversity and the effective population sizes in these species, which is directly relevant to future conservation efforts. PMID:24621616

Halley, Yvette A; Dowd, Scot E; Decker, Jared E; Seabury, Paul M; Bhattarai, Eric; Johnson, Charles D; Rollins, Dale; Tizard, Ian R; Brightsmith, Donald J; Peterson, Markus J; Taylor, Jeremy F; Seabury, Christopher M

2014-01-01

215

Comparison of depositional elements of an ancient and a modern submarine fan complex: Early Pennsylvanian Jackfork and late Pleistocene Mississippi fans  

Energy Technology Data Exchange (ETDEWEB)

Normark urged that all future, meaningful deep-sea fan comparisons be confined to key depositional elements common to most turbidite systems. These elements should include basin size, tectonic and eustatic setting, and depositional process indicators. A test case for elemental comparisons between two widely studied fan complexes is presented and evaluated. The lower Pennsylvanian (Morrowan) Jackfork submarine fan complex extends from central Arkansas to northeast Texas. Sequence analysis suggests that the Jackfork is composed of four to seven depositional episodes and occupies the floor of a deep basin bordered to the north and east by a passive carbonate-siliciclastic shelf margin and to the south and east by a northward-advancing orogenic belt. The Jackfork apparently unrestricted to the west and southwest. The Mississippi submarine fan complex extends from the submerged continental shelf of southern Louisiana to the abyssal depths between Yucatan and Florida. The fan complex is primarily Pleistocene in age, with the present morphologic fan being late Wisconsinian. The Mississippi Fan is composed of 17 depositional episodes. It occupies the floor of a deep basin bordered on the north and west by quiescent( ) halokinetic-siliciclastic shelf margins and to the east and south by passive carbonate margins. Elemental comparisons between the Mississippi fan and a palynspastically restored Jackfork fan complex suggest that both are quite similar, even though the Mississippi fan is up to three times larger in some categories. Comparative study of key depositional elements facilities a more complete understanding of both modern and ancient submarine fans.

Coleman, J.L. Jr. (Amoco Production Co., Houston, TX (USA))

1990-05-01

216

A Draft De Novo Genome Assembly for the Northern Bobwhite (Colinus virginianus) Reveals Evidence for a Rapid Decline in Effective Population Size Beginning in the Late Pleistocene  

Science.gov (United States)

Wild populations of northern bobwhites (Colinus virginianus; hereafter bobwhite) have declined across nearly all of their U.S. range, and despite their importance as an experimental wildlife model for ecotoxicology studies, no bobwhite draft genome assembly currently exists. Herein, we present a bobwhite draft de novo genome assembly with annotation, comparative analyses including genome-wide analyses of divergence with the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata) genomes, and coalescent modeling to reconstruct the demographic history of the bobwhite for comparison to other birds currently in decline (i.e., scarlet macaw; Ara macao). More than 90% of the assembled bobwhite genome was captured within 14,000 unique genes and proteins. Bobwhite analyses of divergence with the chicken and zebra finch genomes revealed many extremely conserved gene sequences, and evidence for lineage-specific divergence of noncoding regions. Coalescent models for reconstructing the demographic history of the bobwhite and the scarlet macaw provided evidence for population bottlenecks which were temporally coincident with human colonization of the New World, the late Pleistocene collapse of the megafauna, and the last glacial maximum. Demographic trends predicted for the bobwhite and the scarlet macaw also were concordant with how opposing natural selection strategies (i.e., skewness in the r-/K-selection continuum) would be expected to shape genome diversity and the effective population sizes in these species, which is directly relevant to future conservation efforts. PMID:24621616

Halley, Yvette A.; Dowd, Scot E.; Decker, Jared E.; Seabury, Paul M.; Bhattarai, Eric; Johnson, Charles D.; Rollins, Dale; Tizard, Ian R.; Brightsmith, Donald J.; Peterson, Markus J.; Taylor, Jeremy F.; Seabury, Christopher M.

2014-01-01

217

Late Pleistocene biomarker records from the central Arctic Ocean (ACEX Hole M0004C and HOTRAX HLY0503-08JPC)  

Science.gov (United States)

Biomarkers were investigated in late Pleistocene sediments collected from the Integrated Ocean Drilling Program (IODP)-Arctic Coring Expedition (ACEX) Hole M0004C (87°52.1'N, 136°11.3'E) from the Lomonosov Ridge and the 2005 Healy-Oden Trans Arctic Expedition (HOTRAX) HLY0503-08JPC (79°35.6'N, 172°30.1'W) from the Mendeleev Ridge in the central Arctic Ocean. In Hole M0004C, the major biomarkers were long-chain n-alkanes, n-fatty acids, and n-alkan-1-ols, indicating fresh organic matter derived predominantly from higher plants. No concrete evidence for phytoplankton biomarkers was found at the study site. The dominance of terrestrial biomarkers is attributed to the severe degradation of organic matter caused by slow sedimentation in oxygen-rich benthic water and/or low primary production due to permanent sea-ice coverage. Hopane concentrations correlated well with ice-rafted debris (IRD) data, suggesting that they are a tracer of mature sedimentary organic matter and may encode the same information as IRD. High organic carbon content was present in the IRD-rich dark gray layer deposited during MIS-6. The layer contained a significant amount of branched GDGTs, suggesting ice erosion of organic-rich continental soils followed by transportation to the central Arctic by drifting ice. We also present the results from Core HLY0503-08JPC and discuss the correlation with ACEX M0004.

Yamamoto, M.; Polyak, L.

2007-12-01

218

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

DEFF Research Database (Denmark)

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 stages were qualitatively defined, comprising well-preserved specimens, three overgrowth (OG1 to OG3) and one etching (E1) stage. Comparing SEM and LM observations, a tentative correlation between the E. huxleyi calcified LM-morphotypes and E. huxleyi SEM-overgrowth stages is proposed here. Our study not only indicates that Emiliania huxleyi coccoliths are strongly influenced by carbonate diagenesis, but also that they show effects of carbonate precipitation and dissolution much more clearly than other coccoliths. The relative abundances of the different LM-morphotypes were used to define an E. huxleyi overgrowth index (EXO) that qualitatively estimates carbonate precipitation/dissolution on coccoliths in this sediment. This resulted in definition of five "Diagenetic" intervals (D1 to D5). Deposition of sapropel S1 was a time of good preservation with variable dissolution and no overgrowth of E. huxleyi coccoliths, whereas calcite overgrowth was high during the Last Glacial Maximum (LGM) and interglacial period and, to a lesser extent, during the Younger Dryas and through the last 5 ka. © 2004 Elsevier B.V. All rights reserved.

Crudeli, D.; Young, J.R.

2004-01-01

219

Are osseous artefacts a window to perishable material culture? Implications of an unusually complex bone tool from the Late Pleistocene of East Timor.  

Science.gov (United States)

We report the discovery of an unusually complex and regionally unique bone artefact in a Late Pleistocene archaeological assemblage (c. 35 ka [thousands of years ago]) from the site of Matja Kuru 2 on the island of Timor, in Wallacea. The artefact is interpreted as the broken butt of a formerly hafted projectile point, and it preserves evidence of a complex hafting mechanism including insertion into a shaped or split shaft, a complex pattern of binding including lateral stabilization of the cordage within a bilateral series of notches, and the application of mastic at several stages in the hafting process. The artefact provides the earliest direct evidence for the use of this combination of hafting technologies in the wider region of Southeast Asia, Wallacea, Melanesia and Australasia, and is morphologically unparallelled in deposits of any age. By contrast, it bears a close morphological resemblance to certain bone artefacts from the Middle Stone Age of Africa and South Asia. Examination of ethnographic projectile technology from the region of Melanesia and Australasia shows that all of the technological elements observed in the Matja Kuru 2 artefact were in use historically in the region, including the unusual feature of bilateral notching to stabilize a hafted point. This artefact challenges the notion that complex bone-working and hafting technologies were a relatively late innovation in this part of the world. Moreover, its regional uniqueness encourages us to abandon the perception of bone artefacts as a discrete class of material culture, and to adopt a new interpretative framework in which they are treated as manifestations of a more general class of artefacts that more typically were produced on perishable raw materials including wood. PMID:24440005

O'Connor, S; Robertson, G; Aplin, K P

2014-02-01

220

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

Science.gov (United States)

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).

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

2012-12-01

 
 
 
 
221

Time-dependent flexural subsidence caused by Holocene and Late Pleistocene sedimentation in the Gulf of Mexico: New inversion modeling of vertical motion data  

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The rate of sedimentary deposition into the world's catchment basins abruptly increased during the transition from Pliocene to Pleistocene climate. Pleistocene periodicity in sedimentation rate has the distinct fingerprints of Milankovich orbital forcing periods 20,000, 41,000 and 100,000 years. We model time-dependent flexure of the Gulf of Mexico by continent-wide sediment transport rate variability over the past 4 Ma. Reconstructions of changes in sediment dispersal occurring during the Late Cenozoic indicate that glacioeustasy may also be a significant role along the shore of the Northern Gulf of Mexico Basin. We employ both spherically layered and self-gravitating viscoelastic models along with a half-space model of very high resolution. We also incorporate the long-wavelength background crustal motion associated with the main Laurentide deglaciation which produces a non-negligible bulge migration. The elastic lithospheric thickness and Maxwell time constants are tuned to both regional and global seismic tomography. The latter data are consistent with a rheologically stiffer than average sub-crustal environment. Hydro-isostatic loading is included in the modeling. Paleosealevel indicators, tide gauges and recent GPS results provide rich data sources for inverse modeling of the load history and solid earth rheology. The sediment rate changes are modeled, in part, as pulsed great megaflood erosional events known to be active during Glacial to Interglacial transitions. Although the model is relatively crude in both space and time, preliminary results indicate that the subsidence rate caused by long-term sedimentary changes could sustain subsidence rates dw/dt of roughly 1 - 12 mm/yr during the past 5,000 years over many hundreds of kilometers of coastline. Geodetic data in the Mississippi Delta region of southern Louisiana show subsidence at rates greater than 5 mm/yr, having many of the spatial characteristics predicted by the sedimentary load model. These data are interpreted in terms of a formal inverse approach and we report optimum solutions for sedimentary loading in for regions where it may be freed as a model parameter.

Ivins, E. R.; Dokka, R.; Blom, R. G.; Wu, X.

2006-12-01

222

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

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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.

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

1990-05-01

223

Geochemical evidence of pollutants from coal-fired generating stations in late Pleistocene plaeosols in the Dalijia Shan, northwestern China  

Energy Technology Data Exchange (ETDEWEB)

Surface palaeosols in two tills and a diamicton from an area in northwestern China were analysed for geochemical pollutants. Elevated levels of Br, As and Sb indicate that pollution from coal-burning and/or coal-fired electricity generating stations is delivered by aeolian transport into palaeosols dating from the last glaciation. Because the climate in the field area is sub-humid (precipitation {lt} 760{mu},) the relative movement of soluble elements in palaeosols dating from early and late stages of the last glaciation is not expected to be high. The glacial and aeolian parent materials of the palaeosols indicate differences that are probably related to their source areas and to the incorporation of geochemical pollutants. 19 refs., 3 figs., 2 tabs.

Mahaney, W.; Hancock, R.G.V. [York University, North York, ON (Canada). Geomorphology and Pedology Dept.

1996-03-01

224

Age estimates and uplift rates for late Pleistocene marine terraces: Southern Oregon portion of the Cascadia forearc  

Energy Technology Data Exchange (ETDEWEB)

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. The authors 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 one to determine terrace ages and uplift rates. Uranium series analysis of fossil coral yields an age of 83 {plus minus} 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. In order to assess the utility of the southern Oregon uplift rates for predicting the behavior of the Cascadia subduction zone, the authors 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 usually high or low. Furthermore, late Quaternary uplift rates show little relationship to the type of convergent margin. 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.

Muhs, D.R.; Whelan, J.F. (Geological Survey, Denver, CO (United States)); Kelsey, H.M.; McInelly, G.W. (Western Washington Univ., Bellingham (United States)); Miller, G.H. (Univ. of Colorado, Boulder (United States)); Kennedy, G.L. (Los Angeles County Museum of Natural History, CA (United States))

1990-05-10

225

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

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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

Sangen, M.

2009-04-01

226

Late Miocene to Plio-Pleistocene fluvio-lacustrine system in the Karacasu Basin (SW Anatolia, Turkey): Depositional, paleogeographic and paleoclimatic implications  

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The sedimentary record of the late Cenozoic Karacasu Basin, a long-lived continental half-graben from southwestern Turkey, is characterized by siliciclastic and carbonate deposits. Sedimentation was controlled by an active NW-SE trending major normal fault along the basin's southern margin and by climatically-induced lake-level changes. Detailed facies analysis subdivides the entire Neogene-Quaternary basin-fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution. Sedimentation commenced in the late Miocene with the deposition of proximal-medial alluvial fan and fluvial facies (Damdere Formation; FA1). At this stage, alluvial fans developed in elevated areas to the south, prograding towards the basin center. At the beginning of the Pliocene, fresh to slightly alkaline, shallow lake deposits (FA2a) of the Karacaören Formation formed. The lake became open and meromictic conditions developed (FA2b). Pollen data from the FA2b facies show that climate was arid to humid. Climate probably changed cyclically through time producing alternation of Artemisia steppe (cold and dry periods) and more forested vegetation (warm and wet). The open lake facies passes upwards into lake margin facies (FA2c), but it was still dominated by alkaline to slightly saline lake conditions. Sedimentation was almost continuous from the late Miocene to Pleistocene. In the early Quaternary, the basin was dissected by the re-activation of basin bounding faults. The unconformable base of the overlying Quaternary deposits (Karacasu Formation; FA3) reflected the basin's transformation from a half-graben into a full-graben system. Oxygen isotope data from carbonates show an alternation of humid climatic periods, when freshwater settings predominated, and semiarid/arid periods in which the basin hosted alkaline and saline water lakes. Neotectonic activity has rejuvenated many of the basin-bounding faults, causing development of talus aprons and local alluvial fans. The basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins. id="ab0010" The study highlights to the paleo-geography/-climatology in the east Mediterranean.

Alçiçek, Hülya; Jiménez-Moreno, Gonzalo

2013-06-01

227

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

Science.gov (United States)

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

Ubeda, J.; Palacios, D.

2009-04-01

228

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

Science.gov (United States)

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.

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

2013-12-01

229

Chronology and evolution of glacio-nival systems of Mongun-Taiga mountain massif in Late Pleistocene and Holocene  

Science.gov (United States)

The main glacial complex of western Tuva - Mongun-Taiga mountain massif (3970.5 m) is situated in the center of Altai-Sayan mountain system. Modern glaciation of the massif has area about 20 km2, average firn line altitude is about 3400 m. Average summer temperatures at the firn line is 0.5°C, precipitation about 270 mm. We studied glacial fluctuations of the past on base of geomorphologic methods and radiocarbon dating of peat, soils and wood samples. Moraines of the Early Stage of the Last Glaciation (MIS 4) extend from cirques and troughs to the flat piedmonts forming lobes reaching the level of 1830 m in the south of the massif and 2200 ° in the north. There are traces of 4 glacial advances, during the maximal the area of glaciation reached 513 km2 with 800 m of depression of firn line. We reconstructed that average summer temperatures were 2.5°C below present with precipitation 2.3 times more than now. During MIS 3 the area of glaciation reduced to less than 0.5 km2 with 450-490 m of elevation of firn line. Samples of moraine-buried wood with with radiocarbon age about 58-39 and 27-25 kBP found 600 m higher than present upper limit of growth of trees give evidence of climatic conditions at least 1.5°C warmer than present (with a correction for tectonics). In the Late Stage of the Last Glaciation glaciers mostly remained inside troughs reaching during the maximum the level of 2200 m in the south and 2400 m in the north, the area of glaciation about 320 km2, firn line depression about 690 m. We estimate cooling in the maximum -3.6 °C with precipitation 65% of present. There are moraine complexes of 4 postglacial advances, in the latest of them, presumably Younger Drias, firn line depression reached 500 m. In the Early Holocene glaciers reduced rapidly, evidence of this reduction are samples of wood with age 9120±110 cal. B.P. that were found about 350 m over the present forest line. According to our reconstruction in the Boreal Holocene optimum (about 9000. B.P.) summer temperature was at least 2.3°C higher than now, minimal elevation of firn line was 270 m relative to present. Corresponding values reconstructed for the Atlantic optimum warming in the interval about 6000-3600 years B.P. are 0.35°C and 50 m. Late Holocene moraines are complexes of 3-4 terminal moraines adjacent or thrust one another. They are thick, bare, with steep foreslopes and contain buried ice. The glacial advance of the historical (subatlantic) stage took part between 3600 and 1200 years B.P., reconstructed depression of firn line is 155 m, probable cooling was 1.5 °C relative to present. Climatic conditions of the interstadial 1200-1130 years B.P. were not colder than present. Glacial advance of the LIA probably had 2 phases, the culmination of the last of them took place in the middle of the XIX century. Reconstructed depression of firn line is 120 m, cooling 0.9 °C relative to present.

Ganushkin, Dmitry; Chistyakov, Kirill

2013-04-01

230

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  

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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

MARÍA TERESA ALBERDI

2007-06-01

231

Late Pleistocene Variations in the Water Current and Ice Rafting Transportations of Organic Matter in the Central Arctic Ocean (ACEX Hole M0004C)  

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Little is known about the source of organic matter and the response of sedimentary organic matter composition to glacial-interglacial changes in the central Arctic Ocean. Here we have generated late Pleistocene records of biomarkers and ice rafted debris (IRD) from IODP-Arctic Coring Expedition (ACEX) Hole M0004C to understand the glacial-interglacial changes of mass transportation in the Arctic Ocean. Major biomarkers detected in Hole M0004C were long-chain n-alkanes, n-fatty acids and n-alkan-1-ols, derived from fresh higher plants, and gem-alkanes (branched aliphatic alkanes with a quaternary substituted carbon atom), derived from unknown source. Minor biomarkers were oleanenes of angiosperm origin, unsaturated fatty acids, bacteria-derived anteiso- and iso-fatty acids, various hydroxy acids, formed by hydroxylation of n-fatty acids by aerobic bacteria, cholesterol and sitosterol, and hopanes, formed by diagenetic alteration of bacterial biohopanoids. There was no concrete evidence for in situ production of phytoplanktons. The concentrations of these biomarkers varied with IRD number variation. During periods of abundant IRD, diagenetic hopanes were abundant, suggesting that clastic materials were supplied by ice rafting. During periods of scarce IRD, the other biomarkers such as long-chain compounds were abundant, suggesting that the riverine discharge was enhanced. The IRD and biomarker variations were synchronized with the eastward expansion of the Fennoscandinavian Ice Sheet to northen Siberia, suggesting that the ice cover of northen Siberia is critical in switching mass transportation mechanisms in the Arctic Ocean.

Yamamoto, M.; Sugisaki, S.; Sakamoto, T.

2006-12-01

232

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)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish 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

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

233

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)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish 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).

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

2013-08-01

234

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)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish 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).

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

235

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)

236

Traces of Late Miocene and Pleistocene tectonics on recent surface morphology in the Western Pannonian Alpine Foothills - a case study of geomorphometry  

Science.gov (United States)

The study area is located at the eastern foothills of the Eastern Alps, which is a transition zone between the still uplifting mountainous region and the subsiding Danube Basin, part of the Pannonian Basin. As the Pannonian Lake filled up during Late Miocene, totally plain surface left behind covering the rugged pre-Tertiary basement. Nowadays, totally flat alluvial plain only recognizable on the easternmost and northeastern part of the investigated area. Slightly undulating hilly surface dissected by N-S and E-W oriented steep scarps prevail the middle part of the area. West from the Austrian-Hungarian border, landscape is quite different. Steep scarps are either observable, however the hills are much more eroded by mostly N-S directed creeks. As Pleistocene rivers drained the Eastern Alps, wide area covered by fluvial, mostly gravel sediments. The whole process span the Pleistocene era with different intensity, forcing drainage reorganization occurred in several steps. Modification of the drainage network were triggered by the general tilting of the study area, normal faults and effects of the basement morphology. In our earlier study, correspondence between surface and basement morphology was detected. Results revealed the differences of the general morphology depend on the pre-Tertiary basement height under the coverage of basement fill. Above South Burgenland Swell (basement ridge of ca. -500 m asl.), recent surface is elevated with ~50 m compared to the close environment. Due to the elevated position of the surface and approximately the same base level, incision of streams are clearly deeper. In this paper we reveal the importance of geomorphometry as a prior investigation method in tectonic geomorphology studies, we show the applicability of tools such as mode of slope, standard deviation of slope in impoundment of surface blocks under different tectonic forces. Sinuosity evaluation of alluvial rivers compared with surface aspect was proven to be very effective method on apparently totally flat area in showing location of tectonic forces. We compared the revealed features with the basement morphology using previously composed basement maps and industrial seismic sections. Latter proved that morphological similarities are not only observable between the basement and the surface, but the geometry of basin-fill lacustrine sediment horizons strengthen the correspondence and in some cases explain the root causes. Our results provide additional information to the geodynamic sketch of the Alpine-Pannonian transition zone and emphasize the applicability of geomorphometry in tectonic studies. The study was supported by Hungarian Scientific Research Fund (OTKA NK83400) and was realized in the frames of TÁMOP 4.2.4.A/2-11-1-2012-0001 high priority "National Excellence Program - Elaborating and Operating an Inland Student and Researcher Personal Support System convergence program" project's scholarship support.

Kovács, Gábor; Telbisz, Tamás; Székely, Balázs

2014-05-01

237

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)

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.

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

2012-04-01

238

Rapid anthropogenic response to short-term aeolian-fluvial palaeoenvironmental changes during the Late Pleistocene-Holocene transition in the northern Negev Desert, Israel  

Science.gov (United States)

Archaeological investigations along Nahal Sekher on the eastern edge of Israel's northwestern Negev Desert dunefield revealed concentrations of Epipalaeolithic campsites associated respectively with ancient water bodies. This study, aimed at better understanding the connections between these camps and the water bodies, is concerned with a cluster of Natufian sites. A comprehensive geomorphological study integrating field mapping, stratigraphic sections, sedimentological analysis and optically stimulated luminescence (OSL) ages was conducted in the vicinity of a recently excavated Natufian campsite of Nahal Sekher VI whose artifacts directly overlay aeolian sand dated by OSL to 12.4 ± 0.7 and 11.7 ± 0.5 ka. Residual sequences of diagnostic silty sediments, defined here as low-energy fluvial fine-grained deposits (LFFDs), were identified within the drainage system of central Nahal Sekher around the Nahal Sekher VI site. LFFD sections were found to represent both shoreline and mid-water deposits. The thicker mid-water LFFD deposits (15.7 ± 0.7-10.7 ± 0.5 ka) date within the range of the Epipalaeolithic campsites, while the upper and shoreline LFFD units that thin out into the sands adjacent to the Nahal Sekher VI site display slightly younger ages (10.8 ± 0.4 ka-7.6 ± 0.4 ka). LFFD sedimentation by low-energy concentrated flow and standing-water developed as a result of proximal downstream dune-damming. These water bodies developed as a result of encroaching sand that initially crossed central Nahal Sekher by 15.7 ± 0.7 ka and probably intermittently blocked the course of the wadi. LFFD deposition was therefore a response to a unique combination of regional sand supply due to frequent powerful winds and does not represent climate change in the form of increased precipitation or temperature change. The chronostratigraphies affiliate the Natufian sites to the adjacent ancient water bodies. These relations reflect a rapid, but temporary anthropogenic response to a transient ‘window' of improved local aeolian-fluvial palaeoenvironmental conditions during the Late Pleistocene-Holocene transition, but don't necessarily point to a wetter or drier palaeoclimate.

Roskin, Joel; Katra, Itzhak; Agha, Nuha; Goring-Morris, A. Nigel; Porat, Naomi; Barzilai, Omry

2014-09-01

239

40Ar/39Ar and U-series ages of a Late Pleistocene geomagnetic excursion in Western North America: The Halina Pali event in Western North America?  

Science.gov (United States)

Here we report 40Ar/39Ar results on two mafic flows, Swift Creek (SC) andesite (17.3 ×1.6ka), located near Mount St. Helens, WA and Tabernacle Hill (TH) basalt (16.9 ×1ka) near Fillmore UT that record paleomagnetic co-latitudes of 28° for SC and 23° for TH, respectively. The remnant directions of these two flows are on the fringe of secular variation and we consider them 'excursionoid'. Because these magnetic directions are somewhat unusual, there are limited matches in the magnetic record preserved in the Mono Lake and Lake Bonneville sediments in this time interval. The best matches to the radiocarbon (calibrated to calendar year age) dated lacustrine magnetic record are at 22 and 18 for the SC flow and 22, 19, or 17 ka for the TH flows. The closest matches for the SC and TH paleomagnetic directions are between 18 and 17 ka, which stratigraphically bracket an excursion recorded in the sediments. Pending additional analyses, our best estimate for the age of the excursion is 17.1 ×1.9ka, which is concordant with the radiocarbon-calibrated age of 17.6 ka for the excursion as determined from the age calibrated paleomagnetic record of the lacustrine sections. In addition to the 40Ar/39Ar ages on the TH flow, we also report an isochron U-Th age of 15 × 4 ka on the outer surface tufa coating, which provides a minimum constraint on the age of the TH lava flows. Discussion: Evidence of a Late Pleistocene geomagnetic excursion event is quite extensive and has been reported from several localities. The earliest report of the excursion, from the Halina Pali scarp, Hawaii, suggested an age of about 17-18 ka [1]. Subsequently, there have been additional reports and age estimates of a similar age excursional event from several other localities; Lake Imurak, Alaska, USA (17-18 ka), Hokkaido, Japan (~23 ka), Lake Baikal, Russia (~20 ka), and from Tule Lake, California, USA (~23 ka), summarized in Oda, [2] and referenced therein, and in China (17-18 ka) [3]. In conclusion, the combined results suggest that the geomagnetic excursion event first reported in the Halina Pali scarp is a 'world-wide' event. The best age estimate of this event is about 17 ka. The age calibrated paleomagnetic records from the lacustrine sections indicate that the duration of this event is on the order of 0.8 to 1.2 ka. 1. Coe et al., 1978, J. Geophys. Res., 83, 1740-175. 2. Oda, 2005, J. Geog 114(2), 174-193. 3. Singer, 2011, AGU Fall meeting, GP13A-04.

Turrin, B. D.; Champion, D. E.; Mortlock, R. A.; Fairbanks, R. G.; Swisher, C. C.

2013-12-01

240

The Late Pleistocene-Holocene community development in Central and SE-Europe in direct fossil record: scope of the approach, common patterns and inter-regional differences.  

Science.gov (United States)

The information provided by modern instrumental approaches (molecular phylogeography, ancient DNA analyses, large scale radiocarbon datings etc.) refined the knowledge on Late Quaternary faunal development and range history of particular taxa in essential way. Nevertheless, the direct fossil record remains still an essential substrate in study of that topics, and to reveal all the information, that it may provide, and integrate it with the outputs of the other approaches presents one of the essential aim of the present meeting. Unfortunately, the immediate use of fossil record for the paleoecologic and paleobiogeographic inferences is often limited by its fragmentarity (both in temporal and spatial respects), taphonomic influences and/or locally specific post-sedimentary effects which all may bias it in a considerable degree. Hence, each particular record is to be carefully reexamined in respect to all factor which may bias it - unfortunately, often it is not too easy to respond that task, particularly when the record is retrived from secondary sources. It should also be remembered that the records representing narrow time slices without a robust lithostratigraphic context do not provide any information on the historical and contextual setting of the respective faunal situation. Such information that is essential for reconstructions of paleobiogeography of community development and similar locally-sensitive phenomena can only be retrived from the continuous sedimentary series which establish the sequence of particular faunal events by direct superposition. A sufficiently dense network of such series provides than a possibility of direct inter-regional comparisons and a high resolution information on the paleobiogeography of the Late Pleistocene-Holocene rearrangements of mammalian communities, local variation in history of particular species and its community context. We illustrate productivity of such approach on with aid of the fossil record obtained from continuous sedimentary sequences from different regions of Czech Republic and Slovakia (850 community samples, 29,800 MNI) and neighbouring countries of Central Europe. Despite common general trends we demonstrated stricking local and regional specificities. Among other they include (a) continuous survival of several woodland elements (Clethrionomys glareolus, Sorex araneus, Micotus subterraneus, Microtus agrestis) throughout Weichselian (including LGM) in the Carpathians, (b) prolonged survival of the glacial elements Ochotona pusilla and Microtus gregalis in Pannonian basin and (c) Dicrostonyx gulielmi in the Carpathian foredeep, contrasting to (d) the early disappearance of them in S-Germany and Bohemia, and (e) similar difference were found also in other cenologic traits. While the glacial communities were nearly homogenous in their structure throughout whole the region, the Holocene development produced a considerable faunal provincialism, which was the most pronounced during Boreal. In contrast to central Europe, the available sequences from the SE-Europe and Asia Minor show only minute faunal changes during the Vistulian and Holocene, no essential rearrangements in community structure were observed (at least as the core species are concerned) and except for Lagurus no glacial immigrant did invade the region. At the same time a degree of local provincialism was continuously high and, in a regional scale, it continuously exceeded that of the Boreal central Europe.

Horacek, Ivan; Lozek, Vojen

2010-05-01

 
 
 
 
241

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)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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.

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

2010-12-01

242

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)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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.

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

243

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)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish 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.

Marcela Sandra, Tonello; Aldo Raúl, Prieto.

2010-12-01

244

Modeling right-lateral offset of a Late Pleistocene terrace riser along the Polaris fault using ground based LiDAR imagery  

Science.gov (United States)

High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwash deposits were collected by using ground based tripod LiDAR (T-LiDAR) to characterize the cumulative fault slip across the recently identified Polaris fault (Hunter et al., 2009) near Truckee, California. The type-section site for the Polaris fault is located 6.5 km east of Truckee where progressive right-lateral displacement of middle to late Pleistocene deposits is evident. Glacial outwash deposits, aggraded during the Tioga glaciation, form a flat lying ‘fill’ terrace on both the north and south sides of the modern Truckee River. During the Tioga deglaciation melt water incised into the terrace producing fluvial scarps or terrace risers (Birkeland, 1964). Subsequently, the terrace risers on both banks have been right-laterally offset by the Polaris fault. By using T-LiDAR on an elevated tripod (4.25 m high), we collected 3D high-resolution (thousands of points per square meter; ± 4 mm) point-cloud imagery of the offset terrace risers. Vegetation was removed from the data using commercial software, and large protruding boulders were manually deleted to generate a bare-earth point-cloud dataset with an average data density of over 240 points per square meter. From the bare-earth point cloud we mathematically reconstructed a pristine terrace/scarp morphology on both sides of the fault, defined coupled sets of piercing points, and extracted a corresponding displacement vector. First, the Polaris fault was approximated as a vertical plane that bisects the offset terrace risers, as well as bisecting linear swales and tectonic depressions in the outwash terrace. Then, piercing points to the vertical fault plane were constructed from the geometry of the geomorphic elements on either side of the fault. On each side of the fault, the best-fit modeled outwash plane is projected laterally and the best-fit modeled terrace riser projected upward to a virtual intersection in space, creating a vector. These constructed vectors were projected to intersection with the fault plane, defining statistically significant piercing points. The distance between the coupled set of piercing points, within the plane of the fault, is the cumulative displacement vector. To assess the variability of the modeled geomorphic surfaces, including surface roughness and nonlinearity, we generated a suite of displacement models by systematically incorporating larger areas of the model domain symmetrically about the fault. Preliminary results of 10 models yield an average cumulative displacement of 5.6 m (1 Std Dev = 0.31 m). As previously described, Tioga deglaciation melt water incised into the outwash terrace leaving terrace risers that were subsequently offset by the Polaris fault. Therefore, the age of the Tioga outwash terrace represents a maximum limiting age of the tectonic displacement. Using regional age constraints of 15 to 13 kya for the Tioga outwash terrace (Benson et al., 1990; Clark and Gillespie, 1997; James et al., 2002) and the above model results, we estimate a preliminary minimum fault slip rate of 0.40 ± 0.05 mm/yr for the Polaris type-section site.

Howle, J. F.; Bawden, G. W.; Hunter, L. E.; Rose, R. S.

2009-12-01

245

Geochronology of the Baye Mn oxide deposit, southern Yunnan Plateau: Implications for the late Miocene to Pleistocene paleoclimatic conditions and topographic evolution  

Science.gov (United States)

40Ar/39Ar laser incremental heating analyses of supergene K-Mn oxides from weathering profiles at the Baye Mn deposit, southern Yunnan Plateau, SW China, were carried out to place constraints on the timing of weathering and derive insights into local paleoclimatic and landscape evolution. Weathering profiles in the Baye Mn mine are dominated by 20-30 m thick saprolites, which are locally covered by unconsolidated alluvial deposits. We analyzed 70 grains from 35 hand samples collected from four sites located at distinct elevations. In most cases, different grains from the same hand sample and different samples from the same site have reproducible 40Ar/39Ar plateau ages. The plateau ages of individual grains are also consistent with the respective isochron, integrated, and ideogram ages. This age consistency attests to the reliability of the geochronological results as numerical constraints on the formation and evolution of these weathering profiles. Sixty-four grains from 32 hand samples collected from weathering profiles at four sites (A to D) yield well-defined plateau or pseudoplateau ages ranging from 2.98 ± 0.07 to years. The incision rate calculated from minimum exposed ages at sites B-D is 33 ± 2 m Myr-1 for the time period of 2.91-1.25 Ma, which is consistent with the slow incision of streams on the ridges over the Yunnan Plateau since the early Pleistocene. Three Mn oxide pebbles contained in the alluvial deposits overlying the saprolite-dominated weathering profiles at the two highest sites provided additional information on the timing of weathering. Four grains from two pebbles yield plateau ages of 6.32 ± 0.19 to 5.27 ± 0.10 Ma, whereas the other two grains from the third pebble indicate the minimum formation ages of 8.2 ± 0.4 and 9.3 ± 0.3 Ma. These ages confirm the existence of older weathering profiles, now dismantled, in the region. Manganese oxide 40Ar/39Ar ages of the Baye deposit, when combined with results from other localities, indicate that lateritic weathering and supergene Mn enrichment and, by inference, warm and humid climates conducive to intense weathering have prevailed over the Plateau since the middle to late Miocene. The climatic conditions inferred from the weathering geochronology are consistent with multiple independent marine and terrestrial sedimentary and paleontological records, confirming that supergene Mn oxides can be used as a useful proxy for past climate. Age clusters of Mn oxides at 2.9-2.4, 1.2-0.8, and 0.6-0.4 Ma are broadly coincident with and thus likely reflect intensification events of the Indian Summer Monsoon that brings moisture and abundant precipitation to the Yunnan Plateau. These clusters also coincide with the periods of significant surface uplift in the Yunnan Plateau, demonstrating a causal link between topographic evolution, plateau uplift, and intensification of the monsoonal climate.

Deng, Xiao-Dong; Li, Jian-Wei; Vasconcelos, Paulo M.; Cohen, Benjamin E.; Kusky, Timothy M.

2014-08-01

246

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)

Full Text Available SciELO Argentina | Language: English Abstract in spanish 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.

Khalid F, Ubeid.

2013-12-01

247

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)

Full Text Available SciELO Argentina | Language: English Abstract in spanish 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.

Khalid F, Ubeid.

248

Contribution to the stratigraphy of the onshore Paraiba Basin, Brazil  

Energy Technology Data Exchange (ETDEWEB)

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)

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

249

Use of spectral gamma-ray data to refine subsurface fluvial stratigraphy: late Cretaceous strata in the Book Cliffs, Utah, USA  

Energy Technology Data Exchange (ETDEWEB)

High-resolution (sub-seismic) stratigraphic correlation in fluvial strata is extremely difficult using conventional subsurface core and wireline-log data (e.g. gamma-ray, neutron, density, sonic logs). Spectral gamma-ray logs provide additional data on lithological composition that can aid identification of chronostratigraphic surfaces in a high-resolution sequence stratigraphic correlation framework. The application of spectral gamma-ray data in constructing such a framework is demonstrated using data from exposures and the subsurface from the Cretaceous non-marine Blackhawk Formation and Castlegate Sandstone of the Book Cliffs area, Utah, USA. The stratigraphic abundance of coals and relatively uniform Th/K ratio, which indicates uniform clay mineralogy, in mudstone sections of the non-marine Blackhawk Formation implies a humid, subtropical climate throughout its deposition. Variations in facies architecture and stratigraphy are therefore interpreted to have been driven principally by fluctuations in relative sea level and hinterland tectonics. It is concluded that within the context of a sound understanding of detrital mineralogy, diagenetic history, facies and appropriate sequence stratigraphic models, spectral gamma-ray data allow sequence boundaries to be identified and correlated in non-marine fluvial strata at least 80 km from the interpreted coeval shoreline.

Hampson, G.J.; Davies, W.; Davies, S.J.; Howell, J.A.; Adamson, K.R. [University of London Imperial College of Science Technology & Medicine, London (United Kingdom). Dept. of Earth Science & Engineering

2005-07-01

250

Multiproxy Late Quaternary stratigraphy of the Nile deep-sea turbidite system — Towards a chronology of deep-sea terrigeneous systems  

Science.gov (United States)

Understanding the recent formation of a sedimentary system such as a deep-sea turbidite system (DSTS) requires an accurate stratigraphic control on deposits. Due to the important terrigeneous input which disrupts the sedimentary record, DSTS is an environment where stratigraphic control is difficult to assess. Most of the time, traditional stratigraphic tools are not accurate enough. This has led to a rather limited number of studies concerning stratigraphy in DSTS. In this study, we examine several hemipelagic long piston cores collected from the Nile DSTS (eastern Mediterranean), in order to understand the recent evolution of the complex sedimentary system in this area. The first aim of this study is to show how to obtain a reliable timeframe in DSTS. Indeed, we provided a detailed ecostratigraphical scheme based on planktonic foraminiferal distribution, oxygen isotope records and lithostratigraphy (sapropels and tephra) of three cores where the sedimentation is least disturbed. We have identified 29 foraminiferal ecozones during the last 250,000 years BP, with an approximately 2000-year time resolution. The time span of each ecozone was constrained by the oxygen isotope record, 14C AMS radiometric data, tephrochronology and the sapropel chronology. These high-resolution ecostratigraphical time subdivisions have been applied in discontinuous mixed hemipelagic/turbiditic sequences of a levee record. This example shows how to date gravity events, formation and time periods of sedimentary accumulations.

Ducassou, E.; Capotondi, L.; Murat, A.; Bernasconi, S. M.; Mulder, T.; Gonthier, E.; Migeon, S.; Duprat, J.; Giraudeau, J.; Mascle, J.

2007-08-01

251

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)

Full Text Available SciELO Argentina | Language: English Abstract in spanish 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.

Kamal M., Hussein.

2006-12-01

252

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)

Full Text Available SciELO Argentina | Language: English Abstract in spanish 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.

Kamal M., Hussein.

253

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)

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.

Diedrich, Cajus G.

2011-07-01

254

Los mamíferos finipleistocénicos de la Formación Quebrada Quereo (IV Región-Chile): biogeografía, bioestratigrafía e inferencias paleoambientales / The Late Pleistocene mammal record of Quebrada Quereo Formation: biogeography, biostratigraphy and paleoclimatic inferences  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish [...] Abstract in english This paper describes the fossil fauna recovered from the Quebrada Quereo Formation (Late Pleistocene - Holocene) located at Choapa Province, IV Region, Chile. In this formation, two cultural levels (Quereo I y II) with Pleistocenic fauna were detected. The remains identified include living species ( [...] Dusycion cf. D. culpaeus), as well as extinguished fauna (Palaeolama sp., Antifer sp., Equus [Amerhippus] sp., cf. Panthera onca, Milodontidae, and Gomphoteriidae). For each of these, we present taxonomic, paleogeographic and paleoclimatic remarks. The possible presence of P. onca in Quebrada Quereo Formation constitutes the first evidence of a locally extinct felid outside the Patagonic area of Chile. The identified faunal assemblage presents differences with those recorded in Argentinean territory; which is explained by the presence of the Cordillera de los Andes. The Chilean paleofaunistic assemblages, therefore, are related to those found in Bolivia and the Andean occidental sector in general, although some enrichment with taxa from the oriental side of the range is not discarded.

Rafael O., Labarca; Patricio G., López.

255

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

Science.gov (United States)

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.

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

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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  

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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.

OMAR P RECABARREN

2011-12-01

257

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)

Full Text Available SciELO Chile | Language: English Abstract in spanish 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.

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

2011-12-01

258

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  

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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.

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

2013-03-01

259

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)

Full Text Available SciELO Chile | Language: English Abstract in spanish 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.

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

260

High-resolution seismic sequence stratigraphy and history of relative sea level changes since the Late Miocene, northern continental margin, South China Sea  

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The northern South China Sea (SCS) margin is suggested as one of the ideal sites for documenting the late Cenozoic sea level changes for its characteristics of rapid sedimentation and relatively stable structural subsidence since the Late Miocene. In this study, high-resolution seismic profiles acquired by the Guangzhou Marine Geological Survey, calibrated by well control from the ODP sites 1146 and 1148, were utilized to construct a time-significant sequence stratigraphic framework, from which the history of relative sea level changes since the Late Miocene on the northern SCS margin was derived. Our study area is situated in the middle segment of the margin, between the Hainan Island to the west and the Dongsha Islands to the east. This region is to a certain degree far away from the active structural zones and is suggested as the most stable region in the margin. Totally 4000 km seismic profiles were used, which controls an area of about 6×104 km2. The seismic data have a vertical resolution of 5 to 15 m for the Upper Miocene to Quaternary interval. Three regional seismic sequence boundaries were identified. They subdivide the Late Miocene to Quaternary into three mega-sequences, which correspond to the Quaternary, Pliocene and Late Miocene, respectively by tying to well control. The Late Miocene mega-sequence, including 13 component sequences, is characterized with a basal incised canyon-developed interval overlain by three sets of progradational sequences formed in deep-water slope environments. The Pliocene mega-sequence consists of four sets of progradational sequences. Each sequence set contains one to three component sequences. At least 7 component sequences can be identified. The Quaternary mega-sequence consists of five sets of progradational sequences, in which the lower two constitute a retrogressive sequence set and the upper three a progradational sequence set. At least 9 component sequences can be recognized. Most of the component sequences within the Pliocene and Quaternary mega-sequences occur adjacent to modern shelf margin, and therefore were interpreted as shelf-marginal progradational deltaic sequences. A relative sea level curve since the Late Miocene was compiled by integrating the shift trajectory of onlap points, the stacking pattern of component sequences, and the chronostratigraphic diagrams. The curve contains about 29 cycles of relative sea level changes, showing a much higher resolution than the previous results in the region. These cycles constitute three large relative sea level rise and fall cycles. General trend of sea level variations is rising since the Late Miocene, which is opposite to the global sea level changes and is in accordance with the previous regional researches. This deviation is ascribed to the combined effects of very rapid regional subsidence and relative deficiency of sediment supply. This research was funded by the National Natural Science Foundation of China (Grant Nos. 91028003 and 41076020).

Zhong, G.; Wang, L.

2013-12-01

 
 
 
 
261

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  

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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.

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

2012-04-01

262

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)  

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Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish 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.

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

2012-06-01

263

Using high-resolution stratigraphy and structural analysis to constrain polyphase tectonics in wedge-top basins: Inferences from the late Tortonian Scillato Basin (central-northern Sicily)  

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The present paper aims to show, both from a stratigraphic and structural points of view, the main features of a wedge-top syntectonic basin which evolved recording polyphase and non-coaxial tectonics. The study area is the Scillato Basin (SB), a roughly N-S-oriented structural depression located in the central-northern sector of the Sicililian Maghrebides. There, an approximately 1300 m-thick upper Serravallian to upper Tortonian succession of clastic units outcrops as a portion of the Neogene syntectonic covers of the Sicilian fold and thrust belt. Within the outcropping succession the upper Tortonian Terravecchia Fm represents the main topic of this paper. A multidisciplinary approach was carried out through an integration of sedimentology, facies, stratal pattern and structural analyses; this was applied to the formation enabling one to recognize in the Scillato Basin a fining to coarsening upward succession, deposited recording an early transgressive and a late regressive depositional stage. In our model these two main depositional stages developed and are directly relatable to a two-step structural evolution of the basin. During the first step, a NW-SE-oriented structural depression existed, enclosed between structural highs and accommodating the lower and middle portion of the upper Tortonian succession. Subsequently, during the second step, the NW-SE depression was non-coaxially deformed by superimposition of high-angle transpressive faults (many of which were SE-dipping), developed in response to the upward propagation of structures enucleated at deeper structural levels. This step was recorded in the basin by development of both depositional and structural interferences recognizable along the upper portion of the Scillato Basin succession. A comparison between field data and deep geophysical data interpreted at the preliminary stage, raises questions about the late Miocene geological evolution of this sector of the Sicilian chain, including: (i) the syn-tectonic deposition of the Terravecchia Fm. in the Scillato Basin clearly recorded the interference of two main and non-coaxial tectonic events; (ii) the younger of these two events has a clear tranpressional character and was active during the very late Tortonian; (iii) as also indicated by many authors in neighboring orogenic wedges, the main control on the location, geometry and depositional evolution of the Scillato wedge-top Basin was carried out by compressional and transpressional structures developed at a deeper structural level. Their deformation propagated upward both into the shallow structural level and sedimentary covers; therefore (iv) the late Miocene structural scenario here depicted is not consistent either with the back-arc-related extension or with the late orogenic gravitational collapse models previously invoked by other authors with regard to this sector of the Sicilian thrust belt.

Gugliotta, C.; Gasparo Morticelli, M.

2012-10-01

264

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)

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)

265

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

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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.

J. A. F. Diniz-Filho

2004-08-01

266

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)

Full Text Available SciELO Argentina | Language: English Abstract in spanish 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.).

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

267

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  

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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..

Silvia Lanés

2008-12-01

268

226Ra/238U dates by non-destructive ?-ray spectrometry of late Pleistocene corals in Minami- and Kita-Daito Island, Okinawa, Japan  

International Nuclear Information System (INIS)

The Ra-226/U-238 method based on nondestructive gamma ray spectrometry is discussed for dating 18 specimens of Pleistocene autochthonous corals in Minami- and Kita-Daito Islands. The U-238 and Ra-226 contents were indirectly determined by their daughter nuclides of Th-234 and Pb-214, respectively, assuming that the radioactive equilibrium between Th-238 and Th-234 and between Ra-226 and Pb-214 has been maintained. All the specimens, initially aragonitic mineral, were powdered, compressed into the disk shape of 50 mm diameter, and made airtight. These specimens were measured by a hyperpure germanium detector for 2 to 3 days. The Ra-226/U-238 dates of 15 specimens in Minami- and 3 specimens in Kita-Daito Island were obtained. The date of highest frequency was 120 to 130 ka, and the mean value was 128±27 ka. The nondestructive Ra-226/U-238 dating by gamma spectrometry has the advantages that elaborate and time-consuming chemical procedure is unnecessary, and the change in the chemical state does not occur in the samples analyzed, therefore, the same sample can be used for further investigation. (K.I.)

269

sup 226 Ra/ sup 238 U dates by non-destructive. gamma. -ray spectrometry of late Pleistocene corals in Minami- and Kita-Daito Island, Okinawa, Japan  

Energy Technology Data Exchange (ETDEWEB)

The Ra-226/U-238 method based on nondestructive gamma ray spectrometry is discussed for dating 18 specimens of Pleistocene autochthonous corals in Minami- and Kita-Daito Islands. The U-238 and Ra-226 contents were indirectly determined by their daughter nuclides of Th-234 and Pb-214, respectively, assuming that the radioactive equilibrium between Th-238 and Th-234 and between Ra-226 and Pb-214 has been maintained. All the specimens, initially aragonitic mineral, were powdered, compressed into the disk shape of 50 mm diameter, and made airtight. These specimens were measured by a hyperpure germanium detector for 2 to 3 days. The Ra-226/U-238 dates of 15 specimens in Minami- and 3 specimens in Kita-Daito Island were obtained. The date of highest frequency was 120 to 130 ka, and the mean value was 128{+-}27 ka. The nondestructive Ra-226/U-238 dating by gamma spectrometry has the advantages that elaborate and time-consuming chemical procedure is unnecessary, and the change in the chemical state does not occur in the samples analyzed, therefore, the same sample can be used for further investigation. (K.I.).

Kawana, Toshio; Taira, Hatsuo; Tanahara, Akira; Aoki, Hiroshige (Ryukyu Univ., Nishihara, Okinawa (Japan)); Ota, Yoko; Omura, Akio; Koba, Motoharu

1991-06-01

270

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)

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.

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

2012-01-01

271

Depositional environments and sequence stratigraphy of the Late Carboniferous-Early Permian coal-bearing successions (Shandong Province, China): Sequence development in an epicontinental basin  

Science.gov (United States)

This study focuses on the Late Carboniferous-Early Permian coal-bearing successions in Shandong Province, North China in order to understand the depositional processes and sequence-stratigraphic framework in an epicontinental basin. Based on detailed analysis of eleven facies, five facies assemblages (FAs) were recognized in the studied succession. FA1-3 are present mainly in the Benxi and Taiyuan formations, and consist of mixed siliciclastic and carbonate lithofacies, representing eluvial-lagoon, barrier-lagoon, and tidal-flat environments. FA4 occurs in the Shanxi formation and consists mainly of interbedded medium to fine sandstone, siltstone, mudstone, and coal lithofacies, representing river-dominated deltaic environments. FA5 is characterized by interbeds of trough cross-stratified coarse sandstone, and silty mudstone, mainly in the Lower Shihezi Formation, which was deposited in meandering river channel and floodplain. Three third-order sequences were established based on the vertical arrangement of facies assemblages and identification of physical surfaces (i.e., subaerial unconformity, transgressive surface, and regressive surface). Each sequence comprises a transgressive systems tract (TST) and a highstand systems tract (HST). TST of sequence 1 is composed of eluvial lagoonal deposits (FA1), whereas HST formed in lagoon-barrier and tidal-flat settings (FA2 and FA3). TST of sequence 2 formed in a barrier-lagoon system (FA2), whereas HST is characterized by repetitive accumulation of interbedded limestone, sandstone, mudstone, and coal, deposited under lagoonal and tidal-flat settings (FA2 and FA3). TST of sequence 3 comprises FA2, and HST mainly FA4, deposited in a river-dominated shallow-water delta system. Sequence 3 is overlain by a fluvial sequence (FA5). The three third-order sequences in the Shandong region are generally correlated with those in the Taebaeksan Basin (South Korea), the eastern part of the North China Block. The relative sea-level curves established in the two regions show a generally similar long-term rising trend.

Lv, Dawei; Chen, Jitao

2014-01-01

272

I depositi a vertebrati continentali del pleistocene della Calabria  

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The inventory of Pleistocene mammal-bearing deposits of Calabria is reported, on the basis of the data available in the literature. Most of the deposits are represented by open-air sites, while cave deposits, always containing human artifacts too, are very scarce; this is to be referred to the lithology of the region, having few outcrops of carbonatic rocks. In many cases, precise informations on the stratigraphy and the composition of the faunal assemblages are lacking. A revision of the fau...

Mangano, G.

2007-01-01

273

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)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish 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.

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

2011-04-01

274

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)

Full Text Available SciELO Chile | Language: English Abstract in spanish 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

Marcelo M, Rivadeneira; Erico R, Carmona.

275

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  

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Full Text Available 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, of 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 hypothesizedEn 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

Marcelo M Rivadeneira

2008-01-01

276

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)

Full Text Available SciELO Chile | Language: English Abstract in spanish 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

Marcelo M, Rivadeneira; Erico R, Carmona.

2008-01-01

277

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)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish 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.

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

278

Late Pliocene To Pleistocene Tectonic Activity In SW Portugal: The S.Teotónio-Aljezur- Sinceira Fault System And Evidence For Coastal Uplift  

Science.gov (United States)

Southwestern Portugal is located close to the Eurasia-Nubia plate boundary. East of the Gloria transform fault, this boundary becomes complex, particularly as it approaches the Gorringe Bank, the Horseshoe Plain, and the Gulf of Cadiz, where deformation related to the NW-SE convergence of Iberia and Nubia, at a rate of ~4-5 mm/ year, becomes distributed across a few hundred kilometer-wide zone. This area corresponds to the inferred seismogenic source zone for the 1755 earthquake and tsunami (estimated ? Mw 8), and also for the Mw 7.9 1969 event. During the past decade, several off-shore active folds and faults have been recognized in this region however, in spite of increased knowledge, none of the recognized active structures are clearly associated with the 1755 earthquake. Major likely sources are the Marquês de Pombal and Horseshoe faults. The Marquês de Pombal fault is a major NNE-SSW trending thrust located ~100 km SW of Cape S.Vicente that exhibits a ~1 km-high, 60 km-long scarp. Assuming rupture of this entire structure suggests earthquake magnitudes in the Mw 7.8 range. The Horseshoe fault, which is oriented NE- SW along a 175 km-long trend parallel to Säo Vicente canyon, a major morphological feature in the off- shore that has been interpreted as a possible extend for the Alentejo-Plasencia fault. Rupture of this entire fault could yield moment magnitude events up to Mw 8, assuming 10 m of average displacement. Neither of these potential sources can likely produce, by themselves, an earthquake that matches the upper estimates for the 1755 earthquake (Mw 8.7). Along the southwestern Portuguese coast, mainly at the western coastline, cliffs in Palaeozoic schist reach more than 100m in altitude, with evidence of uplift in the form of raised beach deposits, paleo-sea cliffs and multiple eolianite units. Several abrasion platforms with regional expression may have formed during multiple marine occupations. In contrast, the southern coast is underlain mainly by Mesozoic limestones and exhibits a generally lower topography accented by karstic morphology. In both areas, little work has been done to map the sequence of marine terraces, nor to determine their ages, although the majority of them are likely Pleistocene. The highest raised marine deposits reach an altitude of 370 m ~13 km inland and may be as old as Pliocene in age. Inland, the Säo Teotónio-Aljezur-Sinceira fault system (STASFS) extends NNE-SSW for 50 km, parallel and close to the southwest Portuguese coast, and controls the development of several small Cenozoic tectonic basins. It comprises onshore faults which may relate to the ongoing plate boundary deformation. This fault system expresses primarily sinistral strike-slip with a minor reverse component. Four cenozoic strike-slip basins occur along the STASFS, generally with lengths of less than 5 km and a maximum width of 1.5 km, filled with Miocene to Pleistocene sediments. In some areas, fault-related post-Pliocene vertical displacements of up to 100 m may have occurred, but generally they only reach a few tens of meters. This coastal region is therefore particularly appropriate for establishing the offshore-onshore link through a detailed neotectonic study of the active faults, including exploration with paleoseismological techniques, and the vertical deformation field using marine terraces as a reference frame.

Figueiredo, P.; Cabral, J.; Rockwell, T.

2008-12-01

279

Arctic ground squirrels of the mammoth-steppe: paleoecology of Late Pleistocene middens (˜24 000 29 450 14C yr BP), Yukon Territory, Canada  

Science.gov (United States)

This paper presents paleoecological analyses of 48 fossil arctic ground squirrel ( Spermophilus parryii) middens (nests and caches) recovered from ice-rich loess sediments in the Klondike region of west-central Yukon Territory. AMS radiocarbon dates and stratigraphic association of middens with Dawson tephra (˜25 300 14C yr BP), indicate these paleoecological data reflect the onset of glacial conditions of early Marine Isotope Stage (MIS) 2 and terminal MIS 3 (˜24 000-29 450 14C yr BP). Plant macrofossils include at least 60 plant taxa, including diverse graminoids ( Poa, Elymus trachycaulus, Kobresia myosuroides), steppe forbs ( Penstemon gormanii, Anemone patens var. multifida, Plantago cf. canescens), tundra forbs ( Draba spp., Bistorta vivipara), dwarf shrubs ( Salix cf. arctica, S. cf. polaris), sage ( Artemisia frigida) and rare trees ( Picea mariana). Many of these taxa identified in the middens represent the first recorded fossils for these plants in Eastern Beringia and add to our knowledge of the floristic composition of Pleistocene vegetation and biogeography in this region. Fossil beetles include typical members of the Eastern Beringian steppe-tundra fauna ( Lepidophorus lineaticollis and Connatichela artemisiae) and others suggesting predominantly dry, open habitats. Cache forage selection is suggested by some plant taxa which were particularly frequent and abundant in the middens ( Bistorta vivipara, Kobresia myosuroides, Ranunculus spp., Potentilla, Erysimum cf. cheiranthoides, Poa, Carex and Draba). Factors such as proximity of vegetation to burrows and abundance of fruits and seeds per plant were probably important in cache selection. Glacial conditions enabled arctic ground squirrels to form widespread and dense populations in regions such as the Klondike in which they are rare or absent at present. This fossil midden record supports previous hypotheses that suggest arctic ground squirrels evolved in and are well-adapted to the open, steppe-tundra vegetation, loessal soils and glacial climates of the mammoth-steppe biome.

Zazula, Grant D.; Froese, Duane G.; Elias, Scott A.; Kuzmina, Svetlana; Mathewes, Rolf W.

2007-04-01

280

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

DEFF Research Database (Denmark)

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.

Thiel, Christine

2013-01-01

 
 
 
 
281

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)

282

Chemostratigraphy and process modeling of late Pleistocene volcanism along the Arco-Big Southern Butte Volcanic Rift Zone, Eastern Snake River Plain, Idaho  

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Seven basalt flow groups were identified using lithologic logs, geophysical logs, paleomagnetic signatures, and geochemistry in corehole USGS 135 (399 m) drilled into the Arco-Big Southern Butte Volcanic Rift Zone (VRZ) on the Eastern Snake River Plain. Fifty-six samples were collected and analyzed using both solution ICP-MS and LA-ICP-MS to determine chemical stratigraphy and to provide insight into the volcanic processes and evolution of the Arco-Big Southern Butte VRZ. These new data plotted against geochemical data by ICP-AES and INAA of nearby coreholes provide a means of correlation between previously identified subsurface lava flows near the VRZ. With the exception of the uppermost flowgroup (#1), lava flows identified in USGS 135, especially flow groups 3—7, are predominately proximal deposits of oxidized shelly pahoehoe, indicating near-vent facies. Also, a scarcity of sediment interbedded between flow groups suggests higher levels of volcanic activity and/or a higher elevation at the time of their emplacement—both manifestations of close proximity to an active VRZ. Geochemical data support the correlation of USGS 135 flowgroup 1, a distal lava flow series ~50 m thick, with the Quaking Aspen Butte (QAB) lava flow series, emplaced at ~60 ka (Kuntz et al., 2007). QAB is a relatively large shield with a central vent located ~10 km SW of USGS 135. The geochemistry of flowgroup 1 suggests that relatively primitive olivine tholeiite magma evolved during eruption to produce significant chemical variation. For example, TiO2 ranges 1.5-2.5 wt %, MgO ranges 7.2-10.2 wt %, and La/Sm ratios range 2.9-3.8. QAB geochemistry demonstrates similar ranges in these and other elements. The presence of thick, distal facies QAB lava as the youngest flowgroup in USGS 135 suggests that a substantial volume of lava flowed against and eventually over the Arco-BSB VRZ en route to the Big Lost Trough located NE of the VRZ. Implications also include the possibility of subsidence of the VRZ during its most recent volcanic history and a greater volume and extent of QAB flows than previously observed.

Potter, K. E.; Hughes, S. S.

2009-12-01

283

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)

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 age); the lava was strongly tilted by structural doming associated with the intrusion. The granophyre was completely crystallized by the time of the final pyroclastic flow eruption that brought the intrusive blocks to the surface. From the pumice in this deposit, the weighted mean Ar-Ar age of two splits of Na-sanidine (density > 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 AVC and far less radiogenic than most basement granites and schists that form escarpments bordering the Danakil Depression and are found as unmelted lithic xenoliths in lavas and tuffs of the AVC. Pb isotopes also rule out significant assimilation of Precambrian basement during genesis of the young granophyre. Similarly zircon grains, analyzed with the Stanford-USGS SHRIMP-RG, show little evidence for inheritance, with only a single 760 Ma zircon (U-Pb age) that was also petrographically different from the 130 other zircons in the mount. The other zircons yielded SHRIMP 238U230Th disequilibrium ages of ages of cores and rims. The weighted mean 238U230Th age of 23 analyzed zircons is 24.7 +/- 3.3 ka. The whole-rock U-Th isotopic values of the granophyre, by TIMS, show extreme enrichment of 230Th ([230Th /232Th] = 1.064; [238U /232Th] = 0.602; Th/U = 5.04). On an activity ratio diagram, the whole-rock value is essentially colinear with clinopyroxene, Na-sanidine, apatite and magnetite separates, forming an apparent isochron of 21.5 +/- 2.4 ka, similar to the zircon data (both SHRIMP and multiple-grain TIMS). The ferroaugite separate is more Th-enriched than the whole-rock, probably due to rare chevkinite inclusions. Isotopic and trace-element data indicate melt generation by partial melting of Quaternary mafic rocks, accompanied by minor (http://wrgis.wr.usgs.gov/docs/geologic/jlwnstrn/alid/ Alidpage.html

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

2001-12-01

284

Palaeoclimatic implications of the growth history and stable isotope (? 18O and ? 13C) geochemistry of a Middle to Late Pleistocene stalagmite from central-western Italy  

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The age structure and stable isotope composition of a stalagmite (CC1) from an upland cave in central-western Italy were studied to investigate regional response to global climatic changes. Four growth phases are constrained by 28 thermal ionization and multi-collector inductively coupled plasma mass spectrometry Th-U ages and reveal intermittent deposition through the period between Marine Isotope Stage (MIS) 11 and 3 (˜380 and ˜43 kyr). Most of the growth took place between ˜380 and ˜280 kyr, a period punctuated briefly by a hiatus in deposition through the glacial maximum of MIS 10. Growth was terminated abruptly at 280 kyr just prior to the MIS 8 glacial maximum. With a present-day chamber temperature of 7.5 °C, the timing of hiatuses close to these glacial maxima point to freezing conditions at the time. No deposition was recorded through the entirety of MIS 7 and most of MIS 6, whilst two minor growth phases occurred at ˜141-125 and ˜43 kyr. Growth at 141 kyr indicates temperatures >0 °C at a time when MIS 6 ice volumes were close to their maximum. High stable carbon isotope (? 13C) values (-2.8‰ to +3.1‰) throughout the stalagmite's growth reflect a persistently low input of biogenic CO 2, indicating that the steep, barren and alpine-like recharge area of today has been in existence for at least the last ˜380 kyr. During MIS 9, the lowest ? 13C values occur well after maximum interglacial conditions, suggesting a lag in the development of post-glacial soils in this high-altitude karst. The stable oxygen isotope (? 18O) trends match the main structural features of the major climate proxy records (SPECMAP, Vostok and Devils Hole), suggesting that the ? 18O of CC1 has responded to global-scale climate changes, whilst remarkable similarity exists between CC1 ? 18O and regional sea-surface temperature reconstructions from North Atlantic core ODP980 and southwest Pacific marine core MD97-2120 through the most detailed part of the CC1 record, MIS 9-8. The results suggest that CC1 and other stalagmites from the cave have the potential to capture a long record of regional temperature trends, particularly in regards to the relative severity of Pleistocene glacial stages.

Drysdale, Russell N.; Zanchetta, Giovanni; Hellstrom, John C.; Fallick, Anthony E.; Zhao, Jian-xin; Isola, Ilaria; Bruschi, Giuseppe

2004-11-01

285

Tephrochronology of the Mont-Dore volcanic Massif (Massif Central, France): new 40Ar/39Ar constraints on the Late Pliocene and Early Pleistocene activity  

Science.gov (United States)

The Mont-Dore Massif (500 km2), the youngest stratovolcano of the French Massif Central, consists of two volcanic edifices: the Guéry and the Sancy. To improve our knowledge of the oldest explosive stages of the Mont-Dore Massif, we studied 40Ar/39Ar-dated (through single-grain laser and step-heating experiments) 11 pyroclastic units from the Guéry stratovolcano. We demonstrate that the explosive history of the Guéry can be divided into four cycles of explosive eruption activity between 3.09 and 1.46 Ma (G.I to G.IV). We have also ascertained that deposits associated with the 3.1-3.0-Ma rhyolitic activity, which includes the 5-km3 "Grande Nappe" ignimbrite, are not recorded in the central part of the Mont-Dore Massif. All the pyroclastites found in the left bank of the Dordogne River belong to a later explosive phase (2.86-2.58 Ma, G.II) and were channelled down into valleys or topographic lows where they are currently nested. This later activity also gave rise to most of the volcanic products in the Perrier Plateau (30 km east of the Mont-Dore Massif); three quarters of the volcano-sedimentary sequence (up to 100 m thick) was emplaced within less than 20 ky, associated with several flank collapses in the northeastern part of the Guéry. The age of the "Fournet flora" (2.69 ± 0.01 Ma) found within an ash bed belonging to G.II suggests that temperate forests already existed in the French Massif Central before the Pliocene/Pleistocene boundary. The Guéry's third explosive eruption activity cycle (G.III) lasted between 2.36 and 1.91 Ma. It encompassed the Guéry Lake and Morangie pumice and ash deposits, as well as seven other important events recorded as centimetric ash beds some 60 to 100 km southeast of the Massif in the Velay region. We propose a general tephrochronology for the Mont-Dore stratovolcano covering the last 3.1 My. This chronology is based on 44 40Ar/39Ar-dated events belonging to eight explosive eruption cycles each lasting between 100 and 200 ky. The occurrence of only one pumice deposit in the 800-ky period between 1.9 and 1.1 Ma suggests that volcanic explosive activity was strongly reduced or quiescent.

Nomade, Sébastien; Pastre, Jean-François; Nehlig, Pierre; Guillou, Hervé; Scao, Vincent; Scaillet, Stéphane

2014-03-01

286

Tectonic and sedimentary evolution of the late Miocene-Pleistocene Dali Basin in the southeast margin of the Tibetan Plateau: Evidences from anisotropy of magnetic susceptibility and rock magnetic data  

Science.gov (United States)

The Cenozoic Dali Basin, located at the northeast of Diancang Shan and south of the first bend of Yangtze River, is tectonically controlled by the Dali fault system in the southeast margin of the Tibetan Plateau. The basin is filled with late Miocene to Pleistocene fluviolacustrine sediments, which provide invaluable information about the tectonic deformation and drainage network reorganization in this area. In this study, we discuss the anisotropy of magnetic susceptibility (AMS) of the Dasongping section in the Dali Basin, which spans an interval from 7.6 to 1.8 Ma. Although rock magnetic experiments indicate that magnetite and hematite are the main remanence carriers, hysteresis loops, low values of bulk susceptibility and low temperature susceptibility suggest that paramagnetic minerals are major contributors to low-field AMS. The rock magnetic parameters indicate that the Dali Basin experienced four stages of infilling and the sediment sources may have changed at 4.2 Ma. The clustering of the minimum principle axes (Kmin) nearly perpendicular to the bedding plane and the pronounced N-S magnetic lineation parallel to the bedding plane indicate that the AMS of the Dali Basin is a superimposed fabric consisting of a sedimentary-compaction and a mild initial deformation overprint. The well-defined N-S magnetic lineation is likely due to the NNW and NNE oblique shear caused by the Heqing and Red River faults.

Li, Shihu; Deng, Chenglong; Paterson, Greig A.; Yao, Haitao; Huang, Sheng; Liu, Chengying; He, Huaiyu; Pan, Yongxin; Zhu, Rixiang

2014-08-01

287

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  

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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.

Choukri Abdelmajid

2008-03-01

288

Paleoceanographic interpretations of late Pleistocene to Holocene sedimentological and geochemical proxy-data from SE-Atlantic abyssal plains (Cape, Angola and Guinea Basin)  

Science.gov (United States)

Sediments of the deep abyssal regions of the Southeast Atlantic (Cape Basin, Angola Basin and Guinea Basin) were studied to reconstruct changes in surface and deep water circulation, bioproductivity, and terrigenous sediment flux. To gain these results various sedimentological and geochemical proxies were imposed, including grain size data, foraminiferal fragmentation, carbonate and organic carbon content, as well as stable oxygen and carbon isotope contents of foraminiferal tests. Samples were gained with a multicorer device during Meteor cruise 63/2 (2005) in water depths between ~5,100 and ~5,600 m. The superficial 30 cm of sediment, sampled in 1/2, 1 and 5 cm steps, were processed for this study. The record covers parts of the Pleistocene and Holocene. Even if the sedimentation conditions seem to be similar in the deep-sea regions of the SE-Atlantic there are clear differences between the three sampled locations. This is caused by major changes in deep water corrosiveness leading to fluctuations in the sedimentation rate and carbonate preservation. Cape Basin localities show a pattern of enhanced carbonate preservation around 12 ka BP possibly indicating a delayed Last Glacial Maximum signal. This pattern, which is typical for Indo-Pacific records, clearly points to an influence of Antarctic Bottom Water (AABW) at water depths below 5000 m in the Northern Cape Basin. The non-correlation between carbonate content and grain size distribution is owing to a coccoliths' dominated carbonate production possibly caused by low nutrient availability in surface waters and the higher dissolution susceptibility of foraminiferal tests. Angola Basin samples delivered highest sand contents, a carbonate peak and low organic carbon values around 8.2 ka BP which indicate a reduced bioproduction and nutrient supply in superficial waters. A connection of the 8.2 ka cold event in the northern hemisphere and central African precipitation, equatorial East Atlantic (EEA) upwelling intensity and bioproduction is likely. Thus we expect the observed peak to be a response to the mentioned cold event at about 8.2 ka. The overall sedimentological record indicates that the Northern Angola Basin sedimentation may not be triggered by changes in the influence of North Atlantic Deep Water (NADW) and AABW as observed in the Northern Cape Basin. Therefore, the Walvis Ridge is expected to be an effective barrier for AABW. Studied Guinea Basin sediments (>5000 m) show quite uniform spatial bioproduction caused by the EEA divergence zone overlying the sample sites. Concerning the Holocene, temporal variations are mirrored in the grain size distribution which can possibly be correlated to changes in the thermocline depth. The trend to higher sand contents, especially in the uppermost sediment layers hints to increasing bioproductivity (foraminifers) and thus upwelling intensity during the Holocene. Dissolution, even in the deepest parts of the Guinea Basin, is minimal during the sampled timespan (low foraminferal fragmentation) owing to a predominant influence of NADW north of the Guinea Rise. Differences in the carbonate content are therefore expected to be caused by dilution by terrigenous material delivered by fluvial (Niger River) and eolian (Trade Winds) transport in combination with a change in bioproductivity.

Piller, W. E.; Müllegger, S.

2009-04-01

289

Late Pleistocene monsoon variability in northwest Thailand: an oxygen isotope sequence from the bivalve Margaritanopsis laosensis excavated in Mae Hong Son province  

Science.gov (United States)

Long, continuous records of Late Quaternary environmental change are rare in Southeast Asia, yet they are crucial for understanding the nature of early human dispersal and occupation in the Australasian region. We present a new record of palaeomonsoon activity extending back to 35,000 BP (years before the present), based on the analysis of oxygen isotope ratios (? 18O) in the freshwater bivalve Margaritanopsis laosensis excavated from the Tham Lod and Ban Rai rockshelters in Mae Hong Son Province, northwest Thailand. Long-term changes in the M. laosensis ? 18O record reflect changes in the ? 18O of the river water in which these organisms grew, and correlate well with changes in speleothem ? 18O records of east Asian monsoon rainfall from Hulu Cave and Dongge Cave in China. The new northwest Thailand ? 18O sequence indicates wetter and relatively unstable climatic conditions from 35,000 to 20,000 BP, followed by drier conditions from 20,000 to 11,500 BP. A period of peak aridity occurred around 15,600 BP during Heinrich Event 1, suggesting that the intertropical convergence zone shifted southward when the North Atlantic region cooled. However, there is little evidence for the Younger Dryas event at ˜12,800-11,500 BP. After 9,800 BP, precipitation increased substantially and climatic variability declined. Our findings provide an improved baseline against which to gauge interactions between early humans and climate change in Southeast Asia. For example, there was no significant change in the prehistoric flake stone technology used at Tham Lod and Ban Rai despite the bivalve ? 18O evidence for substantial climate change in the region. Also, the climatic impact of the Younger Dryas event appears to have been less intense in northwest Thailand compared to the cooling and drying observed in China, and may explain why agriculture made a relatively late appearance in Thailand, possibly involving migrants from China.

Marwick, Ben; Gagan, Michael K.

2011-10-01

290

Pleistocene horses (genus Equus in the central Balkans  

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Full Text Available A review of the fossil horses of the genus Equus from the central Balkans, a mountainous area comprising Serbia and Montenegro, is presented in this paper. The time period covered by the finds is from the late Early to and including the Late Pleistocene, but the record is not complete: the dated finds are Late Pleistocene in age, while Early and Middle Pleistocene are poorly represented. The horses found resemble those from neighbouring countries from the same time period, probably showing the importance of river valleys as migration routes. The Morava River valley runs in a roughly south-to-north direction, connecting, via the Danube and Tisa River valleys the Hungarian Pannonian Plain in the north with northern Greece in the south, via the Vardar River valley in Macedonia. In Pleistocene, large mammals, including horses, probably used this route for dispersal.

Forsten Ann

2003-01-01

291

AMS radiocarbon dating of the marine late Pleistocene-Holocene sediment cores from the western Ulleung Basin, East/Japan Sea  

International Nuclear Information System (INIS)

We present the results on radiocarbon dating of planktonic foraminifera samples from two piston cores collected from the western part of the Ulleung Basin, East/Japan Sea. Until recently, there were no radiocarbon dates from late Quaternary sediments of this location. Eight samples from the Ulleung Basin cores were accelerator mass spectrometry (AMS) 14C-dated, and reservoir-corrected using R-values as 400 yr. The results indicate that the cores cover the time interval from the middle stage of marine isotope stage (MIS) 3 through last glacial maximum (LGM) to Holocene, and the average sedimentation rate of the cores vary from 17.61 cm/kyr to 19.96 cm/kyr. Particularly, it is shown using the calibrated 14C data that in the cores hemipelagic muds (bioturbated and slightly laminated mud facies) were mainly formed during interglacial periods (MIS 1/3), whereas non-hemipelagic muds (laminated and homogenous mud facies) were deposited during glacial period (MIS 2)

292

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)

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.

Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens

2014-05-01

293

Sea-level rise and anthropogenic activities recorded in the late Pleistocene/Holocene sedimentary infill of the Guadiana Estuary (SW Iberia)  

Science.gov (United States)

This study reviews data on sea-level rise during the last 13000 yr cal. BP (13 kyr) as recorded in the estuarine sediments of the Guadiana River (SE Portugal, SW Spain). We combined new data from a 63 m-long borehole, drilled through the entire postglacial sedimentary sequence, with information on five previously studied cores. By integrating sedimentological, geochemical and palaeontological proxies, we were able to make a palaeoenvironmental reconstruction of the Guadiana terminal palaeovalley during the last 13 kyr and propose a curve of sea-level rise for the SW Iberian Atlantic margin. Our foraminifera-based palaeoecological reconstruction, anchored to a 14C age model, reveals rapid sea-level rise from 13 kyr, interrupted during the Younger Dryas and resuming ca 11.5 kyr. The pace of marine transgression slackened ca. 7.5 kyr and since then has progressed upwards at a rate of 1.2 mm yr-1. Holocene-Anthropocene sediments from two boreholes were also analysed to assess the timing, levels and sources of trace metals produced by acid mine drainage from the Iberian Pyrite Belt. Study of metal/aluminium ratios through the profiles allowed background metal concentrations to be estimated from lithostratigraphic units older than ca. 5 kyr (i.e. unaffected by anthropogenic activities). Human activities are especially evident from 4.5 kyr (the beginning of the Copper Age), with anthropogenic sources of metal fluxes prevailing over natural sources (especially Pb, Co, Ni, and Mn, and, to a lesser extent, Zn, Cu, and Ni). Mining activities became particularly intensive between the late Bronze Age and the Roman period (3-1.5 kyr), when the highest metal enrichment factors were recorded: EFPb ? 2, EFCd > 10, EFCr ? 2, EFCu ? 3, EFZn = 1.4.This study reveals the utility of postglacial sedimentary records for reconstructing historical changes in regional water-sediment quality and separating natural and anthropogenic sources of geochemical contaminants.

Delgado, J.; Boski, T.; Nieto, J. M.; Pereira, L.; Moura, D.; Gomes, A.; Sousa, C.; García-Tenorio, R.

2012-02-01

294

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  

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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.

Diedrich C G

2011-11-01

295

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)

Full Text Available SciELO Mexico | Language: English Abstract in spanish 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.

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

296

New camelid (Artiodactyla: Camelidae) record from the late Pleistocene of Calama (Second Region, Chile): a morphological and morphometric discussion / Nuevo registro de camélido (Artiodactyla: Camelidae) del Pleistoceno final de Calama (Segunda Región, Chile): una discusión morfológica y morfométrica  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish En el presente trabajo se describe el material correspondiente a restos fósiles de camélidos del sitio Kamac Mayu (II Región, Chile). Este registro, fue recobrado a partir de excavaciones sistemáticas en depósitos de grava arenosa y arena dispuestos sobre una formación kárstica, erosionadas por curs [...] os fluviales durante el Pleistoceno tardío. Además de los restos de camélidos se recobró material fósil diverso compuesto por Hippidion saldiasi (Mammalia, Equidae), Macrauchenia patachonica (Mammalia, Litopterna), xenarthros indeterminados (Mammalia, Xenarhra) y aves (Aves, Rheidae), junto a especímenes de Planorbidae, Hydrobiidaee and Sphaeriidae (Mollusca) dentro de depósitos formados por el desagüe de la antigua cuenca Chiu Chiu-Calama. El estudio anatómico comparado de los restos fósiles permitió la asignación taxonómica a Lama gracilis (Gervais y Ameghino 1880), constituyéndose en un hallazgo inédito para esta región del país. Abstract in english A description of fossil remains belonging to camelids from the Kamac Mayu site (Second Region, Chile) is presented. This record was recovered from deposits of gravel and sand on karstic formations eroded by rivers during the late Pleistocene. In addition to the remains of camelids, diverse fossil ma [...] terial composed ofHippidion saldiasi (Mammalia, Equidae), Macraucheniapatachonica (Mammalia, Litopterna), undeterminedxenarthrans (Mammalia, Xenarhra) and birds (Aves, Rheidae), were recovered, along with specimens of Planorbidae, Hydrobiidaee and Sphaeriidae (Mollusca) from deposits formed by the drainage of the Chiu Chiu-Calama basin. The comparative anatomical study of the fossil material enabled the taxonomic assignment of the camelid remains to Lama gracilis (Gervais and Ameghino 1880), constituting an unprecedented finding for this region of the country.

Isabel, Cartajena; Patricio, López; Ismael, Martínez.

297

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)

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.

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

298

New camelid (Artiodactyla: Camelidae) record from the late Pleistocene of Calama (Second Region, Chile): a morphological and morphometric discussion / Nuevo registro de camélido (Artiodactyla: Camelidae) del Pleistoceno final de Calama (Segunda Región, Chile): una discusión morfológica y morfométrica  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish En el presente trabajo se describe el material correspondiente a restos fósiles de camélidos del sitio Kamac Mayu (II Región, Chile). Este registro, fue recobrado a partir de excavaciones sistemáticas en depósitos de grava arenosa y arena dispuestos sobre una formación kárstica, erosionadas por curs [...] os fluviales durante el Pleistoceno tardío. Además de los restos de camélidos se recobró material fósil diverso compuesto por Hippidion saldiasi (Mammalia, Equidae), Macrauchenia patachonica (Mammalia, Litopterna), xenarthros indeterminados (Mammalia, Xenarhra) y aves (Aves, Rheidae), junto a especímenes de Planorbidae, Hydrobiidaee and Sphaeriidae (Mollusca) dentro de depósitos formados por el desagüe de la antigua cuenca Chiu Chiu-Calama. El estudio anatómico comparado de los restos fósiles permitió la asignación taxonómica a Lama gracilis (Gervais y Ameghino 1880), constituyéndose en un hallazgo inédito para esta región del país. Abstract in english A description of fossil remains belonging to camelids from the Kamac Mayu site (Second Region, Chile) is presented. This record was recovered from deposits of gravel and sand on karstic formations eroded by rivers during the late Pleistocene. In addition to the remains of camelids, diverse fossil ma [...] terial composed ofHippidion saldiasi (Mammalia, Equidae), Macraucheniapatachonica (Mammalia, Litopterna), undeterminedxenarthrans (Mammalia, Xenarhra) and birds (Aves, Rheidae), were recovered, along with specimens of Planorbidae, Hydrobiidaee and Sphaeriidae (Mollusca) from deposits formed by the drainage of the Chiu Chiu-Calama basin. The comparative anatomical study of the fossil material enabled the taxonomic assignment of the camelid remains to Lama gracilis (Gervais and Ameghino 1880), constituting an unprecedented finding for this region of the country.

Isabel, Cartajena; Patricio, López; Ismael, Martínez.

2010-08-01

299

Morphology and palaeoenvironmental interpretation of deformed soft-sediment clasts: examples from within Late Pleistocene glacial outwash, Tempo Valley, Northern Ireland  

Science.gov (United States)

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.

Knight, Jasper

1999-10-01

300

Quaternary stratigraphy of the western Rolling Plains of Texas: Preliminary findings: Final report  

International Nuclear Information System (INIS)

Quaternary deposits as much as 76 m (250 ft) thick discontinuously cover more than 7800 km2 (3000 mi2) of the western Rolling Plains of northwestern Texas. The stratigraphy of this sedimentary sequence is complex, reflecting changes in paleoclimate during the late Pleistocene and Holocene Epochs. There are clear indications of syngenetic structural control of deposition and postdepositional deformation of the Quaternary strata. These effects were caused by regional and local karstic subsidence resulting from dissolution of Upper Permian evaporites, particularly halite, at depths of 120 to 240 m (400 to 800 ft). Dissolution created voids within the bedded evaporites. As the voids expanded the overlying strata collapsed, forming depressions wherein sediment accumulated preferentially. Subsidence also caused local faulting and downwarping of some of the Quaternary deposits. Affected deposits include beds of coarse-grained sediment eroded from the westward-retreating Caprock Escarpment (adjacent to the Rolling Plains). This sediment was trapped within the zone of subsidence, forming a broad bajada at the base of the escarpment. At most sites the coarse-clastic deposits compose the lowest of three genetic components of the regional Quaternary section. 120 refs., 5 figs