Sample records for late quaternary paleohydrology

  1. Late-Quaternary Molecular Isotopic Paleohydrology of Lake Junin, Peru

    Polissar, P. J.; Liu, C.; Rodbell, D. T.; Abbott, M. B.


    There is great potential for reconstructing past changes in the hydrologic cycle using the hydrogen isotopic composition of plant-wax biomarkers. At present, empirical relationships relating plant-wax hydrogen isotope compositions (δDwax) to source water are almost exclusively based upon modern plants, soils and sediments. Relatively little is known about how plant-wax hydrogen isotopes track source water through time. Here we take advantage of existing paleoisotopic information from Lake Junin in the central Peruvian Andes to evaluate the temporal fidelity of δDwax to source water δD. In Lake Junin and the nearby region, oxygen isotopic records from lacustrine carbonates, speleothems and ice-cores provide robust constraints on the isotopic composition of lake water and precipitation in the past. Combined with new measurements of δDwax in Lake Junin sediments, these data allow us to evaluate the isotopic, climatic and vegetation influences on δDwax over the past 20,000 years. The n-alkanoic acid δDwax values exhibit trends through time that are similar to those for precipitation and lakewater δD. Highly negative δDwax values during the Last Glacial Maximum mirror depleted lakewater and precipitation δD values, more positive δDwax values at the beginning of the Holocene correspond to more enriched water δD values, and decreasing δDwax values over the past 10,000 years parallel the decreasing δD of lakewater and precipitation. However, the magnitude of the δDwax shifts are much larger than can be explained by changing δD water values. For example, the enrichment of δDwax values at the beginning of the Holocene is +30‰ and +80‰ larger than those of lakewater or precipitation δD, respectively. These differences could reflect changes in vegetation type, shifting proportions of aquatic and terrestrial plant sources, or environmental factors such as aridity. Vegetation type is an unlikely explanation as pollen abundances indicate only minor fluctuations, at least during the Holocene. Changing proportions of aquatic plant-wax sources may have had some influence as shorter-chain acids from aquatic macrophytes are more abundant in the early Holocene. However, aridity likely had a major role through greater evaporative isotopic enrichment of leaf and/or soil water. Early Holocene lake waters were significantly more highly evaporated indicating overall more arid conditions when leaf-wax δD values are most positive. Comparison of Lake Junin plant-wax and water δD values over the past 20,000 years indicate that although δDwax reflects trends in water δD, there are potentially large influences from evapotranspiration and shifting proportions of aquatic sources. While these factors have been previously identified in spatial calibration studies, our temporal calibration results emphasize the need to critically evaluate these influences on molecular δD at a single location through time.

  2. Climate predictors of late quaternary extinctions

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram


    Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...

  3. Late Quaternary changes in climate

    Holmgren, K.; Karlen, W. [Stockholm Univ. (Sweden). Dept. of Physical Geography


    This review concerns the Quaternary climate with an emphasis on the last 200 000 years. The present state of art in this field is described and evaluated. The review builds on a thorough examination of classic and recent literature. General as well as detailed patterns in climate are described and the forcing factors and feed-back effects are discussed. Changes in climate occur on all time-scales. During more than 90% of the Quaternary period earth has experienced vast ice sheets, i.e. glaciations have been more normal for the period than the warm interglacial conditions we face today. Major changes in climate, such as the 100 000 years glacial/interglacial cycle, are forced by the Milankovitch three astronomical cycles. Because the cycles have different length climate changes on earth do not follow a simple pattern and it is not possible to find perfect analogues of a certain period in the geological record. Recent discoveries include the observation that major changes in climate seem to occur at the same time on both hemispheres, although the astronomical theory implies a time-lag between latitudes. This probably reflects the influence of feed-back effects within the climate system. Another recent finding of importance is the rapid fluctuations that seem to be a normal process. When earth warmed after the last glaciation temperature jumps of up to 10 deg C occurred within less than a decade and precipitation more than doubled within the same time. The forcing factors behind these rapid fluctuations are not well understood but are believed to be a result of major re-organisations in the oceanic circulation. Realizing that nature, on its own, can cause rapid climate changes of this magnitude put some perspective on the anthropogenic global warming debate, where it is believed that the release of greenhouse gases will result in a global warming of a few C. To understand the forcing behind natural rapid climate changes appears as important as to understand the role

  4. Late Quaternary climate change shapes island biodiversity.

    Weigelt, Patrick; Steinbauer, Manuel Jonas; Cabral, Juliano Sarmento; Kreft, Holger


    Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.

  5. Paleohydrologic investigations in the vicinity of Yucca Mountain: Late Quaternary paleobotanical and polynological records

    Spaulding, W.G.


    The primary objective of this research in the vicinity of the proposed Yucca Mountain Nuclear Waste Repository is the detection of episodes of increased runoff and groundwater discharge in this presently arid area. Ancient, inactive spring deposits in nearby valley bottoms (Haynes, 1967; Quade, 1986; Quade and Pratt, 1989), evidence for perennial water in presently dry canyons (Spaulding, 1992), and recent claims for extraordinary increases in precipitation during the last glacial age (Forester, 1994), provide good reason to further investigate both lowland spring-discharge habitats, and upland drainages. The ultimate purpose is to assess the long-term variability of the hydrologic system in the vicinity of Yucca Mountain in response to naturally occurring climatic changes. The data generated in the course of this study are derived from radiocarbon dated packrat (Neotoma) middens. This report presents the results of an initial assessment of the hydrologic stability of the candidate area based on a limited suite of middens from localities that, on geomorphic and hydrologic grounds, could have been close to ancient stream-side or spring environments. Paleoclimatic reconstructions are another means of studying the long-term climatic hydrologic stability of the Candidate Area include, and are also generated from packrat midden data. A different flora characterized the Candidate Area during the last glacial age in response to a cooler and wetter climate, and the plant species that comprised this flora can be used to reconstruct specific components of past climatic regimes. Thus, a secondary objective of this study is to compare the plant macrofossil data generated in this study to other records from the Candidate Area (Spaulding, 1985; Wigand, 1990) to determine if these new data are consistent with prior reconstructions. 66 refs., 4 figs., 13 tabs.

  6. Late Quaternary record of pteropod preservation from the Andaman Sea

    Sijinkumar, A.V.; Nath, B.N.; Guptha, M.V.S.

    . Millennial/centennial-scale thermocline ventilation changes in the Indian Ocean as reflected by aragonite preservation and geochemical variations in Arabian Sea sediments. Geochimica et Cosmochimica Acta 73, 6771–6788. Brown, B.E., 2007. Coral reefs... Quaternary millennial-scale variability in pelagic aragonite preservation off Somalia. Marine Micropaleontology 59, 171- 183. Klöcker, R., Henrich, R., 2006. Recent and Late Quaternary pteropod preservation on the Pakistan shelf and continental slope...

  7. Session Introduction: Global correlation on late Quaternary paleovalley systems

    Cohen, K.M.; Amorosi, A.; Busschers, F.S.; Hori, K.; Tanabe, S.


    All around the world, paleovalley systems have trapped great amounts of deposits and hold a quite complete Late Quaternary record. Uniquely, these records directly interlink the shelf marine with the hinterland fluvial realms. In the vicinity of ice sheets, in similar ways, paleovalleys interlink th

  8. Significant differences in late Quaternary bedrock erosion and transport

    Andrews, John; Bjørk, Anders Anker; Eberl, Dennis;


    We use quantitative X-ray diffraction to determine the mineralogy of late Quaternary marine sediments from the West and East Greenland shelves offshore from early Tertiary basalt outcrops. Despite the similar basalt outcrop area (60 000–70 000 km2), there are significant differences between East ...

  9. Late Quaternary temperature change velocity in Mesoamerica

    Correa-Metrio, A.; Lozano, S.; Sosa-Nájera, S.; Bush, M. B.


    Quaternary climate has been highly variable, and yet few quantitative continental reconstructions are available for tropical areas. Quantitative records of temperature change during the Quaternary are especially relevant for putting modern climate change into a historic context. Within this perspective, two aspects are of singular relevance: i) Identifying and quantifying past climatic variability, and ii) Providing a means to estimate the seed at which climate change happened in the past. Here we show temperature reconstructions and temperature change velocity calculations for two locations in northern tropical America. Temperature reconstruction was based on two sedimentary records form Lake Chalco (30,000 years), central Mexican highlands, and Lake Petén-Itzá, Guatemalan lowlands (86,000 years). Temperature reconstruction was based on the analysis of fossil pollen on the light of pollen-temperature transfer functions. These functions were calibrated through an extensive survey of modern pollen samples covering an elevational gradient from 0 to 4,218 m asl. Derived temperature profiles show a parallel long-term trend and a similar cooling of approximately 5 oC during the Last Glacial Maximum in the lowlands and highlands of Mexico and Guatemala. Using a digital elevation model, we ere able to reconstruct the velocity at which isotherms displaced to produce the observed temperature anomalies. Spatial velocities of temperature change in the studied areas were at least four times slower than values reported for the last 50 years, but also at least twice as fast as those obtained from recent models. This study demonstrates that modern temperature change has no precedent within the last 86,000 years, but also that tropical climate has been more variable than it has been assumed to date.

  10. Cycling of phosphorus and manganese in the Arabian Sea during the Late Quaternary

    Scheanu, S.J.


    This thesis investigates phosphorus and manganese cycling in the Arabian Sea during the Late Quaternary, using sediment records recovered during the Netherlands Indian Ocean Programme (NIOP) in 1992. The first part is concerned with the reconstruction of Late Quaternary variability in

  11. Cycling of phosphorus and Manganese in the Arabian Sea during the Late Quaternary

    Schenau, S.J.


    This thesis investigates phosphorus and manganese cycling in the Arabian Sea during the Late Quaternary, using sediment records recovered during the Netherlands Indian Ocean Programme (NIOP) in 1992. The first part is concerned with the reconstruction of Late Quaternary variability in

  12. Asynchronous extinction of late Quaternary sloths on continents and islands

    Steadman, David W.; Martin, Paul S.; MacPhee, Ross D. E.; Jull, A. J. T.; McDonald, H. Gregory; Woods, Charles A.; Iturralde-Vinent, Manuel; Hodgins, Gregory W. L.


    Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their “last appearance” datum at ≈11,000 radiocarbon years before present (yr BP) or slightly less in North America, ≈10,500 yr BP in South America, and ≈4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial–interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people. PMID:16085711

  13. Possible Late Quaternary faulting in the Benton Hills, southeastern Missouri

    Palmer, J.R.; Hoffman, D. (Missouri Geological Survey Program, Rolla, MO (United States). Dept. of Natural Resources)


    Geologic mapping in the 1930's by Dan Stewart and Lyle McManamy identified numerous faults in the Thebes Gap area of the Benton Hills, including two post-late Quaternary faults (max. of 10 m displacement) along the southeastern escarpment. Recent geologic mapping (Richard Harrison, pers. comm.) suggests dextral strike-slip displacement on most of these faults; some deformation post-dates the Pliocene-Pleistocene Mounds gravel. Small historical earthquake epicenters have been recorded in the Benton Hills area. Review of these data and analysis of the geologic and structural relationships to small- and large-scale drainage and alluvial features suggest tectonic control of the southeastern escarpment of the Benton Hills. The authors propose the coincidence of geologic structures and landforms resembles tectonically active alluvial basin margins, with the Benton Hills southeastern margin representing a fault block uplift escarpment. Future seismic reflection, drilling and trenching studies are planned to determine if the escarpment is fault controlled and of recent origin.

  14. Late Quaternary deformation, Saddle Mountains anticline, south-central Washington

    West, M. W.; Ashland, F. X.; Busacca, A. J.; Berger, G. W.; Shaffer, M. E.


    Grabens and beheaded streams above a subjacent thrust fault illuminate late Quaternary deformation on the north limb of the Saddle Mountains anticline, Yakima fold belt, Washington. Geologic mapping and trenches excavated across a scarp on the north flank of a 13-km-long graben and a ± 5-m-high scarp north of the graben, confirm that deformation is related to coseismic slip on the underlying Saddle Mountains fault. Graben development began ca. 100 ka and continued into the Holocene. At least 6.5 m of vertical displacement in a ca. 20 40 ka paleosol yields minimum normal fault slip rates of 0.16 0.33 mm/yr. Assuming that normal slip in the hanging wall above the daylighting fault tip is related to primary reverse slip on the fault, resolution of throw on the 30°-dipping Saddle Mountains fault yields minimum slip of 13 m and minimum slip rates of 0.33 0.65 mm/yr, 2.3 9.4 times greater than slip rates used in a recent seismic hazard analysis for the Hanford Reservation.

  15. Late Quaternary carbonate accumulation along eastern South Atlantic Ocean

    Crabill, K.; Slowey, N. C.; Foreman, A. D.; Charles, C. D.


    Water masses originating from both the North Atlantic Ocean and the Southern Ocean intersect the Walvis Ridge and Namibian margin of southwest Africa. Changes in the distribution and properties of these water masses through time are reflected by variations in the nature of the sediments accumulating along this margin. As part of our ongoing studies, we are investigating the interrelationships between oceanographic/climatic change and the accumulation of carbonate minerals during the late Quaternary. A suite of cores that possess sediment records corresponding to the most recent glacial-interglacial cycles was collected from the water depth range of 500 to 3000 meters. Cores that preserve records of key water masses were selected for detailed analyses. Sediment bulk density, the concentration of calcium carbonate, and the relative proportions of carbonate minerals were precisely determined at regular depth intervals in these cores. Foraminiferal d18O and C-14 dates provide chronologic control. Results will be used to calculate how the accumulation rates of carbonate minerals on the seafloor vary through time, and the correspondence of such variation to changes in ocean circulation and climate will be assessed.

  16. Late Quaternary environments, vegetation and agriculture in northern New Zealand

    Horrocks, M.; Nichol, S. L.; Augustinus, P. C.; Barber, I. G.


    A sedimentological and plant microfossil history of the Late Quaternary is preserved in two sediment cores from early Polynesian ditch systems on southern Aupouri Peninsula. The study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings: a floodplain and a relatively closed peat swamp. The data fill part of the current gap in the environmental record from northern New Zealand, namely MIS 3 (57k-26k yr BP). There is evidence for an increase in fire frequency in the region after 40k 14C yr BP, suggesting a shift to drier (and cooler) conditions. Pollen records show that conifer-hardwood forest dominated by podocarps (especially Dacrydium) prevailed prior to Polynesian arrival and deforestation within the last millennium, with Fuscopsora insignificant throughout. Both cores show sections with gaps in deposition or preservation, possible flood-stripping of peat during the pre-Holocene and mechanical disturbance by early Polynesians. The identification of prehistoric starch grains and other microremains of introduced Colocasia esculenta (taro) in both cores supports indirect evidence that the ditch systems of far northern New Zealand were used for the extensive cultivation of this crop. Copyright

  17. Global late Quaternary megafauna extinctions linked to humans, not climate change

    Sandom, Christopher; Faurby, Søren; Sandel, Brody; Svenning, Jens-Christian


    The late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial...

  18. Late Quaternary geology of the Lower Central Plain, Thailand

    Sinsakul, Sin


    The Lower Central Plain or Chao Phraya Plain, located in the upper Gulf of Thailand, has an average elevation of 2 m above the present mean sea level. It is a fault bounded basin developed in the Plio-Pleistocene epoch. Consequently, the basin has been filled with Quaternary sediment reaching a thickness of almost 2000 m, of which only the upper 300 m is known. The Pleistocene deposits of the Lower Central Plain represent a complex interplay of alluvial, fluvial and deltaic environments of the Chao Phraya River and its tributaries. The upper sequence of sand and stiff clay with iron-oxide concretions on the surface was deposited in a fluviatile environment subjected to a regressive period in the late Pleistocene. The term "Chao Phraya delta" is used to define the landform where the Chao Phraya River interacted with marine processes as the sea level changed during the Holocene transgression. These strata indicated that the Holocene sea reached its maximum height of 4 m above the present mean sea level around 6000 years B.P.; from then on sea level fluctuated until it reached its present level around 1500 years B.P. This complex sea level history has caused the progradation of tidal flat, and tide-dominated delta deposits, consisting of soft marine clay, that covered the Lower Central Plain to an average depth of 15 m in the Bangkok area. The soft marine clay or Bangkok clay is the most important unit in the stratigraphic sequence in terms of land subsidence in the Lower Central Plain. Evidence of coastal erosion is also considerable in the low tidal flat area on the west bank of the Chao Phraya River mouth and adjacent coast.

  19. Late Quaternary sackungen in the highest mountains of the Carpathians

    Pánek, Tomáš; Mentlík, Pavel; Engel, Zbyněk; Braucher, Règis; Zondervan, Albert


    Sackungen represents a common mode of deep-seated rock-slope failures in alpine landscapes, but proof of their temporal and causal relationship to extrinsic factors such as climatic changes, glacier retreat or seismic activity remains elusive. Based on the terrestrial cosmogenic nuclide (TCN) dating of 18 sackung scarps supported by one radiocarbon-dated scarp, we reconstructed the post-glacial chronology of sackungen in the Tatra Mts. (central Europe, Slovakia and Poland), the highest part of the Carpathians. The obtained ages (∼15.7-4.3 ka) indicate that sackungen post-date the regional LGM and some of them originated soon after the glacier withdrawal from adjacent valleys. Furthermore, systematic decrease of scarp ages with their increasing altitude suggests a direct link between sackung origin and post-LGM glacier thinning. However, substantial lag (>5 ka) of some sackungen in respect to glacier retreat implies complex relationships between sackung onset and deglaciation where retreat of glaciers acted predominantly as a preparatory, not a triggering factor during the genesis of these slope deformations. They originated either as a consequence of stress relaxation within the rock mass lasting several ka or alternatively could be triggered by climatic processes or seismicity. Indeed, a significant part of sackung activity took place during predominantly warmer and more humid periods, with some dates coinciding with the Bølling-Allerød chronozone, but especially with the onset of the Holocene and the Holocene Climatic Optimum. Earthquake triggering is less probable, as the Tatra Mts. lack significant modern and historic seismic activity and there is no geomorphic evidence of fault offsets on the Late Quaternary landforms. In concert with other recent studies, we propose that large rock slope failures in high mountains seldom react immediately to glacier withdrawal, but could display temporal delay lasting up to several millennia.

  20. Late Quaternary rates of stream incision in Northeast Peloponnese, Greece

    Karymbalis, Efthimios; Papanastassiou, Dimitrios; Gaki-Papanastassiou, Kalliopi; Ferentinou, Maria; Chalkias, Christos


    This study focuses on defining rates of fluvial incision for the last 580±5 kyr along valley systems of eight streams that drain the eastern part of the northern Peloponnese. The streams are developed on the uplifted block of the offshore-running Xylokastro normal fault, one of the main faults bounding the southern edge of the Gulf of Corinth half-graben, and have incised a set of ten uplifted marine terraces having an amphitheatric shape. These terraces range in age from 60±5 kyr to 580±5 kyr and have been mapped in detail and correlated with late Pleistocene oxygen-isotope stages of high sea-level stands by previous studies. The terraces were used in this paper as reference surfaces in order to define fluvial incision rates at the lower reaches of the studied streams. To evaluate incision rates, thirty-three topographic valley cross-sections were drawn using fieldwork measurements as well as using a highly accurate (2×2 cell size) Digital Elevation Model (DEM) at specific locations where streams cut down the inner edges of the marine terraces. For each cross-section the ratio of valley floor width to valley height (Vf) and long-term mean stream incision rates were estimated for the last 580±5 kyr, while rock uplift rates were estimated for the last 330±5 kyr. The geomorphic evolution of the valleys on the uplifted block of the Xylokastro fault has been mainly driven by the lithology of the bedrock, sea level fluctuations during the late Quaternary, and incision of the channels due to the tectonic uplift. Stream incision rates range from 0.10±0.1 mm/yr for the last 123±7 kyr to 1.14±0.1 mm/yr for the last 310±5 kyr and are gradually greater from east to west depending on the distance from the trace of the fault. Downcutting rates are comparable with the rock uplift rates, which range from 0.4±0.02 mm/yr to 1.49±0.12 mm/yr, over the last 330±5 kyr.

  1. Shift in detrital sedimentation in the eastern Bay of Bengal during the late Quaternary

    PrakashBabu, C.; Pattan, J.N.; Dutta, K.; Basavaiah, N.; Prasad, G.V.K.; Ray, D.K.; Govil, P.

    the late Quaternary period. Units 2 (43-24 cm) and 1 (24-0 cm) represent enhanced and reduced supply of coarse-grained detrital sediments from the Ganges River during early and late Holocene period, respectively. Increased terrigenous supply dilutes calcium...

  2. Late Quaternary Megafaunal Extinctions in Northern Eurasia: Latest Results

    Stuart, Anthony


    Anthony J. Stuart1 & Adrian M. Lister2 1 Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. Email: 2 Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. Email: The global extinction of many spectacular species of megafauna (large terrestrial mammals, together with a few large reptiles and birds) within the last c. 50,000 years (Late Quaternary) has been attributed on the one hand to ‘overkill' by human hunters and on the other to environmental change. However, in spite of more than half a century of active interest and research the issue remains unresolved, largely because there are insufficient dated records of megafaunal species for most parts of the world. Northern Eurasia is an especially fruitful region in which to research megafaunal extinctions as it has a wealth of megafaunal material and crucially most extinctions occurred well within the range of radiocarbon dating. Our approach, in a series of projects over the last decade funded by the UK Natural Environment Research Council (NERC), involves amassing radiocarbon dates made directly on megafaunal material from across the entire region: a) by submitting a substantial number of samples (so far c. 500 dates) for AMS dating at Oxford (ORAU); b) obtaining AMS dates from colleagues working on aDNA projects; and c) carefully screening (‘auditing') dates from the literature. The dates (calibrated using OxCal) are plotted as time-sliced maps and as chronological/geographical charts. In our previous work we targeted a range of extinct species from Northern Eurasia: woolly mammoth, woolly rhinoceros, giant deer, cave bear (in collaboration with Martina Pacher), cave lion, and spotted hyaena (which survives today only in Sub-Saharan Africa). By this means we have established a reliable chronology for these extinctions which we are able to compare with the climatic, vegetational and

  3. The influence of climate on species distribution over time and space during the late Quaternary

    Carotenuto, F.; Di Febbraro, M.; Melchionna, M.; Castiglione, S.; Saggese, F.; Serio, C.; Mondanaro, A.; Passaro, F.; Loy, A.; Raia, P.


    Understanding the effect of climate on the composition of communities and its change over time and space is one of the major aims in ecology and paleoecology. Herein, we tackled on this issue by studying late Quaternary large mammal paleocommunities of Eurasia. The late Quaternary was a period of strong environmental instability, especially characterized by the occurrence of the last glacial maximum (LGM). We used community phylogenetics and joint species distribution models in order to understand the factors determining paleocommunity composition in the late Quaternary. Our results support the existence of strong climatic selection operating on the LGM fauna, both through the disappearance of warm-adapted species such as Elephas antiquus, Hippopothamus amphibious, and Stephanorhinus hemitoechus, and by setting the stage for the existence of a community characterized by cold-adapted large mammals. Patterns of abundance in the fossil record, co-occurrence between species pairs, and the extent of climatic forcing on faunal composition, differ between paleocommunities, but not between extinct and extant species, which is consistent with the idea that climate change, rather than the presence of humans, exerted a major effect on the survival of the late Quaternary megafauna.

  4. A chronology of alluvial fan response to Late Quaternary sea level and climate change, Crete

    Pope, Richard J. J.; Candy, Ian; Skourtsos, Emmanuel


    To better understand how fluvial systems respond to late Quaternary climatic forcing OSL and U-series dating was applied to stratigraphically significant sedimentary units within a small (aggradation to occur except during major climatic driven transitions i.e. major sea level fall and postglacial vegetation development.

  5. Late Quaternary faulting and historic seismicity in the western Lake Mead area, Nevada, Arizona and California

    Anderson, L.W.; O' Connel, D.R. (Bureau of Reclamation, Denver, CO (United States))


    As part of a regional seismic hazard study for Reclamation dams on the northern lower Colorado River, the age and distribution of known and suspected late Quaternary faults were investigated and historic seismicity was analyzed for the western Lake Mead area. Late Quaternary faults in the area consist of the Mead Slope, Black Hills, Frenchman Mountain, and California Wash faults. Geologic mapping and scarp profiles indicate that of these late Quaternary faults, the Black Hills fault displays evidence for the youngest (probably mid-Holocene) surface faulting. No information about the ages of older events was obtained for any of the faults; however, the ages of the most recent surface-rupturing events for individual faults suggest recurrence intervals of tens of thousands of years for specific faults and regional recurrence rates of several thousand years for M[sub 3] [>=] 6 1/2 events. Since 1936 when Hoover Dam was completed and the initial filling of Lake Mead began, the Boulder Basin area, the largest and deepest part of Lake Mead, has experienced abundant seismic activity that includes some of the largest historic earthquakes in southern Nevada (at least 21 M 4 events and one M 5). Based on earthquake locations from early networks (1937--1950) and those from temporary networks operating in 1975--1976 and 1988, earthquakes are clearly associated with the northeast-striking Mead Slope and Black Hills faults; one of the few associations of seismicity with late Quaternary faults in the Basin and Range. However, earthquakes also appear to be associated with the Fortification fault, a north-striking fault with no evidence of Quaternary surface faulting. Focal mechanisms for some of the 1975--1976 and 1988 events (all events M [<=] 3) suggest active strike-slip/oblique-slip motion on north-striking faults and normal/oblique-slip motion on northeast-striking structures.

  6. Late Quaternary environments and biogeography in the Great Basin

    Thompson, R. S.; Mead, J. I.


    Plant and animal remains found in packrat ( Neotoma spp.) middens and cave fill from the eastern and southern Great Basin region reveal the presence of subalpine conifers and boreal mammals at relatively low elevations during the Late Wisconsin. Limber pine ( Pinus flexilis) and bristlecone pine ( P. longaeva) were important in the late Pleistocene plant communities throughout this region. Spruce ( Picea cf. engelmannii) and common juniper ( Juniperus communis) were present in some of the more northerly localities, and Douglas fir ( Pseudotsuga menziesii) and white fir ( Abies concolor) were present in southern and eastern localities. Single needle pinyon pine ( Pinus monophylla), common across this region today, was apparently not present north of the Sheep Range of southern Nevada during the Late Wisconsin. Pikas ( Ochotona cf. princeps), small boreal mammals present in only a few Great Basin mountain ranges today, were common throughout the region. Heather voles ( Phenacomys cf. intermedius) have been found in two cave fill deposits in Nevada, though they are unknown in the Great Basin today. Limber and bristlecone pines are generally restricted to rocky substrates in modern subalpine habitats in the Great Basin, and this may also have been the case when these plants grew at lower elevations during the Late Wisconsin. Subalpine conifers were present on the rock outcrops sampled by the packrat middens, but shrub communities, perhaps dominated by sagebrush ( Artemisia spp.), may have been present on alluvial valley-bottom substrates. Forested habitats would thus have been isolated habitat islands, as they are today. Boreal small mammals, including pikas and heather voles, were able to colonize the Great Basin mountain ranges during the late Pleistocene. We suggest that these mammals were able to survive in the intervening valley-bottoms under a cool-summer climatic regime, and that continuous forest or woodland corridors were not necessary for migration.

  7. Mapping the late Quaternary evolution of the lower Mississippi Valley

    Haugerud, R. A.; Simon, K. M.; James, T. S.


    The lower Mississippi Valley (LMV) extends from Cape Girardeau to Natchez and from Little Rock to Memphis. Extensive Quaternary terraces within the LMV have been considered to reflect downstream changes in base level (global sea level) and (or) upstream changes in water and sediment input because of glaciation. We suggest that the first-order control on terrace development was glacial-isostatic adjustment (GIA). Observed variation in heights of Quaternary alluvial surfaces at Memphis is 50 m (Rittenour et al., 2007). GIA modeling by Clark et al. (1994) predicted vertical displacement of as much as 130 m at Memphis over the last 18,000 years. ICE-5G models predict smaller displacement and reinforce the viability of GIA as the primary cause of LMV aggradation and incision. Existing analyses of LMV terraces are built on geomorphic maps by Saucier and colleagues (1974, 1994; Autin et al., 1991) that were interpreted from aerial photographs and inch-to-the-mile contour maps. Geomorphic mapping from high-resolution DEMs is more accurate, more rapid, and more reproducible than mapping from aerial photography and intermediate-resolution contours. Working from lidar DEMs (1-5 m XY resolution) and the 10 m National Elevation Dataset (NED) DEM largely derived from 1:24,000 scale contours, Haugerud is mapping the geomorphology of the LMV at ~1:500,000 scale. Goals are to explore the GIA-terrace hypothesis and improve the geomorphic and stratigraphic context for studies of New Madrid seismicity. Mapping leads to several observations: 1. The Holocene floodplain of the Mississippi River onlaps older surfaces. The river appears to be filling a hole created by collapse of the Laurentide forebulge. Continued filling of this accommodation space will, barring human intervention, enable the river to abandon its course through Thebes Gap in favor of a lower-elevation route through Oran Gap. 2. Within Holocene meander belts, younger levee crests are higher than older levee crests. The

  8. Late Quaternary transgressive large dunes on the sediment-starved Adriatic shelf

    Correggiari, A.; Field, M.E.; Trincardi, F.


    The Adriatic epicontinental basin is a low-gradient shelf where the late-Quaternary transgressive systems tract (TST) is composed of thin parasequences of backbarrier, shoreface and offshore deposits. The facies and internal architecture of the late-Quaternary TST in the Adriatic epicontinental basin changed consistently from early transgression to late transgression reflecting: (1) fluctuations in the balance between sediment supply and accommodation increase, and (2) a progressive intensification of the oceanographic regime, driven by the transgressive widening of the basin to as much as seven times its lowstand extent. One of the consequences of this trend is that high-energy marine bedforms such as sand ridges and sand waves characterize only areas that were flooded close to the end of the late-Quaternary sea-level rise, when the wind fetch was maximum and bigger waves and stronger storm currents could form. We studied the morphology, sediment composition and sequence-stratigraphical setting of a field of asymmetric bedforms (typically 3 m high and 600 m in wavelength) in 20-24 m water depth offshore the Venice Lagoon in the sediment-starved North Adriatic shelf. The sand that forms these large dunes derived from a drowned transgressive coastal deposit reworked by marine processes. Early cementation took place over most of the dune crests limiting their activity and preventing their destruction. Both the formation and deactivation of this field of sand dunes occurred over a short time interval close to the turn-around point that separates the late-Quaternary sea-level rise and the following highstand and reflect rapid changes in the oceanographic regime of the basin.

  9. Late Quaternary loss of genetic diversity in muskox (Ovibos

    Mol Dick


    Full Text Available Abstract Background The modern wildherd of the tundra muskox (Ovibos moschatus is native only to the New World (northern North America and Greenland, and its genetic diversity is notably low. However, like several other megafaunal mammals, muskoxen enjoyed a holarctic distribution during the late Pleistocene. To investigate whether collapse in range and loss of diversity might be correlated, we collected mitochondrial sequence data (hypervariable region and cytochrome b from muskox fossil material recovered from localities in northeastern Asia and the Arctic Archipelago of northern North America, dating from late Pleistocene to late Holocene, and compared our results to existing databases for modern muskoxen. Results Two classes of haplotypes were detected in the fossil material. "Surviving haplotypes" (SHs, closely similar or identical to haplotypes found in modern muskoxen and ranging in age from ~22,000 to ~160 yrbp, were found in all New World samples as well as some samples from northeastern Asia. "Extinct haplotypes" (EHs, dating between ~44,000 and ~18,000 yrbp, were found only in material from the Taimyr Peninsula and New Siberian Islands in northeastern Asia. EHs were not found in the Holocene muskoxen specimens available for this study, nor have they been found in other studies of extant muskox populations. Conclusion We provisionally interpret this evidence as showing that genetic variability was reduced in muskoxen after the Last Glacial Maximum but before the mid-Holocene, or roughly within the interval 18,000-4,000 yrbp. Narrowing this gap further will require the recovery of more fossils and additional genetic information from this interval.

  10. Late quaternary evolution of the Orinoco Delta, Venezuela

    Warne, A.G.; Guevara, E.H.; Aslan, A.


    The modern Orinoco Delta is the latest of a series of stacked deltas that have infilled the Eastern Venezuelan Basin (EVB) since the Oligocene. During the late Pleistocene sea-level lowstand (20,000 to 16,000 yrs BP), bedrock control points at the position of the present delta apex prevented the river channel from incising as deeply as many other major river systems. Shallow seismic data indicate that the late Pleistocene Orinoco incised into the present continental shelf, where it formed a braided-river complex that transported sediment to a series of shelf-edge deltas. As sea level rose from 16,000 to 9,500 yrs BP, the Orinoco shoreline shifted rapidly landward, causing shallow-marine waves and currents to form a widespread transgressive sand unit. Decelerating sea-level rise and a warmer, wetter climate during the early Holocene (9,500 to 6,000 yrs BP) induced delta development within the relatively quiet-water environment of the EVB embayment. Sea level approached its present stand in the middle Holocene (6,000 to 3,000 yrs BP), and the Orinoco coast prograded, broadening the delta plain and infilling the EVB embayment. Significant quantities of Amazon sediment began to be transported to the Orinoco coast by littoral currents. Continued progradation in the late Holocene caused the constriction at Boca de Serpientes to alter nearshore and shelf hydrodynamics and subdivide the submarine delta into two distinct areas: the Atlantic shelf and the Gulf of Paria. The increased influence of littoral currents along the coast promoted mudcape development. Because most of the water and sediment were transported across the delta plain through the Rio Grande distributary in the southern delta, much of the central and northwestern delta plain became sediment starved, promoting widespread accumulation of peat deposits. Human impacts on the delta are mostly associated with the Volca??n Dam on Can??o Manamo. However, human activities have had relatively little effect on the

  11. Geological and geomorphological evolution of a sedimentary periglacial landscape in Northeast Siberia during the Late Quaternary


    A wide variety of environmental records is necessary for analysing and understanding the complex Late Quaternary dynamics of permafrost-dominated Arctic landscapes. A NE Siberian periglacial key region was studied in detail using sediment records, remote sensing data, and terrain modelling, all incorporated in a geographical information system (GIS). The study area consists of the Bykovsky Peninsula and the adjacent Khorogor Valley in the Kharaulakh Ridge situated a few kilometres southeast o...

  12. Fluctuations in productivity and denitrification in the southeastern Arabian Sea during the Late Quaternary

    Kessarkar, P.M.; Rao, V.P.; Naqvi, S.W.A.; Chivas, A.R.; Saino, T.

    , D. W., The effect of millennial-scale changes in Arabian Sea denitrification on atmos- pheric CO 2 . Nature, 2002, 415, 159–162. 8. Reichart, G. J., Lourens, L. J. and Zachariasse, W. J., Temporal variability in the northern Arabian Sea Oxygen.... Suthhof, A., Ittekkot, V. and Gaye-Haake, B., Millennial-scale oscillations of denitrification intensity in the Arabian Sea during the late Quaternary and its potential influence on atmospheric N 2 O and global climate. Glob. Biogeochem. Cycles, 2001...

  13. Paleoenvironmental changes during the late Quaternary as inferred from foraminifera assemblages in the Laizhou Bay

    YAO Jing; YU Hongjun; XU Xingyong; YI Liang; CHEN Guangquan; SU Qiao


    Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C (AMS14C) and opti-cally stimulated luminescence (OSL) ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of ma-rine isotopic stage 7 (MIS7), the last interglacial period (MIS5) and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the fora-minifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.

  14. Clay minerals as palaeomonsoon proxies: Evaluation and relevance to the late Quaternary records from SE Arabian Sea

    Thamban, M.; Rao, V.P.

    as palaeoclimatic proxies are evaluated and discussed. Systematic investigations using several sediment cores from the SE Arabian Sea reveal that despite the influence of several complicating factors, variations in clay mineral composition during the late Quaternary...

  15. Radiocarbon chronologies and extinction dynamics of the Late Quaternary mammalian megafauna of the Taimyr Peninsula, Russian Federation

    MacPhee, RDE; Tikhonov, AN; Mol, D; Maliave, CD; Van der Plicht, H; Greenwood, AD; Flemming, C; Agenbroad, L; MacPhee, Ross D.E.; Tikhonov, Alexei N.; Marliave, Christian de; Greenwood, Alex D.


    This paper presents 75 new radiocarbon dates based on late Quaternary mammal remains recovered from eastern Taimyr Peninsula and adjacent parts of the northern Siberian lowlands, Russian Federation, including specimens of woolly mammoth (Mammuthus primigenius), steppe bison (Bison priscus), muskox (

  16. Tectonic control on the Late Quaternary hydrography of the Upper Tiber Basin (Northern Apennines, Italy)

    Benvenuti, Marco; Bonini, Marco; Moroni, Adriana


    We examine the intramontane Upper Tiber Basin in the Northern Apennines (central Italy), where sub-orthogonal fault systems forced river deviation and the abandonment of alluvial fans since the late Middle Pleistocene. Archaeological material, spanning the Middle Palaeolithic-Iron Age, was collected mostly from the surface of the Late Quaternary alluvial landforms and related deposits (MUP and HOL units). This information contributed to the partial dating of seven major stages of drainage development. Normal faults parallel and transverse to the basin trend were active at different times and conditioned the valley pattern of the Middle (MUP1-2)-Late (MUP3) Pleistocene Tiber, Singerna, Sovara and Tignana rivers, which still flow today into the basin. The MUP1 and the MUP3 fans were beheaded by the displacement of their feeder valleys along the basin-transverse Carmine and Montedoglio faults. In some cases, the former feeder rivers underwent stream piracy but their courses mostly deviated in response of the topographic gradient created by faulting, as well as through the incision of new valleys that exploited the lithological contrast along the fault lines. The MUP3 Tignana fan was abandoned mostly due to the activity of the basin-parallel, dip-slip Sansepolcro fault. Subsidence driven by the basin-parallel Anghiari and Sansepolcro fault systems also provided the accommodation space for the MUP3 and HOl1-2 Afra fans between Late Pleistocene and early-mid Holocene. This study exemplifies the interplay between longitudinal and transverse fault systems, and the Late Quaternary hydrographic evolution of an extensional basin settled in the axial zone of an active fold-and-thrust belt. Although the faulting has interacted with the forcing exerted by the Late Quaternary climate fluctuations on the basin drainage systems, the tectonic rates are sufficiently high to represent the prime controller on base-level change and drainage routing patterns.

  17. Origin of the late quaternary dune fields of northeastern Colorado

    Muhs, D.R.; Stafford, T.W.; Cowherd, S.D.; Mahan, S.A.; Kihl, R.; Maat, P.B.; Bush, C.A.; Nehring, J.


    Stabilized eolian deposits, mostly parabolic dunes and sand sheets, cover much of the landscape of northeastern Colorado and adjacent parts of southwestern Nebraska in four geographically distinct dune fields. Stratigraphic and soil-geomorphic relations and accelerator radiocarbon dating indicate that at least three episodes of eolian sand movement occurred between 27 ka and 11 ka, possibly between 11 ka and 4 ka, and within the past 1.5 ka. Thus, eolian sand deposition took place under both glacial and interglacial climatic conditions. In the youngest episodes of eolian sand movement, Holocene parabolic dunes partially buried Pleistocene sand sheet deposits. Late Holocene sands in the Fort Morgan and Wray dune fields, to the south of the South Platte River, have trace element ratios that are indistinguishable from modern South Platte River sands, but different from Ogallala Formation bedrock, which has previously been cited as the main source of dune sand on the Great Plains. Sands in the Greeley dune field, to the north of the South Platte River, have trace element concentrations that indicate a probable Laramie Formation source. Measurements of parabolic dunes indicate paleowinds from the northwest in all dune fields, in good agreement with resultant drift directions calculated for nearby weather stations. Thus, paleowinds were probably not significantly different from present-day winds, and are consistent with a South Platte River source for the Fort Morgan and Wray dune fields, and a Laramie Formation source for the Greeley dune field. Sand accumulated downwind of the South Platte River to form the Fort Morgan dune field. In addition, sand was also transported farther downwind over the upland formed by the calcrete caprock of the Ogallala Formation, and deposited in die lee of the upland on the southeast side. Because of high wind energy, the upland itself served as a zone of sand transport, but little or no sand accumulation took place on this surface. These

  18. Late Quaternary environmental change in the Bonneville basin, western USA

    Madsen, D.B.; Rhode, D.; Grayson, D.K.; Broughton, J.M.; Livingston, S.D.; Hunt, J.; Quade, Jay; Schmitt, D.N.; Shaver, M. W.


    Excavation and analyses of small animal remains from stratified raptor deposits spanning the last 11.5 ka, together with collection and analysis of over 60 dated fossil woodrat midden samples spanning the last 50 ka, provide a detailed record of changing climate in the eastern Great Basin during the late Pleistocene and Holocene. Sagebrush steppe dominated the northern Bonneville basin during the Full Glacial, suggesting that conditions were cold and relatively dry, in contrast to the southern basin, which was also cold but moister. Limber pine woodlands dominated ???13-11.5 ka, indicating increased dryness and summer temperatures ???6-7??C cooler than present. This drying trend accelerated after ???11.5 ka causing Lake Bonneville to drop rapidly, eliminating 11 species of fish from the lake. From ???11.5-8.2 ka xerophytic sagebrush and shadscale scrub replaced more mesophilic shrubs in a step-wise fashion. A variety of small mammals and plants indicate the early Holocene was ???3??C cooler and moister than at present, not warmer as suggested by a number of climatic models. The diversity of plants and animals changed dramatically after 8.2 ka as many species disappeared from the record. Some of the upland species returned after ???4 ka and Great Salt Lake became fresh enough at ???3.4 and ???1.2 ka to support populations of Utah chub. ?? 2001 Elsevier Science B.V.

  19. Late Quaternary sedimentary features of Bear Lake, Utah and Idaho

    Smoot, J.P.


    Bear Lake sediments were predominantly aragonite for most of the Holocene, reflecting a hydrologically closed lake fed by groundwater and small streams. During the late Pleistocene, the Bear River flowed into Bear Lake and the lake waters spilled back into the Bear River drainage. At that time, sediment deposition was dominated by siliciclastic sediment and calcite. Lake-level fluctuation during the Holocene and late Pleistocene produced three types of aragonite deposits in the central lake area that are differentiated primarily by grain size, sorting, and diatom assemblage. Lake-margin deposits during this period consisted of sandy deposits including well-developed shoreface deposits on margins adjacent to relatively steep gradient lake floors and thin, graded shell gravel on margins adjacent to very low gradient lake-floor areas. Throughout the period of aragonite deposition, episodic drops in lake level resulted in erosion of shallow-water deposits, which were redeposited into the deeper lake. These sediment-focusing episodes are recognized by mixing of different mineralogies and crystal habits and mixing of a range of diatom fauna into poorly sorted mud layers. Lake-level drops are also indicated by erosional gaps in the shallow-water records and the occurrence of shoreline deposits in areas now covered by as much as 30 m of water. Calcite precipitation occurred for a short interval of time during the Holocene in response to an influx of Bear River water ca. 8 ka. The Pleistocene sedimentary record of Bear Lake until ca. 18 ka is dominated by siliciclastic glacial fl our derived from glaciers in the Uinta Mountains. The Bear Lake deep-water siliciclastic deposits are thoroughly bioturbated, whereas shallow-water deposits transitional to deltas in the northern part of the basin are upward-coarsening sequences of laminated mud, silt, and sand. A major drop in lake level occurred ca. 18 ka, resulting in subaerial exposure of the lake floor in areas now covered by

  20. Late Quaternary glaciation of the Upper Soca River Region (Southern Julian Alps, NW Slovenia)

    Bavec, Milos; Tulaczyk, Slawek M.; Mahan, Shannon; Stock, Gregory M.


    Extent of Late Quaternary glaciers in the Upper Soc??a River Region (Southern Julian Alps, SE Europe) has been analyzed using a combination of geological mapping, glaciological modeling, and sediment dating (radiocarbon, U/Th series and Infrared Stimulated Luminescence-IRSL). Field investigations focused mainly on relatively well preserved Quaternary sequences in the Bovec Basin, an intramontane basin located SW of the Mediterranean/Black Sea divide and surrounded by mountain peaks reaching from approximately 2100 up to 2587 m a.s.l. Within the Basin we recognized two Late Quaternary sedimentary assemblages, which consist of the same facies association of diamictons, laminated lacustrine deposits and sorted fluvial sediments. Radiocarbon dating of the upper part of the lake sediments sequence (between 12790??85 and 5885??60 14C years b.p.) indicates that the younger sedimentary assemblage was deposited during the last glacial maximum and through early Holocene (Marine Isotope Stage 21, MIS 2-1). Sediment ages obtained for the older assemblage with U/Th and IRSL techniques (between 154.74??22.88 and 129.93??7.90 ka b.p. for selected samples) have large errors but both methods yield results consistent with deposition during the penultimate glacial-interglacial transition (MIS 6-5). Based on analyses of field data combined with glaciological modeling, we argue that both sediment complexes formed due to high sediment productivity spurred by paraglacial conditions with glaciers present in the uplands around the Bovec Basin but not extending down to the basin floor. Our study shows that the extent and intensity of direct glacial sedimentation by Late Quaternary glaciers in the region was previously significantly overestimated. ?? 2004 Elsevier B.V. All rights reserved.

  1. Late Quaternary relative sea level in Southern California and Monterey Bay

    Reynolds, Laura C.; Simms, Alexander R.


    Few records of late Quaternary relative sea level (RSL) are available for the Pacific coast of North America south of San Francisco Bay, a region where RSL data would be particularly useful for constraining vertical rates of tectonic motion. This paper provides the first regional, uplift-corrected late Quaternary RSL history for southern California derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore, estuarine, and freshwater deposits in sediment cores from coastal southern California. We also provide a local, uplift-corrected RSL history for Monterey Bay, central California, generated from 48 radiocarbon ages from Elkhorn Slough and surrounding environments. Our resulting compilations show rapid sea-level rise from 15 ka which begins to decelerate to present mean sea level (PMSL) between 6 and 8 ka. Late Holocene (Bay in central California. Both rates of late Holocene RSL rise calculated are lower than recent RSL rates from southern California (˜1.61 ± 0.34 to 2.4 ± 1.04 mm a-1) and Monterey Bay (1.49 ± 0.95 mm a-1), derived from uplift-corrected, 20th century tide gauge data. This new RSL data fills geographical gaps in relative sea-level histories, as well as provides important datums for local tectonic processes.

  2. Albedo changes, Milankovitch forcing, and late quaternary climate changes in the central Andes

    Kull, C.; Grosjean, M. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Dept. of Geography


    Late quaternary humidity changes resulted in substantial modifications of the land surface characteristics in the Altiplano of the Atacama desert, central Andes. Reconstructions of surface albedo, top-of-atmosphere (TOA) albedo, and shortwave net radiation in the Andes of northern Chile for 20,14,10,7 and 0 ka suggest that surface and TOA albedo increased substantially during periods of relatively humid environmental conditions (i.e., with large palaeolakes, glaciers and dense vegetation). The decrease of summer shortwave net radiation and seasonality during the late-glacial/early Holocene humid phase (14 to 10 ka) due to Earth`s surface and atmospheric characteristics added to the effect of orbitally driven negative deviations of southern Hemisphere austral summer insolation and minimum seasonality at 20 S. Therefore, in situ radiative forcing is, in contrast to the Northern Hemisphere tropics, not a suitable explanation for enhanced convective precipitation and, ultimately, humid climatic conditions. Our results suggest that late Quaternary humidity changes on the Altiplano reflect a collective response to (1) environmental changes in the source area of the moisture (e.g., reexpansion of the rain forest and increased release of latent heat over Amazonia and the Chaco, warm sea surface temperatures in the E Pacific) and, (2) large-scale circulation patterns and wave structures in the upper troposphere (strength and position of the Bolivian high, divergent flow stimulating convection over the Altiplano), or that they even reflect a response to (3) interhemispherical teleconnections. (orig.) With 5 figs., 2 tabs., 45 refs.

  3. Late Quaternary incision and deposition in an active volcanic setting: The Volturno valley fill, southern Italy

    Amorosi, Alessandro; Pacifico, Annamaria; Rossi, Veronica; Ruberti, Daniela


    Extensive illustration of depositional facies, ostracod and foraminiferal assemblages, and Late Quaternary stratigraphic architecture is offered for the first time from beneath the modern coastal plain of Volturno River, the longest river in southern Italy. Proximity to an active volcanic district, including quiescent Vesuvius Volcano, provides an easily identifiable stratigraphic marker (Campania Grey Tuff or CGT), up to 55 m thick, emplaced 39 ky cal BP by a large-volume explosive pyroclastic eruption. Identification of top CGT to a maximum depth of 30 m allows tracing out the shape of a 15-20 km wide Late Quaternary palaeovalley incised by Volturno River into the thick ignimbritic unit immediately after its deposition. A terraced palaeotopography of the valley flanks is reconstructed on the basis of core data. Above the basal fluvial deposits, the early Holocene transgressive facies consist of a suite of estuarine (freshwater to brackish) deposits. These are separated from overlying transgressive barrier sands by a distinctive wave ravinement surface. Upwards, a distinctive shallowing-upward succession of middle-late Holocene age is interpreted to reflect initiation and subsequent progradation of a wave-dominated delta system, with flanking strandplains, in response to reduced rate of sea-level rise. The turnaround from transgressive to highstand conditions is identified on the basis of subtle changes in the meiofauna. These enable tracking of the maximum flooding surface into its updip (lagoonal/estuarine) counterpart, thus highlighting the role of refined palaeontological criteria as a powerful tool for high-resolution sequence-stratigraphic studies.

  4. Fluvial responses to late Quaternary climate change in the Shiyang River drainage system, western China

    Gao, Hongshan; Li, Zongmeng; Pan, Baotian; Liu, Fenliang; Liu, Xiaopeng


    As a drainage system located in arid western China, the Shiyang River, combined with considerable fluvial strata and landform information, provides an environmental context within which to investigate fluvial responses to late Quaternary climate change. Sedimentological analysis and optically stimulated luminescence (OSL) dating enabled us to reconstruct the processes and fluvial styles of three sedimentary sequences of the Shagou and Hongshui rivers in the Shiyang drainage system. Our results present a variety of river behaviors during the late Quaternary in these areas. In the upstream Shiyang River, Zhangjiadazhuang (ZJDZ) profile of the Shagou was dominated by aggradation and a meandering channel pattern at 10.6-4.2 ka, while a noticeable channel incision occurred at ~ 4.2 ka followed by lateral channel migration. In the downstream Shiyang River, Datugou (DTG) profile of the Hongshui was an aggrading meandering river from 39.7 to 7.2 ka while channel incision occurred at 7.2 ka. Another downstream profile, Wudunwan (WDW) of the Hongshui was also characterized by aggradation from 22.4 to 4.8 ka; however, its channel pattern shifted from braided to meandering at ~ 13 ka. A discernable downcutting event occurred at ~ 4.8 ka, followed by three channel aggradation and incision episodes prior to 1.8 ka. The last 1.8 ka has been characterized by modern channel and floodplain development. The fluvial processes and styles investigated have a close correlation with late Quaternary climate change in the Shiyang River drainage. During cold phases, the WDW reach was dominated by aggradation with a braided channel pattern. During warm phases, the rivers that we investigated were also characterized by aggradation but with meandering channel patterns. Channel incision events and changes of fluvial style occurred mainly during climate transitions.

  5. Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary

    Tierney, J.; Russell, J.M.; Sinninghe Damsté, J.S.; Huang, Y.S.; Verschuren, D.


    Both Atlantic and Indian Ocean climate dynamics exert influence over tropical African hydroclimate, producing complex patterns of convergence and precipitation. To isolate the Indian Ocean influence on African paleohydrology, we analyzed the deuterium/hydrogen ratio of higher plant leaf waxes (delta

  6. Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary

    Tierney, J.E.; Russell, J.M.; Sinninghe Damsté, J.S.; Huang, Y.S.; Verschuren, D.


    Both Atlantic and Indian Ocean climate dynamics exert influence over tropical African hydroclimate, producing complex patterns of convergence and precipitation. To isolate the Indian Ocean influence on African paleohydrology, we analyzed the deuterium/hydrogen ratio of higher plant leaf waxes (δDwax

  7. Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary

    Tierney, J.; Russell, J.M.; Sinninghe Damsté, J.S.; Huang, Y.S.; Verschuren, D.


    Both Atlantic and Indian Ocean climate dynamics exert influence over tropical African hydroclimate, producing complex patterns of convergence and precipitation. To isolate the Indian Ocean influence on African paleohydrology, we analyzed the deuterium/hydrogen ratio of higher plant leaf waxes (delta

  8. Human Dispersals Along the African Rift Valley in the Late Quaternary

    Tryon, C. A.; Faith, J. T.; Peppe, D. J.


    Climate- and tectonic-driven environmental dynamics of the East African Rift System (EARS) during the Quaternary played an important role in the demographic history of early Homo sapiens, including expansions of modern humans across and out of Africa. Human forager population size, geographic range, and behaviors such as hunting strategies and residential mobility likely varied in response to changes in the local and regional environment. Throughout the Quaternary, floral and faunal change was linked at least in part to variations in moisture availability, temperature, and atmospheric CO2, which in addition to uplift and faulting, contributed to the expansion and contraction of a number of large lakes that served as biogeographic barriers to many taxa. This is particularly clear for the Lake Victoria basin, where biogeographic, geological, and paleontological evidence documents repeated expansion and contraction of the ranges of species in response to lake level and vegetation change. Across much of eastern Africa, the topography of the rift facilitated north-south dispersals, the timing of which may have depended in part on the expansion and contraction of the equatorial forest belt. Dispersal potential likely increased during the more arid periods of the late Quaternary, when the roles of lakes and forests as dispersal barriers was reduced and the extent of low net primary productivity dry grasslands increased, the latter requiring large home ranges for human foragers, conditions suitable for range expansions within H. sapiens.

  9. Palaeoenvironmental dynamics inferred from late Quaternary permafrost deposits on Kurungnakh Island, Lena Delta, Northeast Siberia, Russia

    Wetterich, Sebastian; Kuzmina, Svetlana; Andreev, Andrei A.; Kienast, Frank; Meyer, Hanno; Schirrmeister, Lutz; Kuznetsova, Tatyana; Sierralta, Melanie


    Late Quaternary palaeoenvironments of the Siberian Arctic were reconstructed by combining data from several fossil bioindicators (pollen, plant macro-fossils, ostracods, insects, and mammal bones) with sedimentological and cryolithological data from permafrost deposits. The record mirrors the environmental history of Beringia and covers glacial/interglacial and stadial/interstadial climate variations with a focus on the Middle Weichselian interstadial (50-32 kyr BP). The late Pleistocene to Holocene sequence on Kurungnakh Island reflects the development of periglacial landscapes under changing sedimentation regimes which were meandering fluvial during the Early Weichselian, colluvial or proluvial on gently inclined plaines during the Middle and Late Weichselian, and thermokarst-affected during the Holocene. Palaeoecological records indicate the existence of tundra-steppe vegetation under cold continental climate conditions during the Middle Weichselian interstadial. Due to sedimentation gaps in the sequence between 32 and 17 kyr BP and 17 and 8 kyr BP, the Late Weichselian stadial is incompletely represented in the studied outcrops. Nevertheless, by several palaeoecological indications arctic tundra-steppe vegetation under extremely cold-arid conditions prevailed during the late Pleistocene. The tundra-steppe disappeared completely due to lasting paludification during the Holocene. Initially subarctic shrub tundra formed, which later retreated in course of the late Holocene cooling.

  10. Late Quaternary stratigraphic development in the lower Luni, Mahi and Sabarmati river basins, western India

    M Jain; S K Tandon; S C Bhatt


    This study reviews the Quaternary alluvial stratigraphy in three semi-arid river basins of western India i.e., lower Luni (Rajasthan), and Mahi and Sabarmati (Gujarat alluvial plains). On the basis of OSL chronologies, it is shown that the existing intra-valley lithostratigraphic correlations require a revision. The sand, gravel and mud facies are present during various times in the three basins, however, the fluvial response to climate change, and the resulting facies associations, was different in the Thar desert as compared to that at the desert margin; this makes purely lithostratigraphic correlations unviable. It is further shown that the rivers in the Thar desert were more sensitive to climate change and had small response times and geomorphic thresholds as compared to the desert-margin rivers. This is illustrated during the early OIS 1, when the Luni river in the Thar desert was dynamic and showed frequent variations in fluvial styles such as gravel bedload braided streams, sand-bed ephemeral streams and meandering streams, all followed by incision during the early Holocene. The coeval deposits in Sabarmati, however, only show a meandering, floodplain-dominated river. Late Quaternary alluvial deposits in these basins unconformably overlie some older deposits that lack any absolute chronology. Based on the facies types and their associations, and the composition and architecture of the multistoried gravel sheets in the studied sections, it is suggested that older deposits are of pre-Quaternary age. This hypothesis implies the presence of a large hiatus incorporating much of the Quaternary period in the exposed sections.

  11. Distinguishing allogenic from autogenic causes of bed elevation change in late Quaternary alluvial stratigraphic records

    Daniels, J. Michael


    Allogenic and autogenic mechanisms both cause changes in the bed elevation of rivers and thereby influence the characteristics of alluvial stratigraphic records (ASRs). Allogenic forcing mechanisms can be grouped into five categories whose relative influence varies with timescale: climate, tectonism, base level, land use/land cover and direct human modification of channels. Late Quaternary ASRs are influenced by the greatest range of allogenic forcing variables with climate among the most important. Autogenic mechanisms of bed elevation change are ubiquitous throughout fluvial systems and are always time-transgressive. Autogenic bed elevation change propagates through drainage networks at predictable rates and results in a time-space envelope within which its effects are capable of operating. ASRs that can be correlated over geographical areas large enough and time intervals small enough to exist outside this envelope most likely result from allogenic forcing. This formulation represents a quantitative and geographic set of threshold criteria for distinguishing between autogenic and allogenic mechanisms. Over late Quaternary timescales (10 2 to 10 5 years) in tectonically stable regions climate change is the dominant allogenic mechanism and, therefore, the first-order control on the morphology, sedimentology, pedologic characteristics and chronology of alluvial stratigraphic records that meet or exceed the threshold criteria for demonstrating allogenic causality.

  12. Eolian sediment responses to late Quaternary climate changes: Temporal and spatial patterns in the Sahara

    Swezey, C.


    This paper presents a compilation of eolian-based records of late Quaternary climate changes in the Sahara. Although the data are relatively sparse, when viewed as a whole, they reveal a general pattern of widespread eolian sediment mobilization prior to 11,000 cal. years BP, eolian sediment stabilization from 11,000 to 5000 cal. years BP, and a return to widespread eolian sediment mobilization after 5000 cal. years BP. Furthermore, an eolian-based record from southern Tunisia reveals the existence of millennial-scale changes in eolian sediment behavior. These millennial-scale variations provide examples of eolian sediment responses to climate changes at a scale intermediate between seasonal and orbital ('Milankovitch') changes, and they are also coincident with abrupt atmospheric and oceanic changes. The general synchroneity of the eolian stratigraphic records and their coincidence with various oceanic and atmospheric changes suggest that global forcing mechanisms have influenced late Quaternary eolian sediment behavior in the Sahara. ?? 2001 Elsevier Science B.V.

  13. Estimates of late Quaternary mode and intermediate water silicic acid concentration in the Pacific Southern Ocean

    Rousseau, Jonathon; Ellwood, Michael J.; Bostock, Helen; Neil, Helen


    The Southern Ocean plays a critical role in the exchange of carbon between the ocean and atmosphere over glacial-interglacial timescales. Hypotheses used to explain late Quaternary variations in atmospheric carbon dioxide (CO2) implicate changes in the nutrient dynamics and circulation of the Southern Ocean. Here we present silicon isotope (δ30Si) records of late Quaternary sponges and diatoms from the NZ-sector of the Southern Ocean. Analysis of our sponge δ30Si records strongly suggests that the silicic acid concentration at mode and intermediate depths was higher during the LGM and the deglacial period compared to the present day. Our diatom δ30Si record suggests biological productivity near of the Polar Front was greater during the deglacial period, but not significantly different during the LGM compared to the present day. Taking our dataset in context with other regional paleoceanographic records, we interpret the predicted elevation in LGM and deglacial silicic acid concentration to reflect a shoaling of water masses during the LGM and 'leakage' of excess Southern Ocean dissolved silicon during the deglacial period.

  14. Paleoclimatic, paleovegetational and provenance change in the Ganga Plain during the late Quaternary

    Shailesh Agrawal; Prasanta Sanyal; Melinda K Bera; Jitendra K Dash; Srinivasan Balakrishnan


    Present study aims at reconstructing the paleomonsoonal rainfall, paleovegetation and provenance change during the late Quaternary. Towards this, Bhognipur core, collected from the southern Ganga Plain, have been sampled for soil carbonate (SC) and soil. The 18O values of SC (18OSC) range from −7.6 to −4.9‰. The variations in 18OSC values suggest that during the late Quaternary, the monsoon intensified during MIS 3 and MIS 1 and the maximum lowering of rainfall intensity is observed during MIS 2. The 13C value of SC (13CSC), organic matter dispersed in the soil (13CSOM) and occluded in the carbonate nodules (13CNOM) ranges from −4.1 to +1.4‰, −25.6 to −16.3‰, and −27.7 to −25.0‰, respectively, implies mixed C3–C4 vegetation over the Ganga Plain. Variations in 13CSOM and 13CNOM values at same depth imply preservation problem of pristine organic matter signature. Therefore, it is important to assess the preservation of residual organic matter before using it for paleovegetational reconstruction. The monsoon-vegetation relationship indicates that relative abundances of C3–C4 vegetation were mainly driven by variations in monsoonal rainfall intensity. Using 87Sr/86Sr in SC, we show that the Himalayan river was supplying sediments in the southern part of the Ganga Plain during MIS 3.

  15. Research of the Late Quaternary Recent Activity of the Middle Segment of Kouquan Fault

    Xu Wei; Liu Xudong; Zhang Shimin


    Systematic research of the characteristics of late Quaternary activity of the middle part of Kouquan fault has been done through conducting 1:50000 geologic mapping combining with remote sensing interpretation of spot imaging, field validating and chronology research of the research area. Studies suggest that the middle part of Kouquan fault has had strong activity since the late Quaternary which controls the tectonic evolvement of the nearby mountains and Datong basin. The recent activity of this fault has faulted the sandy gravel layers of T1 terrace and the lower part of dark loessial soils over the terrace on the north of Chanfang village. The maximum vertical displacement is over 3m in the area between Xiaoyukou village and Louzikou village, and to the south of Dayukou village and the north of Emaokou village, the displacement decreases to 0. 5m and 0. 25m respectively. Based on the recent faulted landforms and combined with dating, we determined the age of recent activity of the fault in the research area to be between 7. 71ka B.P. to 3. 00 ka B.P. Discussions are made on this in combination with previous research.

  16. Reconnaissance study of late quaternary faulting along cerro GoDen fault zone, western Puerto Rico

    Mann, P.; Prentice, C.S.; Hippolyte, J.-C.; Grindlay, N.R.; Abrams, L.J.; Lao-Davila, D.


    The Cerro GoDen fault zone is associated with a curvilinear, continuous, and prominent topographic lineament in western Puerto Rico. The fault varies in strike from northwest to west. In its westernmost section, the fault is ???500 m south of an abrupt, curvilinear mountain front separating the 270- to 361-m-high La CaDena De San Francisco range from the Rio A??asco alluvial valley. The Quaternary fault of the A??asco Valley is in alignment with the bedrock fault mapped by D. McIntyre (1971) in the Central La Plata quadrangle sheet east of A??asco Valley. Previous workers have postulated that the Cerro GoDen fault zone continues southeast from the A??asco Valley and merges with the Great Southern Puerto Rico fault zone of south-central Puerto Rico. West of the A??asco Valley, the fault continues offshore into the Mona Passage (Caribbean Sea) where it is characterized by offsets of seafloor sediments estimated to be of late Quaternary age. Using both 1:18,500 scale air photographs taken in 1936 and 1:40,000 scale photographs taken by the U.S. Department of Agriculture in 1986, we iDentified geomorphic features suggestive of Quaternary fault movement in the A??asco Valley, including aligned and Deflected drainages, apparently offset terrace risers, and mountain-facing scarps. Many of these features suggest right-lateral displacement. Mapping of Paleogene bedrock units in the uplifted La CaDena range adjacent to the Cerro GoDen fault zone reveals the main tectonic events that have culminated in late Quaternary normal-oblique displacement across the Cerro GoDen fault. Cretaceous to Eocene rocks of the La CaDena range exhibit large folds with wavelengths of several kms. The orientation of folds and analysis of fault striations within the folds indicate that the folds formed by northeast-southwest shorTening in present-day geographic coordinates. The age of Deformation is well constrained as late Eocene-early Oligocene by an angular unconformity separating folDed, Deep

  17. Late Quaternary Faulting along the San Juan de los Planes Fault Zone, Baja California Sur, Mexico

    Busch, M. M.; Coyan, J. A.; Arrowsmith, J.; Maloney, S. J.; Gutierrez, G.; Umhoefer, P. J.


    As a result of continued distributed deformation in the Gulf Extensional Province along an oblique-divergent plate margin, active normal faulting is well manifest in southeastern Baja California. By characterizing normal-fault related deformation along the San Juan de los Planes fault zone (SJPFZ) southwest of La Paz, Baja California Sur we contribute to understanding the patterns and rates of faulting along the southwest gulf-margin fault system. The geometry, history, and rate of faulting provide constraints on the relative significance of gulf-margin deformation as compared to axial system deformation. The SJPFZ is a major north-trending structure in the southern Baja margin along which we focused our field efforts. These investigations included: a detailed strip map of the active fault zone, including delineation of active scarp traces and geomorphic surfaces on the hanging wall and footwall; fault scarp profiles; analysis of bedrock structures to better understand how the pattern and rate of strain varied during the development of this fault zone; and a gravity survey across the San Juan de los Planes basin to determine basin geometry and fault behavior. The map covers a N-S swath from the Gulf of California in the north to San Antonio in the south, an area ~45km long and ~1-4km wide. Bedrock along the SJPFZ varies from Cretaceous Las Cruces Granite in the north to Cretaceous Buena Mujer Tonalite in the south and is scarred by shear zones and brittle faults. The active scarp-forming fault juxtaposes bedrock in the footwall against Late Quaternary sandstone-conglomerate. This ~20m wide zone is highly fractured bedrock infused with carbonate. The northern ~12km of the SJPFZ, trending 200°, preserves discontinuous scarps 1-2km long and 1-3m high in Quaternary units. The scarps are separated by stretches of bedrock embayed by hundreds of meters-wide tongues of Quaternary sandstone-conglomerate, implying low Quaternary slip rate. Further south, ~2 km north of the

  18. The late Quaternary tephrostratigraphical record of the San Gregorio Magno basin (southern Italy)

    Munno, R.; Petrosino, P.


    Twenty-one primary pyroclastic layers were found embedded in the lacustrine sediments of the San Gregorio Magno basin (Southern Apennines). These sand-sized layers were characterised by a noticeable juvenile fragments content and by a sharp basal contact with the underlying clay and silt sediments. The tephra layers have been correlated with terrestrial counterparts from well-known eruptive events of the Campanian volcanic area, or with reference layers from deep sea sediment cores and from the Monticchio maar sequence. The investigation of the San Gregorio Magno tephra layers made it possible to deduce that lacustrine sedimentation at San Gregorio Magno basin began before 170k yr BP and lasted at least until the emplacement of the Neapolitan Yellow Tuff, which occurred about 15k yr BP. The tephrochronology allowed determination of the varying sedimentation rate that occurred in the basin. Correlation of the lacustrine record with marine sequences has allowed development of a late Quaternary tephrostratotype for southern Italy. Copyright

  19. Climate change not to blame for late Quaternary megafauna extinctions in Australia.

    Saltré, Frédérik; Rodríguez-Rey, Marta; Brook, Barry W; Johnson, Christopher N; Turney, Chris S M; Alroy, John; Cooper, Alan; Beeton, Nicholas; Bird, Michael I; Fordham, Damien A; Gillespie, Richard; Herrando-Pérez, Salvador; Jacobs, Zenobia; Miller, Gifford H; Nogués-Bravo, David; Prideaux, Gavin J; Roberts, Richard G; Bradshaw, Corey J A


    Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world's most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.

  20. Late Quaternary fine silt deposits of Jammu, NW Himalaya: Genesis and climatic significance

    Rajinder K Ganjoo; Vinod Kumar


    The fine silt deposits of Jammu (J & K State, India) stretch all along the Siwalik foothills from Jammu to the Potwar Plateau in Pakistan. The post-Siwalik deposits, first discussed by de Terra and Paterson (1939), are attributed to wind action. The deposits termed as ‘Potwar loessic silt’ comprising sandy silt are essentially of late Quaternary age (75–18 ka) and are re-looked herein from the point of view of genesis and climatic significance. The sorting, skewness and kurtosis parameters of fine silts of Jammu suggest fluvial environment of the deposits wherein the water budget fluctuated. The weak pedogenesis of fine silts at certain intervals corroborate to periods of less or no sedimentation. The bivariant plot studies further suggest fluvial environment of deposition for the fine silt at Jammu, with regular fluctuations in the budget of river water that was perhaps in consonance with oscillations in the climate of the region.

  1. Geomorphic expression of late Quaternary sea level changes along the southern Saurashtra coast, western India

    Nilesh Bhatt; Uday Bhonde


    Geomorphic expression of land-sea interaction is preserved in the form of abandoned cliffs, marine terraces,shore platforms and marine notches along the southern Saurashtra coast. These features have been used to ascertain the magnitude of sea level changes during late Quaternary.Notch morphology and associated biological encrustation have been used to estimate the magnitude and duration of palaeo-sea strands.Marine notches and other erosive features occurring between 12 and 15 m above the present Biological Mean Sea Level (BMSL) are attributed to the last interglacial corresponding to the Marine Isotopic Stage 5 (MIS-5). However,6 to 9 m upliftment of the coastal fringe is attributed to this sea level.The second major high sea strand was identified during the mid-Holocene when the sea rose 2 m above the present level.Notches corresponding to this high sea level are recorded 4 to 5 m above the present BMSL.

  2. The late Quaternary decline and extinction of palms on oceanic Pacific islands

    Prebble, M.; Dowe, J. L.


    Late Quaternary palaeoecological records of palm decline, extirpation and extinction are explored from the oceanic islands of the Pacific Ocean. Despite the severe reduction of faunal diversity coincidental with human colonisation of these previously uninhabited oceanic islands, relatively few plant extinctions have been recorded. At low taxonomic levels, recent faunal extinctions on oceanic islands are concentrated in larger bodied representatives of certain genera and families. Fossil and historic records of plant extinction show a similar trend with high representation of the palm family, Arecaceae. Late Holocene decline of palm pollen types is demonstrated from most islands where there are palaeoecological records including the Cook Islands, Fiji, French Polynesia, the Hawaiian Islands, the Juan Fernandez Islands and Rapanui. A strong correspondence between human impact and palm decline is measured from palynological proxies including increased concentrations of charcoal particles and pollen from cultivated plants and invasive weeds. Late Holocene extinctions or extirpations are recorded across all five of the Arecaceae subfamilies of the oceanic Pacific islands. These are most common for the genus Pritchardia but also many sedis fossil palm types were recorded representing groups lacking diagnostic morphological characters.

  3. Micromorphological investigations of the Late Quaternary loess-paleosol sequences of the Kashmir Valley, India

    Dar, Reyaz Ahmad; Chandra, Rakesh; Romshoo, Shakil Ahmad; Kowser, Nazia


    The loess-paleosol sequences of the Karewa Group preserve a valuable repository of the Late Quaternary climatic changes and the landscape evolution history of the Karewa Basin of Kashmir Valley in their lithological and pedogenic records. Three representative loess-paleosol sections at Shankerpora (SP), Khan Sahib (KS) and Pattan (PT) localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections. Lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south-west to north-west of the Karewa Basin suggesting the availability of land-surface for periodic loess deposition. The SP section is marked by 6 (SP-S6, S7, S8, S9, S10, S12), KS section by 3 (KS-S2, S4, S5) and PT section by 2 (PT-S1, S3) thick mature paleosol profiles. Theses paleosols have well developed 'Ah' and 'Btk' horizons representing prolonged land-surface stability when pedogenic processes outpace loess deposition. On the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition. Micromorphological observations of thin sections suggested that clay illuviation and CaCO3 accumulation have operated within the paleosol profiles. CaCO3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation. Pedogenic CaCO3 probably resulted from the precipitation of the soil solution near the average depth of wetting front. The pedogenic CaCO3, illuvial clay, mottles, iron manganese features, pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess-paleosol sections. The morphological (both micro- and macro-morphological) attributes of loess-paleosols suggest variation of climatic conditions during the Late Quaternary period in the Karewa Basin of Kashmir Valley, India.

  4. Neotectonics of interior Alaska and the late Quaternary slip rate along the Denali fault system

    Haeussler, Peter J.; Matmon, Ari; Schwartz, David P.; Seitz, Gordon G.


    The neotectonics of southern Alaska (USA) are characterized by a several hundred kilometers–wide zone of dextral transpressional that spans the Alaska Range. The Denali fault system is the largest active strike-slip fault system in interior Alaska, and it produced a Mw 7.9 earthquake in 2002. To evaluate the late Quaternary slip rate on the Denali fault system, we collected samples for cosmogenic surface exposure dating from surfaces offset by the fault system. This study includes data from 107 samples at 19 sites, including 7 sites we previously reported, as well as an estimated slip rate at another site. We utilize the interpreted surface ages to provide estimated slip rates. These new slip rate data confirm that the highest late Quaternary slip rate is ∼13 mm/yr on the central Denali fault near its intersection with the eastern Denali and the Totschunda faults, with decreasing slip rate both to the east and west. The slip rate decreases westward along the central and western parts of the Denali fault system to 5 mm/yr over a length of ∼575 km. An additional site on the eastern Denali fault near Kluane Lake, Yukon, implies a slip rate of ∼2 mm/yr, based on geological considerations. The Totschunda fault has a maximum slip rate of ∼9 mm/yr. The Denali fault system is transpressional and there are active thrust faults on both the north and south sides of it. We explore four geometric models for southern Alaska tectonics to explain the slip rates along the Denali fault system and the active fault geometries: rotation, indentation, extrusion, and a combination of the three. We conclude that all three end-member models have strengths and shortcomings, and a combination of rotation, indentation, and extrusion best explains the slip rate observations.

  5. Stable isotopes reflect the ecological stability of two high-elevation mammals from the late Quaternary of Colorado

    McLean, Bryan S.; Emslie, Steven D.


    The vertebrate fossil record of Cement Creek Cave, Colorado, spans from > 45,000 yr ago to the present and represents the richest stratified series of high-elevation (> 2900 m) mammal remains known from the late Quaternary of North America. Stable carbon and oxygen isotope analyses of tooth enamel were used to assess potential ecological responses of two species found commonly throughout the cave, Yellow-bellied marmots (Marmota flaviventris) and Bushy-tailed woodrats (Neotoma cinerea), to late Quaternary climate and environmental changes of the Southern Rocky Mountains. Results indicate that despite such perturbations, the dietary ecologies of both species were maintained across this period. Neither taxon shifted to consuming C4 taxa or different C3 functional groups; similarly, no significant shifts in surface water use were detected. Variations in enamel δ13C were observed, however, that represent the physiological responses of high-elevation plants to changing levels of late Quaternary atmospheric CO2. While our findings extend both the geographic and elevational record of this plant CO2 response, they simultaneously highlight the ecological stability of high-elevation M. flaviventris and N. cinerea during climate changes of late Quaternary magnitude.

  6. Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells

    Pigati, Jeff S.; McGeehin, John P.; Muhs, Daniel R.; Bettis, E. Arthur


    Constraining the ages and mass accumulation rates of late Quaternary loess deposits is often difficult because of the paucity of organic material typically available for 14C dating and the inherent limitations of luminescence techniques. Radiocarbon dating of small terrestrial gastropod shells may provide an alternative to these methods as fossil shells are common in loess and contain ∼12% carbon by weight. Terrestrial gastropod assemblages in loess have been used extensively to reconstruct past environmental conditions but have been largely ignored for dating purposes. Here, we present the results of a multi-faceted approach to understanding the potential for using small terrestrial gastropod shells to date loess deposits in North America. First, we compare highly resolved 14C ages of well-preserved wood and gastropod shells (Succineidae) recovered from a Holocene loess section in Alaska. Radiocarbon ages derived from the shells are nearly identical to wood and plant macrofossil ages throughout the section, which suggests that the shells behaved as closed systems with respect to carbon for at least the last 10 ka (thousands of calibrated 14C years before present). Second, we apply 14C dating of gastropod shells to late Pleistocene loess deposits in the Great Plains using stratigraphy and independent chronologies for comparison. The new shell ages require less interpretation than humic acid radiocarbon ages that are commonly used in loess studies, provide additional stratigraphic coverage to previous dating efforts, and are in correct stratigraphic order more often than their luminescence counterparts. Third, we show that Succineidae shells recovered from historic loess in the Matanuska River Valley, Alaska captured the 20th century 14C bomb spike, which suggests that the shells can be used to date late Holocene and historic-aged loess. Finally, results from Nebraska and western Iowa suggest that, similar to other materials, shell ages approaching ∼40 ka should

  7. Late Quaternary river channel migrations of the Kura River in Transcaucasia - tectonic versus climatic causes

    von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik


    Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold

  8. Geomorphological facies reconstruction of Late Quaternary alluvia by the application of fluvial architecture concepts

    Houben, Peter


    This paper investigates the methodical implications, the benefits, and the constraints of applying the fluvial architecture concept to Late Quaternary shallow-subsurface alluvial deposits. The focus is upon a typical small- to mesoscale valley floor of the temperate zone. The studied reach is part of the river Wetter catchment (517 km 2) in central Germany. A large number of studies on Late Quaternary terrestrial paleoenvironmental change of the temperate zone refer to such small- to mesoscale catchments, which are mostly occupied by mixed- to suspended-load rivers. As in many cases mostly coring-based evidence is available, the observation and measurement is limited to lithology and lithofacies boundaries; facies geometry must be inferred. Moreover, in those environments differences in lithofacies are obscured by a significantly reduced range of grain size distributions. An example of an ancient channel belt of Late Glacial to Holocene age serves to delineate the methodical practice and utility of the fluvial architecture approach. Field evidence is obtained from detailed cross-sectional surveys and comprises descriptions of lithofacies, structural, pedogenetical, biotic features, Munsell color, and total organic carbon magnetic volume susceptibility. Cross-sectional lithofacies information is represented by spatially attributed, scaled borehole logs. The example also accentuates the need for applying additional stratigraphical methods such as physical age determination, macrofossil analysis, and tephrological stratigraphy. These methods form the basis to discern stacked channel facies and derive a diachrony of channel forms. Thus, the adapted architecture approach provides a significant surplus of information on channel dimensions, ages, and channel-floodplain interconnectedness. Distinct fluvial landforms such as channels, levees, abandoned channels, swamps, and floodplain flats can be highlighted. A number of methodical constraints are discussed in detail, e

  9. Late Quaternary landscape evolution in the Great Karoo, South Africa: Processes and drivers.

    Oldknow, Chris; Hooke, Janet; Lang, Andreas


    The Great Karoo spans the north-central part of South Africa at a major climatic boundary. The characteristics, sequences, spatial patterns and drivers of river response to Late Quaternary climate changes in this region remain unclear due to the fragmentary alluvial/colluvial stratigraphic record and the lack of dated palaeoclimatic archives. Dendritic gully networks incised into deep deposits (up to 6 m) of colluvium and alluvium in the upper Sundays River catchment expose a legacy of "cut and fill" features. In 1st order tributaries, these are predominantly discontinuous palaeochannels and flood-outs with localised palaeosols, whereas in 2nd & 3rd order tributaries there are: 1) incised palaeo-geomorphic surfaces, 2) semi-continuous inset terrace sequences, 3) buried palaeo-gully topography. Using a combination of field mapping, logging of sediment outcrops, soil micromorphological and grain size analysis, mineral magnetic measurements and radiometric dating (OSL & 14C), we derive a stratigraphic evolution model which demonstrates a) the number of phases of incision, aggradation and pedogenesis, b) the spatial and temporal extent of each phase and c) the drivers of alluviation and associated feedbacks. Our reconstruction of regional valley alluviation indicates four distinct terrace units of contrasting depositional age. The base of the succession reflects slow aggradation under periglacial conditions associated with the Last Glacial Maximum. Subsequent channel entrenchment, causing terrace abandonment (T1) occurred in the deglacial period when vegetation and rainfall were in anti-phase. Re-instatement of connectivity with deep upland colluvial stores resulted in the injection of a pulse of sediment to valley floors, triggering compartmentalised backfilling (aggradation of T2) which propagated upstream as far as the second order drainage lines. This backfilling restructured the local hydrology, which, in concert with enhanced summer-rainfall, contributed to a

  10. Environmental and Archaeological Implications of a Late Quaternary Palynological Sequence, Poyang Lake, Southern China

    Jiang, Qinhua; Piperno, Dolores R.


    Paleoecological data from Poyang Lake, southern China, indicate that significant natural and human-induced vegetational changes have occurred during the Late Quaternary in the Middle Yangtze River valley, the likely location of rice (Oryza sativa L.) domestication. During the late Pleistocene (from ca. 12,830 to ca. 10,500 yr B.P.), the climate was cooler and drier than today's. The subtropical, mixed deciduous-evergreen broad-leaved forest which constitutes the modern, potential vegetation was reduced and herbaceous vegetative cover expanded. A hiatus in sedimentation occurred in Poyang Lake, beginning sometime after ca. 10,500 yr B.P. and lasting until the middle Holocene (ca. 4000 yr B.P.). At ca. 4000 yr B.P., the regional vegetation was a diverse, broad-leaved forest dominated by many of the same arboreal elements (e.g., Quercus, Castanopsis, Liquidambar) that grow in the area today. A significant reduction of arboreal pollen and an increase of herbaceous pollen at ca. 2000 yr B.P. probably reflect human influence on the vegetation and the expansion of intensive rice agriculture into the dryland forests near the river valleys.

  11. Vegetation and aquatic communities responses to late Quaternary climate change in central Mexico

    Lozano-Garcia, S.; Caballero, M.; Correa-Metrio, A.


    A significant amount of information regarding the glacial history of volcanoes, vegetation history and lakes evolution of the Trans Mexican Volcanic Belt (TMVB) is available. The TMVB is a volcanically active highland area, and during its geological history numerous lakes basins have been formed. Climate change has been a significant factor in promoting transformations of the landscape and changes in the vegetation and lake levels during the Quaternary. Paleoclimatic studies carried out in central Mexico have documented variations in temperature and humidity during the late Pleistocene. In order to explore the response of vegetation to late glacial climatic and geological change, multyproxy records of lacustrine sequences from a series of lakes in the western and central sections of the TMVB have been under analysis. Calculated ecological change and its associated rates (RoCs) for six sites that follow an altitudinal and longitudinal gradient of central Mexico offer information on vegetation and dynamics of the lakes in the area. Most of these records show high variability. Dry periods in Lakes Cuitzeo and Zacapu (the most western and lower locations) show high RoC and seem to coincide with Heinrich events (H4 and H5). Contrastingly, RoC in Chalco and Texcoco records (the eastern and higher locations) seem more variable. The observed patterns are most likely the result of the confluence of climate, geologic events, and human occupation, all of them interacting at different time scales and posing difficulties when interpreting fossil sequences from the area.

  12. Late Quaternary dietary shifts of the Cape grysbok ( Raphicerus melanotis) in southern Africa

    Faith, J. Tyler


    The Cape grysbok is endemic to southern Africa's Cape Floral Region where it selectively browses various species of dicotyledonous vegetation. Fossil evidence indicates that the grysbok persisted under glacial and interglacial conditions throughout the late Quaternary and inhabited a range of environments. This study employs mesowear analysis to reconstruct grysbok diets over time and in response to changing environments at Nelson Bay Cave, Die Kelders Cave 1, Klasies River Mouth, and Swartklip 1. Results indicate that the amount of grasses (monocots) versus leafy vegetation (dicots) included in the diet fluctuated over time and largely in agreement with changes in faunal community structure. The case for dietary flexibility is particularly clear at Nelson Bay Cave, where there is a significant trend from mixed feeding towards increased browsing from the late Pleistocene (~ 18,500 14C yr BP) through the Holocene. Dietary shifts at Nelson Bay Cave are consistent with the hypothesis that declining grassland productivity is responsible for the terminal Pleistocene extinction of several large ungulates in southern Africa. Furthermore, the short-term dietary shifts demonstrated here (100s to 1000s of years) provide an important caution against relying on taxonomic uniformitarianism when reconstructing the dietary preferences of fossil ungulates, both extant and extinct.

  13. Shift in detrital sedimentation in the eastern Bay of Bengal during the late Quaternary

    C Prakash Babu; J N Pattan; K Dutta; N Basavaiah; G V Ravi Prasad; D K Ray; P Govil


    Down-core variations of granulometric, geochemical and mineral magnetism of a 70-cm long sediment core retrieved from the eastern Bay of Bengal abyssal region were studied to understand sedimentation pattern and sediment provenance during the last ∼12 kyr BP. Based on down-core physical and elemental variations, three units were identified: unit 3 (70–43 cm) is a ∼30 cm thick clayey silt organic carbon-rich (0.5–0.92%) turbidite probably delivered by the Brahmaputra River during the late Quaternary period. Units 2 (43–24 cm) and 1 (24–0 cm) represent enhanced and reduced supply of coarse-grained detrital sediments from the Ganges River during early and late Holocene period, respectively. Increased terrigenous supply dilutes calcium carbonate (CaCO3) and biogenic elements (P, Ba and Cu) in units 3 and 2. On the contrary, a reduction in detrital input enhances CaCO3 and biogenic elements in unit 1. Lithogenic elements (Ti, Al, K and Rb) and shale-normalized REE patterns in all three units suggest terrigenous source. The shift in provenance from the Brahmaputra to the Ganges derived sediments is evident by a sharp increase in sediment grain size, increased concentration and grain size assemblages of magnetic minerals, lithogenic elements concentration and Lan/Ybn ratio. This study highlights terrigenous dilution on biogenic sedimentation in the eastern Bay of Bengal sediments.

  14. Late Quaternary paleoenvironmental records from the Chatanika River valley near Fairbanks (Alaska)

    Schirrmeister, Lutz; Meyer, Hanno; Andreev, Andrei; Wetterich, Sebastian; Kienast, Frank; Bobrov, Anatoly; Fuchs, Margret; Sierralta, Melanie; Herzschuh, Ulrike


    Perennially-frozen deposits are considered as excellent paleoenvironmental archives similar to lacustrine, deep marine, and glacier records because of the long-term and good preservation of fossil records under stable permafrost conditions. A permafrost tunnel in the Vault Creek Valley (Chatanika River Valley, near Fairbanks) exposes a sequence of frozen deposits and ground ice that provides a comprehensive set of proxies to reconstruct the late Quaternary environmental history of Interior Alaska. The multi-proxy approach includes different dating techniques (radiocarbon-accelerator mass spectrometry [AMS 14C], optically stimulated luminescence [OSL], thorium/uranium radioisotope disequilibria [230Th/U]), as well as methods of sedimentology, paleoecology, hydrochemistry, and stable isotope geochemistry of ground ice. The studied sequence consists of 36-m-thick late Quaternary deposits above schistose bedrock. Main portions of the sequence accumulated during the early and middle Wisconsin periods. The lowermost unit A consists of about 9-m-thick ice-bonded fluvial gravels with sand and peat lenses. A late Sangamon (MIS 5a) age of unit A is assumed. Spruce forest with birch, larch, and some shrubby alder dominated the vegetation. High presence of Sphagnum spores and Cyperaceae pollen points to mires in the Vault Creek Valley. The overlying unit B consists of 10-m-thick alternating fluvial gravels, loess-like silt, and sand layers, penetrated by small ice wedges. OSL dates support a stadial early Wisconsin (MIS 4) age of unit B. Pollen and plant macrofossil data point to spruce forests with some birch interspersed with wetlands around the site. The following unit C is composed of 15-m-thick ice-rich loess-like and organic-rich silt with fossil bones and large ice wedges. Unit C formed during the interstadial mid-Wisconsin (MIS 3) and stadial late Wisconsin (MIS 2) as indicated by radiocarbon ages. Post-depositional slope processes significantly deformed both, ground

  15. Stratigraphical and palynological appraisal of the Late Quaternary mangrove deposits of the west coast of India

    Kumaran, K. P. N.; Nair, K. M.; Shindikar, Mahesh; Limaye, Ruta B.; Padmalal, D.


    The organic deposits derived from the mangrove swamps form reliable stratigraphic markers within the Late Quaternary sequence of Kerala-Konkan Basin. Three generations of such deposits have been identified. The older one is dated to around 43,000-40,000 14C yr B.P., with a few dates beyond the range of radiocarbon. The younger ones date from the Middle Holocene to latest Pleistocene (10,760-4540 14C yr B.P.) and the Late Holocene (mangrove vegetation. Peat accumulation during the period 40,000-28,000 14C yr B.P. can be correlated with the excess rainfall, 40-100% greater than modern values, of the Asian summer monsoon. The low occurrence of mangrove between 22,000 and 18,000 14C yr B.P. can be attributed to the prevailing aridity and/or reduced precipitation associated worldwide with Last Glacial Maximum, because exposure surfaces and ferruginous layers are commonly found in intervals representing this period. The high rainfall of 11,000-4000 14C yr B.P. is found to be the most significant as the mangrove reached an optimum growth around 11,000 14C yr B.P. but with periods of punctuated weaker monsoons. From the present and previous studies, it has been observed that after about 5000 or 4000 14C yr B.P., the monsoons became gradually reduced leading to drying up of many of the marginal marine mangrove ecosystems. A case study of Hadi profile provided an insight to the relevance of magnetic susceptibility (χ) to record the ecological shift in Late Holocene.

  16. Late Quaternary Tephrostratigraphy of South-Central Chile (~ 38 - 40 °S)

    Fontijn, K.; Rawson, H. L.; Van Daele, M. E.; Moernaut, J.; Abarzúa, A. M.; Pyle, D. M.; Mather, T. A.; De Batist, M. A. O.; Moreno-Roa, H.; Naranjo, J. A.


    The volcanoes of the Siete Lagos region ("Lake District") in South-Central Chile form part of the Southern Volcanic Zone of the Andes and include some of the most active volcanoes in South America, i.e. Villarrica and Llaima. The Late Quaternary (~ last 15 ka) regional tephrostratigraphic record for this region is however still poorly developed. We combine detailed stratigraphic logging of terrestrial sections in the vicinity of Llaima, Sollipulli, Villarrica, Quetrupillan, Mocho-Choshuenco and Puyehue-Cordón Caulle volcanoes with petrological, whole-rock and glass geochemical data, and 14C dating on charcoal entrained in volcanic deposits, and correlate the on-land sequences with tephra layers in existing 14C-dated lacustrine records of Laguna Las Ranas and Lagos Villarrica, Calafquén and Riñihue. The combined record includes previously described major eruptions, e.g. Llaima Pumice (Llaima) and Alpehue Pumice (Sollipulli), which help to constrain the relative timing of events. These correlations suggest that several widespread volcanic units are several hundreds to thousands of years older than previously thought. The record also includes newly described pumice-producing events, e.g. for the poorly studied Quetrupillan volcano, and provides new insights into the post-glacial eruptive frequency in the Southern Volcanic Zone. The newly updated stratigraphy with high-quality geochemical data also contributes to the regional tephrochronological framework which helps to significantly improve age models for lacustrine palaeoseismological and palaeoenvironmental archives.

  17. A Mid-Late Quaternary loess-paleosol record in Simmons Farm in southern Illinois, USA

    Wang, Hongfang; Lundstrom, C.C.; Zhang, Z.; Grimley, D.A.; Balsam, W.L.


    In unglaciated areas of the Mississippi Valley region, the typical full loess-paleosol succession contains the Modern Soil developed in Peoria Silt, weakly developed Farmdale Geosol developed in Roxana Silt, Sangamon Geosol developed in Loveland Silt, and Yarmouth Geosol developed in Crowley's Ridge Silt. Although a fifth loess called the Marianna Silt is reported at one area, the paleosol that separates the Crowley Ridge and Marianna Silts is not well defined. Previous thermoluminescence (TL) and optical stimulated luminescence (OSL) age chronology has suggested multiple phases of Sangamon Geosol developed in Loveland Silt, but clear morphological evidence of polygenetic Sangamon Geosol profiles have not been found. Recently, a thick loess-paleosol sequence has been studied in the middle Mississippi Valley in unglaciated southern Illinois, USA. Soil morphology and analytical results revealed five loesses and associated paleosol units. Two Sangamon Bt horizons were found separated by a thick ACtk horizon, interpreted to indicate two phases of Sangamon Geosol development. This well-preserved loess-paleosol succession provides one of the most complete mid-late Quaternary loess records in the middle Mississippi Valley to date, and is important for studying the stratigraphic framework and paleoclimate and environment changes. ?? 2008 Elsevier Ltd. All rights reserved.

  18. Late Quaternary climate variability in the Sahel: inferences from marine dust records offshore Senegal

    Stuut, J. W.; Meyer, I.; Fischer, H.; Mollenhauer, G.; Mulitza, S.; Pittauerova, D.; Zabel, M.; Schulz, M.


    Societies and ecosystems in northern Africa are strongly affected by the availability of water. As a consequence, long-term absence of rainfall has very dear effects on the ecosystems, as was dramatically shown in the 70'ies and 80'ies of the 20th century. Recent high-resolution reconstructions of Sahel palaeoclimate allow for new insights into these drastic climate variations and to disentangle the effects of the different components of the climate system on African climate change. In this study we extend the instrumental record of climate variability using marine sediment cores that were retrieved off the coast of Senegal, northwest Africa. The sediment records contain continuous high-resolution records of dust sedimentation ranging from about 4,000 to about 57,000 years. A 210Pb age model for the youngest sediments allows for a matching of the proxy rainfall record with instrumental precipitation data. Specifically, variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997) are used to reconstruct rainfall variability on land throughout the late Quaternary.

  19. Late Quaternary strata and carbon burial records in the Yellow River delta, China

    Zhao, Guangming; Ye, Siyuan; Li, Guangxue; Ding, Xigui; Yuan, Hongming


    Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in Yellow River delta (YRD), detailed analysis of benthic foraminifera, total carbon (TC), organic carbon (Corg), sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units (designated U1-U8 in ascending order) were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to determine the precise depositional ages of the modern Yellow River delta (MYRD), from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon (IC) and Corg occurred in the delta front (U5), and the minimum in the shallow sea (U3). Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g (m2 yr)-1, and that of IC reaching 13741±808 g (m2 yr)-1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.

  20. Late Quaternary lacustrine paleoenvironments in the Cuenca de México

    Bradbury, J.P.


    A late Quaternary paleolimnological history from the Mexican highlands has been obtained by diatom analysis of short cores and stratigraphic sections of lake and marsh sediments from the Cuenca de México, the large, endorheic, graben basin that holds Mexico City. The records, dated by radiocarbon and tephrochronologic methods, extend back to about 30 ka BP and document the presence of extensive, saline lakes in the basin until 25 ka BP. Thereafter, lake levels fell and marginal sites became shallow and fresh under the influence of surficial drainage and (especially) spring discharge. A shallow, saline lake existed 18 ka BP in Texcoco, the central and lowest basin in the system, reflecting moderately increased effective moisture at that time. By 16 ka BP, Lake Texcoco had become so shallow that diatoms were no longer preserved. However, marginal sites nourished by spring flow recorded changes in the local hydrologic balance resulting from increased infiltration at higher elevations. These changes appear to coincide with glacial advances between about 14 and 10 ka BP on the volcanic mountains surrounding the basin. Dry climates with reduced infiltration characterized the early Holocene, but by 5 ka BP a modest increase in precipitation established the modern climatic regime.

  1. Tropical Rain Forest and Climate Dynamics of the Atlantic Lowland, Southern Brazil, during the Late Quaternary

    Behling, Hermann; Negrelle, Raquel R. B.


    Palynological analysis of a core from the Atlantic rain forest region in Brazil provides unprecedented insight into late Quaternary vegetational and climate dynamics within this southern tropical lowland. The 576-cm-long sediment core is from a former beach-ridge "valley," located 3 km inland from the Atlantic Ocean. Radio-carbon dates suggest that sediment deposition began prior to 35,000 14C yr B.P. Between ca. 37,500 and ca. 27,500 14C yr B.P. and during the last glacial maximum (LGM; ca. 27,500 to ca. 14,500 14C yr B.P.), the coastal rain forest was replaced by grassland and patches of cold-adapted forest. Tropical trees, such as Alchornea, Moraceae/Urticaceae, and Arecaceae, were almost completely absent during the LGM. Furthermore, their distributions were shifted at least 750 km further north, suggesting a cooling between 3°C and 7°C and a strengthening of Antarctic cold fronts during full-glacial times. A depauperate tropical rain forest developed as part of a successional sequence after ca. 12,300 14C yr B.P. There is no evidence that Araucaria trees occurred in the Atlantic lowland during glacial times. The rain forest was disturbed by marine incursions during the early Holocene period until ca. 6100 14C yr B.P., as indicated by the presence of microforaminifera. A closed Atlantic rain forest then developed at the study site.

  2. Episodic Late Quaternary slopewash deposition as recorded in colluvial aprons, Southeastern Wyoming

    Hanson, Paul R.; Mason, Joseph A.; Goble, Ronald J.


    Colluvial aprons found along fluvial terraces of the Laramie River and Sybille Creek in southeastern Wyoming are interpreted as late Quaternary slopewash deposits. Each apron studied contained multiple buried soils, interpreted to indicate that slopewash activity was episodic and short-lived, and was followed by relatively long periods of landscape stability and soil development. Apron deposits were described and subsequently correlated based on their internal stratigraphy and their relative degree of soil development. Optical dating was used to chronologically constrain periods of slopewash deposition, and based on 17 optical ages taken from five aprons, aggradation occurred at ˜65-56, 16.0, 12.9, 11.8, 8.1, 7.3, 5.0, and 1.7 ka. Several of these events correspond with climatic transitions such as the termination of Heinrich Event 1, the onset and termination of the Younger Dryas, and the 8.2 ka event, suggesting that apron aggradation was driven by changes in climatic regime. Although either increased aridity or a change in precipitation regime could result in increased erosion of terrace scarps, apron aggradation events do not correlate with regional records of aridity. Instead, periods of increased precipitation intensity and/or frequency that occur during climatic transitions most likely drive apron aggradation events.

  3. Modern and late Quaternary clay mineral distribution in the area of the SE Mediterranean Sea

    Hamann, Yvonne; Ehrmann, Werner; Schmiedl, Gerhard; Kuhnt, Tanja


    The present-day clay mineral distribution in the southeastern Levantine Sea and its borderlands reveals a complex pattern of different sources and distribution paths. Smectite dominates the suspended load of the Nile River and of rivers in the Near East. Illite sources are dust-bearing winds from the Sahara and southwestern Europe. Kaolinite is prevalent in rivers of the Sinai, in Egyptian wadis, and in Saharan dust. A high-resolution sediment core from the southeastern Levantine Sea spanning the last 27 ka shows that all these sources contributed during the late Quaternary and that the Nile River played a very important role in the supply of clay. Nile influence was reduced during the glacial period but was higher during the African Humid Period. In contrast to the sharp beginning and end of the African Humid Period recorded in West African records (15 and 5.5 ka), our data show a more transitional pattern and slightly lower Nile River discharge rates not starting until 4 ka. The similarity of the smectite concentrations with fluctuations in sea-surface temperatures of the tropical western Indian Ocean indicates a close relationship between the Indian Ocean climate system and the discharge of the Nile River.

  4. Late Quaternary tectonic landforms and fluvial aggradation in the Saryu River valley: Central Kumaun Himalaya

    Kothyari, Girish Ch.; Luirei, Khayingshing


    The present study has been carried out with special emphasis on the aggradational landforms to explain the spatial and temporal variability in phases of aggradation/incision in response to tectonic activity during the late Quaternary in the Saryu River valley in central Kumaun Himalaya. The valley has preserved cut-and-fill terraces with thick alluvial cover, debris flow terraces, and bedrock strath terraces that provide signatures of tectonic activity and climate. Morphostratigraphy of the terraces reveals that the oldest landforms preserved south of the Main Central Thrust, the fluvial modified debris flow terraces, were developed between 30 and 45 ka. The major phase of valley fill is dated between 14 and 22 ka. The youngest phase of aggradation is dated at early and mid-Holocene (9-3 ka). Following this, several phases of accelerated incision/erosion owing to an increase in uplift rate occurred, as evident from the strath terraces. Seven major phases of bedrock incision/uplift have been estimated during 44 ka (3.34 mm/year), 35 ka (1.84 mm/year), 15 ka (0.91 mm/year), 14 ka (0.83 mm/year), 9 ka (1.75 mm/year), 7 ka (5.38 mm/year), and around 3 ka (4.4 mm/year) from the strath terraces near major thrusts. We postulate that between 9 and 3 ka the terrain witnessed relatively enhanced surface uplift (2-5 mm/year).

  5. Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

    Zuffa, G.G.; De Rosa, R.; Normark, W.R.


    Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

  6. Human impact on late Quaternary landscapes in the Central Spanish Pyrenees

    Hirsch, F.; Raab, T. A.


    Like the Alps in Central Europe the Pyrenees in Southeast Europe are well known for their glacial history. Within the scope of the ongoing research project Post-LGM pedogenesis and geomorphodynamics in the Aragonese Pyrenees, Spain, funded by the Deutsche Forschungsgemeinschaft (DFG), we are studying the landscapes in the Gallego valley and the Aragon valley formed during the late Quaternary period. The aim of this research is to describe and characterize the soil development since the retreat of the valley glaciers from the LGM-moraines which are supposed to have an age of up to 60 ka yrs. To these purposes soil profiles are excavated in sediments and landforms of different ages (LGM to Holocene) and different genesis (glacigenic, glacifluvial, fluvial, gravitational). The soil profiles are arranged as catenas and provide insight into the pedo-stratigraphy of moraines, fluvial terraces, glacis and alluvial fans. Our preliminary results show that besides geogenic process past human land use must be considered as a main trigger of landscape development during the late Holocene. Truncated soil profiles in the backslopes and the correlate sediments of soil erosion burying soil horizons in the footslopes clearly indicate one or even more periods of re-shaping the landforms after deglaciation. Considerable amounts of small charcoal and tile fragments in the translocated sediments hint to an anthropogenic agent. The disturbance in the soil profiles and sediments is visible in the field and by micromorphology. Although 14C and OSL datings on the base of the correlate sediments of soil erosion indicate at least one phase of erosion and redeposition at the end of the 17th century, the onset of afresh pedogenic processes in the correlate sediments of soil erosion indicate young soil formation.

  7. Late Quaternary eolian and alluvial response to paleoclimate, Canyonlands, southeastern Utah

    Reheis, M.C.; Reynolds, R.L.; Goldstein, H.; Roberts, H.M.; Yount, J.C.; Axford, Y.; Cummings, L.S.; Shearin, N.


    In upland areas of Canyonlands National Park, Utah, thin deposits and paleosols show late Quaternary episodes of eolian sedimentation, pedogenesis, and climate change. Interpretation of the stratigraphy and optically stimulated luminescence ages of eolian and nearby alluvial deposits, their pollen, and intercalated paleosols yields the following history: (1) Eolian deposition at ca. 46 ka, followed by several episodes of alluviation from some time before ca. 40 ka until after 16 ka (calibrated). (2) Eolian deposition from ca. 17 ka to 12 ka, interrupted by periods of pedogenesis, coinciding with late Pleistocene alluviation as local climate became warmer and wetter. (3) A wetter period from 12 to 8.5 ka corresponding to the peak of summer monsoon influence, during which soils formed relatively quickly by infiltration of eolian silt and clay, and trees and grasses were more abundant. (4) A drier period between ca. 8.5 and 6 ka during which sheetwash deposits accumulated and more desertlike vegetation was dominant; some dunes were reactivated at ca. 8 ka. (5) Episodic eolian and fluvial deposition during a wetter, cooler period that began at ca. 6 ka and ended by ca. 3-2 ka, followed by a shift to drier modern conditions; localized mobilization of dune sand has persisted to the present. These interpretations are similar to those of studies at the Chaco dune field, New Mexico, and the Tusayan dune field, Arizona, and are consistent with paleoclimate interpretations of pollen and packrat middens in the region. A period of rapid deposition and infiltration of eolian dust derived from distant igneous source terranes occurred between ca. 12 and 8 ka. Before ca. 17 ka, and apparently back to at least 45 ka, paleosols contain little or no such infiltrated dust. After ca. 8 ka, either the supply of dust was reduced or the more arid climate inhibited translocation of dust into the soils. ?? 2005 Geological Society of America.


    吴时国; 黄孝健


    Seismic stratigraphic analysis of 150 km of high-resolution seismic profiles (G E OPULSE and 3.5 kHz) obtained along the muddy coast off Taishan, Guangdong pr ovided valuable information on the offshore Quaternary stratigraphy, tectonics, sedimentary evol ution, and environmental and engineering geology of this area.The following late Quaternary stratigraphic sequences were mapped. (1) Pleistoce ne alluvial silty sand and shallow marine clay; (2) coarse fluvial channel sand; (3 ) nearshore and bay clayey sediments. The incision of fluvial channels occurred in two stages: duri ng the Late Pleistocene and at the beginning of the Holocene. The Pleistocene fluvial channe ls have been filled by coarse sand overlain by more than 10 m of late Pleistocene clay and 20-30 m o f Holocene clay.The coastal area is dissected by two major fault systems: the first group strike s ENE-WSW and controls the evolution of the adjacent Quaternary basin, while the second one tr ends NNE-SSW. These fault systems must be taken into account in any coastal engineering consid erations. In addition, both granitic and metamorphic basements were recognized.

  9. Late Quaternary fluvial incision rates in a marine terraced landscape, southeastern Crete, Greece

    Karymbalis, Efthimios; Papanastassiou, Dimitris; Valkanou, Kanella; Gaki-Papanastassiou, Kalliopi


    Along the southern coast of the island of Crete, a series of five east-west oriented Late Pleistocene marine terraces exist, demonstrating the significant coastal uplift of this area. These terraces, ranging in elevation from 10 to 160m, are deformed by the vertical movements of the NNE-SSW trending and dipping west normal fault of Ierapetra. This study focuses on defining rates of fluvial incision for the last 410 Ka along valley systems that drain the tectonically uplifting area of Ierapetra, south Crete. The studied streams have a N-S flow direction and discharge into the Libyan Sea. Some of them are developed on the uplifted block of the Ierapetra normal fault whereas others drain the subsiding area west of the fault. The lower reaches of the study streams cut down through these marine terraces, which have been recognized, mapped in detail and correlated with Late Pleistocene Oxygen-Isotope Stages of high sea-level stands following the global sea-level fluctuations. These terraces of known age were used as reference surfaces in order to determine fluvial incision rates as the lower reaches of the streams cut down through these platforms. To evaluate incision rates, thirty five topographic valley cross-sections were drawn through fieldwork measurements as well as using a digital elevation model (DEM) produced by detailed topographic diagrams at the scale of 1:5,000. Cross valley profiles were constructed at specific locations where streams cut down the inner edges of the marine terraces because these points correspond precisely to the age of the palaeo-shoreline during the interglacial stage. For each cross-section the ratio of valley floor width to valley height (Vf) and long-term mean stream incision rates were estimated for the last 410 Ka. The geomorphic evolution of the valleys has been mainly affected by the lithology of the bedrock, sea level fluctuations during the late Quaternary, the head-ward erosion and incision of the channels, as well as both the

  10. Late Quaternary vegetation history of Rough Canyon, south-central New Mexico, USA

    Betancourt, J.L.; Rylander, Kate Aasen; Penalba, C.; McVickar, J.L.


    South-central New Mexico, USA, at the junction of the Rocky Mountains, High Plains and Chihuahuan Desert, is one of the better known regions in the late Quaternary of North America. Plant macrofossils and pollen from a packrat midden series in Rough Canyon, New Mexico allows refinement of plant distributions and paleoclimates in this transitional area since full glacial times. From 17 000 to 12 000 14C yr BP, Pinus edulis–Juniperus scopulorum woodlands dominated limestone substrates between 1800 and 1490 m, with Pseudotsugamenziesii and other mixed-conifer species restricted to shady, north-facing slopes. Juniperus deppeana, the dominant juniper today above 2000 m in southern New Mexico, is conspicuously absent from glacial middens and must have been displaced south of the US–Mexico border. The minimum climatic conditions for P. edulis–J. scopulorum woodlands are ca 20% wetter and 3.5–5°C cooler (July mean maximum temperatures) than the modern climate at Rough Canyon. Holocene warming/drying may have started as early as 12 000 14C yr BP with the extirpation of J. scopulorum from Rough Canyon, and was completed by at least 10 54014C yr BP. The record for arrivals of some desert species is confounded by traces of pollen and macrofossils in some of the glacial middens, which could signify either earliest occurrence or temporal mixing (contamination) of assemblages. AMS 14C dating can discriminate between early arrival and contamination in midden macrofossils but not in pollen. AMS dates show that Choisya dumosa, presently near its northern (cold) limits at Rough Canyon, endured late glacial winters, possibly as clonal populations. Some Larrea tridentata leaves and pollen occur in middens dominated by conifers and oaks no longer at the site; an AMS date of 3205 14C yr BP on Larrea leaves from one midden indicates contamination. Evidence for some macrofossil contamination, however, does not rule out the possibility that pollen of desert

  11. Siliceous microfossils as late Quaternary paleo-environmental indicators at Braamhoek wetland, South Africa

    Finné, M.; Norström, E.; Risberg, J.; Scott, L.


    phytolith indices (Iph and Ic) interpreted as indicators of climatic change, show periods of increased wetness and possibly minor temperature fluctuations during the late Quaternary. The fossil diatom record infer changes in past moisture conditions. Unlike the modern wetland, which is dominated by benthic and aerophilic diatoms, the late Pleistocene-early Holocene wetland favoured growth of planktonic species requiring deeper water. Abundance of planktonic diatoms suggests three main phases of greater water depth than today at c.13.6 ka, 11.3 ka and 10.4-10.0 ka. As part of a multi-proxy comparison, siliceous microfossil indications of past fluctuations in humidity in the Braamhoek wetland generally accord with the results from previous studies of pollen, charcoal fragments and stable isotopes in the same core.

  12. Late Quaternary Alluvial Fans of Southern Baja California, Mexico: Relation to Eastern Pacific Tropical Cyclones

    Antinao, J.; McDonald, E.


    In the arid, non-glaciated regions of the Southwestern USA and Northwestern Mexico, aggradation in alluvial fan systems has been traditionally linked to cold and humid periods (e.g., Last Glacial Maximum) or to the transition to warm periods (e.g., the Pleistocene-Holocene transition, PHT). However, major intervals of sediment transport and aggradation have also occurred during climatically warm periods in these regions. These periods have also been identified as portraying enhanced humidity or “monsoonal’ conditions. Investigations on the weather systems able to perform geomorphic work during predominantly warm periods, i.e. the North American Monsoon (NAM) and Eastern Pacific (EP) Tropical Cyclones (TCs), have concentrated mainly in the USA. To understand the relative contribution of these systems to sediment transport over millennial timescales, we have mapped and characterized preliminarily the alluvial fans in four different areas of the Southern Baja California peninsula, Mexico. This region is dominated by EPTC precipitation, which in turn is driving the sediment transport along alluvial channels. Detailed geomorphologic mapping shows that a distinct Late Quaternary chronostratigraphy of alluvial fan units can be developed using geochronological and pedological tools. Specifically, a soil chronosequence can be compared to sequences in the SW USA, allowing a correlation to Late Pleistocene - Holocene events in the region. At least five alluvial units can be identified. Older units have well defined gravel pediments, Av and B horizons and pervasive pedogenic carbonate morphology, with alluvial terraces that rise tens of meters above the present channel. Intermediate age units have developed B horizons and carbonate morphology at different stages. The younger units have thin soil horizons, no carbonate morphology in the soil profile, and some of them are subject to episodic flooding during TC activity. The chronosequence developed is the first step towards

  13. Late Quaternary activity along the Ferrara thrust inferred from stratigraphic architecture and geophysical surveys

    Stefani, Marco; Bignardi, Samuel; Caputo, Riccardo; Minarelli, Luca; Abu-Zeid, Nasser; Santarato, Giovanni


    Since Late Miocene, the Emilia-Romagna portion of the Po Plain-Adriatic foredeep basin was progressively affected by compressional deformation, due to the northward propagation of the Apennines fold-and-thrust belt. The major tectonic structures within the basin have been recognised and are relatively well known, thanks to the widespread, even if outdated, seismic survey, performed after WW II, for hydrocarbon exploration. More recently, a large amount of surface and shallow-subsurface information has been provided by the CARG geological mapping project. The region therefore provides a valuable opportunity to discuss the genetic relationship between tectonic deformation, eustatic-paleoclimatic fluctuations, and depositional architecture. The activity of blind thrusts and fault-propagation folds induced repeated angular unconformities and impressive lateral variations in the Pliocene-Quaternary stratigraphy, causing thickness changes, from a few metres, close to the Apennines piedmont line, to more than 9 km, in fast subsiding depocenters (e.g. Lido di Savio). In the Ferrara region, the post-Miocene succession ranges from about 4 km, west of Sant'Agostino, to less than 200 m, on the Casaglia anticline, where Late Quaternary fluvial strata rest on Miocene marine marls, with an angular unconformity relationship. In this sector of the Po Plain, the tip-line of the northernmost thrust has been reconstructed north of the Po River (Occhiobello) and is associated with the growth of a large fold (Ferrara-Casaglia anticline), cross-cut by a complex splay of minor backthrusts and reverse faults. The thrust-anticline structure hosts an energy producing geothermal field, whose hydrogeological behaviour is largely influenced by the fracture pattern. The Apennines frontal thrust probably provided the seismic source for the earthquakes that severely damaged Ferrara, during the 1570 a.D. fall season, as documented by the structural damage still visible in many historic buildings (e

  14. Deep-sea ostracode species diversity: Response to late Quaternary climate change

    Cronin, T. M.; DeMartino, D.M.; Dwyer, Gary S.; Rodriguez-Lazaro, J.


    Late Quaternary ostracode assemblages from the North Atlantic Ocean were studied to establish the effect of climatic changes of the past 210,000 yr (marine oxygen isotope stages 7–1) on deep-sea benthic biodiversity and faunal composition. Two-hundred and twenty five samples from the Chain 82-24 Core 4PC (41°43′N, 32°51′W, 3427 m water depth) on the western Mid-Atlantic Ridge revealed high amplitude fluctuations in ostracode abundance and diversity coincident with orbital and suborbital scale climate oscillations measured by several paleoceanographic proxy records. During the past 210,000 yr, ostracode biodiversity as measured by species number (S) and the Shannon–Weaver index, H(S), oscillated from H(S)=0.4 during glacial periods (marine isotope stages 6, 5d, 5b, 4, and 2) to H(S)=1.1 during interglacial and interstadial periods (stages 7, 5e, 5c, 5a, 3 and 1). A total of 23 diversity peaks could be recognized. Eleven of these signify major periods of high diversity [H(S)>0.8, S = 10–21] occurring every 15–20 ka. Twelve were minor peaks which may represent millennial-scale diversity oscillations. The composition of ostracode assemblages varies with Krithe-dominated assemblages characterizing glacial intervals, and Argilloecia–Cytheropteron characterizing deglacials, and trachyleberid genera (Poseidonamicus, Echinocythereis, Henryhowella, Oxycythereis) abundant during interglacials. Diversity and faunal composition changes can be matched to independent deep-sea paleoceanographic tracers such as benthic foraminiferal carbon isotopes, Krithe trace elements (Mg/Ca ratios), and to North Atlantic region climate records such as Greenland ice cores. When interpreted in light of ostracode species' ecology, these faunal and diversity patterns provide evidence that deep-sea benthic ecosystems experience significant reorganization in response to climate changes over orbital to millennial timescales.

  15. Setting the Time Frame - Investigating Culture-Environment Interactions in the Late Quaternary

    Klasen, N.; Just, J.; Rethemeyer, J.


    We present a status update of luminescence age estimates of sediments from Ethiopia and the Iberian Peninsula that are related to human occupation and are currently being investigated in the interdisciplinary Collaborative Research Center "Our way to Europe - Culture-Environment Interaction and Human Mobility in the Late Quaternary" (CRC806). The aim of the project is to investigate the dispersal of anatomically modern humans from Africa to Europe, and a robust chronology is essential. In the CRC806, dating is provided by luminescence, palaeomagnetic and radiocarbon techniques. A key site of the CRC806 is Chew Bahir in Ethiopia. This lake basin is located in the source area of the emergence of anatomically modern humans. Radiocarbon, luminescence and palaeomagnetic dating have been used to develop an age-depth model for drill core sediments that date back to 115 ka over 42 m depth. The model is independent of palaeoclimatic proxy interpretation. On the Iberian Peninsula cave deposits have been dated with luminescence techniques and compared to radiocarbon ages wherever applicable. Recently, existing radiocarbon chronologies on the Iberian Peninsula have been revised in light of methodological developments. Robust luminescence dating is therefore especially important in this region, where the stratigraphy is difficult to constrain. We aim to improve the precision of luminescence age estimates by comparing different measurement techniques for equivalent dose and dose-rate determinations, and by using Bayesian statistics to develop age-depth models. Combining different chronological techniques has enabled the development of accurate and precise chronologies, which will allow a better understanding of the emergence of modern humans.

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

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


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

  17. Mineral magnetic characteristics of the late Quaternary coastal red sands of Bheemuni, East Coast (India)

    Srivastava, Priyeshu; Sangode, S. J.; Parmar, Nikita; Meshram, D. C.; Jadhav, Priyanka; Singhvi, A. K.


    The voluminous red sand deposits of Bheemuni in the east coast of India provide record of coastal land-sea interaction during the late Quaternary climatic and eustatic oscillations. Limited information on the origin and depositional environments of these red sands and their chronology is available. We studied two inland to coast cross profiles from Bheemuni red sand deposits using mineral magnetism, color characteristics and Citrate-bicarbonate-dithionite (CBD) extractable pedogenic iron oxides over 23 horizons along with optically stimulated luminescence (OSL) chronology at 6 horizons. The oldest exposed bed had an optical age of 48.9 ± 1.7 ka. Differential ages between the two parallel sections (SOS = 48.9 ± 1.7 to 12.1 ± 0.3 ka and IMD = 29.3 ± 3.5 ka) suggest laterally shifting fluvial sedimentation. Both the profiles show significant amount of antiferromagnetic oxide (hematite) along with ferrimagnetic (magnetite/maghemite) mineral composition. The granulometric (/domain-) sensitive parameters (χFD, χARM, SIRM/χLF and χARM/χLF) indicate variable concentration of superparamagnetic (SP) and single domain (SD) particles between the two profiles. The higher frequency dependent and pedogenic magnetic susceptibilities (χFD and χpedo) in the younger (IMD) profile suggest enhanced pedogenesis under a warm-wet climate post 29.3 ka and also during Holocene. A combination of hard isothermal remanent magnetization (HIRM) and redness rating (RR) index indicates distinct but variable concentration of a) crystalline and b) poorly crystalline (pigmentary) hematites in both the profiles. We consider that the former (#a) is derived from hinterland red soils and possibly due to post-depositional diagenesis, and the latter (#b) precipitated from the dissolved iron under fluvial regime imparting the unique red coloration to Bheemuni sands. Partial to complete alteration of ferromagnesian minerals due to pedogenesis in hinterlands under warm-wet climate was therefore the

  18. Distinct phases of eustatic and tectonic forcing for late Quaternary landscape evolution in southwest Crete, Greece

    V. Mouslopoulou


    Full Text Available The extent to which climate, eustasy and tectonics interact to shape the late Quaternary landscape is poorly known. Alluvial fans often provide useful indexes that allow the decoding of information recorded on complex coastal landscapes, such as those of the eastern Mediterranean. In this paper we analyse and date (using infrared stimulated luminescence (IRSL dating a double alluvial fan system on southwest Crete, an island straddling the forearc of the Hellenic subduction margin, in order to constrain the timing and magnitude of its vertical deformation and discuss the factors contributing to its landscape evolution. The studied alluvial system is exceptional because each of its two juxtaposed fans records individual phases of alluvial and marine incision, thus providing unprecedented resolution in the formation and evolution of its landscape. Specifically, our analysis shows that the fan sequence at Domata developed during Marine Isotope Stage (MIS 3 due to five distinct stages of marine transgressions and regressions and associated river incision, in response to sea-level fluctuations and tectonic uplift at averaged rates of  ∼ 2.2 mm yr−1. Interestingly, comparison of our results with published tectonic uplift rates from western Crete shows that uplift during 20–50 kyr BP was minimal (or even negative. Thus, most of the uplift recorded at Domata must have occurred in the last 20 kyr. This implies that eustasy and tectonism impacted the landscape at Domata over mainly distinct time intervals (e.g. sequentially and not synchronously, with eustasy forming and tectonism preserving the coastal landforms.

  19. Glacial meltwater impounding: Evidence from the late Quaternary glaciogenic sediments in the Sangla valley, district Kinnaur, Himachal Pradesh, India

    R K Ganjoo; M N Koul


    Sangla valley is situated at an altitude of ∼3500m above mean sea level and lies in the Kinnaur district of Himachal Pradesh. It is fed by river Baspa, a tributary of river Sutlej, that entrenches through the Quaternary glaciogenic deposits before emerging out of the valley and joining the river Sutlej at Karcham. The unstratified to stratified glaciogenic deposits consist of large boulders to fine silt and are classified into four major depositional facies on the basis of sedimentary texture and depositional environment. The facies — basal conglomerates, debris flow, water/sheet flow and laminites — represents the change in the environment of deposition from glaciofluvial to lacustrine and also the extent of the glacier to the valley floor during late Quaternary.

  20. A Late Quaternary shortening rate for the frontal thrust of the Andean Precordillera north of Mendoza

    Schmidt, S.; Kuhlmann, J.; Hetzel, R.; Mingorance, F.; Ramos, V. A.


    Although large historical earthquakes occurred in the Andean back-arc region between 28° and 34°S - for instance Mendoza was destroyed by an earthquake of magnitude MS = 7.0 in 1861 - the slip rates of active faults remain unknown. We report a slip rate for the 50-km-long Las Penas thrust, which constitutes the frontal thrust of the Precordillera. In its southern part, a well preserved fluvial terrace along La Escondida Creek (Costa et al., 2000) is displaced vertically by 10.6 ± 0.7 m as documented by several fault scarp profiles. Apart from radiocarbon dating of plant remnants, three different approaches for 10Be exposure dating have been applied to constrain the age of the terrace. Amalgamated sandstone pebbles (corrected for an inherited 10Be component using similar pebbles from the active creek) and a depth profile obtained from four sand samples yield 10Be exposure ages of 12.2 ± 1.5 and 11.3 ± 2.0 kyr, respectively. Both ages are in excellent agreement with the 14C age of 12.61 ± 0.20 cal kyr BP. In contrast, 10Be ages of five sandstone boulders vary significantly and exceed the age of the terrace by 10 to 70 kyr, which demonstrates that the widely used assumption of a negligible inherited component is not valid here. The age of the river terrace combined with the vertical fault offset yields an uplift rate of ~0.8 mm/yr for the Las Penas thrust. Combined with the fault dip of 25°, we determine a Late Quaternary horizontal shortening rate of ~1.8 mm/yr, which is about 40% of the GPS derived shortening rate of 4.5 ± 1.7 mm/yr in the back-arc region of the Andes (Brooks et al., 2003). References Brooks, B.A., Bevis, M., Smalley, R., Kendrick, E., Manceda, R., Lauria, E., Maturana, R. & Araujo, M. (2003): Crustal motion in the Southern Andes (26° - 36°S): Do the Andes behave like a microplate? Geochem. Geophys. Geosyst., 4 (10), pp. 14, 1085, doi 10.1029/2003GC000505. Costa, C.H., Gardini, C.E., Diederix, H., Cortés, J.M. (2000): The Andean orogenic

  1. Late Quaternary palaeoenvironmental information inferred from terrestrial archives in the central Sahara

    Brauneck, J.; Baumhauer, R.


    Reconnaissance surveys in northeastern Niger since 1977 have revealed, from such evidence as diatomite-lined depressions, the existence of palaeolakes there. Initial research has shown that the palaeolimnic sediments and palaeosoils found are suitable for reconstructing its Late Quaternary palaeoenvironment. The most valuable and best-investigated study site is the sebkha of Seggedim, where a core of 15 meters length could be extracted which revealed a composition of high-resolution sections. Stratigraphical, structural and geochemical investigations as well as the analysis of thin sections allow the characterisation of different environmental conditions throughout the core. Most importantly, a complex age-depth model could be constructed, based on 21 accelerator mass spectrometry (AMS) radiocarbon measurements and reaching from Early to Mid Holocene. The results obtained from the core are compared with those from terrestrial and lacustrine sediments from outside the depression, situated a few hundred kilometres further to the north. Within the plateau landscape of Djado, Mangueni and Tchigai, two depressions and a valley containing lacustrine deposits, were investigated for palaeoenvironmental reconstruction. Depending on modifying local factors, these sediment archives were of shorter existence than the lake, but reveal additional information about the landscape dynamics from Early to Mid Holocene. The few perennial lacustrine climate archives still active to present day within the Sahara reveal apparently unique characteristics, as the local conditions that led to their existence are indeed exceptional. The interpretation of such a standalone location has to be performed with caution, as it inhibits several sources of error. The Seggedim depression may be considered such a unique spot at least for a limited time. The information obtained from the initial and freshwater lake sediments showed no noticeable signs of climatic alterations until Mid Holocene

  2. Review and evaluation of paleohydrologic methodologies

    Foley, M.G.; Zimmerman, D.A.; Doesburg, J.M.; Thorne, P.D.


    A literature review was conducted to identify methodologies that could be used to interpret paleohydrologic environments. Paleohydrology is the study of past hydrologic systems or of the past behavior of an existing hydrologic system. The purpose of the review was to evaluate how well these methodologies could be applied to the siting of low-level radioactive waste facilities. The computer literature search queried five bibliographical data bases containing over five million citations of technical journals, books, conference papers, and reports. Two data-base searches (United States Geological Survey - USGS) and a manual search were also conducted. The methodologies were examined for data requirements and sensitivity limits. Paleohydrologic interpretations are uncertain because of the effects of time on hydrologic and geologic systems and because of the complexity of fluvial systems. Paleoflow determinations appear in many cases to be order-of-magnitude estimates. However, the methodologies identified in this report mitigate this uncertainty when used collectively as well as independently. That is, the data from individual methodologies can be compared or combined to corroborate hydrologic predictions. In this manner, paleohydrologic methodologies are viable tools to assist in evaluating the likely future hydrology of low-level radioactive waste sites.

  3. Late Quaternary Advance and Retreat of an East Antarctic Ice Shelf System: Insights from Sedimentary Beryllium-10 Concentrations

    Guitard, M. E.; Shevenell, A.; Domack, E. W.; Rosenheim, B. E.; Yokoyama, Y.


    Observed retreat of Antarctica's marine-based glaciers and the presence of warm (~2°C) modified Circumpolar Deep Water on Antarctica's continental shelves imply ocean temperatures may influence Antarctic cryosphere stability. A paucity of information regarding Late Quaternary East Antarctic cryosphere-ocean interactions makes assessing the variability, timing, and style of deglacial retreat difficult. Marine sediments from Prydz Bay, East Antarctica contain hemipelagic siliceous mud and ooze units (SMO) alternating with glacial marine sediments. The record suggests Late Quaternary variability of local outlet glacier systems, including the Lambert Glacier/Amery Ice Shelf system that drains 15% of the East Antarctic Ice Sheet. We present a refined radiocarbon chronology and beryllium-10 (10Be) record of Late Quaternary depositional history in Prydz Channel, seaward of the Amery Ice Shelf system, which provides insight into the timing and variability of this important outlet glacier system. We focus on three piston cores (NBP01-01, JPC 34, 35, 36; 750 m water depth) that contain alternating SMO and granulated units uninterrupted by glacial till; the record preserves a succession of glacial marine deposits that pre-date the Last Glacial Maximum. We utilize the ramped pyrolysis preparatory method to improve the bulk organic carbon 14C-based chronology for Prydz Channel. To determine if the SMO intervals reflect open water conditions or sub-ice shelf advection, we measured sedimentary 10Be concentrations. Because ice cover affects 10Be pathways through the water column, sedimentary concentrations should provide information on past depositional environments in Prydz Channel. In Prydz Channel sediments, 10Be concentrations are generally higher in SMO units and lower in glacial units, suggesting Late Quaternary fluctuations in the Amery Ice Shelf. Improved chronologic constraints indicate that these fluctuations occurred on millennial timescales during the Last Glacial

  4. Late Quaternary vegetation and glacial history in the St. Lawrence Lowlands, Canada

    Lasalle, Pierre


    This paper presents data of various kinds concerning the Quaternary geology of the St. Lawrence Lowlands: pollen diagrams, C14 dates, and diatom floras. These data show that the highest parts of the St. Lawrence Lowlands were already deglaciated more than 12,000 years ago, as appears from the existe

  5. Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe fault

    RAN YongKang; CHEN LiChun; CHENG JianWu; GONG HuiLing


    The Anninghe fault is an important active fault along the eastern boundary of Sichuan-Yunnan active tectonic block, and the study of its surface deformation and rupture behavior during strong earthquake in the late Quaternary is of fundamental importance for understanding the future seismic risk of the fault zone or even the entire western Sichuan region.Using the methods of detailed geomorphic and geological survey, digital image analysis, total station instrument survey, excavation of combined trench and dating, we analyze the geomorphologic sequences of the offset strata at several sites where the late Quaternary deformation remnants are fairly well preserved and obtain some new results as follows: Strong earthquake events with left-lateral displacements of about 3 m occurred at the two sites of Zimakua and Yejitong at 1634-1811,1030-1050 and 280-550 a BP, respectively, and the recurrence interval is 520-660 a; The youngest event in the area of Dahaizi-Ganhaizi should be the earthquake of 1536, other events are at 1768-1826, 2755-4108 and 4108-6593 a BP, respectively, with a recurrence interval of 1300-1900 a.The strong earthquake activity shows a clustering character.The possibility of occurrence of a strong earthquake exists on the north segment of the Anninghe fault sometime in the future.

  6. Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe fault


    The Anninghe fault is an important active fault along the eastern boundary of Sichuan-Yunnan active tectonic block, and the study of its surface deformation and rupture behavior during strong earthquake in the late Quaternary is of fundamental importance for understanding the future seismic risk of the fault zone or even the entire western Sichuan region. Using the methods of detailed geomorphic and geological survey, digital image analysis, total station instrument survey, excavation of combined trench and dating, we analyze the geomorphologic sequences of the offset strata at several sites where the late Quaternary deformation remnants are fairly well preserved and obtain some new results as follows: Strong earthquake events with left-lateral displacements of about 3 m occurred at the two sites of Zimakua and Yejitong at 1634-1811, 1030-1050 and 280-550 a BP, respectively, and the recurrence interval is 520-660 a; The youngest event in the area of Dahaizi-Ganhaizi should be the earthquake of 1536, other events are at 1768-1826, 2755-4108 and 4108-6593 a BP, respectively, with a recurrence interval of 1300-1900 a. The strong earthquake activity shows a clustering character. The possibility of occurrence of a strong earthquake exists on the north segment of the Anninghe fault sometime in the future.

  7. Coupling genetic and species distribution models to examine the response of the Hainan Partridge (Arborophila ardens to late quaternary climate.

    Jiang Chang

    Full Text Available Understanding the historical dynamics of animal species is critical for accurate prediction of their response to climate changes. During the late Quaternary period, Southeast Asia had a larger land area than today due to lower sea levels, and its terrestrial landscape was covered by extensive forests and savanna. To date, however, the distribution fluctuation of vegetation and its impacts on genetic structure and demographic history of local animals during the Last Glacial Maximum (LGM are still disputed. In addition, the responses of animal species on Hainan Island, located in northern Southeast Asia, to climate changes during the LGM are poorly understood. Here, we combined phylogeographic analysis, paleoclimatic evidence, and species distribution models to examine the response of the flightless Hainan Partridge (Arborophila ardens to climate change. We concluded that A. ardens survived through LGM climate changes, and its current distribution on Hainan Island was its in situ refuge. Range model results indicated that A. ardens once covered a much larger area than its current distribution. Demographic history described a relatively stable pattern during and following the LGM. In addition, weak population genetic structure suggests a role in promoting gene flow between populations with climate-induced elevation shifts. Human activities must be considered in conservation planning due to their impact on fragmented habitats. These first combined data for Hainan Partridge demonstrate the value of paired genetic and SDMs study. More related works that might deepen our understanding of the responses of the species in Southeast Asia to late Quaternary Climate are needed.

  8. Using of microvertebrate remains in reconstruction of late quaternary (Holocene paleoclimate, Eastern Iran

    Narges Hashemi


    Full Text Available Introduction   Study of quaternary microvertebrate remains in eastern Iran, according to a few of the sediments is very important. Reconstruction of quaternary climate in many parts of West and North West of Iran as the biggest karst state is possible, such as cave Kani Mikaiel (Hashemi et al. 2005, 2006, 2007a;b, 2008; 2010, Jangjoo et al . 2010, Yafteh cave (Otte et al. 2007, Hashemi et al. 2015. However, such studies were very poor in eastern and north-eastern Iran (Hashemi and darvish 2006; Hashemi et al. 2008, 2015. Investigation of taxonomic identification; quantification and distribution of micromammals revealed that these remains are useful in paleontology and archaeological research, because their abundance is useful for paleobiostratigraphy and dating of continental sediments. The recent research is about reconstruction of paleoclimate in two archeological sites of Konar sandal (KS (Jiroft and Tapeh Naderi (TN (Mashhad based on the microvertebrate and especially Tatera indica species. In these sites we attempted to solve the palaeoenvironment condition by analysis of rodent remains which hold the greatest potential to monitoring of ecological parameters (Hoover et al. 1977; Getz 1961; Reig 1970; Merritt 1974. Combining of a rich network of data with using of morphological and morphometric methods; reconstruction of paleoenvironment; documentation and investigation of their relationship with the environment is the main result of this research .       Material & Methods   In both zooarchaeological samples which are composed of juveniles and young individual rodent, (KS, NISP=800 and TN, NISP=3 cranial and postcranial remains were sorted anatomically and washed with water. Dental pattern of mandible and maxillary tooth rows were drowns using a drawing tube connecting to a stereomicroscope (Olympus SZH-10. All recovered teeth fragments were measured based on the greatest dental length and width of the upper and lower jaw molars when

  9. Late Quaternary sea-ice history of northern Fram Strait/Arctic Ocean

    Kremer, Anne; Stein, Rüdiger; Fahl, Kirsten; Matthießen, Jens; Forwick, Matthias; O'Regan, Matt


    One of the main characteristics of the Arctic Ocean is its seasonal to perennial sea-ice cover. Variations of sea-ice conditions affect the Earth's albedo, primary production, rate of deep-water etc.. During the last decades, a drastic decrease in sea ice has been recorded, and the causes of which, i.e., natural vs. anthropogenic forcings, and their relevance within the global climate system, are subject of intense scientific and societal debate. In this context, records of past sea-ice conditions going beyond instrumental records are of major significance. These records may help to better understand the processes controlling natural sea-ice variability and to improve models for forecasts of future climatic conditions. During RV Polarstern Cruise PS92 in summer 2015, a 860 cm long sediment core (PS92/039-2) was recovered from the eastern flank of Yermak Plateau north of the Svalbard archipelago (Peeken, 2015). Based on a preliminary age model, this sediment core probably represents the time interval from MIS 6 to MIS 1. This core, located close to the modern summer ice edge, has been selected for reconstruction of past Arctic sea-ice variability based on specific biomarkers. In this context, we have determined the ice-algae-derived sea-ice proxy IP25 (Belt et al., 2007), in combination with other biomarkers indicative for open-water conditions (cf., Müller et al., 2009, 2011). Furthermore, organic carbon fluxes were differentiated using specific biomarkers indicative for marine primary production (brassicasterol, dinosterol) and terrigenous input (campesterol, β-sitosterol). In this poster, preliminary results of our organic-geochemical and sedimentological investigations are presented. Distinct fluctuations of these biomarkers indicate several major, partly abrupt changes in sea-ice cover in the Yermak Plateau area during the late Quaternary. These changes are probably linked to changes in the inflow of Atlantic Water along the western coastline of Svalbard into

  10. Geochemical registers of Late Quaternary paleoclimatic conditions at Sonora and Chihuahua Deserts, Mexico: comparison and synthesis

    Roy, P.; Perez-Cruz, L. L.; Lozano-Garcia, S.


    Sonora and Chihuahua Deserts form the southwestern and southeastern parts of North American Desert system and spread over at least 5 different states in the northern Mexico. Presently, Sonora Desert receives annual precipitation in a bi-modal distribution, whereas Chihuahua Desert receives dominant summer precipitation. Paleoclimatic registers from Mojave Desert suggest that the spatial extent and magnitude of both the summer and winter precipitation varied during the last glacial period and such fluctuations were linked to the volume of the Laurentide ice sheet, changing winter-summer insolation, North Atlantic climatic variability and ENSO dynamics. We present multi-elemental concentrations, magnetic susceptibility, organic and inorganic carbon from 750 cm long sediment core collected from paleolake San Felipe (31°N, western Sonora Desert) and 970 cm long sediment core collected from paleolake Babicora (29°N, western Chihuahua Desert) in order to understand the paleohydrological and paleoclimatic evolution in the arid region of northern Mexico. 6 AMS 14C dates constrain the San Felipe sediment core between 49 cal kyr BP and present. Similarly, 8 AMS 14C dates put the Babicora core in the age bracket between 76 cal kyr BP and present with two different hiatus at 4-8 cal kyr BP and 40-45 cal kyr BP. Due to the special geomorphology of San Felipe basin, Ti concentration was used as a proxy for pluvial discharge and to differentiate regimes of dominant summer and winter precipitation. Aeolian deposition was constrained at >48 cal kyr BP. Period of lower pluvial discharge during 14-48 cal kyr BP is related to a regime of dominant winter frontal storms. During 3-14 cal kyr BP, higher catchment erosion and transportation of REE bearing heavy minerals into the basin are possibly as a result of higher pluvial discharge related to a regime of dominant summer precipitation. In paleolake Babicora, high resolution Ti suggests higher pluvial inflow prior to 60 cal kyr BP (H

  11. Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia.

    Wan, Xinru; Zhang, Zhibin


    Climate change and humans are proposed as the two key drivers of total extinction of many large mammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal-spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates of warming and range shifts of species are much faster than those from the Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period- and region-specific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming.

  12. Assessing Biological and Stratigraphic Determinants of Fossil Abundance: A Case Example from the Late Quaternary of Po Plain, Italy

    Kowalewski, Michal; Azzarone, Michele; Kusnerik, Kristopher; Dexter, Troy; Wittmer, Jacalyn; Scarponi, Daniele


    Absolute fossil abundance [AFA] can be defined as a relative concentration of identifiable fossils per unit of sediment. AFA, or "sediment shelliness", is controlled by the interplay between the rate of input of skeletal remains (biological productivity), pace of shell destruction (taphonomy), rate of sedimentation, and sediment compaction. Understanding the relative importance of those drivers can augment both stratigraphic and biological interpretations of the fossil record. Using 336 samples from a network of late Quaternary cores drilled in Po Plain (Italy), we examined the importance of those factors in controlling the stratigraphic distribution of fossils. All samples were vertically and volumetrically equivalent, each representing a 10 cm long interval of a core with a diameter of 7 cm ( 0.375 dm3 sediment per sample). Sample-level estimates of AFA (1) varied over 4 orders of magnitudes (from 4000 specimens per dm3) were characterized by exceedingly low evenness reflecting dominance by one super-abundant species (Berger-Parker index > 0.8 in all cases). These super-abundant species were limited to small r-selective mollusks capable of an explosive population growth: the marine corbulid bivalve Lentidium mediterraneum and the brackish hyrdobiid gastropod Ecrobia ventrosa. Moreover, despite high mollusk diversity (534 species total), >80% of samples are dominated by one of the five mollusk species, which all represent small, r-selective, deposit and suspension feeders. Trends in absolute fossil abundance within late Quaternary deposits of the Po Plain appear to have been driven primarily by biological productivity of opportunistic shelly species from lowest trophic levels. In the studied system, biodiversity and shelliness of samples is unlikely to reflect stratigraphic or taphonomic overprints, but rather records the ecological importance of r-selective species that dominated the investigated area throughout the late Quaternary. The joint consideration of

  13. Apparent late Quaternary fault slip rate increase in the southwestern Lower Rhine Graben, central Europe

    Gold, Ryan D.; Friedrich, Anke M.; Kubler, Simon; Salamon, Martin


    In regions of low strain, long earthquake recurrence intervals (104–106  yrs) and erosive processes limit preservation of Quaternary markers suitable for distinguishing whether faults slip at uniform or secularly varying rates. The Lower Rhine graben in the border region of Germany, The Netherlands, and Belgium provides a unique opportunity to explore Quaternary slip‐rate variations in a region of low strain using the basal (2.29±0.29  Ma) and surface (700±80  ka) contacts of the regionally extensive main terrace (“Hauptterrasse”), deposited by the Rhine and Maas Rivers. These surfaces are vertically offset 3–140 m and 0–68 m, respectively, across individual fault strands within a distributed network of northwest‐trending, slow‐slipping (earth digital terrain models, which we synthesize with existing constraints on the offset basal contact of this fluvial deposit (n=91 collocated sites with displacement constraints). We find that >80% of the sites record an apparent increase in slip rate for the more recent interval from 700 ka to present, which corresponds to a period of increased uplift of the nearby Rhenish Massif and regional volcanism. However, the apparent increase in slip rate could result, in part, from erosion of the footwall surface below the main terrace, leading to an apparent displacement that is smaller than the total vertical offset since the start of the Quaternary. Prior work focused on characterization of these faults as seismic sources in the Lower Rhine graben has preferentially relied on the average fault‐slip rate constrained using the base of the main terrace. We suggest that average fault‐slip rates calculated using the ∼700  ka main terrace surface are subjected to fewer uncertainties and sample a time interval that is more relevant for seismic‐hazard analysis.

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

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


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

  15. Ecosystem resilience to abrupt late Quaternary change in continental southern Siberia

    Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander


    Quaternary climate variability is dominated by long term orbital forcing along with abrupt sub-Milankovitch events on the scales of millennia to centuries, driven by internal feedback mechanisms, volcanic forcing and fluctuating solar activity. Although these are well documented in the North Atlantic region, their expression is poorly understood in Siberia, particularly in relation to abrupt climatic events. Siberia has the world's highest level of continentality offering an opportunity to study changes remote from oceanic influences and improving understanding of interactions between the Siberian High and other atmospheric systems including the Aleutian Low, Arctic oscillation and Icelandic Low1 and ENSO2. Understanding of palaeoenvironmental change in Siberia is essential due to the region's high sensitivity to climatic change, with warming rates considerably higher than the global average over the past 50 years3, triggering significant environmental changes, including permafrost degradation, shifts in the forest-steppe biome, increases in forest fires and warming of seasonally ice-covered lakes. Additionally, the region provides essential palaeoenvironmental context for early hominins, for example at globally important sites such as Denisova cave4, and megafauna extinctions5. This presentation outlines ongoing work at Lake Baunt, SE Siberia including: key quaternary climate forcings, the site and its regional context, the key methods and preliminary results. These include a dated record back to ˜30ka BP (based on multiple 14C dates and Bayesian age modelling), multiproxy indicators of palaeoproductivity (e.g. biogenic silica and diatom analyses) and lake mixing regimes (inferred from diatom analyses). Together these highlight several key Quaternary fluctuations potentially correlated to events recorded in Greenland Ice Cores (GS2, GS2.1, GI1, GS1), and these are considered against key Quaternary records including those from nearby Lake Baikal and Hulu Cave in

  16. Late-Quaternary recharge determined from chloride in shallow groundwater in the central Great Plains

    MacFarlane, PA; Clark, JF; Davisson, ML; Hudson, GB; Whittemore, DO


    An extensive suite of isotopic and geochemical tracers in groundwater has been used to provide hydrologic assessments of the hierarchy of flow systems in aquifers underlying the central Great Plains (southeastern Colorado and western Kansas) of the United States and to determine the late Pleistocene and Holocene paleotemperature and paleorecharge record. Hydrogeologic and geochemical tracer data permit classification of the samples into late Holocene, late Pleistocene-early Holocene, and much...

  17. Permafrost sequences on Kurungnakh Island, Lena Delta (NE Siberia, Russia) as key site of the late Quaternary environmental history of West Beringia

    Wetterich, S.; Kuzmina, S.; Andreev, A. A.; Kienast, F.; Meyer, H.; Schirrmeister, L.; Kuznetsova, T.; Sierralta, M.


    Late Quaternary permafrost sequences are widely distributed in the arctic lowlands of Siberia. Because the existence of permafrost has been sensitive to climate changes during the Quaternary past, such frozen deposits are regarded as an archive of palaeoenvironmental dynamics. Late Quaternary palaeoenvironments of the Siberian Arctic were reconstructed by combining data from several fossil bioindicators (pollen, plant macro-fossils, ostracods, insects, and mammal bones) with sedimentological and cryolithological data from permafrost deposits. The late Pleistocene to Holocene sequence on Kurungnakh Island (Lena Delta, NE Siberia) reflects the environmental history of West Beringia and covers glacial/interglacial and stadial/interstadial climate variations with a focus on the Middle Weichselian interstadial (50-32 kyr BP). The record mirrors the development of periglacial landscapes under changing sedimentation regimes which were meandering fluvial during the Early Weichselian, colluvial or proluvial on gently inclined plaines during the Middle and Late Weichselian, and thermokarst-affected during the Holocene. Palaeoecological records indicate the existence of tundra-steppe vegetation under cold continental climate conditions during the Middle Weichselian interstadial. Due to sedimentation gaps in the sequence between 32 and 17 kyr BP and 17 and 8 kyr BP, the Late Weichselian stadial is incompletely represented in the studied outcrops. Nevertheless, by several palaeoecological indications arctic tundra-steppe vegetation under extremely cold-arid conditions prevailed during the late Pleistocene. The tundra-steppe disappeared completely due to lasting paludification during the Holocene. Initially subarctic shrub tundra formed, which later retreated in course of the late Holocene cooling.

  18. Modeling global vegetation in the late Quaternary: What progress have we made and what are the priorities for the future?

    Kaplan, Jed


    More than two decades ago, the development of the first global biogeography models led to an interest in simulating global land cover in the past. These models promised the possibility of creating a coherent picture of the Earth's vegetation that went beyond qualitative extrapolation of site-based observations, e.g., from paleoecological archives, and was not limited to areas with a high density of sites. Then as now, the goal of much work simulating past vegetation was to explore and understand the role of biogeophysical and biogeochemical feedbacks between the Earth's land surface and the climate system. Paleovegetation modeling for the late Quaternary has also influenced debates on the character of natural vegetation, conservation and ecological restoration goals, and the co-evolution of humans, civilizations, and the landscapes in which they live. The first simulations of global land cover in the past used equilibrium vegetation models, e.g., BIOME1, BIOME3, and BIOME4, and focused on well-known timeslices of interest in paleoclimate research, including the Last Glacial Maximum (21,000 BP) and the mid-Holocene (6,000 BP). Questions addressed included: quantification of the importance of terrestrial vegetation in the glacial carbon cycle, the role of changing vegetation cover on glacial inception, and the influence of biogeophysical feedbacks on the amplitude and spatial pattern of the mid-Holocene African Monsoon. In the intervening years, as both vegetation and climate models evolved and improved, the spatial resolution, number of periods studied, and the type of research questions addressed expanded greatly. Studies covered the dynamics of Arctic vegetation, wetland area, wetland methane emissions, and paleo-atmospheric chemistry, dust emissions and effects on paleoclimate, among others. A major recent advance in paleovegetation modeling for the late Quaternary has come with the development of Dynamic Global Vegetation Models (DGVMs) that are capable of

  19. Pre-Wisconsinan mammals from Jamaica and models of late Quaternary extinction in the greater Antilles

    MacPhee, R. D. E.; Ford, Derek C.; McFarlane, Donald A.


    The vertebrate fauna recovered from indurated conglomerates at Wallingford Roadside Cave (central Jamaica) is shown to be in excess of 100,000 yr old according to uranium series and electron spin resonance dating. The Wallingford local fauna is therefore pre-Wisconsinan in age, and Roadside Cave is now the oldest radiometrically dated locality in the West Indies containing identifiable species of land mammals. In the absence of a good radiometric record for Quaternary paleontological sites in the Caribbean, there is no satisfactory basis for determining whether most extinct Antillean mammals died out in a "blitzkrieg"-like event immediately following initial human colonization in the mid-Holocene. Fossils of Clidomys (Heptaxodontidae, Caviomorpha), the giant Wallingford rodent, have never been found in situ in sediments of demonstrably Holocene age, and its extinction may antedate the middle Holocene. This is also a possibility for the primate Xenothrix mcgregori, although its remains have been found in loose cave earth. A major, climate-driven bout of terrestrial vertebrate extinction at about 14,000-12,000 yr B.P. has been hypothesized for the West Indies by G. Pregill and S. L. Olson ( Annual Review of Ecology and Systematics12, 75-98, 1981), but at present there is nothing to connect the disappearance of Clidomys with this event either. Quaternary extinctions in the Caribbean may prove to be of critical significance for evaluating the reality of New World blitzkrieg, but not until an effort is mounted to constrain them rigorously using modern radiometric approaches.

  20. Erosion and deposition on the Pajarito Plateau, New Mexico, and implications for geomorphic responses to late Quaternary climatic changes

    Reneau, S.L.; McDonald, E.V.; Gardner, J.N.; Longmire, P.A. [Los Alamos National Lab., NM (United States); Kolbe, T.R. [Woodward-Clyde Federal Services, Oakland, CA (United States); Carney, J.S. [Kent State Univ., OH (United States). Dept. of Geology; Watt, P.M. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences


    The Pajarito Plateau of northern New Mexico contains a rich and diverse record of late Quaternary landscape changes in a variety of geomorphic settings that include gently-sloping mesa tops, steep canyon walls, and canyon bottoms. A broad range of investigations during the past decade, motivated by environmental and seismic hazard concerns, have resulted in examination of the characteristics, stratigraphy, and age of sediments and soils at numerous locations throughout the Plateau. Geochronologic control is provided by >140 radiocarbon dates supplemented by soil characterization and tephrochronology. In this paper we first summarize some of the results of recent and ongoing work on late Quaternary deposits on the Pajarito Plateau, illustrating both the complexity of the geomorphic record and some common elements that have been observed in multiple locations. We then use these observations, in combination with other work in the Southwest, to make some inferences about the local geomorphic response to regional climatic changes. Because the geomorphic and paleoclimatic records are fragmentary, and because the relations between large scale climate changes and local variations in precipitation, vegetation, and geomorphic processes are not fully understood, many uncertainties exist concerning the response of the local landscape to past climatic fluctuations. In addition, variations in local landscape sensitivity related to prior erosional history and spatial variations in vegetation, and the localized nature of many storms, probably contribute to the complexity of the geomorphic record. Nevertheless, the work discussed in this paper suggests a strong relation between regional climatic changes and local geomorphic history, and provides a framework for considering relations between modem processes, the record of past landscape changes, and future erosion and deposition on the Plateau and in surrounding areas.

  1. Lidar-Based Mapping of Late Quaternary Faulting Along the Grizzly Valley Fault, Walker Lane Seismic Belt, California

    Hitchcock, C. S.; Hoirup, D. F.; Barry, G.; Pearce, J.; Glick, F.


    The Grizzly Valley fault (GVF) is located within the northern Walker Lane, a zone of right-lateral shear between the Sierra Nevada and the Basin and Range in Plumas County. The GVF extends southeasterly from near Mt. Ingalls along the eastern side of Lake Davis. It may partially connect with the Hot Creek fault within Sierra Valley and extend south to Loyalton with an overall approximate length of 50 km. Comparison of high-resolution topography developed from LiDAR data with published bedrock geologic mapping documents the presence of geomorphic features that provide information on fault activity of the GVF. Field mapping verified tectonically deformed and offset late Quaternary surfaces identified on bare-earth LiDAR imagery across the GVF within glacial deposits on the eastern margin of Lake Davis, and alluvial deposits in Sierra Valley. Along the GVF, conspicuous geomorphic and hydrologic features include scarps in alluvial surfaces, elongated depressions aligned with adjacent linear escarpments, truncated bedrock spurs, closed depressions, linear swales, right-lateral deflections of creeks and river courses, and shutter ridges, as well as springs and linear seeps consistent with right-lateral strike-slip faulting. The discontinuous nature of observed fault traces combined with the apparent down-to-the-west offset of alluvial surfaces at the southern and northern ends of the eastern margin of Lake Davis are consistent with a broad bend or step over in the fault. Scarp profiles of apparently faulted surfaces extracted from LiDAR data document vertical offsets of up to 14 m. Our study suggest that the GVF is an oblique, right-lateral fault that has been active in the late Quaternary. This study complements on-going investigations by DWR to assess the impact of seismic hazards on State Water Project infrastructure.

  2. Signatures and significance of aeolian, fluvial, bacterial and diagenetic magnetic mineral fractions in Late Quaternary marine sediments off Gambia, NW Africa

    Just, A.; Dekkers, M.J.; Dobeneck, T. von; Hoesel, A. van; Bickert, T.


    Two gravity cores retrieved off NW Africa at the border of arid and subtropical environments (GeoB 13602–1 and GeoB 13601–4) were analyzed to extract records of Late Quaternary climate change and sediment export. We apply end-member (EM) unmixing to 350 acquisition curves of isothermal remanent magn

  3. Paleoenvironmental Reconstruction of Late Quaternary Insect Fossils, Halashazi Site, Altai Region, China.

    Zhang, Tianshu; Elias, Scott; Angus, Robert


    The Altai region northwest China, is located in the middle of arid central Asia and is therefore sensitive to climate change. However, there is a debate on the heat-moisture pattern (warm-dry pattern or cold-dry pattern) during the early Holocene in the Altai region, and a debate on the dominant atmospheric circulation (westerlies or monsoon) control for central Asian climate changes during the Holocene, and the mechanisms that cause the arid early Holocene in central Asia. Thus, the principal aim of the project is use the MCR method to produce quantified temperature and precipitation estimates, and a high-precision palaeoclimatic record for the Altai region, based on fossil beetle assemblages, to reveal the heat-moisture pattern and its mechanisms. This project will begin to fill in the blank of Quaternary beetle research in China. Using Quaternary beetles to reconstruct palaeoenvironments is a new research method for this region, and has never before been done in China, which will provide new evidence for the palaeoenvironmental study in this area. Furthermore, this project will contribute to the beetle faunal research in Eurasia. The sample site for this project - Halashazi Wetland (048°06'54"N, 088°21'48"E), is located at the crossroad of the Altai Mountains and the Dzungarian Basin, where two ecosystems meet. Thus the fossil beetle assemblages should show dramatic change in response to changes of climate. The sampled deposits are made up entirely of sedge peat. Two different profiles were sampled, with depths of 160 cm and 200 cm, respectively. Both profiles were sampled at 5 cm intervals, with approximately 2 kg of material in each unit. The results of the radiocarbon dating will be available in December 2016. Based on other previous studies, the bottom of the peat sediment is 11,500 cal yr BP, so project focuses on the Holocene period approximately from 10,000 cal yr BP. More than 80 species of Coleoptera from 55 genera, 22 families have been recognised so

  4. Environmental Magnetic Signature Of Late Quaternary Climate and Paleoceanography in the Bering Sea

    Platzman, E. S.; Lund, S.; Kirby, M. E.


    High latitude drilling during IODP expedition 323 in the Bering Sea provides a unique opportunity to study in detail the evolution of Quaternary paleoceanography, climate and glacial history of the Bering Sea gateway to the Arctic Ocean. Our study focuses on a 400 ky interval of Quaternary marine sediments cored along the Bering Slope. Samples for magnetic analysis were obtained from sites U1339, U1343, U1344, U1345, at depths of 1008-3484 m. Sediments in these cores are a mixture of siliclastic material, derived primarily from terrigeneous sources, and biogenic material. Detailed measurements of the variation in bulk magnetic properties including natural remanent magnetization (NRM), susceptibility, ARM, and IRM, have been used to monitor changes in concentration, composition and grainsize of the magnetic components. In addition, sediment grain size analysis was preformed on biogenic free aliquots at selected intervals. Our results indicate that the dramatic bimodal magnetic intensity signal that alternates between a strong and weak NRM and magnetic susceptibility is associated with relatively course and fine grain sizes repectively. This is the opposite to the pattern estimated by our initial IODP Ex. 323 reports. Current models propose that, as has been observed in the North Atlantic, high intensities are likely to be related to high contributions of terrigenous and glaciomarine sediments deposited during glacial periods and low intensities are likely to occur during interglacials when continental sediments become trapped on the on the shelf. Contrary to this hypothesis, however, we find compelling evidence for a substantial increase in terrigenous input during the interglacial periods and what appears to be a predominantly pelagic signal during the glacial periods. Comparison of our data with other proxy data including oxygen isotopes, NGR, GRA allows us to investigate the possible causal links between these changes and the environmental history of the North

  5. Changes in Late Cretaceous-Quaternary Caribbean plate motion directions inferred from paleostress measurements from striated fault planes

    Batbayar, K.; Mann, P.; Hippolyte, J.


    We compiled paleostress analyses from previous research works collected at 591 localities of striated fault planes in rocks ranging in age from Late Cretaceous to Quaternary in the circum-Caribbean and Mexico. The purpose of the study is to quantify a progressive clockwise rotation of the Caribbean plate during its Late Cretaceous to recent subduction of the Proto-Caribbean seaway. Paleostress analysis is based on the assumption that slickenside lineations indicate both the direction and sense of maximum resolved shear stress on that fault plane. We have plotted directions of maximum horizontal stress onto plate tectonic reconstructions of the circum-Caribbean plate boundaries and infer that these directions are proxies for paleo-plate motion directions of the Caribbean plate. Plotting these stress directions onto reconstructions provided a better visualization of the relation of stress directions to blocks at their time of Late Cretaceous to recent deformation. Older, more deformed rocks of Late Cretaceous to Eocene ages yield a greater scatter in derived paleostress directions as these rocks have steeper dips, more pervasive faulting, and were likely affected by large rotations as known from previous paleomagnetic studies of Caribbean plate margins. Despite more scatter in measurements from older rock units, four major events that affected the Caribbean plate and the Great Arc of the Caribbean (GAC) are recognizable from changing orientations of stress directions: 1) Late Cretaceous collision of the GAC with southern Mexico and Colombia is consistent with NE directions of maximum compression in rocks of this age range in southern Mexico and EW directions in Colombia as the GAC approached the Proto-Caribbean seaway; 2) Paleocene-Eocene collision of the GAC with the Bahamas platform in Cuba and Hispaniola and with the South American plate in Venezuela is consistent with CW rotations of stress directions in rocks of these ages in the northern Caribbean and CCW

  6. Late Quaternary environmental and climate history of Rauer Group, East Antarctica

    Berg, S.; Wagner, B.; Cremer, H.; Leng, M.J.; Melles, M.


    The Rauer Group is an archipelago in Prydz Bay, East Antarctica. The ice-free islands and the surrounding shallow marine areas provide valuable archives for the reconstruction of the late Pleistocene and Holocene environmental and climatic history of the region. Two sediment records from two marine

  7. Organic and inorganic geochemical aspects of Mediterranean Late Quaternary sapropels and Messinian evaporitic deposits

    Haven, H.L. ten


    This thesis describes the results of organic and inorganic geochemical investigations obtained for samples collected from the eastern Mediterranean sea floor and from Italy. The samples vary in age from the Late Miocene up to the Holocene. The environmental conditions prevailing during deposition of

  8. Calibrating Late Quaternary terrestrial climate signals: radiometrically dated pollen evidence from the southern Sierra Nevada, USA

    Litwin, Ronald J.; Smoot, Joseph P.; Durika, Nancy J.; Smith, George I.


    We constructed a radiometrically calibrated proxy record of Late Pleistocene and Holocene climate change exceeding 230,000 yr duration, using pollen profiles from two cores taken through age-equivalent dry lakes - one core having greater age control (via 230Th alpha mass-spectrometry) and the other having greater stratigraphic completeness. The better dated of these two serial pollen records (Searles Lake) served as a reference section for improving the effective radiometric age control in a nearby and more complete pollen record (Owens Lake) because they: (1) are situated ~90 km apart in the same drainage system (on, and immediately leeward of, the eastern flank of the Sierra Nevada), and (2) preserved strikingly similar pollen profiles and concordant sequences of sedimentological changes. Pollen assemblages from both lakes are well preserved and diverse, and document serial changes in Late Pleistocene and Holocene plant zone distribution and composition in the westernmost Great Basin; they consist of taxa now inhabiting montane forest, woodland, steppe, and desert-scrub environments. The studied core intervals are interpreted here to be the terrestrial equivalent of marine δ18O stages 1 through 9; these pollen profiles now appear to be among the best radiometrically dated Late Pleistocene records of terrestrial climate change known.

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

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


    This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage/MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a

  10. Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA

    Winkler, Tyler S.; van Hengstum, Peter J.; Horgan, Meghan C.; Donnelly, Jeffrey P.; Reibenspies, Joseph H.


    of enhanced limestone dissolution and cave formation (speleogenesis) during lower paleo water levels. Further work is still required to (a) determine whether precipitation of the ferromanganese deposits is inorganically or biologically mediated, (b) temporally constrain the emplacement history of the primary sedimentary styles, and (c) determine the full geographic extent of these sedimentary signals. However, these preliminary observations suggest that sedimentation in the inland underwater caves of northwestern Florida is related to Quaternary-scale hydrographic variability in the Apalachicola River drainage basin in response to broader ocean and atmospheric forcing.

  11. Vegetation and climate variability in tropical and subtropical South America during the late Quaternary

    Behling, H.


    Detailed palynological studies from different ecosystems in tropical and subtropical South America reflect interesting vegetation and climate dynamics, in particular during glacial and late glacial times. Records from ecosystems such as the Amazon rainforest, savanna, Caatinga, Atlantic rainforest, Araucaria forest and grasslands provide interesting insight of past climate variability. The influence of events such as Dansgaard-Oeschger, Heinnrich stadials, changes in the thermohaline circulation (THC) will be discussed. In particular the Younger Dryas (YD) period shows at different places distinct vegetational changes, revealing unexpected past climatic conditions.

  12. Paleoclimatic significance of Late Quaternary eolian deposition on the Piedmont and High Plains, Central United States

    Forman, Steven L.; Oglesby, Robert; Markgraf, Vera; Stafford, Thomas


    Presently stabilized dune systems on the piedmont of eastern Colorado and adjacent High Plains have been repeatedly re-activated during the past 20,000 years. Radiocarbon and thermoluminescence age estimates indicate eolian activity late in the last glacial cycle ca. 20,000-12,000 yr B.P. and subsequent episodes of dune reactivation at ca. 6000, 4500 and 1000 yr B.P. Pollen analysis from aggraded buried soil A horizons show a shift from grasses and shrubs to goosefoot, a disturbance indicator. The association of maximum goosefoot levels with the coarsest part of the buried A horizon immediately prior to burial by eolian sand indicates a substantial reduction in grass and dominance of shrubs with onset of eolian activity. The vegetation change and eolian depositional sequence indicates a reduction in plant coverage with regional drought, possibly augmented by bison grazing and surface heating effects. We infer an increase in summer monsoonal precipitation between 13,000 and 9000 yr B.P. reflecting a heightened land-to-sea temperature gradient associated with rising summer solar-insolation values and a meltwater cooled Gulf of Mexico. Dune reactivation in the middle and late Holocene appears to be independent of summer insolation values, but rather reflects a small (< 10°) easterly shift of the Bermuda High and western ridge aloft, difficult parameters to link to a cause and to resolve with climate models.

  13. The distribution of late-Quaternary woody taxa in northern Eurasia: evidence from a new macrofossil database

    Binney, Heather A.; Willis, Katherine J.; Edwards, Mary E.; Bhagwat, Shonil A.; Anderson, Patricia M.; Andreev, Andrei A.; Blaauw, Maarten; Damblon, Freddy; Haesaerts, Paul; Kienast, Frank; Kremenetski, Konstantin V.; Krivonogov, Sergey K.; Lozhkin, Anatoly V.; MacDonald, Glen M.; Novenko, Elena Y.; Oksanen, Pirita; Sapelko, Tatiana V.; Väliranta, Minna; Vazhenina, Ludmila


    We present a database of late-Quaternary plant macrofossil records for northern Eurasia (from 23° to 180°E and 46° to 76°N) comprising 281 localities, over 2300 samples and over 13,000 individual records. Samples are individually radiocarbon dated or are assigned ages via age models fitted to sequences of calibrated radiocarbon dates within a section. Tree species characteristic of modern northern forests (e.g. Picea, Larix, tree-Betula) are recorded at least intermittently from prior to the last glacial maximum (LGM), through the LGM and Lateglacial, to the Holocene, and some records locate trees close to the limits of the Scandinavian ice sheet, supporting the hypothesis that some taxa persisted in northern refugia during the last glacial cycle. Northern trees show differing spatio-temporal patterns across Siberia: deciduous trees were widespread in the Lateglacial, with individuals occurring across much of their contemporary ranges, while evergreen conifers expanded northwards to their range limits in the Holocene.

  14. Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

    Lu, H.; Mason, J.A.; Stevens, T.; Zhou, Y.; Yi, S.; Miao, X.


    This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long-held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well-dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11-8ka and 1-0ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post-depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. ?? 2011 John Wiley & Sons, Ltd.

  15. Late Quaternary climatic events and sea-level changes recorded by turbidite activity, Dakar Canyon, NW Africa

    Pierau, Roberto; Hanebuth, Till J. J.; Krastel, Sebastian; Henrich, Rüdiger


    The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan-Sahelian zone may have provided a source for this dust.

  16. Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

    Barnosky, Anthony D.; Lindsey, Emily L.; Villavicencio, Natalia A.; Bostelmann, Enrique; Hadly, Elizabeth A.; Wanket, James; Marshall, Charles R.


    Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems' large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway.

  17. Late Quaternary history of contourite drifts and variations in Labrador Current flow, Flemish Pass, offshore eastern Canada

    Marshall, Nicole R.; Piper, David J. W.; Saint-Ange, Francky; Campbell, D. Calvin


    Contourite drifts of alternating sand and mud, shaped by the Labrador Current, formed during the late Quaternary in Flemish Pass seaward of the Grand Banks of Newfoundland, Canada. The drifts preserve a record of Labrador Current flow variations through the last glacial maximum. A high-resolution seismic profile and a transect of four cores were collected across Beothuk drift on the southeast side of Flemish Pass. Downcore and lateral trends in grain size and sedimentation rate provide evidence that, between 16 and 13 ka, sediment was partitioned across Beothuk drift and the adjacent Flemish Pass floor by a strong current flow but, from 29 to 16 ka, sedimentation was more of a blanketing style, represented by draped reflections interpreted as being due to a weaker current. The data poorly resolve the low sedimentation rates since 13 ka, but the modern Labrador Current in Flemish Pass is the strongest it has been in at least the past 29 ka. Pre-29 ka current flow is interpreted based on reflection architecture in seismic profiles. A prominent drift on the southwestern side of Flemish Pass formed above a mid-Miocene erosion surface, but was buried by a mass-transport deposit after the penultimate glacial maximum and after drift deposition switched to eastern Flemish Pass. These findings illustrate the temporal complexity of drift sedimentation and provide the first detailed proxy for Labrador Current flow since the last glacial maximum.

  18. Land-sea duel in the late Quaternary at the mouth of a small river with high sediment yield

    Yang, Rick J.; Liu, James T.; Fan, Daidu; Burr, George S.; Lin, Hui-Ling; Chen, Ting-Ting


    The transition between sedimentary environments is compressed along land-sea boundaries in space and time. At river mouths on high standing islands, sedimentary records with high temporal resolutions formed as a result of large sediment loads and pervasive post-glacial sea level rise. Here we report on sediment core records covering the late Quaternary from the mouth of a small mountainous river in Taiwan. Results show that the study site was initially terrestrial under fluvial control. Beginning at about 10,000 yr BP (before present) the site became inundated by the rising sea and the environmental facies transitioned from a floodplain/incised river valley to a succession of marine environments, from shoreface to offshore. As the rising sea level came to a pause at 6000 yr BP, fluvial processes became dominant and sediments began to aggrade at the river mouth. After 4500 yr BP, the accumulated sediment began to prograde seaward, taking on the form of a river delta, and subtidal sand ridges appeared in the nearshore. This also introduces the deltaic development, which was limited by topography of the receiving basin. The chronology expresses the duel between sea level and fluvial processes that determined the depositional environments along the land-sea boundary at the study site.

  19. Late Quaternary Glacial Chronology in the Cordillera de Talamanca, Costa Rica, Investigated Using Cosmogenic Cl-36 Surface Exposure Dating

    Li, Y.; Potter, R.; Horn, S.; Orvis, K. H.


    The role of the tropics in past and future climate change has garnered significant attention in recent decades, but debate still exists over climate linkages between the tropics and the middle and high latitudes. Glaciers in tropical mountains are highly sensitive indicators of climate, and glacial landforms left behind by past glacier fluctuations provide key evidence of paleoclimate trends and their forcing mechanisms. We investigated late Quaternary glacial chronology from two glaciated valleys on the Chirripó massif in the Cordillera de Talamanca, Costa Rica. Previous studies in this highland have constrained the most recent deglaciation to 12.4-9.7 ka cal BP based on radiocarbon dates on basal sediments of glacial lakes within the cirque at the head of the Morrenas Valley. However, no studies have been conducted to constrain the ages of the moraines located down valley. We dated the formation ages of these moraines in the Morrenas and Talari valleys using cosmogenic Cl-36 surface exposure dating. Our results indicate a major glacial event ~21-18 ka, broadly synchronous with the global Last Glacial Maximum (LGM). Glaciers during this period advanced 3.2-3.4 km down valley on both sides of the Chirripó massif. Our ages also suggest periods of glacial retreat or standstills ~18-10 ka before complete deglaciation of this highland ~10 ka. These results provide insight into the timing and extent of glacial events in this tropical highland that is of critical importance for reconstructing regional and global climate patterns.

  20. The age measures and its layer sequence tratigraphy of Late Quaternary sediment in Lushan Dajiaochang of China

    Hu Dongsheng; Hu Rong; Li Xiaoyu; Hu Wenxuan; Wang Xulong; Tian Xingong; Liu Weiguo; Zhang Guowei


    Through the scientific investigation on Lushan for a long time,detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism,electronics spin resonance (ESR),36Cl and lumines-cence dating,etc. Corresponding to these data,it identified the paleomagnetic polarity events including Biwa-Ⅲevent (320 kaBP),Biwa-Ⅱevent (260 kaBP),Biwa-Ⅰevent (180 kaBP,scarcity due to the disturbance of the iron dish),Blake event (100 kaBP) and Laschamp event (20 kaBP,didn’t grow due to the activities of the surface), etc. Combined with the sequence stratigraphy,layer type characteristics and its sediment environment,the strati-graphic can be divided into 4 stages of development respectively:StageⅠis the climate period of glacial epoch (200~400 kaBP);stageⅡis the climate period of interglacial epoch (100~200 kaBP);stageⅢis the climate peri-od of periglacial epoch (10~100 kaBP);stageⅣis the climate period of postglacial epoch (0~10 kaBP).

  1. Clay mineral records of East Asian monsoon evolution during late Quaternary in the southern South China Sea

    LIU Zhifei; C. Colin; A. Trentesaux; D. Blamart


    High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 190 ka during late Quaternary from core MD01-2393 off the Mekong River in the southern South China Sea are reported to reconstruct a history of East Asian monsoon evolution.The dominating clay mineral components indicate a strong glacial-interglacial cyclicity, with high glacial illite, chlorite, and kaolinite contents and high interglacial smectites content. The provenance analysis indicates the direct input of clay minerals via the Mekong River drainage basin.Illite and chlorite derived mainly from the upper reach of the Mekong River, where physical erosion of meta-sedimentary rocks is dominant. Kaolinite derived mainly from active erosion of inhered clays from reworked sediments in the middle reaches. Smectites originated mainly through bisiallitic soils in the middle to lower reaches of the Mekong River. The smectites/(illite+chlorite)and smectites/kaolinite ratios are determined as mineralogical indicators of East Asian monsoon variations. Relatively high ratios occur during interglacials and indicate strengthened summer-monsoon rainfall and weakened winter-monsoon winds; relatively lower ratios happened in glacials, indicating intensified winter monsoon and weakened summer monsoon. The evolution of the summer and winter monsoons provides an almost linear response to the summer insolation of the Northern Hemisphere, implying an astronomical forcing of the East Asian monsoon evolution.

  2. Differences in Late Quaternary primary productivity between the western tropical Pacific and the South China Sea: Evidence from coccoliths

    Su, Xiang; Liu, Chuanlian; Beaufort, Luc; Barbarin, Nicolas; Jian, Zhimin


    Changes in Late Quaternary oceanic primary productivity in the western tropical Pacific were reconstructed using coccolith counts from the improved SYRACO system in piston core MD01-2386 retrieved from the Halmahera Sea near northwest New Guinea. The calculated primary productivity exhibits cycles on obliquity and precession timescales over the last 192 ka. There are marked differences between primary productivity records from the western tropical Pacific and the South China Sea (SCS), with the former being dominated by precession, and the latter showing all three Milankovitch cycles (eccentricity, obliquity and precession). Empirical Orthogonal Function (EOF) analyses reveal two significant EOF modes in the western tropical Pacific and SCS records. EOF-1 accounts for 38% of the total variance and exhibits obvious precessional cycles corresponding to Northern Hemisphere summer insolation, while EOF-2 accounts for 22% of the total variance and exhibits strong 41-kyr periodicity, suggesting different biological responses to hydroclimate changes in the two regions. A more complex hydroclimate regime influenced by the East Asian monsoon and the large contrast in regional topography and circulation during glacial cycles are considered to be the primary drivers of the stronger temporal variability in productivity in the SCS compared to the relatively stable western tropical Pacific.

  3. Climate-Induced Dynamics of Periglacial Landscapes in NE Siberia: The Western Edge of Beringia During the Late Quaternary

    Grosse, G.; Schirrmeister, L.; Siegert, C.; Meyer, H.; Andreev, A. A.; Kunitsky, V. V.; Derevyagin, A. Y.; Hubberten, H.


    Periglacial landscape dynamics have direct impacts on energy and matter cycles as well as ecosystems in large parts of the Arctic. Over the last decade, modern processes and past environments of periglacial landscapes in the Laptev Sea coastal lowlands were intensively studied within Russian and joint German- Russian research projects. A variety of palaeo-environmental records exists now for assessing the Late Quaternary dynamics of permafrost-dominated landscapes of this westernmost edge of Beringia. The main focus of this presentation is on the spatial and temporal dimensions of regional landscape changes in the Laptev Sea region induced by climatic change, especially by Holocene climate warming. For this purpose, we combine a variety of palaeo-environmental studies with remote sensing, terrain modelling, and GIS-based analyses of the modern landscape composition. We assess the landscape dynamics at the study site level and then draw conclusions for the whole region. Due to the low global sea level during the Late Weichselian cold stage, the Laptev Sea lowlands extended far on the shelf forming part of the unique continental environment of Western Beringia. The special periglacial environmental conditions of this period are recorded in frozen sediment sequences with palaeo-proxies ranging from lithology, ground ice, plant and animal fossils, to geomorphology. The Late Weichselian depositional environment there was characterized by ice-rich permafrost deposits (so-called Yedoma or Ice Complex formation) with up to 75 wt% absolute ice content. The Yedoma accumulated in lowland plains with polygonal tundra surrounding bedrock hills and mountain ridges. Additionally, the tundra plains were segmented by large river systems depositing fluvial sandy sediments. Major environmental changes affecting hydrology, geocryology, accumulation, and ecosystems in the region took place during the climate warming at the Late-Glacial Holocene transition. Within a short period in the

  4. Late Quaternary tectonics and active ground deformation in the Catania urban area (eastern Sicily): New constraints from a geological investigation

    Catalano, Stefano; Pavano, Francesco; Romagnoli, Gino; Tortorici, Giuseppe


    New surface and subsurface geological data on the Catania urban area, in eastern Sicily, are here illustrated by a detailed geological map of the city and by four significant cross-sections. Our study aims at defining the prolongation of the principal regional Late Quaternary tectonic features, beneath the city. The resulting geometry of the investigated structures completes the tectonic pictures of two different stages of deformation. The earlier structural association, ranging in age from 600 to 125 ka, consists of a transpressive dextral belt that include E-W oblique thrust ramp, located to the south and the north of the city respectively, connected by a wide NE-SW oriented anticline crossing the urban area. The younger structural association developed since the Late Pleistocene and includes a set of ENE-trending folds that originated at the hangingwall of a main thrust ramp running just beneath the old town (Catania Thrust Ramp). These contractional features have been active during the last 60 ka and their geometry is consistent with the active ground deformation observed by the available geodetic data (GPS vectors and DInSAR analyses). The entire set of the recent structures are bordered to the north by a dextral transfer zone, reactivating part of the previous E-W alignment, that now represents the tectonic boundary with the Mt. Etna Volcano transtensional domain. Our data suggest that the Catania Thrust Ramp could play a main role in the active deformation pattern of the region, thus representing a potential seismotectonic feature to be carefully investigated for the re-evaluation of the seismic hazard of the area.

  5. Late Quaternary speleogenesis and landscape evolution in a tropical carbonate island: Pango la Kuumbi (Kuumbi Cave, Zanzibar

    Nikos Kourampas


    Full Text Available Kuumbi Cave is one of a group of caves that underlie a flight of marine terraces in Pleistocene limestone in eastern Zanzibar (Indian Ocean. Drawing on the findings of geoarchaeological field survey and archaeological excavation, we discuss the formation and evolution of Kuumbi Cave and its wider littoral landscape. In the later part of the Quaternary (last ca. 250,000 years?, speleogenesis and terrace formation were driven by the interplay between glacioeustatic sea level change and crustal uplift at rates of ca. 0.10-0.20 mm/yr. Two units of backreef/reef limestone were deposited during ‘optimal’ (highest highstands, tentatively correlated with MIS 7 and 5; (mainly erosive marine terraces formed in these limestones in ‘suboptimal’ highstands. Kuumbi and other sub-terrace caves developed as flank margin caves, in the seaward portion of freshwater lenses during such ‘suboptimal’ highstands. Glacioeustacy-induced fluctuations of the groundwater table may have resulted in shifts from vadose (with deposition of well-developed speleothems to phreatic/epiphreatic conditions in these caves. At Kuumbi, Late Pleistocene (pre-20,000 cal. BP ceiling collapse initiated colluvial deposition near-entrance and opened the cave to large plants and animals, including humans. A phase of terminal Pleistocene human occupation ca. 18,500-17,000 cal. BP resulted in the deposition of a dense assemblage of Achatina spp. landsnails, alongside marine molluscs and mammal remains (including zebra, buffalo and other taxa now extinct on Zanzibar. The Holocene part of the cave stratigraphy near-entrance records phases of abandonment and intensified late Holocene human use.

  6. Late Quaternary delta evolution on an uplifted coastal area (Wadi Haida Sultanate of Oman, Arabian Peninsula)

    Quraishi, K. Al; Balushi, N. Al; Roepert, A.; Rupprechter, M.; Hoffmann, G.


    The Sultanate of Oman is situated in the Northeastern part of the Arabian Peninsula. The coastal morphology allows delineating areas of subsidence and uplift. The study area is located on the eastern shoreline facing the Indian Ocean. The coast is characterized by 6-7 wave cut terraces which are situated up to 400 m above present sea level. Whereas the higher - and therefore older - terraces are mainly erosional, the lower ones are depositional in style. We aim at quantifying the differential land movement along the coast (Rupprechter et al. 2012, Hoffmann et al. 2012 ). The study presented here aims at revealing the processes that resulted in the formation of the depositional terraces. Relevant processes are: (a) ongoing land uplift; (b) sea-level oscillations; (c) faulting. Historic evidence gave rise to the speculation of recent earthquake activity: the city of Qalhat, situated 7 km south of the study site was probably destroyed by an earthquake at the end of the 15th century (Musson 2009). The delta under investigation here formed at the mouth of the 15 km long Wadi Haida that drains the adjacent Selma Plateau (up to 2000 m high). The apex is situated 1.6 km from the present shoreline and the delta is some 2 km across. The delta sediments make up the lowermost terrace and are exposed along a cliff section. In the central part the cliff is 12 m high and cliff heights are lower to the North and South, reflecting the convex shape of the delta. The Quaternary delta deposits were deposited on top of an Eocene limestone. This formation is only observed in the northern part of the study area. In the southern part the formation is located below beach level, due to normal faulting. The lowermost unit related to the delta formation is a mudstone with in-situ coral reefs. The maximum thickness observed is 3 m. The coral reefs are capped by a 1.5 m thick layer of unconsolidated gravel. The sorting is very poor, individual boulders are up to 70 cm in diameter and angular

  7. Neotectonic impact and Palaeohydrology of Gaxun Nur Basin (NW China) during the Late Quaternary

    Hartmann, K.; Wünnemann, B.; Zhang, H.


    . The displacements of lake sediments at the southern margin of the modern Gaxun Nur basin imply a subsidence of at least 0.81m/1000 yrs since 25 kyr as a result of a pull-apart development due to the left stepping faults in a sinistral system. Frequently lakes are of tectonic origin. Their sediments and nearby catchment topography provide an excellent archive for reconstructing young tectonic movement. In this respect palaeohydrological reconstruction of lake catchments has to consider the occurrence of tectonic. In classical proxies of hydrological changes, both signals in the same archive interfere with each other. Complex system variables derived from large datasets by multivariate approaches are able to dissolve the processes (Hartmann & Wünnemann 2007). References Hartmann, K. (2003): Spätpleistozäne und holozäne Morphodynamik im nördlichen Gaxun Nur Becken, Innere Mongolei, NW China. Ph D-Thesis, Dept. of Geosciences, Freie Universitaet Berlin. Hartmann, K. & B. Wünnemann (2009): Hydrological changes and Holocene climate variations in NW China, inferred from lake sediments of Juyanze palaeolake by factor analyses. Quaternary International 194, 28-44. Hölz, S., Polag, D., Becken, M. Fiedler-Volmer, R., Zhang, HC., Hartmann,K., Burkhardt, H. (2007): Electromagnetic and Geoelectric Investigation of the Gurinai Structure, Inner Mongolia, NW China. Tectonophysics 445, (Issues 1-2): 26-48. Wünnemann, B., Hartmann, K., Altmann, N., Pachur, H.-J., Hambach, U. (2007): Glacial and Interglacial fingerprints from lake deposits in the Gobi Desert, NW China. In: Siroko, F., Clausen & M. Sanchez-Goni (Editors): The Climate of the Past Interglacials, pp. 323-348, Elevier, Amsterdam, N.Y..

  8. Global late Quaternary megafauna extinctions linked to humans, not climate change

    Sandom, Christopher James; Faurby, Søren; Sandel, Brody Steven


    by glacial–interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong...... of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based...... on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132 000 years BP and the late Holocene 1000 years BP, testing the relative roles played...

  9. The linkages among hillslope-vegetation changes, elevation, and the timing of late-Quaternary fluvial-system aggradation in the Mojave Desert revisited

    J. D. Pelletier


    Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late-Quaternary fluvial-system aggradation and incision. Perhaps the most well-constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode – i.e., the paleovegetation-change hypothesis (PVCH) – posits that a reduction in hillslope vegetation cover associated with the transition from Pleist...

  10. Geochemistry of late Quaternary tephra-sediment sequence from north-eastern Basin of Mexico (Mexico): implications to tephrochronology, chemical weathering and provenance

    Priyadarsi D. Roy; José Luis Arce; Rufino Lozano; M.P. Jonathan; Elena Centeno; Socorro Lozano


    A ca.30 m thick tephra-sediment sequence from the north-eastern Basin of Mexico (Pachuca subbasin, central Mexico) is investigated for stratigraphy and multi-element geochemistry to understand the tephrochronology, provenance and conditions of chemical weathering during Late Quaternary. Chemical compositions of tephra layers are compared with products from surrounding volcanic structures (Apan- Tezontepece, Acoculco, Huichapan, Sierra de las Cruces and Tláloc) in order to identify their sourc...

  11. Late Quaternary vegetation development and disturbance dynamics from a peatland on Mount Gorongosa, central Mozambique

    McWethy, David B.; Neumann, Frank H.; Steinbruch, Franziska; Ryan, Casey M.; Valsecchi, Verushka


    Few long-term climate and environmental records are available for southeast Africa where millennial scale shifts in the north-south position of the Intertropical Convergence Zone (ITCZ) and changes in Indian Ocean sea surface temperatures interact with local controls (e.g., fire, hydrology) to influence vegetation and ecosystem dynamics. Reconstruction of late-Pleistocene - Holocene environmental change from peat sediments obtained from Mount Gorongosa, central Mozambique, provides insight into vegetation, climate and disturbance interactions over the past c. 27 kyr. During the late Pleistocene, cool and wet climatic conditions supported Podocarpus forest and Ericaceae-heathland until drier conditions led to grassland expansion and a hiatus in peat deposition between c. 22.5 and 7.2 cal kBP. Increased temperatures and fire activity since c. 7.2 cal kBP led to further expansion of grasslands. Continued warming helped maintain grasslands and fostered a diverse mix of Podocarpus forest with a large number of subtropical trees and miombo woodland taxa (especially Brachystegia spp.) until regional land-use associated with the rise of Iron Age activity promoted an increase of disturbance related taxa over the last 1-2 millennia. Recent migration of people onto the Mount Gorongosa massif in the last fifty years are linked to an increase in fire activity that is unprecedented in the 27 kyr record, resulting in shifts in vegetation composition and structure. This long-term record of environmental change from central Mozambique highlights complex interaction between overlapping climatic influences and documents important vegetation transitions linked to millennial scale climatic controls, disturbance processes and more recent land-use change from a region where few records exist.

  12. The role of tectonics and climate in the late Quaternary evolution of a northern Amazonian River

    Cremon, Édipo Henrique; Rossetti, Dilce de Fátima; Sawakuchi, André de Oliveira; Cohen, Marcelo Cancela Lisboa


    The Amazon basin has most of the largest rivers of the world. However, works focusing the geological evolution of the trunk river or its tributaries have been only partly approached. The Branco River constitutes one of the main northern Amazonian tributaries. A previous work proposed that, before flowing southward into the Negro-Amazon Rivers, the Branco River had a southwest to northeast course into the Caribbean Sea. The present work aimed to establish if the proposed change in the course of this river is supported by morphological and sedimentological data. Other goals were to discuss the factors influencing river development and establish its evolution over time within the chronological framework provided by radiocarbon and optically stimulated luminescence dating. The work considered the entire course of the Branco River downstream of the Precambrian Guiana Shield, where the river presumably did not exist in ancient times. The river valley is incised into fluvial sedimentary units displaying ages between 100 and 250 ky old, which record active and abandoned channels, crevasse splay/levees, and point bars. The sedimentary deposits in the valley include two alluvial plain units as old as 18.7 ky and which intersects a Late Pleistocene residual megafan. These characteristics suggest that a long segment of the Branco River was established only a few thousand years ago. Together with several structural anomalies, these data are consistent with a mega-capture at the middle reach of this river due to tectonic reactivation in the Late Pleistocene. This integrated approach can be applied to other Amazonian tributaries to unravel how and when the Amazonian drainage basin became established.

  13. Late Quaternary Stratigraphy, Glacial Limits, and Paleoenvironments of the Marresale Area, Western Yamal Peninsula, Russia

    Forman, Steven L.; Ingólfsson, Ólafur; Gataullin, Valery; Manley, William; Lokrantz, Hanna


    Stratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula, Russia, yield new insight on ice-sheet dynamics and paleoenvironments for northern Eurasia. Field studies identify nine informal stratigraphic units from oldest to youngest (the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat, and Chum sand) that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of ca. 35,000 to 45,000 yr from Varjakha peat and silt that immediately overlies Kara diamicton place the glaciation >40,000 yr ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between ca. 35,000 and 12,000 cal yr B.P. associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of the Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10,000 yr, with local additions of the eolian Chum sand starting ca. 1000 yr ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees ca. 10,000 to 9000 cal yr old and indicates a >200-km shift northward of the treeline from the present limits, corresponding to a 2° to 4°C summer warming across northern Eurasia.

  14. Great Basin semi-arid woodland dynamics during the late quaternary

    Wigand, P.E.; Hemphill, M.L.; Sharpe, S.E. [Univ. and Community College System of Nevada, Reno, NV (United States)] [and others


    Semi-arid woodlands have dominated the middle elevations of Great Basin mountain ranges during the Holocene where subalpine woodlands prevailed during the Pleistocene. Ancient woodrat middens, and in a few cases pollen records indicate in the late Pleistocene and early Holocene woodland history lowered elevation of subalpine woodland species. After a middle Holocene retrenchment at elevations in excess of 500 meters above today, Juniper-dominated semi-arid woodland reached its late Holocene maximum areal extent during the Neoglacial (2 to 4 ka). These records, along with others indicate contracting semi-arid woodland after the Neoglacial about 1.9 ka. Desert shrub community expansion coupled with increased precariousness of wetland areas in the southern Great Basin between 1.9 and 1.5 ka coincide with shrinking wet-lands in the west-central and northern Great Basin. Coincident greater grass abundance in northern Great Basin sagebrush steppe, reaching its maximum between 1.5 and 1.2 ka, corresponds to dramatic increases in bison remains in the archaeological sites of the northern Intermontane West. Pollen and woodrat midden records indicate that this drought ended about 1.5 ka. Succeeding ameliorating conditions resulted in the sudden northward and downward expansion of pinon into areas that had been dominated by juniper during the Neoglacial. Maximum areal extent of pinon dominated semi-arid woodland in west-central Nevada was centered at 1.2 ka. This followed by 100 years the shift in dominance from juniper to pinon in southern Nevada semi-arid woodlands. Great Basin woodlands suffered from renewed severe droughts between .5 to .6 ka. Effectively wetter conditions during the {open_quotes}Little Ice Age{close_quotes} resulted in re-expansion of semi-arid woodland. Activities related to European settlement in the Great Basin have modified prehistoric factors or imposed new ones that are affecting woodland response to climate.

  15. Identifying the pollen of an extinct spruce species in the Late Quaternary sediments of the Tunica Hills region, south-eastern United States

    Luke Mander,; Jacklyn Rodriguez,; Pietra G. Mueller,; Jackson, Stephen T.; Surangi W. Punyasena,


    Late Quaternary fluvial deposits in the Tunica Hills region of Louisiana and Mississippi are rich in spruce macrofossils of the extinct species Picea critchfieldii, the one recognized plant extinction of the Late Quaternary. However, the morphology of P. critchfieldii pollen is unknown, presenting a barrier to the interpretation of pollen spectra from the last glacial of North America. To address this issue, we undertook a morphometric study of Picea pollen from Tunica Hills. Morphometric data, together with qualitative observations of pollen morphology using Apotome fluorescence microscopy, indicate that Picea pollen from Tunica Hills is morphologically distinct from the pollen of P. glauca, P. mariana and P. rubens. Measurements of grain length, corpus width and corpus height indicate that Picea pollen from Tunica Hills is larger than the pollen of P. mariana and P. rubens, and is slightly larger than P. glauca pollen. We argue that the morphologically distinctive Tunica Hills Picea pollen was probably produced by the extinct spruce species P. critchfieldii. These morphological differences could be used to identify P. critchfieldii in existing and newly collected pollen records, which would refine its paleoecologic and biogeographic history and clarify the nature and timing of its extinction in the Late Quaternary.

  16. Late quaternary vegetation of southern Isla Grande de Chiloñ, Chile

    Villagran, Carolina


    Late-glacial-Holocene forest history of southern Isla Chiloé (latitude 43°10' S) was reconstructed on the basis of pollen analysis in three profiles (Laguna Soledad, Laguna Chaiguata, Puerto Carmen). Prior to 12,500 yr B.P. pollen records are dominated by plant taxa characteristic of open habitats (Zone I). From 12,500 yr B.P. to the present, tree species predominate in the pollen records (Zones II-V). Between 12,500 and 9500 yr B.P. ombrophyllous taxa ( Nothofagus, Podocarpus nubigena. Myrtaceae, Fitzroya/Pilgerodendron, and Drimys) are frequent in all pollen diagrams, suggesting a wetter and colder climate than the present. Between 9000 and 5500 yr B.P. Valdivian forest elements, such as Nothofagus dombeyi type, Weinmannia, and Eucryphia/Caldcluvia, dominate, indicating a period of drier and warmer climate. From 5500 yr B.P. onward, the expansion of mixed North Patagonian-Subantarctic forest elements and the increased frequence of Tepualia suggest increased rainfall and temperatures oscillating around the modern values. The change from open to forest vegetation (ca. 12,500 yr B.P.) probably represents the most pronounced climatic change in the record and can be interpreted as the glacial-postglacial transition in the study area.

  17. Plant Functional Variability in Response to Late-Quaternary Climate Change Recorded in Ancient Packrat Middens

    Holmgren, C. A.; Potts, D. L.


    Responses of plant functional traits to environmental variability are of enduring interest because they constrain organism performance and ecosystem function. However, most inferences regarding plant functional trait response to climatic variability have been limited to the modern period. To better understand plant functional response to long-term climate variability and how adjustments in leaf morphology may contribute to patterns of species establishment, persistence, or extirpation, we measured specific leaf area (SLA) from macrofossils preserved in ancient packrat middens collected along the Arizona/New Mexico border, USA. Our record spanned more than 32,000 years and included six woodland and Chihuahuan Desert species: Berberis cf. haematocarpa, Juniperus cf. coahuilensis, Juniperus osteosperma, Larrea tridentata, Prosopis glandulosa and Parthenium incanum. We predicted that regional climatic warming and drying since the late Pleistocene would result in intraspecific decreases in SLA. As predicted, SLA was positively correlated with midden age for three of the six species (L. tridentata, J. osteosperma, B. cf. haematocarpa). SLA was also negatively correlated with December (L. tridentata, J. cf. coahuilensis) or June (B. cf. haematocarpa, J. osteosperma) insolation. A unique record of vegetation community dynamics, plant macrofossils preserved in packrat middens also represent a rich and largely untapped source of information on long-term trends in species functional response to environmental change.

  18. Late Quaternary activity along the Scorciabuoi Fault (Southern Italy as inferred from electrical resistivity tomographies

    A. Loperte


    Full Text Available The Scorciabuoi Fault is one of the major tectonic structures affecting the Southern Apennines, Italy. Across its central sector, we performed several electrical resistivity tomographies with different electrode spacing (5 and 10 m and using a multielectrode system with 32 electrodes. All tomographies were acquired with two different arrays, the dipole-dipole and the Wenner-Schlumberger. We also tested the different sensitivity of the two arrays with respect to the specific geological conditions and research goals. Detailed geological mapping and two boreholes were used to calibrate the electrical stratigraphy. In all but one tomography (purposely performed off the fault trace, we could recognise an abrupt subvertical lateral variation of the main sedimentary bodies showing the displacement and sharp thickening of the two youngest alluvial bodies in the hanging-wall block. These features are interpreted as evidence of synsedimentary activity of the Scorciabuoi Fault during Late Pleistocene and possibly as recently as Holocene and allow accurate location of the fault trace within the Sauro alluvial plain.

  19. Late Quaternary landscape evolution of northeastern Amazonia from pollen and diatom records



    Full Text Available The main goal of this study was to reconstruct the Late Pleistocene-Holocene floristic composition in an area of the northern Brazilian Amazonia, comparing the results with other Amazonian localities in order to discuss the factors that have influenced phytophysiognomic changes over this time period. The work in eastern Marajó Island at the mouth of the Amazonas River was approached based on analysis of 98 pollen and diatom samples from core data distributed along a proximal to distal transect of a paleoestuarine system. The results indicated high concentration of Rhizophora, associated with arboreal pollen grains typical of the modern Amazonian rainforest during the last 40,000 cal yrs BP. Pollen composition also included wetland herbs. Diatoms were dominated by marine and fresh water taxa. Wetland forest, mangrove and, subordinately herbs remained constant during most of the latest Pleistocene-early/middle Holocene. At 5,000 cal yrs BP, there was a distinguished change from forest and mangrove to wet grassland savanna due to sea level fluctuation. As marine influence decreased, the estuary gave rise to fresh water lacustrine and swamp environments, with establishment of herbaceous campos. A main conclusion from this study is that solely the occurrence of herbaceous savanna can not be used as a definitive indicator of past dry climates in Amazonian areas.

  20. Late quaternary environmental changes in the upper Las Vegas valley, Nevada

    Quade, Jay


    Five stratigraphic units and five soils of late Pleistocene to Holocene age crop out in dissected badlands on Corn Creek Flat, 30 km northwest of Las Vegas, Nevada, and at Tule Springs, nearer to Las Vegas. The record is dominantly fluvial but contains evidence of several moister, marsh-forming periods: the oldest (Unit B) dates perhaps to the middle Wisconsin, and the more widespread Unit D falls between 30,000 and 15,000 yr B.P. Unit D therefore correlates with pluvial maximum lacustrine deposits elsewhere in the Great Basin. Standing water was not of sufficient depth or extent during either period to form lake strandlines. Between 14,000 and 7200 yr B.P. (Unit E), standing surface water gradually decreased, a trend also apparent in Great Basin pluvial lake chronologies during the same period. Groundwater carbonate cementation and burrowing by cicadas (Cicadae) accompany the moist-phase units. After 7200 yr B.P., increased wind action, decreased biotic activity, and at least 25 m of water-table lowering accompanied widespread erosion of older fine-grained deposits. Based on pack-rat midden and pollen evidence, this coincides with major vegetation changes in the valley, from sagebrush-dominated steppe to lower Mohave desertscrub.

  1. Late Quaternary landscape evolution of northeastern Amazonia from pollen and diatom records.

    Castro, Darciléa F; De Oliveira, Paulo E; Rossetti, Dilce F; Pessenda, Luiz C R


    The main goal of this study was to reconstruct the Late Pleistocene-Holocene floristic composition in an area of the northern Brazilian Amazonia, comparing the results with other Amazonian localities in order to discuss the factors that have influenced phytophysiognomic changes over this time period. The work in eastern Marajó Island at the mouth of the Amazonas River was approached based on analysis of 98 pollen and diatom samples from core data distributed along a proximal to distal transect of a paleoestuarine system. The results indicated high concentration of Rhizophora, associated with arboreal pollen grains typical of the modern Amazonian rainforest during the last 40,000 cal yrs BP. Pollen composition also included wetland herbs. Diatoms were dominated by marine and fresh water taxa. Wetland forest, mangrove and, subordinately herbs remained constant during most of the latest Pleistocene-early/middle Holocene. At 5,000 cal yrs BP, there was a distinguished change from forest and mangrove to wet grassland savanna due to sea level fluctuation. As marine influence decreased, the estuary gave rise to fresh water lacustrine and swamp environments, with establishment of herbaceous campos. A main conclusion from this study is that solely the occurrence of herbaceous savanna can not be used as a definitive indicator of past dry climates in Amazonian areas.

  2. Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

    Reynolds, R.L.; Reheis, M.C.; Neff, J.C.; Goldstein, H.; Yount, J.


    in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

  3. Late Quaternary deglacial history of the Mérida Andes, Venezuela

    Stansell, Nathan D.; Abbott, Mark B.; Polissar, Pratigya J.; Wolfe, Alexander P.; Bezada, Maximiliano; Rull, Valentí


    Radiocarbon-dated sediment cores from seven lakes and two bogs spanning the Cordillera de Mérida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22 750 and 19 960 cal. yr BP. On the wetter southeastern side of the Cordillera de Mérida, glaciers had significantly retreated by 15 700 cal. yr BP, followed by several minor glacial advances and retreats between 14 850 and 13 830 cal. yr BP. At least one major glacial readvance occurred between 13 830 and 10 000 cal. yrBP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Mérida records initial glacial retreat by 14240cal.yrBP. Multiple sites on both sides of the Mérida Andes record a further phase of extensive deglaciation approximately 10000cal.yrBP. However, the north-northwest facing Mucubají catchment remained partially glaciated until ca. 6000cal.yrBP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter-hemispheric deglacial lag in the northern tropics of the order of two thousand years.

  4. A late Quaternary record of seasonal sea surface temperatures off southern Africa

    Loftus, E.; Sealy, J.; Leng, M. J.; Lee-Thorp, J. A.


    The southern Cape coastal region is important for understanding both the behavioural history of modern humans, and regional and global climate dynamics, because it boasts a long archaeological record and occupies a key geographical location near the intersection of two major oceans. The western boundary Agulhas Current, implicated in global heat exchange dynamics, is an important modulator of southern African climates and yet we understand its past behaviour only broadly as the Current itself scours the coastal shelf and marine sediment core records necessarily provide little detail. Numerous archaeological sites from both the late Pleistocene and Holocene provide the opportunity for reconstruction of near-shore seasonal SST records, which respond both to localized wind-driven upwellings and Agulhas temperature shifts, corresponding in turn with terrestrial precipitation trends in the near-coastal and summer rainfall regions. Here we present a record of seasonal SSTs extending over MIS5, MIS4, and the Holocene, from serial δ18O measurements of a single gastropod species, Turbo sarmaticus. The results show that mean SST shifts accord well with global SST trends, although they are larger than those recorded in the Agulhas Current from coarser-scale marine sediment records. Comparison with a record of Antarctic sea-ice suggests that annual SST amplitude responds to Antarctic sea-ice extent, reflecting the positioning of the regional wind systems that drive upwelling dynamics along the coast. Thus, near-shore SST seasonality reflects the relative dominance of the westerly and easterly wind systems. These data provide a new climate archive for an important but understudied climate system.

  5. Isotopic and geochemical signatures of Late Quaternary sediments in the Fram Strait area

    Maccali, J.; Hillaire-Marcel, C.; Carignan, J.; Reisberg, L. C.


    Arctic freshwater/sea-ice export through Fram Strait contributes to the Atlantic Meridional Overturning Circulation (AMOC) and acts as a trigger or feedback mechanism in the climate/ocean system. Here, geochemical and isotopic analyses of cores raised along a transect through the Strait are used to document changes in sediment sources and sea-ice transport since the LGM. Radiogenic isotope and elemental data in leachable fractions vs residues are used as proxies for water mass vs sediment source signatures, respectively. Unequivocal linkage between leachates and water-mass properties are illustrated by the anthropogenic-lead overprint in leachates from core-top sediments. Below this polluted layer, leachates and residues from late Holocene sediments carry distinct geochemical signatures E and W of the Strait. Eastward, below the North Atlantic Water (NAW) mass flowing northward, Th/Zr and Th/Pb concentration ratios ranging 0.040-0.041 and 0.85-0.90, respectively, label GIN seas and western Spitzbergen sediment-sources. Westward, below outflowing Arctic waters and sea-ice routes, these ratios range 0.032-0.035 and 0.72-0.75, respectively, and label NE Greenland and Arctic sediment sources. Pb-isotopes exhibit a similar pattern with sediment carrying a mixed Variscan-Pan-African signature below the NAW route, and a mixture of less radiogenic sources in sediments deposited below the outflowing Arctic waters and sea-ice route. Back in time, divergent trends in some radiogenic isotope values are recorded westward, below the outflowing Arctic waters and sea-ice route. Whereas isotopic properties of residues suggest sedimentary supplies originating from the Canadian Arctic and/or the NW Greenland margin, lead data from leachates bear an "Arctic Ocean" signature illustrating variable relative contributions from the Russian vs Canadian ice-margins and/or rivers. During deglacial times, a significant change in sedimentary supplies is recorded at ~ 14 ka along with some

  6. Late Quaternary hydrology in North Africa and the Near East (Hans Oeschger Medal Lecture)

    Gasse, Françoise


    The present-day arid-semiarid belt from North Africa to West Asia has experienced huge hydrological changes together with a long history of human civilisations. This belt straddles the boundary between a temperate domain (winter rains linked to the mid-latitude Westerlies), and a subtropical one (rare monsoonal summer precipitation). What are the timing and direction of major hydrological changes in these two domains ? How does the transitional zone migrate through time, and why ? How did human societies respond to changes in water availability ? These questions are addressed using records illustrating both long and short-term environmental changes. At the glacial-interglacial time scale, hydrological changes broadly follow the orbitally-induced Northern Hemisphere summer insolation, but with different regional expressions. In the winter rain domain, the best-dated records come from southern Levant : stable isotope records from speleothems in Israel (120-230 ka) show a remarkable consistency with those from the Eastern Mediterranean Sea(1,2), but the prominant role of rainfall amount or of moisture source isotopic composition on inland records is still debated (1-4); lake-level reconstructions in the Lisan-Dead Sea basin during the past 70 ka demonstrate higher winter rains during the last glacial period than during the Holocene (4,5). However, a new multi-proxy lacustrine record (230 ka) from northern Levant (Yammoûneh, Lebanon) shows relatively wet environments during interglacial periods(6,7), suggesting temporal changes in the NS climatic gradients over the Levantine region. Extratropical rainfalls apparently remained predominant over northern Sahara, with a major period of aquifer recharge during the Late Pleistocene(8). Conversely, south of about 25-22° N, the subtropical deserts experienced pluvial periods during interglacials, including the remarkable early-Mid Holocene wetting of the Saharan heart(8). Older pluvial periods, precisely dated in speleothems

  7. Late quaternary floodplain sedimentation along the Pomme de Terre River, southern Missouri

    Brakenridge, G. Robert


    New cross sections and dates from along the Pomme de Terre River clarify the complex local history of valley development and floodplain sedimentation. The observed history begins with a series of ancient bedrock strath terraces that record past bedrock valley positions at 15.5 to more than 58 m above the modern bedrock floor. Each strath is capped by 1-2 m of channel gravel and sand permeated by red clay. Sometime previous to ca. 140,000 yr B.P., a much lower bedrock valley only about 5-6 m above the modern level was excavated. By 140,000 yr B.P., accumulation of red and gray mottled silty clay had commenced, and had reached to 8.5 m above the modern floodplain before 48,900 ± 900 14C yr B.P. Sometime between ca. 49,000 and 45,000 14C yr B.P., erosion caused abandonment of an oxbow meander, and lowered the bedrock valley to about its present depth. Younger yellowish-red and gray mottled silty clay alluvium then began accumulating. This mid-Wisconsinan fill reached to 2.5 m above the modern floodplain sometime before 31,800 ± 1340 14C yr B.P., at which time another erosional phase was in progress. A late Wisconsinan olive clay accumulated between 27,480 ± 1950 and ca. 23,000 14C yr B.P., followed by approximate stability until 13,550 ± 400 14C yr B.P. After stability, an erosional episode began, but by 10,200 ± 330 14C yr B.P., deposition of a distinctive brown clayey silt was underway. This early Holocene fill reached to about the same level as the mid-Wisconsinan fill by 8100 ± 140 14C yr B.P. Erosion occurred between this date and 7490 ± 170 14C yr B.P., but the former floodplain level was rapidly reattained, and was apparently stable until ca. 5000 14C yr B.P. Finally, erosional unconformities and 17 dates from the brown clayey silt, and from younger grayish-brown silty sand underlying the modern floodplain, record subsequent episodes of floodplain erosion at ca. 5000, 2900, 1500 and 350 14C yr B.P. The timing of Pomme de Terre floodplain sedimentary

  8. Faulted terrace risers place new constraints on the late Quaternary slip rate for the central Altyn Tagh fault, northwest Tibet

    Gold, R.D.; Cowgill, E.; Arrowsmith, J.R.; Chen, X.; Sharp, W.D.; Cooper, K.M.; Wang, X.-F.


    The active, left-lateral Altyn Tagh fault defines the northwestern margin of the Tibetan Plateau in western China. To clarify late Quaternary temporal and spatial variations in slip rate along the central portion of this fault system (85??-90??E), we have more than doubled the number of dated offset markers along the central Altyn Tagh fault. In particular, we determined offset-age relations for seven left-laterally faulted terrace risers at three sites (Kelutelage, Yukuang, and Keke Qiapu) spanning a 140-km-long fault reach by integrating surficial geologic mapping, topographic surveys (total station and tripod-light detection and ranging [T-LiDAR]), and geochronology (radiocarbon dating of organic samples, 230Th/U dating of pedogenic carbonate coatings on buried clasts, and terrestrial cosmogenic radionuclide exposure age dating applied to quartz-rich gravels). At Kelutelage, which is the westernmost site (37.72??N, 86.67??E), two faulted terrace risers are offset 58 ?? 3 m and 48 ?? 4 m, and formed at 6.2-6.1 ka and 5.9-3.7 ka, respectively. At the Yukuang site (38.00??N, 87.87??E), four faulted terrace risers are offset 92 ?? 12 m, 68 ?? 6 m, 55 ?? 13 m, and 59 ?? 9 m and formed at 24.2-9.5 ka, 6.4-5.0 ka, 5.1-3.9 ka, and 24.2-6.4 ka, respectively. At the easternmost site, Keke Qiapu (38.08??N, 88.12??E), a faulted terrace riser is offset 33 ?? 6 m and has an age of 17.1-2.2 ka. The displacement-age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8-12 mm/yr. However, additional analysis is required to test how much temporal variability in slip rate is permitted by this data set. ?? 2011 Geological Society of America.

  9. Evolution and variation of the Tsushima warm current during the late Quaternary: Evidence from planktonic foraminifera, oxygen and carbon isotopes

    LI TieGang; SUN RongTao; ZHANG DeYu; LIU ZhenXia; LI Qing; JIANG Bo


    The evolution and variation history of the Tsushima warm current during the late Quaternary was reconstructed based on the quantitative census data of planktonic foraminiferal fauna, together with oxygen and carbon isotope records of mixed layer dweller G ruber and thermocline dweller N. dutertrei in piston core CSH1 and core DGKS9603 collected separately from the Tsushima warm current and the Kuroshio dominated area. The result showed that the Tsushima warm current vanished in the Iowstand period during 40-24 cai ka BP, while the Kuroshio still flowed across the Okinawa Trough, arousing strong upwelling in the northern Trough. Meanwhile, the influence of freshwater greatly increased in the northern Okinawa Trough, as the broad East China Sea continental shelf emerged. The freshwater reached its maximum during the last glacial maximum (LGM), when the upwelling obviously weakened for the lowest sea-level and the depression of the Kuroshio. The modern Tsushima warm current began its development since 16 cai ka BP, and the impact of the Kuroshio increased in the middle and northern Okinawa Trough synchronously during the deglaciation and gradually evolved as the main water source of the Tsushima current. The modern Tsushima current finally formed at about 8.5 cai ka BP,since then the circulation structure has been relatively stable. The water of the modern Tsushima current primarily came from the Kuroshio axis. A short-term wiggle of the current occurred at about 3 cai ka BP, probably for the influences from the enhancement of the winter monsoon and the depression of the Kuroshio. The cold water masses greatly strengthened during the wiggle.

  10. Late Quaternary development of the Croatan Beach Ridge Complex, Bogue Sound, Bogue Banks, NC, USA and implications for coastal evolution

    Lazar, Kelly B.; Mallinson, David J.; Culver, Stephen J.


    Foraminiferal, sedimentological, geophysical, and geochronologic data were utilized to elucidate the late Quaternary geologic development of the Croatan Beach Ridge Complex (CBRC), Bogue Sound, and Bogue Banks, North Carolina, USA. The CBRC is a relict beach ridge feature located on the mainland. It is separated from the modern barrier island, Bogue Banks, by Bogue Sound. Seventeen cores along shore-normal and shore-parallel transects provided material for sedimentologic and foraminiferal analysis and resulted in the recognition of seven depositional facies representing a variety of coastal depositional environments. Chronologic and depositional facies data suggest the CBRC was initiated during MIS 5a and rapid southward progradation produced a cape structure. Eolian reactivation of the upper sand of the CBRC occurred during the last glacial maximum (∼18 ka). The age of flood tide delta deposits in Bogue Sound suggests that the Holocene barrier island, Bogue Banks, had formed by ∼6 ka. Shoreface ravinement resulted in a shoreface landward of the present shoreline by ∼3.5 ka. Seaward and westward spit progradation of Bogue Banks began ∼1.7 ka and continued to ∼1.3 ka. Normal marine salinity conditions were present in Bogue Sound ∼1.1 ka, suggesting removal of at least the narrowest parts of the barrier island, coeval with a previously documented segmentation of the southern Outer Banks barrier islands. Previous work has linked this segmentation to climate warming and increased tropical storm activity during the Medieval Climate Anomaly. This study illustrates the complex response of this coastal system to Pleistocene and Holocene sea-level and climate change over two major sea-level cycles. In particular, the regional geomorphology during MIS5a and the Holocene sea-level highstand differ significantly and this, in large part, was controlled by the antecedent geologic framework, resulted in the contrasting more localized coastal geomorphic response.

  11. Vegetation evolution on the central Chinese Loess Plateau since late Quaternary evidenced by elemental carbon isotopic composition

    ZHOU Bin; SHEN ChengDe; ZHENG HongBo; ZHAO MeiXun; SUN YanMin


    There are many controversial issues in loess studies such as natural vegetation types on the Chinese Loess Plateau during the historical periods and the spatial and temporal evolution of C3/C4 plants.Elemental carbon isotopic composition (δ13Cec) in the loess section may offer new evidence for these problems. Elemental carbon (EC) is produced by incomplete combustion of vegetation, and its carbon isotopic composition has a very small difference from that of the formal vegetation, then δ13Cec can be used as a record to recover the changes of vegetation. Elemental carbon was extracted by applying the oxidation method from the loess-paleosol sequence in the central Chinese Loess Plateau, and its carbon isotope composition was analyzed by the isotope mass spectrometer. The results showed that the vegetation in this region was a mixed type of C3 and C4 plants, dominated with C3 plants in most of the time. Since late Quaternary, C3/C4 plants may not follow a simple glacial-interglacial cycle mode on the Chinese Loess Plateau, but showing fluctuations. C3 plants increased gradually in L4 period, and more C3 plants occurred during S3 period, and C4 plants increased again during L3-L2 periods, after that, C3plants dominated again during S1-S0 periods. During periods of paleosol development, C3 plants were abundant in S3 and S1, and there were more C4 plants in S2 and S0. During periods of loess sedimentation, there were more C3 plants in L4 and L1, and there were more C4 plants in L3 and L2. On the orbital timescale, the vegetation variations revealed by δ13Cec record are consistent with the results of pollen data and also similar to the results obtained by organic carbon isotopic composition since the last glacial period.

  12. Late Quaternary vegetational and climate dynamics in northeastern Brazil, inferences from marine core GeoB 3104-1

    Behling, Hermann; W. Arz, Helge; Pätzold, Jürgen; Wefer, Gerold


    Late Quaternary paleoenvironments from northeastern (NE) Brazil have been studied by pollen analysis of marine sediment. The studied core GeoB 3104-1 (3°40' S, 37°43' W, 767 m b.s.l.) from the upper continental slope off NE Brazil is 517 cm long and >42,000 14C yr BP old. Chronological control was obtained by 12 radiocarbon (AMS) dates from individuals of the foraminiferal species Globigerinoides sacculifer. Modern pollen analogs were received from 15 river, lake and forest soil surface samples from NE Brazil. Marine pollen dates indicate the predominance of semi-arid caatinga vegetation in NE Brazil during the recorded period between >42,000 and 8500 14C yr BP. The increased fluvial input of terrigenous material, with high concentrations of pollen and specially fern spores, into the marine deposits, about 40,000, 33,000 and 24,000 14C yr BP and between 15,500 and 11,800 14C yr BP, indicate short-term periods of strong rainfall on the NE Brazilian continent. The expansion of mountain, floodplain and gallery forests characterize the interval between 15,500 and 11,800 14C yr BP as the wettest recorded period in NE Brazil, which allowed floristic exchanges between Atlantic rain forest and Amazonian rain forest, and vice versa. The paleodata from core GeoB 3104-1 confirm the, in general, dry pre-Last Glacial Maximum (LGM) and LGM conditions and the change to wet Lateglacial environments in tropical South America. The annual movement of the intertropical convergence zone over NE Brazil, the strong influence of the Antarctic cold fronts and changes of the high-pressure cell over the southern Atlantic, may explain the very wet Lateglacial period in NE Brazil. The documented NE Brazilian short-term signals correlate with the documented Dansgaard-Oeschger cycles and Heinrich events from the northern Hemisphere and suggest strong teleconnections.

  13. Evolution and variation of the Tsushima warm current during the late Quaternary: Evidence from planktonic foraminifera, oxygen and carbon isotopes


    The evolution and variation history of the Tsushima warm current during the late Quaternary was reconstructed based on the quantitative census data of planktonic foraminiferal fauna, together with oxygen and carbon isotope records of mixed layer dweller G. ruber and thermocline dweller N. dutertrei in piston core CSH1 and core DGKS9603 collected separately from the Tsushima warm current and the Kuroshio dominated area. The result showed that the Tsushima warm current vanished in the lowstand period during 40―24 cal ka BP, while the Kuroshio still flowed across the Okinawa Trough, arousing strong upwelling in the northern Trough. Meanwhile, the influence of freshwater greatly increased in the northern Okinawa Trough, as the broad East China Sea continental shelf emerged. The freshwater reached its maximum during the last glacial maximum (LGM), when the upwelling obviously weakened for the lowest sea-level and the depression of the Kuroshio. The modern Tsushima warm current began its development since 16 cal ka BP, and the impact of the Kuroshio increased in the middle and north- ern Okinawa Trough synchronously during the deglaciation and gradually evolved as the main water source of the Tsushima current. The modern Tsushima current finally formed at about 8.5 cal ka BP, since then the circulation structure has been relatively stable. The water of the modern Tsushima cur- rent primarily came from the Kuroshio axis. A short-term wiggle of the current occurred at about 3 cal ka BP, probably for the influences from the enhancement of the winter monsoon and the depression of the Kuroshio. The cold water masses greatly strengthened during the wiggle.

  14. Physical data of soil profiles formed on late Quaternary marine terraces near Santa Cruz, California

    Munster, Jennie; Harden, Jennifer W.


    The marine terraces in and around Santa Cruz, California, represent a set of well-preserved terraces formed as a product of geology, sea level, and climate. A marine terrace begins as a wave cut platform. Eustatic sea level changes, seacliff erosion, and tectonic uplift work together to generate marine terraces. "When a wave-cut platform is raised (due to tectonic activity) above sea level and cliffed by wave action it becomes a marine terrace" (Bradley, 1957, p. 424). During glacial periods, eustatic sea level is estimated to have dropped by 150 meters (Fairbanks, 1989). Cliff retreat measured from aerial photographs between 1930 and 1980 vary from 0.0 to 0.2 m yr–1 (Best and Griggs, 1991). Estimates of uplift rates along the Santa Cruz coastline vary from 0.10 to 0.48 m kyr–1 (Bradley and Griggs, 1976; Weber and others, 1999). Uplift mechanisms include coseismic uplift associated both with a reverse component of slip on the steeply SW dipping Loma Prieta fault in the restraining bend of the San Andreas Fault and a small component of reverse slip on the steeply SE dipping San Gregorio fault (Anderson and Menking 1994). Previous work studying physical properties on these terraces include Pinney and others (in press) and Aniku (1986) and Bowman and Estrada (1980). Sedimentary deposits of the marine terraces are a mixture of terrestrial and marine sediments but generally consist of a sheet of marine deposits overlying the old platform and a wedge of nonmarine deposits banked against the old sea cliff (Bradley, 1957). Bedrock underlying the terraces in the Santa Cruz area is generally either Santa Margarita Sandstone or Santa Cruz Mudstone. The Santa Margarita Sandstone represents an upper Miocene, transgressive, tidally dominated marine-shelf deposit with crossbedded sets of sand and gravel and horizontally stratified and bioturbated invertebrate-fossils beds (Phillips, 1990). The siliceous Santa Cruz Mudstone, of late Miocene age, conformably overlies the Santa

  15. Late Quaternary paleoearthquakes along the northern segment of the Nantinghe fault on the southeastern margin of the Tibetan Plateau

    Sun, Haoyue; He, Honglin; Wei, Zhanyu; Shi, Feng; Gao, Wei


    The strong earthquake behaviors of faults are significant for learning crustal deformation mechanisms and for assessing regional seismic risk. To date, faults that bound tectonic blocks have attracted considerable concern and many studies; however, scant attention has been paid to faults within blocks that can also host devastating earthquakes. The Nantinghe fault is a left-lateral strike-slip fault within the Southwestern Yunnan Block, and it slips at ∼4 mm/yr suggesting strong activity in the late Quaternary. Nevertheless, no earthquake greater than 6 has ever been recorded along it, except for the 1941 M ∼7 earthquake near the Myanmar-China border region. In contrast, many earthquakes have occurred in the near region, delineating a seismic gap near the Nantinghe fault. Although several studies have been conducted upon it, the activity of its northern segment is confusing, and whether this fault segment has loaded sufficient stress to fail remains debatable. Furthermore, previous work failed to conduct any paleoseismological studies bringing out great uncertainty in learning its activity and faulting behavior, as well as in assessing the regional seismic risk. To solve these problems, we mapped the fault traces utilizing high-resolution satellite images and aerial photographs, and conducted three paleoseismological trenches along the northern segment of the Nantinghe fault. The trench excavations revealed a ∼45,000-year incomplete paleoearthquake history and confirmed that this fault segment has been active since the late Pleistocene but was not ruptured during the 1941 earthquake. Additionally, at least five paleoearthquakes are identified with their respective age ranges of before 39,030 BCE; 38,500-37,220 BCE; 28,475-5445 BCE; 3535 BCE-800 CE; and 1320-1435 CE based on radiocarbon dating. Among the paleoearthquakes, the latest is suggested to have generated a surface rupture much longer than 14 km with a magnitude likely up to Ms 7.0. Furthermore, based

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

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


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

  17. Late Quaternary geomorphic history of a glacial landscape - new sedimentary and chronological data from the Cordillera de Cochabamba (Bolivia)

    May, J.-H.; Preusser, F.; Zech, R.; Ilgner, J.; Veit, H.


    Throughout the Central Andes, glacial landscapes have long been used for the reconstruction of Late Quaternary glaciations and landscape evolution. Much work has focused on the Andes in Peru, Chile and the Bolivian Altiplano, whereas relatively little data has been published on glaciation history in the eastern Andean ranges and slopes. Even less is known with regard to the postglacial evolution of these glacial landscapes. In the Cordillera de Cochabamba (Bolivia), local maximum advances probably peaked around 20-25 ka BP and were followed by significant readvances between ~12-16 ka BP. This generally points to temperature controlled maximum glacial advances along the humid eastern slopes of the Central Andes, which is supported by glacier-climate-modelling studies. However, most studies include only marginal information with regard to the complex geomorphic and sedimentary situation in the Cordillera de Cochabamba. Furthermore, the chronological results are afflicted with several methodological uncertainties inherent to surface exposure dating and call for application of alternative, independent age dating methods. Therefore this study aims at i) documenting and interpreting the complex glacial geomorphology of the Huara Loma valley in the Cordillera de Cochabamba (Bolivia), ii) analyzing the involved units of glacial sediments, and iii) improving the chronological framework by applying optically stimulated luminescence (OSL) and radiocarbon dating (14C). For this purpose, geomorphic mapping was combined with field documentation of sedimentary profiles. The involved sediments were subject to geochemical and mineralogical analysis in order to deduce information on their erosional and weathering histories. In addition, the interpretation of OSL ages from glacial and proglacial sediments integrated several methodological procedures with regard to sample preparation and statistical analysis of the measurements in order to increase the degree of confidence. These

  18. Large-scale avulsion of the late Quaternary Sutlej river in the NW Indo-Gangetic foreland basin

    Singh, Ajit; Gupta, Sanjeev; Sinha, Rajiv; Carter, Andrew; Thomsen, Kristina J.; Mark, Darren F.; Buylaert, Jan-Pieter; Mason, Philippa J.; Murray, Andrew S.; Jain, Mayank; Paul, Debajyoti


    River avulsions are important processes in the spatial evolution of river systems in tectonically active sedimentary basins as they govern large-scale patterns of sediment routing. However, the pattern and timing of avulsions in large river systems are poorly documented and not well understood. Here we document late Quaternary paleo-river channel changes in the Indo-Gangetic basin of northwest India. Using a combination of satellite remote sensing and detailed sediment coring, we analyse the large-scale planform geometry, and detailed sedimentary and stratigraphic nature of a major fluvial sedimentary deposit in the shallow subsurface. This sediment body records aggradation of multiple fluvial channel fills. Satellite remote sensing analysis indicates the trace of the buried channel complex and demonstrates that it exists in region of the Himalayan foreland where no major rivers are currently present. Thus it records the former drainage pathway of a major river, which has since been diverted. We use optically stimulated luminescence dating techniques to develop an age model for the stratigraphic succession and hence constrain the timing of river channel existence and diversion. Provenance analysis based on U-Pb dating of detrital zircons and detrital mica Ar-Ar ages indicate sediment sources in the Higher Himalayan Crystalline and Lesser Himalayan Crystalline Series indicating that this paleo-river channel system formed a major perennial river derived from the main body of the Himalaya. Specifically we are able to fingerprint bedrock sources in the catchment of the present-day Sutlej river indicating that the paleo-fluvial system represents the former course of the Sutlej river prior to a major nodal avulsion to its present day course. Our results indicate that on geologically relatively short time-scales, we observe dramatic along strike shifts in the location of major Himalayan rivers. Our sediment records when combined with high-resolution dating and

  19. CO2 outburst events in relation to seismicity: Constraints from microscale geochronology, geochemistry of late Quaternary vein carbonates, SW Turkey

    Ünal-İmer, Ezgi; Uysal, I. Tonguç; Zhao, Jian-Xin; Işık, Veysel; Shulmeister, James; İmer, Ali; Feng, Yue-Xing


    calcite veins. Vein calcite formed in fault-induced fractures offers insights into structural features, genetic characterisation of the parental fluids, and late Quaternary degassing of subsurface CO2 accumulations.

  20. Late Quaternary chronology of paleo-climatic changes in Caspian Sea region based on Lower Volga sections

    Kurbanov, Redzhep; Yanina, Tamara; Murray, Andrew; Svitoch, Alexander; Tkach, Nikolai


    Lower Volga is a unique region for understanding the history of the Caspian Sea in the Pleistocene, its correlation of paleogeographic events with glacial-interglacial rhythms of the East European Plain and the global and regional climate changes. The reason is representativeness of Quaternary sections, their completeness, presence of both marine and subaerial sediments, paleontological richness of the materials and available for study. The purpose of this work is to reconstruct the paleogeographic events in the Late Pleistocene of the Lower Volga region on the basis of summarizing the study results for the Srednyaya Akhtuba reference section. Located near city of Volgograd, at Khvaynian plain natural outcrop of Srednyaya Akhtuba section, reveals in a series of exposures a unique to the region series of marine Caspian continental deposits with four levels of buried soil horizons and loess. The results were obtained during 2015 and 2016 complex field research with application of lithological, paleopedological, paleontological, paleocryological, OSL-dating, paleomagnetic methods, that allowed more fundamental approach to the chronological assessment of individual horizons. The structure of the Srednyaya Akhtuba reference section reflects a number of paleogeographic stages of development of the study area. The oldest phase (layers 22-19) is not characterized by OSL dating or faunal material. Based on the sequence of dated layers, we assume its Middle Pleistocene age (MIS-6 stage), corresponding to Moscow stage of the Dnieper glaciation of the East European Plain and the final stage of Early Khazarian transgressive era of Caspian sea. The next stage (layers 18-14), represented by three horizons of paleosols, refers to the first half of the Late Pleistocene (MIS 5). Epoch of soil formation, based on the results the OSL-dating, can be referred to the warm sub-stages (MIS 5c and 5a), with unstable climatically transitional phase from Mikulino (Eemian) interglacial to the

  1. Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary

    Moller, P.; Lubinski, D.J.; Ingolfsson, O.; Forman, S.L.; Seidenkrantz, M.S.; Bolshiyanov, D.Y.; Lokrantz, H.; Antonov, O.; Pavlov, M.; Ljung, K.; Zeeberg, J.J.; Andreev, A.


    Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from

  2. Tectonic and climatic controls on late quaternary sedimentary processes in a neotectonic intramontane basin. (The Pitalito Basin, South Colombia).

    Bakker, J.


    The present study deals with the influence of tectonics and climatic changes on sedimentation patterns in the Quaternary Pitalito Basin (lat. 1°52'N, long. 76°02'W). This intramontane sedimentary basin is 15 km in width and 20 kin in length and is located in the Eastern Cordillera of the southern Co

  3. Severnaya Zemlya, arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary

    Möller, Per; Lubinski, David J.; Ingólfsson, Ólafur


    Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from...

  4. Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary

    Moller, P.; Lubinski, D.J.; Ingolfsson, O.; Forman, S.L.; Seidenkrantz, M.S.; Bolshiyanov, D.Y.; Lokrantz, H.; Antonov, O.; Pavlov, M.; Ljung, K.; Zeeberg, J.J.; Andreev, A.


    Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from ra

  5. Tectonic and eustatic controls of late quaternary shelf sedimentation along the Central California (Santa Cruz) continental margin: high-resolution seismic stratigraphic evidence

    Mullins, Henry T.; Nagel, David K.; Dominguez, Laura L.


    A high-resolution "uniboom", seismic stratigraphic investigation of a portion of the central California continental shelf has demonstrated that depositional patterns and sequences are controlled largely by an interplay of glacioeustatic sea-level fluctuations superimposed on local tectonics. Wrench tectonics, associated with active right-lateral shear along the San Gregorio fault zone, and the Pigeon Point Basement High control the location, distribution and overall geometry of depositional sequences via en echelon folding and differential subsidence. Areas of relatively thick and thin late Quaternary sediments conform in large part with structures produced during wrenching. Glacioeustatic sea-level oscillations have also shaped depositional patterns and sequences. Correlation of our seismic stratigraphic data with a southern California continental margin sea-level curve, suggests that during the last glacial maximum, approximately 18,000 yrs ago, a relative lowstand resulted in the erosion of a distinct unconformity upon which late Quaternary sediments have accumulated. A rapid rise of sea level to a relative stillstand, approximately 12,000 yrs ago, produced a concave-up, marine terrace profile across the mid-shelf, that has since been infilled with as much as 22 m of Holocene clastic sediments. A relative drop of sea level, approximately 11,000 yrs ago, allowed sediments to build seaward as a series of prograding clinoforms that form the basal sequences of the late Quaternary sediment fill. The succeeding Holocene transgression partially eroded the top of this earlier regressive sequence, and has now established a typical, wave-graded shelf along which sediments fine in a seaward direction to water depths of 90-100 m. At greater shelf water depths, surface sediments coarsen and appear to be relicts of previous relative sea-level lowstands. The presence of now submerged and buried marine terraces along both the central and southern California continental margins

  6. Late Quaternary normal faulting and its kinematic mechanism of eastern piedmont fault of the Haba-Yulong Snow Mountains in northwestern Yunnan, China


    The regional geologic and geomorphic observations show that an active arcuate normal fault constitutes the main boundary fault of the Haba-Yulong Snow Mountains (HYSM). This fault is called eastern piedmont fault of Haba-Yulong Snow Mountains (HYPF). The fault consists of two segments with differential trend; the northern segment is NW-trending and NE-dipping and the southern section is S-N trending and E-dipping. Three sets of fault scarps cutting late Quaternary landforms and their dating results indicate that the fault is a prominent Holocene active fault and its throw rates are 0.3―1.4 mm/a during late Quaternary. The geometry and kinematics of the fault suggest that the arcuate normal faulting or rifting are typical surface deformation pattern at the two tips of the Z-shaped rift zone of northwestern Yunnan, which is related to regional east-west extension accompanying clockwise rota- tion of micro-block.

  7. Planktonic Foraminiferal Assemblage Variations of Ontong-Java Plateau during Late Quaternary and Their Implications for Paleotemperature in the Western Pacific Warm Pool

    Jin Haiyan; Jian Zhimin; Tian Jun


    Ocean Drilling Program (ODP) Site 807A was recovered from the Ontong-Java plateau, western equatorial Pacific. Quantitative analysis of planktonic foraminifera, combined with oxygen and carbon isotope data, reveals the glacial-interglacial variations of sea-surface temperature and the upper water vertical structure in this region during the late Quaternary. Our results indicate that since 530 ka sea-surface temperature (SST) and the depth of thermocline (DOT) have changed significantly in the western Pacific warm pool (WPWP). The average glacial-interglacial annual SST difference was up to 4.2 ℃, and the DOT fluctuations could exceed more than 100 m, further suggesting the instability of the WPWP. The spectral analyses of SST and DOT reveal two dominating cyclicities-the typical 100 ka cycle and the semi-precessional cycle, which is significant in the tropical spectrum, indicating that late Quaternary paleoceanographic changes in the study area were influenced not only by a high latitude forcing but also by tropic-driving factors.

  8. The geomorphology of Patagonian ice dammed lake basins: Insights from remote sensing of a modern lake and reconstruction of a Late Quaternary lake drainage event

    Thorndycraft, Varyl


    The geomorphology of ice dammed lake basins can be complex due to geomorphic responses to multiple base level changes from repeated filling and emptying, as well as the potential for catastrophic drainage events. Refining landscape models of Quaternary ice dammed palaeolake systems has the potential to improve our understanding of glacier and meltwater dynamics during deglaciation phases. In this poster two case studies are presented to shed light on the range of geomorphic processes exhibited within ice dammed lake basins. Using Google Earth Pro and repeat LANDSAT imagery the geomorphology resulting from multiple base level changes of an ice dammed lake of the Viedma Glacier (Southern Patagonia Icefield) is presented. The LANDSAT imagery shows transgressive lake phases inundating already formed delta and terrace surfaces, whilst the high resolution Google Earth Pro images reveal a complex suite of incised terrace levels developed on the valley floor following lake drainage events. Secondly, the impact of catastrophic drainage of the Late Pleistocene Palaeolake Cochrane (Northern Patagonia Icefield) is investigated through geomorphological mapping. Here an outburst flood and rapid lowering of the lake has led to large scale eddy scouring of glacio-lacustrine sediments, with scarp slopes of ca. 30-40 m in height, and the formation of boulder bars during the final stages of lake fall. The implications of the mapping for interpretations of Late Quaternary palaeolake sediment-landform assemblages and rates of landscape change are discussed.

  9. Late Quaternary normal faulting and its kinematic mechanism of eastern piedmont fault of the Haba-Yulong Snow Mountains in northwestern Yunnan, China

    WU ZhongHai; ZHANG YongShuang; HU DaoGong; ZHAO XiTao; YE PeiSheng


    The regional geologic and geomorphic observations show that an active arcuate normal fault consti-tutes the main boundary fault of the Haba-Yulong Snow Mountains (HYSM). This fault is called eastern piedmont fault of Haba-Yulong Snow Mountains (HYPF). The fault consists of two segments with dif-ferential trend; the northern segment is NW-trending and NE-dipping and the southern section is S-N trending and E-dipping. Three sets of fault scarps cutting late Quaternary landforms and their dating results indicate that the fault is a prominent Holocene active fault and its throw rates are 0.3-1.4 mm/a during late Quaternary. The geometry and kinematics of the fault suggest that the arcuate normal faulting or rifting are typical surface deformation pattern at the two tips of the Z-shaped rift zone of northwestern Yunnan, which is related to regional east-west extension accompanying clockwise rota-tion of micro-block.

  10. Linking glacial melting to Late Quaternary sedimentation in climatically sensitive mountainous catchments of the Mount Chlemos compex, Kalavryta, southern Greece

    Pope, Richard; Hughes, Philip


    Compared to the mountainous areas of northern Greece (e.g. Woodward et al., 2008), the influence of deglaciation cycles on sedimentation in mountainous catchments in southern Greece remains poorly understood due to the poor preservation of small moraines and limited opportunities to date glacial and fluvial sediment dynamics fluvial sediments (Pope, unpublished data). Nevertheless, intriguing new insight into links between glacial cycles and sediment transfer/deposition phases in upland catchments have emerged by applying multiple dating techniques to well-preserved multiple generations of moraines and extensive glacio-fluvial fan systems on Mount Chelmos (2355 m a.s.l.). U-series dating of calcites within proximal fan sediments constrain the earliest phase of glacio-fluvial sedimentation to 490 (±21.0)(ka (MIS 12), while OSL dating of fine sands constrains the deposition of extensive medial glacio-fluvial gravels in (valley we walked down through trees) to between 250.99 (±20.67) and 160.82 (±11.08) ka. By comparison, cosmogenic dating of moraine boulders indicates that three generations of well-preserved moraines in the highest cirque areas date to 31-23 ka, 17-16 ka and 12-11.5 ka. OSL dating also provides ages of 18 and 17 (±11.08) for an extensive glacio-fluvial terrace in a major valley draining the southern flanksof Mount Chelmos. The initial Mount Chelmos geochronology suggests that the earliest and middle phases of glacio-fluvial sedimentation are coincident with the Middle Pleistocene glacial stages stages recorded in the Pindus range (Hughes et al, 2006). These include the Skamnellian (MIS 12) and the Vlasian (MIS 6) Stages as well as other cold stage between these (e.g. MIS 8).Evidence of glacio-fluvial outwash in MIS 8 is interesting since evidence for this in the moraine records has remained elusive although is suggested further north in the Balkans (Hughes et al., 2011). The valley moraines and glacio-fluvial terraces (late MIS 2) post-date the

  11. Late Quaternary sediment deposition of core MA01 in the Mendeleev Ridge, the western Arctic Ocean: Preliminary results

    Park, Kwang-Kyu; Kim, Sunghan; Khim, Boo-Keun; Xiao, Wenshen; Wang, Rujian


    Late Quaternary deep marine sediments in the Arctic Ocean are characterized by brown layers intercalated with yellowish to olive gray layers (Poore et al., 1999; Polyak et al., 2004). Previous studies reported that the brown and gray layers were deposited during interglacial (or interstadial) and glacial (or stadial) periods, respectively. A 5.5-m long gravity core MA01 was obtained from the Mendeleev Ridge in the western Arctic Ocean by R/V Xue Long during scientific cruise CHINARE-V. Age (~450 ka) of core MA01 was tentatively estimated by correlation of brown layers with an adjacent core HLY0503-8JPC (Adler et al., 2009). A total of 22 brown layers characterized by low L* and b*, high Mn concentration, and abundant foraminifera were identified. Corresponding gray layers are characterized by high L* and b*, low Mn concentration, and few foraminiferal tests. Foraminifera abundance peaks are not well correlated to CaCO3 peaks which occurred with the coarse-grained (>0.063 mm) fractions (i.e., IRD) both in brown and gray layers. IRDs are transported presumably by sea ice for the deposition of brown layers and by iceberg for the deposition of gray layers (Polyak et al., 2004). A strong correlation coefficient (r2=0.89) between TOC content and C/N ratio indicates that the major source of organic matter is terrestrial. The good correlations of CaCO3 content to TOC (r2=0.56) and C/N ratio (r2=0.69) imply that IRDs contain detrital CaCO3 which mainly originated from the Canadian Arctic Archipelago. In addition, high kaolinite/chlorite (K/C) ratios mostly correspond to CaCO3 peaks, which suggests that the fine-grained particles in the Mendeleev Ridge are transported from the north coast Alaska and Canada where Mesozoic and Cenozoic strata are widely distributed. Thus, the Beaufort Gyre, the predominant surface current in the western Arctic Ocean, played an important role in the sediment delivery to the Mendeleev Ridge. It is worthy of note that the TOC and CaCO3 peaks are

  12. The Rise of Late Tertiary and Quaternary Erosion and Weathering Rates revisited (Ralph Alger Bagnold Medal Lecture)

    von Blanckenburg, Friedhelm


    increased, the isotope ratio of Be-10 to Be-9 would have decreased by roughly the same factor. Over the past 10 My, records of chemical marine deposits (Fe-Mn crusts and authigenic deep sea sediments) show no change in this ratio after correction for radioactive decay of Be-10. Therefore, these records support the hypothesis of constant global erosion and weathering fluxes. If this hypothesis is true, neither Late Tertiary mountain building nor Quaternary cooling affected or was affected by a change in silicate weathering rates. Instead, a more continuous mechanism is suggested in that subtle ongoing hillslope rejuvenation in any soil-mantled hillslopes in kinetically-limited settings enable the feedback that stabilizes atmospheric CO2 and climate levels through silicate weathering. In fact, in steep, active mountain belts an increase of relief and erosion rates to those that are in excess of conditions were soils are stable lead to a decrease, not an increase of weathering rate. But the aim here is not to discount active mountains as premier agents of CO2 withdrawal. Silicate weathering may still take place within the adjacent sedimentary basins, and large carbon deposits could also be buried there in the organic form. (1) P. Z. Zhang, P. Molnar, W. R. Downs, Nature 410, 891 (2001). (2) J. Kuhlemann, W. Frisch, B. Székely, I. Dunkl, M. Kázmér, Int J Earth Sci) 91, 818 (2002). (3) F. Métivier, Y. Gaudemer, P. Tapponier, M. Klein, Geophys. J. Int 137, 280 (1999). (4) P. M. Sadler, GeoResearch Forum 5, 15 (1999). (5) F. von Blanckenburg, R. K. O'Nions, Earth and Planet. Sci. Letters 167, 175 (1999).

  13. Preliminary research on Mesalake Jilantai-Hetao in the arid areas of China during the Late Quaternary



    preserved on the top of profiles in the embankments at higher elevations. All this evidence suggests that there was once a huge palaeo-lake covering the Jilantai region and most part of the Hetao Plain with the highest lake level reaching ~1080 m a.s.l. We refer to the huge paleolake, which was larger than modern Lake Baikal, as "Megalake Jilantai-Hetao." OSL dating results indicate that the megalake formed before ~60-50 ka, and the four shorelines at elevations between 1060 and 1035 m a.s.l, likely represent the lake level variations from ~60-~50 ka to the early Holocene. The discovery of the Megalake Jilantai-Hetao likely will impact understanding of the development of the Yellow River during the late Quaternary, the evolution of the Ulan Buh and Kubq deserts, neotectonism in the region, and possibly regional climatic changes.

  14. Synthesis of Late Cretaceous-Quaternary tectonic, sedimentary and magmatic processes and basin formation related to episodic subduction-collision in the easternmost Mediterranean region

    Robertson, Alastair; Kinnaird, Timothy; McCay, Gillian; Palamakumbura, Romesh; Taslı, Kemal


    Mesozoic oceanic crust of the easternmost Mediterranean has experienced northwards subduction during Late Cretaceous-Cenozoic, either continuously or discontinuously based on kinematic evidence. Much of the existing information on sedimentation within the easternmost Mediterranean oceanic basin comes from the non-emplaced continental margins of the Levant and North Africa. In addition, sedimentary basins related to plate convergence are recorded along the northern margin of the Southern Neotethyan ocean, mainly in the Kyrenia Range of northern Cyprus and its extension into the Misis Mountains of southern Turkey, coupled with the adjacent submerged areas. In a setting of only incipient continental collision such as the easternmost Mediterranean the sedimentary basins would be expected to remain entirely submarine. In contrast, the Kyrenia Range has been strongly uplifted and subaerially exposed during Late Pliocene-Quaternary time. This allows the recognition of a number of discrete phases of sedimentary basin formation: 1. Late Cretaceous (Campanian-Maastrichtian): silicic volcanism to create a subaqueous volcaniclastic apron; 2. Maastrichtian-Paleocene: pelagic carbonate deposition interspersed with proximal gravity flows and within-plate type alkaline volcanics; 3. Early Eocene: large-scale sedimentary melange (olistostrome) emplacement; 4. Late Eocene-Late Miocene: terrigenous gravity-flow deposition in a deep-water fault dissected 'fore arc' setting. Initial, Late Eocene non-marine coarse clastic alluvial fan deposition was succeeded by Oligocene-Miocene deep-marine siliciclastic gravity flow deposits, fining and shallowing upwards during the Late Miocene; 5. Messinian: localised precipitation of evaporites in small fault-controlled basins; 6. Pliocene: shallow-marine siliciclastic-carbonate deposition in a shelf-depth, overall regressive setting; 7. Latest Pliocene to mid-Pleistocene: gravitational accumulation of coarse talus along a strongly uplifting

  15. Disappearance of the last lions and hyenas of Europe in the Late Quaternary - a chain reaction of large mammal prey migration, extinction and human antagonism

    Diedrich, Cajus G.


    In the Eemian to Early/Middle Weichselian (Late Pleistocene), when the Scandinavian and Alpine Glaciers were still small, and northern Germany under mammoth steppe to taiga palaoenvironment conditions, Late Quaternary steppe lions were well distributed in northern to central Germany, whereas generally all over Central Europe bones and rarely articulated skeletons were found less at open air but mainly at cave sites (Diedrich 2007a, 2008a-b, 2009a-b, 2010a-c, k, in review a-b; Diedrich and Rathgeber in review). A similar distribution, but more dense, is reported for the Late Quaternary Ice Age spotted hyenas (Diedrich 2005, 2006, 2007b-c, 2008a, c, 2010f-j, in review c-d, Diedrich and Žák 2006). The last lions of northern Europe were thought to have reached into the final Magdalénan (cf. Musil 1980). This can be not concluded with a restudy of the bone material from the Late Magdalenian (V-VI) Teufelsbrücke stone arch site near Saalfeld (Thuringia, Central Germany) and many other Magdalenian stations (open air and caves) in northern to central Germany (Münsterland Bay, Sauerland Karst, Harz Mountain Karst, Thuringian Karst). None of those sites yield remains of final Upper Pleistocene spotted hyenas or steppe lion bones anymore, nor in the few preserved Late Magdalenian mobile art can those be recognized in those regions. The last lion remains seem to reach into the Aurignacian or possibly into the Early Gravettian (early Late Weichselian) documented especially at the cave bear den, hyena den and overlapping Neandertalian to Modern human camp site Balve Cave (Sauerland Karst, cf. archaeology in Günther 1964) where still a mammoth fauna is documented for that time (Diedrich 2010a). The last and by archaeological layers dated hyena remains were also found in the Balve Cave and are from the Late Middle Palaeolithic cave site reaching a maximum Aurignacian age documenting an overlapping of hyena den and human camp site use (Diedrich 2010a, b). In northern Germany

  16. Spotted hyena and steppe lion predation behaviours on cave bears of Europe - ?Late Quaternary cave bear extinction as result of predator stress

    Diedrich, Cajus G.


    Cave bears hibernated in caves all over Eurasia (e.g. Rabeder et al., 2000) including alpine regions using mainly larger caves for this purpose. Late Quaternary spotted hyenas Crocuta crocuta spelaea instead occupied mainly areas close to the cave entrances as their dens (Diedrich and Žák 2006, Diedrich 2010). The largest predator, the steppe lion Panthera leo spelaea was only a sporadic cave dweller (Diedrich 2007b, 2009b). His presence and its remains from caves all over Europe can be recently explained best as result of imported carcasses after killing by their largest antagonists, the Late Quaternary spotted hyenas. In some cases the kill might have happened in the hyena den cave itself during the theft of prey remains by lions (Diedrich 2009a). Another reason of their remains in caves of Europe is the hunting onto the herbivorous cave bears, especially during hibernation times, when megafauna prey was less available in the open environments (Diedrich 2009c). These lion remains from caves of Europe, nearly all of which were from adult animals, provide evidence of active predation by lions onto cave bears even in medium high alpine regions (Diedrich 2009b, in review). Lion skeletons in European cave bear dens were therefore often found amongst originally articulated cave bear skeletons or scattered cave bear remains and even close to their hibernation nests (Diedrich et al. 2009c, in review). Not only lions fed on cave bears documented mainly by the large quantities of chewed, punctured and crushed cave bear long-bones; even damaged skulls reveal that hyenas scavenged primarily on cave bear carcasses which were mainly responsible for the destruction of their carcasses and bones (Diedrich 2005, 2009d). Predation and scavenging on cave bears by the two largest Late Quaternary predators C. c. spelaea and P. l. spelaea explains well the large quantity of fragmented cave bear bones over all European caves in low to medium high mountainous elevations, whereas in

  17. Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California

    Personius, Stephen F.; Crone, Anthony J.; Machette, Michael N.; Mahan, Shannon; Lidke, David J.


    The 86-km-long Surprise Valley normal fault forms part of the active northwestern margin of the Basin and Range province in northeastern California. We use trench mapping and radiocarbon, luminescence, and tephra dating to estimate displacements and timing of the past five surface-rupturing earthquakes on the central part of the fault near Cedarville. A Bayesian OxCal analysis of timing constraints indicates earthquake times of 18.2 ± 2.6, 10.9 ± 3.2, 8.5 ± 0.5, 5.8 ± 1.5, and 1.2 ± 0.1 ka. These data yield recurrence intervals of 7.3 ± 4.1, 2.5 ± 3.2, 2.7 ± 1.6, and 4.5 ± 1.5 ka and an elapsed time of 1.2 ± 0.1 ka since the latest surface-rupturing earthquake. Our best estimate of latest Quaternary vertical slip rate is 0.6 ?? 0.1 mm/a. This late Quaternary rate is remarkably similar to long-term (8-14 Ma) minimum vertical slip rates (>0.4-0.5 ± 0.3 mm/a) calculated from recently acquired seismic reflection and chronologic and structural data in Surprise Valley and the adjacent Warner Mountains. However, our slip rate yields estimates of extension that are lower than recent campaign GPS determinations by factors of 1.5-4 unless the fault has an unusually shallow (30°-35°) dip as suggested by recently acquired seismic reflection data. Coseismic displacements of 2-4.5 ± 1 m documented in the trench and probable rupture lengths of 53-65 km indicate a history of latest Quaternary earthquakes of M 6.8-7.3 on the central part of the. Surprise Valley fault.

  18. Dating of the late Quaternary volcanic events using Uranium-series technique on travertine deposit: A case study in Ihlara, Central Anatolia Volcanic Province

    Karabacak, Volkan; Tonguç Uysal, İ.; Ünal-İmer, Ezgi


    Dating of late Quaternary volcanism is crucial to understanding of the recent mechanism of crustal deformation and future volcanic explosivity risk of the region. However, radiometric dating of volcanic products has been a major challenge because of high methodological error rate. In most cases, there are difficulties on discrimination of the volcanic lava flow relations in the field. Furthermore, there would be unrecorded and unpreserved volcanoclastic layers by depositional and erosional processes. We present a new method that allows precise dating of late Quaternary volcanic events (in the time range of 0-500,000 years before present) using the Uranium-series technique on travertine mass, which is thought to be controlled by the young volcanism. Since the high pressure CO2 in the spring waters are mobilized during crustal strain cycles and the carbonates are precipitated in the fissures act as conduit for hot springs, thus, travertine deposits provide important information about crustal deformation. In this study we studied Ihlara fissure ridge travertines in the Central Anatolia Volcanic Province. This region is surrounded by many eruption centers (i.e. Hasandaǧı, Acıgöl and Göllüdaǧı) known as the late Quaternary and their widespread volcanoclastic products. Recent studies have suggested at least 11 events at around Acıgöl Caldera for the last 180 ka and 2 events at Hasandaǧı Stratovolcano for the last 30 ka. Active travertine masses around Ihlara deposited from hotwaters, which rise up through deep-penetrated fissures in volcanoclastic products of surrounding volcanoes. Analyses of the joint systems indicate that these vein structures are controlled by the crustal deformation due to young volcanism in the vicinity. Thus, the geological history of Ihlara travertine mass is regarded as a record of surrounding young volcanism. We dated 9 samples from 5 ridge-type travertine masses around Ihlara region. The age distribution indicates that the crustal

  19. Combining the least cost path method with population genetic data and species distribution models to identify landscape connectivity during the late Quaternary in Himalayan hemlock.

    Yu, Haibin; Zhang, Yili; Liu, Linshan; Qi, Wei; Li, Shicheng; Hu, Zhongjun


    Himalayan hemlock (Tsuga dumosa) experienced a recolonization event during the Quaternary period; however, the specific dispersal routes are remain unknown. Recently, the least cost path (LCP) calculation coupled with population genetic data and species distribution models has been applied to reveal the landscape connectivity. In this study, we utilized the categorical LCP method, combining species distribution of three periods (the last interglacial, the last glacial maximum, and the current period) and locality with shared chloroplast, mitochondrial, and nuclear haplotypes, to identify the possible dispersal routes of T. dumosa in the late Quaternary. Then, both a coalescent estimate of migration rates among regional groups and establishment of genetic divergence pattern were conducted. After those analyses, we found that the species generally migrated along the southern slope of Himalaya across time periods and genomic makers, and higher degree of dispersal was in the present and mtDNA haplotype. Furthermore, the direction of range shifts and strong level of gene flow also imply the existence of Himalayan dispersal path, and low area of genetic divergence pattern suggests that there are not any obvious barriers against the dispersal pathway. Above all, we inferred that a dispersal route along the Himalaya Mountains could exist, which is an important supplement for the evolutionary history of T. dumosa. Finally, we believed that this integrative genetic and geospatial method would bring new implications for the evolutionary process and conservation priority of species in the Tibetan Plateau.

  20. Size variation in Tachyoryctes splendens (East African mole-rat) and its implications for late Quaternary temperature change in equatorial East Africa

    Faith, J. Tyler; Patterson, David B.; Blegen, Nick; O'Neill, Chris J.; Marean, Curtis W.; Peppe, Daniel J.; Tryon, Christian A.


    This study develops a new proxy for Quaternary temperature change in tropical Africa through analysis of size variation in East African mole-rat (Tachyoryctes splendens). In modern mole-rats, mandibular alveolar length is unrelated to annual precipitation, precipitation seasonality, temperature seasonality, or primary productivity. However, it is inversely correlated with mean annual temperature, in agreement with Bergmann's rule. This relationship is observed at temperatures below ˜17.3 °C, but not at higher temperatures. We apply these observations to late Quaternary mole-rats from Wakondo (˜100 ka) and Kisaaka (˜50 ka) in the Lake Victoria region and Enkapune ya Muto (EYM; ˜7.2-3.2 ka) in Kenya's central rift. The Lake Victoria mole-rats are larger than expected for populations from warm climates typical of the area today, implying cooler temperatures in the past. The magnitude of temperature decline needed to drive the size shift is substantial (˜4-6 °C), similar in magnitude to the degree of change between the Last Glacial Maximum and Holocene, but is consistent with regional temperature records and with scenarios linking equatorial African temperature to northern hemisphere summer insolation. Size changes through time at EYM indicate that rising temperatures during the middle Holocene accompanied and potentially contributed to a decline in Lake Naivasha and expansion of grassland vegetation.

  1. Provenance of late Oligocene to quaternary sediments of the Ecuadorian Amazonian foreland basin as inferred from major and trace element geochemistry and Nd-Sr isotopic composition

    Roddaz, Martin; Christophoul, Frédéric; Burgos Zambrano, José David; Soula, Jean-Claude; Baby, Patrice


    Oligocene to Quaternary deposits from the Oriente Amazonian foreland basin (Ecuador and Peru) were analyzed for major and trace element geochemistry (46 and 32 samples respectively) and Nd-Sr isotopic systematics (n = 10). Chemical Index of Alteration values lower than those of other Amazonian foreland basin sediments and scattering along the AK join in the A-CN-K diagram indicate that the Oriente foreland basin has been continuously fed by poorly to moderately weathered sediments having an overall Andesitic composition since the Oligocene. Chemical ratios such as Cr/Th and Th/Sc as well as Eu anomaly and Nd-Sr isotopic compositions indicate that most of the analyzed sediments contained a greater proportion of volcanic arc rock material than the other Amazonian foreland basin sediments. When compared with the older sediments The Quaternary sediments are characterized by a greater contribution of the volcanic arc source. The composition of the sediments deposited in the Ecuadorian Amazonian foreland basin is mainly controlled by geodynamic processes. We suspect the Late Pliocene-Pleistocene subduction of the Carnegie ridge to be responsible for the back arc volcanism feeding the Amazonian foreland with more basic materials. Input of young Ecuadorian volcanic rocks may explain the difference in Sr and Nd isotopic ratios of suspended sediments between the Solimoes and the Madeira rivers.

  2. Using Bryophytes and Stable isotopes to Assess Paleohydrological Changes in a Subarctic Alaskan Peatland

    Jones, M.; Peteet, D.; Sambrotto, R.


    Hydrologic changes resulting from climate change have important effects on vegetation change and global feedback cycles in the high latitudes. In an attempt to move beyond pollen analysis to interpret past climate, a number of geochemical and biological proxies were used, including bulk peat δ 13C, δ15N, and bryophytes, to make paleohydrological inferences from peat cores in south central Alaska. Bryophyte species distribution and composition are sensitive to water table position and pH, making them good candidates for paleohydrologic analyses. Bryophyte species were identified in \\1-m2 plots from the forest edge to the wettest swale across numerous peatland sites on the Kenai Peninsula, taking pH, conductivity, and temperature measurements for each plot. This modern calibration was used to conduct bryophyte analysis from two peatland cores from the Kenai Peninsula lowlands dated to 14.2 ka and 18.8 ka. Both records exhibit good preservation of both leaves and stems, allowing for analysis and identification. Late-glacial domination of brown moss species denotes rich fen conditions, and high moisture availability, as is indicated in the δ13C record. Increased δ13C values ca. 10 ka indicate a shift from moister to drier conditions, and the bryophyte species switch to higher hummock brown moss species and Sphagnum spp. Similar shifts in δ15N from negative values to near 0‰ suggest a switch of nutrient input to the fen from combined nitrogen pools to atmospheric nitrogen sources. The bryophyte species composition shows a dominance of acidic poor fen conditions in the mid- to late- Holocene. These shifts corroborate what was previously interpreted in the pollen and macrofossil record from these peatland sites.

  3. Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution


    High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are reported to reconstruct a history of East Asian monsoon evolution.Variations in Illite,chlorite,and kaolinite contents indicate a strong glacial-interglacial cyclicity,while changes in smectite content present a higher frequency cyclicity.The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea.Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands.Illite and chlorite originated mainly from the Mekong and Red rivers.Kaolinite was provided mainly by the Pearl River.Spectral analysis of the kaolinite/(illite+chlorite) ratio displays a strong eccentricity period of 100 ka,implying the ice sheet-forced winter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka,and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well,implying the tropical-forced summer monsoon evolution.The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity,with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere,with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation.The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons,respectively,implying their diplex and self-contained forcing mechanism.

  4. Isotope paleohydrology at the northern Boreal treeline, Canada and Russia (paleohydrology climate change)

    Wolfe, B.B.


    A Canada-Russia international research project was established to better understand the relationship between the northern treeline region and climate change. The study involved the oxygen and carbon isotope analysis of lake sediment cores using several different sedimentological, biological and geochemical techniques. The study has provided an insight into Holocene paleohydrology and watershed carbon cycling in arctic Canada and Russia. Results showed that periods of treeline advance and climate warming in central Canada and central and eastern Russia were characterized by distinct changes in moisture conditions. During these intervals, summer relative humidity increased by 10 to 15 per cent in central Canada. Central Russia was also wetter, but a drier climate was associated with treeline advance in eastern Russia. Carbon isotope records have suggested that lake carbon reservoirs at boreal treeline were greatly influenced by catchment hydrology as well as soil and vegetation development. Nitrogen isotope composition of lacustrine bulk organic matter was also useful for determining nutrient dynamics in these watersheds. It was concluded that lake sediment organic isotope tracers are an effective approach for paleoenvironmental reconstruction.

  5. Molecular signals for late Tertiary/early Quaternary range splits of an Eurasian steppe plant: Clausia aprica (Brassicaceae).

    Franzke, A; Hurka, H; Janssen, D; Neuffer, B; Friesen, N; Markov, M; Mummenhoff, K


    Several vegetation belts stretch continuously from Europe to Asia, taiga and steppe being most prominent. Numerous plant species within these belts share a conspicuous distribution area, which is longitudinally contracted or disrupted approximately along longitude 70 degrees E. To date no hypothesis for this intriguing distribution pattern has been put forward. We detected molecular footprints in the contemporary genetic composition in nuclear DNA (ITS1, ITS2) and chloroplast DNA (trnL-trnF spacer region) of the steppe element Clausia aprica (Brassicaceae) providing evidence for a severe longitudinal range split and genetic differentiation east of the Ural Mountains about 1 million years ago caused by Quaternary climatic oscillations. Clausia aprica provides the first phylogeographical analysis on the intraspecific evolution of an Eurasian steppe plant.

  6. Evaluation of simple geochemical indicators of aeolian sand provenance: Late Quaternary dune fields of North America revisited

    Muhs, Daniel R.


    Dune fields of Quaternary age occupy large areas of the world's arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba compositions. Over the Basin and Range and Great Plains regions of North America, the hypothesized sediment sources of dune fields are reviewed and assessed using K/Rb and K/Ba values in dune sands and in hypothesized source sediments. In some cases, the origins of dunes assessed in this manner are consistent with previous studies and in others, dune fields are found to have a more complex origin than previously thought. Use of K/Rb and K/Ba for provenance studies is a robust method that is inexpensive, rapid, and highly reproducible. It exploits one of the most common minerals found in dune sand, K-feldspar. The method avoids the problem of using simple concentrations of key elements that may be subject to interpretative bias due to changes in mineralogical maturity of Quaternary dune fields that occur over time.

  7. The C32 alkane-1,15-diol as a proxy of late Quaternary riverine input in coastal margins

    Lattaud, Julie; Dorhout, Denise; Schulz, Hartmut; Castañeda, Isla S.; Schefuß, Enno; Sinninghe Damsté, Jaap S.; Schouten, Stefan


    The study of past sedimentary records from coastal margins allows us to reconstruct variations in terrestrial input into the marine realm and to gain insight into continental climatic variability. There are numerous organic proxies for tracing terrestrial input into marine environments but none that strictly reflect the input of river-produced organic matter. Here, we test the fractional abundance of the C32 alkane 1,15-diol relative to all 1,13- and 1,15-long-chain diols (FC32 1, 15) as a tracer of input of river-produced organic matter in the marine realm in surface and Quaternary (0-45 ka) sediments on the shelf off the Zambezi and nearby smaller rivers in the Mozambique Channel (western Indian Ocean). A Quaternary (0-22 ka) sediment record off the Nile River mouth in the eastern Mediterranean was also studied for long-chain diols. For the Mozambique Channel, surface sediments of sites most proximal to Mozambique rivers showed the highest F1, 15 - C32 (up to 10 %). The sedimentary record shows high (15-35 %) pre-Holocene F1, 15 - C32 and low (caused the Zambezi River mouth to become more distal to our study site, thereby decreasing riverine input at the core location. Some small discrepancies are observed between the records of the BIT index and FC32 1, 15 for Heinrich Event 1 (H1) and the Younger Dryas (YD), which may be explained by a change in soil sources in the catchment area rather than a change in river influx. Like for the Mozambique Channel, a significant correlation between FC32 1, 15 and the BIT index (r2 = 0.38, p changes in the catchment area.

  8. Paleochannel and paleohydrology of a Middle Siwalik (Pliocene) fluvial system, northern India

    Z A Khan; R C Tewari


    Late Cenozoic fresh water molasses sediments (+6000 m thick) deposited all along the length of the Himalayan fore deep, form the Siwalik Supergroup. This paper reports the results of the paleodrainage and paleohydrology of the Middle Siwalik subgroup of rocks, deposited in non-marine basins adjacent to a rising mountain chain during Pliocene. Well-exposed sections of these rocks have provided adequate paleodrainage data for the reconstruction of paleochannel morphology and paleohydrological attributes of the Pliocene fluvial system. Cross-bedding data has been used as inputs to estimate bankfull channel depth and channel sinuosity of Pliocene rivers. Various empirical relationships of modern rivers were used to estimate other paleohydrological attributes such as channel width, sediment load parameter, annual discharge, and channel slope and flow velocity. Computed channel depth, channel slope and flow velocity are supported independently by recorded data of scour depth, cross-bedding variability and Chezy’s equation. The estimates indicate that the Middle Siwalik sequence corresponds to a system of rivers, whose individual channels were about 400 m wide and 5.2–7.3 m deep; the river on an average had a low sinuous channel and flowed over a depositional surface sloping at the rate of 53 cm/km. The 700-km long Middle Siwalik (Pliocene) river drained an area of 42925 km2 to the north–northeast, with a flow velocity of 164–284 cm/s, as it flowed generally south–southwest of the Himalayan Orogen. Bed-load was about 15% of the total load of this river, whose annual discharge was about 346–1170 m3/s normally and rose to approximately 1854 m3/s during periodic floods. The Froude number of 0.22 suggests that the water flows in the Pliocene river channels were tranquil, which in turn account for the profuse development of cross-bedded units in the sandstone. The estimated paleochannel parameters, bedding characteristics and the abundance of coarse clastics in the

  9. Differential insect and mammalian response to Late Quaternary climate change in the Rocky Mountain region of North America

    Elias, Scott A.


    Of the 200 beetle species identified from Rocky Mountain Late Pleistocene insect faunal assemblages, 23% are no longer resident in this region. None of the 200 species is extinct. In contrast to this, only 8% of 73 identified mammal species from Rocky Mountain Late Pleistocene assemblages are no longer resident in the Rockies, and 12 species are now extinct. Since both groups of organisms are highly mobile, it would appear that their responses to the large-scale fluctuations of climate associated with the last 125,000 years have been considerably different. Most strikingly contrasting with the insects, there are no mammals in the Rocky Mountain Late Pleistocene fossil record that are found exclusively today in the Pacific Northwest (PNW) region. The PNW does have a distinctive modern mammalian fauna, but only one of these, Keen's Myotis, has a fossil record outside the PNW region, in the eastern and central United States. No modern PNW vertebrate species have been found in any Rocky Mountain fossil assemblages. Based on these data, it appears that there has been little or no mammalian faunal exchange between the PNW region and the Rocky Mountains during the Late Pleistocene or Holocene. This is in stark contrast to the fossil beetle record, where PNW species are a substantial component in many faunas, right through to the Late Holocene.

  10. Age assessment and implications of late Quaternary periglacial and paraglacial landforms on Muckish Mountain, northwest Ireland, based on Schmidt-hammer exposure-age dating (SHD)

    Wilson, Peter; Matthews, John A.


    Schmidt-hammer exposure-age dating (SHD) was applied to a variety of late Quaternary periglacial and paraglacial landforms composed of coarse rock debris on Muckish Mountain, northwest Ireland. Landform ages were determined using a linear high-precision age-calibration curve, derived from young and old control surfaces of known age on the same rock type. The SHD ages represent maximum estimates of the time elapsed since the boulders stabilised and the landforms became inactive. Most ages are also minimum estimates for the start of landform development because older boulders are buried beneath the sampled surface boulders. Ages and 95% confidence intervals obtained for blockfield, boulder lobes and talus indicate these features were likely active during several of the early Holocene cold events evidenced in Greenland ice cores and North Atlantic sediment records. Activity ceased at different times ~ 9-7 ka BP. These landforms are the first indication of a geomorphological response to early Holocene cooling in the oceanic mountains of Ireland. Late Holocene ages, obtained for rock-slope failure run-out debris and debris cone boulders, overlap with shifts to cooler and/or wetter conditions, including the Little Ice Age. Geomorphological impacts associated with these changes in climate have not previously been recorded in the Irish uplands. The SHD results indicate that previously implied timings for the stabilisation of some accumulations of coarse rock debris on mountain slopes are in need of revision.

  11. A grain-size record from Beijing region in Northern China: Late Quaternary paleoclimate oscillation in response to global change

    Guifang YANG; Zhiliang GE; Qing DAI; Jie CHENG; Gongming YIN; Lihong ZAN; Jingwei LIU


    Numerous samples taken from one core at the Beijing plain were utilized to characterize the paleocli-matic configuration of the study area and its possible relation to global control since the last interglaciation. We presented here a detailed grain-size record for the full length of Late Pleistocene, along with the optical simulated luminescence (OSL) dating. Our findings revealed that Late Pleistocene of the study area started approximately at 110 ka B.P. represented by the thick sediments of 31 m in Changping depression. Four sedimentary cycles were outlined in the core during Late Pleistocene, corresponding to marine isotope stage (MIS) 5 to 2. Controlled by regional geology and global climatic setting, eight paleoclimatic periods were identified simultaneously in the study area on the time scale of 104 year, with the warm and moist climate being found at 110- 96, 92- 76, 67- 56,and 28-18ka B.P.. The climatic instabilities on a millennial scale in Late Pleistocene were characterized largely by the occurrence of 6 strong Heinrich events shown by comparatively coarse groups. These variations correlate well with those documented in the GRIP Greenland and in the Northern Atlantic Ocean, though more complex features may exist on the long time scale.

  12. Wetlands and Paleolakes in the Hyperarid Atacama Desert During the Late Quaternary and Their Implications for Early Human Occupation of South America

    Pfeiffer, M.; Latorre Hidalgo, C.; Santoro, C.; Gayo, E.; McRostie, V.; Finstad, K. M.; Amundson, R.


    The hyperarid Atacama Desert has long been considered a natural barrier to human dispersal. However, several archaeological sites dating from the late Pleistocene have been recently reported on, and other as yet unpublished evidence is rapidly accumulating. It has been established that these occupations were facilitated by increased fluvial activity and biologically productive riparian ecosystems along the western slope of the Andes, and that the presence of humans disappeared with declines in this water flow. The considerable evidence for regional stream flow suggests that basins and lowlands should have contained lakes or wetlands contemporaneous with the ages of the fluvial activity, but there has been no published data on late Quaternary lakes in the region. Here, we report on our observations that possibly many present day salars (salt covered basins) were fresh water lakes and marshlands during the Central Andean Pluvial Event (CAPE) that occurred during the late Pleistocene and early Holocene. We performed radiocarbon analysis of described stratigraphic profiles on paleo-shorelines or in paleo-lake basins that lie within the Pampa del Tamarugal (PDT) basin. We additionally described gastropods, plant remnants, phytoliths and diatomea, which provide a reliable source for paleoenvironmental facies interpretation. These data indicate that a paleolake existed at the location of the present-day Salar de Bellavista, and that wetlands (and possibly lakes) were present at the Salar de Llamara and Pintados. These past aquatic systems are coeval with the activation of the riparian systems of the PDT reported by previous studies. Furthermore, they would have contributed to a starkly different set of resource constraints for early inhabitants than the inhospitable conditions existing today. Additionally, the presence of these water sources provides guidance in the search for additional evidence of human occupation in the region, and for understanding the geographical

  13. Late Quaternary chronostratigraphic framework of terraces and alluvium along the lower Ohio River, southwestern Indiana and western Kentucky, USA

    Counts, Ronald C.; Murari, Madhav K.; Owen, Lewis A.; Mahan, Shannon; Greenan, Michele


    The lower Ohio River valley is a terraced fluvial landscape that has been profoundly influenced by Quaternary climate change and glaciation. A modern Quaternary chronostratigraphic framework was developed for the lower Ohio River valley using optically stimulated luminescence (OSL) dating and allostratigraphic mapping to gain insights into the nature of fluvial responses to glacial–interglacial/stadial–interstadial transitions and Holocene climate change. River deposits, T0 (youngest) to T7 (oldest), were mapped along a 75 km reach of the lower Ohio River and were dated using 46 OSL and 5 radiocarbon samples. The examination of cores combined with OSL and radiocarbon dating shows that fluvial sediments older than marine oxygen isotope stage (MIS) 2 are present only in the subsurface. Aggradation during MIS 6 (Illinoian glaciation) filled the valley to within ∼7 m of the modern floodplain, and by ∼114 ka (MIS 5e/Sangamon interglacial) the Ohio River had scoured the MIS 6 sediments to ∼22 m below the modern floodplain surface. There were no fluvial sediments in the valley with ages between MIS 5e and the middle of MIS 3. The MIS 3 ages (∼39 ka) and stratigraphic position of T5 deposits suggest the Ohio River aggraded 8–14 m during MIS 4 or MIS 3. Near the end of MIS 3, the Ohio River incised the mid Last Glacial (mid-Wisconsinan) deposits ∼10 m and began aggrading again by ∼30 ka. Aggradation continued into MIS 2, with maximum MIS 2 aggradation occurring before ∼21 ka, which is coincident with the global Last Glacial Maximum (LGM). As the Ohio River adjusted to changing fluxes in sediment load and discharge following the LGM, it formed a sequence of fill-cut terraces in the MIS 2 outwash that get progressively younger with decreasing elevation, ranging in age from ∼21 ka to ∼13 ka. From ∼14 ka to ∼13 ka the Ohio River rapidly incised ∼3 m to form a new terrace, and by ∼12 ka at the onset of the Holocene, the Ohio River

  14. Late Quaternary Planktic Foraminifer Fauna andMonsoon Upwelling Records from the Western South China Sea, Near the Vietnam

    Pai-Sen Yu


    Full Text Available Marine sediment core MD012394 from the Vietnam coastal upwelling area in the western South China Sea was investigated in order to reconstruct the last Quaternary monsoon upwelling based on planktic foraminifer fauna assemblages and fauna-based sea surface temperature (SST estimates. The age model of core MD012394 was constructed using oxygen isotope stratigraphy of the planktic foraminifer G. sacculifer, with 10 accelerator mass spectrometry (AMS 14C dating of planktic foraminifers from the sediment samples. Our studies on the relative and absolute abundances of planktic foraminifer assemblages reveal eight dominant species in core MD012394: N. dutertrei + N. pachyderma (right coiling, G. ruber, G. glutinata, G. sacculifer, P. obliquiloculata, G. menardii + G. tumida, G. calida, and G. inflata. In a Q-mode factor analysis of the fauna abundance data, the fauna factors show variations that do not parallel the glacial/interglacial changes throughout the last 135 kyr. The relative abundance patterns of G. inflata and N. dutertrei (including N. pachyderma-R are interpreted as hydrographic proxies for East Asian summer and winter monsoon, respectively, in the current study. We calculated the fluctuations in the SST using the Revised Analog Method (RAM in MD012394 and found that the abundance changes of the summer monsoon upwelling indicator G. inflata were similar and nearly synchronous. This suggests that the summer monsoon-driven upwelling signal was strong near the local summer insolation maximum, which induced low SSTs, particular around ~11, 33, 59, and 83 kya. Our studies support the view that the strengths of both summer insolation and the East Asian summer monsoon have determined the relative abundance of planktic foraminifers and the SSTs in the western SCS during the last 135 kyr.

  15. The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

    Edwards, Mary E.; Grosse, Guido; Jones, Benjamin M.; McDowell, Patricia F.


    Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~ 11,000–12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~ 9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to  5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area differs from that described from other thermokarst-affected regions; regional responses to future environmental change may be equally individualistic.

  16. Catastrophic rock slope failures and late Quaternary developments in the Nanga Parbat-Haramosh Massif, Upper Indus basin, northern Pakistan

    Hewitt, Kenneth


    The Nanga Parbat-Haramosh Massif has some of the greatest relief on Earth and highest measured rates of uplift, denudation, and river incision in bedrock. Many studies have sought to understand how its morphology relates to geotectonic evolution and glaciations. However, few catastrophic rock slope failures had been recognised and many of their impacts had been attributed to other processes. Recently more than 150 of these landslides have been found within a 100-km radius of Nanga Parbat (8125 m). New discoveries are reported east, north and west of Nanga Parbat along the Indus streams. Most generated long-run-out rock avalanches that dammed the Indus or its tributaries, some impounding large lakes. They initiated episodes of intermontane sedimentation followed by trenching and removal of sediment. Valley-floor features record a complex interplay of impoundment and sedimentation episodes, superimposition of streams in pre-landslide valley floors, and exhumation of buried features. These findings depart from existing reconstructions of Quaternary events. A number of the rock-avalanche deposits were previously misinterpreted as tills or moraine and their associated lacustrine deposits attributed to glacial lakes. Features up to 1000 m above the Indus, formerly seen as tectonically raised terraces, are depositional features emplaced by landslides, or erosion terraces recording the trenching of valley fill in landslide-interrupted river reaches. Unquestionably, tectonics and glaciation have been important but decisive and misread formative events of the Holocene involve a post-glacial, landslide-fragmented fluvial system. The latter has kept valley developments in a chronic state of disequilibrium with respect to climatic and geotectonic controls. Accepted glacial chronologies are put in doubt, particularly the extent and timing of the last major glaciation. The pace and role processes in the Holocene have been seriously underestimated.

  17. The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

    Edwards, Mary; Grosse, Guido; Jones, Benjamin M.; McDowell, Patricia


    Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~ 11,000-12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~ 9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to 5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area differs from that described from other thermokarst-affected regions; regional responses to future environmental change may be equally individualistic.

  18. Ground-ice stable isotopes and cryostratigraphy reflect late Quaternary palaeoclimate in the Northeast Siberian Arctic (Oyogos Yar coast, Dmitry Laptev Strait)

    Opel, Thomas; Wetterich, Sebastian; Meyer, Hanno; Dereviagin, Alexander Y.; Fuchs, Margret C.; Schirrmeister, Lutz


    To reconstruct palaeoclimate and palaeoenvironmental conditions in the northeast Siberian Arctic, we studied late Quaternary permafrost at the Oyogos Yar coast (Dmitry Laptev Strait). New infrared-stimulated luminescence ages for distinctive floodplain deposits of the Kuchchugui Suite (112.5 ± 9.6 kyr) and thermokarst-lake deposits of the Krest Yuryakh Suite (102.4 ± 9.7 kyr), respectively, provide new substantial geochronological data and shed light on the landscape history of the Dmitry Laptev Strait region during Marine Isotope Stage (MIS) 5. Ground-ice stable-isotope data are presented together with cryolithological information for eight cryostratigraphic units and are complemented by data from nearby Bol'shoy Lyakhovsky Island. Our combined record of ice-wedge stable isotopes as a proxy for past winter climate conditions covers about 200 000 years and is supplemented by stable isotopes of pore and segregated ice which reflect annual climate conditions overprinted by freezing processes. Our ice-wedge stable-isotope data indicate substantial variations in northeast Siberian Arctic winter climate conditions during the late Quaternary, in particular between glacial and interglacial times but also over the last millennia to centuries. Stable isotope values of ice complex ice wedges indicate cold to very cold winter temperatures about 200 kyr ago (MIS7), very cold winter conditions about 100 kyr ago (MIS5), very cold to moderate winter conditions between about 60 and 30 kyr ago, and extremely cold winter temperatures during the Last Glacial Maximum (MIS2). Much warmer winter conditions are reflected by extensive thermokarst development during MIS5c and by Holocene ice-wedge stable isotopes. Modern ice-wedge stable isotopes are most enriched and testify to the recent winter warming in the Arctic. Hence, ice-wedge-based reconstructions of changes in winter climate conditions add substantial information to those derived from paleoecological proxies stored in

  19. Interplay between down-slope and along-slope sedimentary processes during the late Quaternary along the Capo Vaticano margin (southern Tyrrhenian Sea, Italy)

    Martorelli, Eleonora; Bosman, Alessandro; Casalbore, Daniele; Falcini, Federico


    Late Quaternary along-slope and down-slope sedimentary processes and structures in the upper slope-shelf sector of the Calabro-Tyrrhenian continental margin off Capo Vaticano have been investigated using very high-resolution single-channel seismic profiles and multibeam bathymetric data. The results show that a competition among along-slope bottom currents-vs down-slope mass-wasting mostly contributed in shaping the seafloor and controlling deposition of sedimentary units during the Late Quaternary. Along-slope processes mostly formed elongated drifts located on the upper continental slope and outer shelf, between -90 and -300 m. The contourite deposits and associated erosive elements indicate the presence of a northwestward geostrophic flow that can be related to the modified-LIW issued by the Messina Strait. According to the proposed stratigraphic reconstruction it is likely that the activity of bottom-currents off Capo Vaticano was intensified around the LGM period and during the post-glacial sea-level rise, whereas they were less intense during the Holocene. Gravity-driven down-slope processes formed mass-transport deposits and turbidite systems with erosive channels, locally indenting the present-day shelf. Several slide events affected the upper 10-20 m of the stratigraphic record, dismantling considerable volume of contourite sediment. High-resolution seismic profiles indicate that failure processes appear to be dominated by translational sliding with glide plains mainly developed within contourite deposits. The most striking feature is the Capo Vaticano slide complex, which displays a large spatial coverage (area of about 18 km2) and is composed by several intersecting slide scars and overlapping deposits; these characteristics are peculiar for the Tyrrhenian continental margins, where slide events developed in open-slope areas are usually less complex and smaller in size. The presence of high-amplitude reflectors within contourite deposits (representing

  20. Discovering buried channels of the Yamuna in alluvial plains of NW India using geophysical investigations: implications for major drainage reorganization during Late Quaternary

    Paul, D.; Khan, I.; Sinha, R.


    Climatic changes and active tectonic movements in the northwestern plains of India during the Late Quaternary have led to the migration and abandonment of drainage systems and formation of a large number of palaeochannels. It has been postulated by previous workers that the Yamuna was flowing along the present-day dry palaeochannels of Ghaggar-Hakra riverbed >120 Ka ago and was relocated to its current position only during the Late Quaternary. However, till date, no conclusive evidence has been provided as to when and why the Yamuna avulsion occurred. This study aims to establish sub-surface existence of buried channels of paleo-Yamuna as possible courses of the paleo-Ghaggar river. Geo-electric studies using vertical electrical resistivity soundings (1D-VES), multi electrode electrical resistivity tomography (2D-ERT) and multi probe well log surveys have been carried out in one of the paleochannels of the Yamuna to map the large-scale geometry and architecture of the palaeochannel system in the subsurface. The main objective is to reconstruct the shallow subsurface stratigraphy and alluvial architecture of the interfluve between the modern Yamuna and Sutlej Rivers, in particular the linkage of the paleocourses of the Yamuna River to the drainage network of the northwestern alluvial plains. The geophysical signatures recorded as VES on two transects trending NW-SE in Karnal and Kaithal districts of Haryana at 9 and 13 locations respectively along with continuous ERT reveals the presence of subsurface fine to coarse sand bodies (20 to 30m thick) interbedded with silty clay layers that are laterally stacked. The occurrence of thick and wide subsurface sand bodies in the subsurface implies that these are the deposits of a large river system and suggests that the Yamuna was connected to the paleo-Ghaggar River as hypothesized by earlier workers based on remote sensing techniques. However, detailed sedimentological and chronological constraints are required to establish

  1. Faulted terrace riser position with respect to meanders constrains late Quaternary slip history of the Honey Lake fault, NE California

    Gold, R. D.


    Faulted terrace risers are prevalent semi-linear features commonly used to constrain Quaternary slip rates along strike-slip faults. Terrace risers are difficult to date directly and therefore the bracketing upper and lower terrace surfaces commonly are used to constrain their ages. However, if there is a significant difference in the age of the upper and lower terrace surfaces, then large uncertainties in slip rate result. Some investigators try to reduce uncertainties by arguing that either the upper- or lower-terrace age closely approximates the age of a terrace riser. To evaluate where this approach is valid, we use 0.25-m airborne lidar data to analyze three sites where terrace risers are laterally offset by the right-lateral Honey Lake fault in NE California. The terrace risers are bracketed by the same sub-horizontal surfaces: an upper surface defined by the bed of abandoned Lake Lahontan having an age of 15.8 ka and a lower fluvial terrace abandoned after 4.7 ka. We estimate a >4x difference in the amount of lateral offset recorded by the risers, ranging from 7 to 30 m. The amount of offset appears to correspond to the riser position relative to modern stream meanders: smaller offsets are in cutbank locations and the largest offset is in the point-bar location. At face value, the results yield slip rates of 0.5 to 6.4 mm/yr. However, in detail, the largest lateral displacement ( 30 m) places a minimum bound on slip rate of 2 mm/yr since 15.8 ka and the smallest displacement ( 7 m) places a maximum bound on slip rate of 1.5 mm/yr since 4.7 ka. This investigation highlights the challenge of correctly determining whether an upper or lower terrace best approximates the age of a faulted terrace riser. To reduce uncertainties, we advocate considering the terrace riser position in the stream system and characterizing numerous faulted and dated landforms.

  2. Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilis and Mammuthus columbi), Channel Islands NationalPark, California, USA

    Muhs, Daniel R.; Simmons, Kathleen R.; Groves, Lindsey T.; McGeehin, John P.; Schumann, R. Randall; Agenbroad, Larry D.


    Fossils of Columbian mammoths (Mammuthus columbi) and pygmy mammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace with MIS 5.1, a time of relatively high sea level. Mammoths likely immigrated to the islands by swimming during the glacial periods MIS 6 (~ 150 ka) or MIS 8 (~ 250 ka), when sea level was low and the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.

  3. Changes in the source and transport mechanism of terrigenous input to the Indian sector of Southern Ocean during the late Quaternary and its palaeoceanographic implications

    M Thamban; S S Naik; R Mohan; A Rajakumar; N Basavaiah; Witty D'Souza; Sarita Kerkar; M M Subramaniam; M Sudhakar; P C Pandey


    Changes in the terrigenous sediment source and transport mechanisms during the late Quaternary have been investigated using four sediment cores within the Indian sector of Southern Ocean, using the magnetic susceptibility (MS)and sedimentological records.Sediments deposited during the Holocene and other interglacial periods were characterised by low MS,low sand content, reduced ice-rafted detritus (IRD)input and increased illite possibly transported via hydrographic advection from the south.The glacial intervals are characterised by high MS,high sand content, increased IRD input and reduced illite clays,derived from both local as well as Antarctic sources. Significant reduction in clay fraction and illite content during glacials suggests that the erosive and transporting capabilities of the deep and bottom waters could have reduced compared to the interglacial times.The changes in terrigenous in flux to this region were signi ficantly in fluenced by the rhythmic glacial –interglacial fluctuations in bottom circulation and the position of the Polar Front.

  4. A species-level phylogeny of all extant and late Quaternary extinct mammals using a novel heuristic-hierarchical Bayesian approach.

    Faurby, Søren; Svenning, Jens-Christian


    Across large clades, two problems are generally encountered in the estimation of species-level phylogenies: (a) the number of taxa involved is generally so high that computation-intensive approaches cannot readily be utilized and (b) even for clades that have received intense study (e.g., mammals), attention has been centered on relatively few selected species, and most taxa must therefore be positioned on the basis of very limited genetic data. Here, we describe a new heuristic-hierarchical Bayesian approach and use it to construct a species-level phylogeny for all extant and late Quaternary extinct mammals. In this approach, species with large quantities of genetic data are placed nearly freely in the mammalian phylogeny according to these data, whereas the placement of species with lower quantities of data is performed with steadily stricter restrictions for decreasing data quantities. The advantages of the proposed method include (a) an improved ability to incorporate phylogenetic uncertainty in downstream analyses based on the resulting phylogeny, (b) a reduced potential for long-branch attraction or other types of errors that place low-data taxa far from their true position, while maintaining minimal restrictions for better-studied taxa, and (c) likely improved placement of low-data taxa due to the use of closer outgroups. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Stable isotopes in yellow-bellied marmot (Marmota flaviventris) fossils reveal environmental stability in the late Quaternary of the Colorado Rocky Mountains

    Reynard, Linda M.; Meltzer, David J.; Emslie, Steven D.; Tuross, Noreen


    High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ18O, δD, δ15N, δ13C, and 14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

  6. Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach

    May, Jan-Hendrik; Zech, Jana; Zech, Roland; Preusser, Frank; Argollo, Jaime; Kubik, Peter W.; Veit, Heinz

    Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating ( 14C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29-25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20-18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~ 17-16 ka, followed by several smaller readvances until ~ 10-11 ka, and complete deglaciation at the end of the Early Holocene.

  7. Late quaternary sea level changes of Gabes coastal plain and shelf: Identification of the MIS 5c and MIS 5a onshore highstands, southern Mediterranean

    Maher Gzam; Noureddine El Mejdoub; Younes Jedoui


    The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore highstands, by the genesis of forced regressive beach ridges situated respectively at –19 m b.s.l/100 ka and –8 m b.s.l/80 ka. This area, considered as a stable domain since at least the last 130 ka (Bouaziz et al. 2003), is a particular zone for the reconstruction of the late quaternary sea-level changes in the region. Shuttle Radar Topography Mission (SRTM) data and field observations are highlighted to deduce interaction between hydrodynamic factors and antecedent topography. Variations in geomorphology were attributed to geological inheritance. Petrography and sedimentary facies of the submerged coastal ridges reveal that the palaeocoastal morphology was more agitated than today and the fluvial discharges are consistent. Actual morphologic trend deduced from different environment coasts (sandy coasts, sea cliffs and tidal flat) is marked by accumulation of marine sands and progradation.

  8. Investigation of late Quaternary fault block uplift along the Motagua/Swan Islands fault system: Implications for seismic/tsunami hazard for the Bay of Honduras

    Cox, Randel Tom; Lumsden, David N.; Gough, Kevin; Lloyd, Roger; Talnagi, Joseph


    Uplifted and warped coastal landforms (fossil coral reef and beachrock, wave-cut and beach terraces) on the western part of Roatan Island off the northern Honduran coast record at least two late Holocene earthquakes that we estimate to have had magnitudes of > M7. Uplift has been primarily related to a fault that follows the southern coast of western Roatan, herein termed the "Flowers Bay fault", a subsidiary fault of the Motagua/Swan Islands Fault System which marks the boundary between the North American and Caribbean plates. Using electron spin resonance (ESR) and radiocarbon ages of calcium carbonate samples and a late Quaternary sea level elevation curve that is compatible with Caribbean sea level data, we constrain the ages and long-term uplift rates of the displaced landforms on Roatan caused by the vertical component of slip on the Flowers Bay fault. The fossil reef that is uplifted along the fault grew between 43 and 34 ka, and the beachrock horizon and lowest uplifted terrace along the southern and western coasts developed between 1000 and 1700 AD. We describe evidence of one earthquake that raised the south coast ~ 3 m (as much as 5 m locally) and that post-dates 1700 AD. We interpret this event to be the great earthquake of August 1856 that generated a tsunami which ran as much as 24 km onto the mainland. Another earthquake circa 900 AD produced a similar amount of uplift as the 1856 event and likely generated a similar tsunami. The age and elevation of the fossil reef suggest a long-term uplift rate of 3 mm/year, consistent with a recurrence interval of ~ 1000 years for these large earthquakes.

  9. Glaciomarine sedimentation and bottom current activity on the north-western and northern continental margins of Svalbard during the late Quaternary

    Chauhan, Teena; Noormets, Riko; Rasmussen, Tine L.


    Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2-1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.

  10. Late Quaternary depositional history, Holocene sea-level changes, and vertical crustal movement, southern San Francisco Bay, California

    Atwater, Brian F.; Hedel, Charles W.; Helley, Edward J.


    Sediments collected for bridge foundation studies at southern San Francisco Bay, Calif., record estuaries that formed during Sangamon (100,000 years ago) and post-Wisconsin (less than 10,000 years ago) high stands of sea level. The estuarine deposits of Sangamon and post-Wisconsin ages are separated by alluvial and eolian deposits and by erosional unconformities and surfaces of nondeposition, features that indicate lowered base levels and oceanward migrations of the shoreline accompanying low stands of the sea. Estuarine deposits of mid-Wisconsin age appear to be absent, suggesting that sea level was not near its present height 30,000–40,000 years ago in central California. Holocene sea-level changes are measured from the elevations and apparent 14C ages of plant remains from 13 core samples. Uncertainties of ±2 to ±4 m in the elevations of the dated sea levels represent the sum of errors in determination of (1) sample elevation relative to present sea level, (2) sample elevation relative to sea level at the time of accumulation of the dated material, and (3) postdepositional subsidence of the sample due to compaction of underlying sediments. Sea level in the vicinity of southern San Francisco Bay rose about 2 cm/yr from 9,500 to 8,000 years ago. The rate of relative sea-level rise then declined about tenfold from 8,000 to 6,000 years ago, and it has averaged 0.1–0.2 cm/yr from 6,000 years ago to the present. This submergence history indicates that the rising sea entered the Golden Gate 10,000–11,000 years ago and spread across land areas as rapidly as 30 m/yr until 8,000 years ago. Subsequent shoreline changes were more gradual because of the decrease in rate of sea-level rise. Some of the sediments under southern San Francisco Bay appear to be below the level at which they initially accumulated. The vertical crustal movement suggested by these sediments may be summarized as follows: (1) Some Quaternary(?) sediments have sustained at least 100 m of

  11. Late Quaternary vegetation and lake system dynamics in north-eastern Siberia: Implications for seasonal climate variability

    Biskaborn, B. K.; Subetto, D. A.; Savelieva, L. A.; Vakhrameeva, P. S.; Hansche, A.; Herzschuh, U.; Klemm, J.; Heinecke, L.; Pestryakova, L. A.; Meyer, H.; Kuhn, G.; Diekmann, B.


    Although the climate development over the Holocene in the Northern Hemisphere is well known, palaeolimnological climate reconstructions reveal spatiotemporal variability in northern Eurasia. Here we present a multi-proxy study from north-eastern Siberia combining sediment geochemistry, and diatom and pollen data from lake-sediment cores covering the last 38,000 cal. years. Our results show major changes in pyrite content and fragilarioid diatom species distributions, indicating prolonged seasonal lake-ice cover between ∼13,500 and ∼8900 cal. years BP and possibly during the 8200 cal. years BP cold event. A pollen-based climate reconstruction generated a mean July temperature of 17.8 °C during the Holocene Thermal Maximum (HTM) between ∼8900 and ∼4500 cal. years BP. Naviculoid diatoms appear in the late Holocene indicating a shortening of the seasonal ice cover that continues today. Our results reveal a strong correlation between the applied terrestrial and aquatic indicators and natural seasonal climate dynamics in the Holocene. Planktonic diatoms show a strong response to changes in the lake ecosystem due to recent climate warming in the Anthropocene. We assess other palaeolimnological studies to infer the spatiotemporal pattern of the HTM and affirm that the timing of its onset, a difference of up to 3000 years from north to south, can be well explained by climatic teleconnections. The westerlies brought cold air to this part of Siberia until the Laurentide ice-sheet vanished 7000 years ago. The apparent delayed ending of the HTM in the central Siberian record can be ascribed to the exceedance of ecological thresholds trailing behind increases in winter temperatures and decreases in contrast in insolation between seasons during the mid to late Holocene as well as lacking differentiation between summer and winter trends in paleolimnological reconstructions.

  12. Soils and late-Quaternary landscape evolution in the Cottonwood River basin, east-central Kansas: Implications for archaeological research

    Beeton, J.M.; Mandel, R.D.


    Temporal and spatial patterns of landscape evolution strongly influence the temporal and spatial patterns of the archaeological record in drainage systems. In this geoarchaeological investigation we took a basin-wide approach in assessing the soil stratigraphy, lithostratigraphy, and geochronology of alluvial deposits and associated buried soils in the Cottonwood River basin of east-central Kansas. Patterns of landscape evolution emerge when stratigraphic sequences and radiocarbon chronologies are compared by stream size and landform type. In the valleys of high-order streams (???4th order) the Younger Dryas Chronozone (ca. 11,000-10,000 14C yr B.P.) was characterized by slow aggradation accompanied by pedogenesis, resulting in the development of organic-rich cumulic soils. Between ca. 10,000 and 4900 14C yr B.P., aggradation punctuated by soil formation was the dominant process in those valleys. Alluvial fans formed on the margins of high-order stream valleys during the early and middle Holocene (ca. 9000-5000 14C yr B.P.) and continued to develop slowly until ca. 3000-2000 14C yr B.P. The late-Holocene record of high-order streams is characterized by episodes of entrenchment, rapid aggradation, and slow aggradation punctuated by soil development. By contrast, the early and middle Holocene (ca. 10,000-5000 14C yr B.P.) was a period of net erosion in the valleys of low-order streams. However, during the late Holocene small valleys became zones of net sediment storage. Consideration of the effects of these patterns of landscape evolution on the archaeological record is crucial for accurately interpreting that record and searching for buried archaeological deposits dating to specific cultural periods. ?? 2011 Wiley Periodicals, Inc. ?? 2011 Wiley Periodicals, Inc..

  13. Late-Quaternary records of vegetation and fire in southeastern North Carolina from Jones Lake and Singletary Lake

    Spencer, Jessica; Jones, Kaylee B.; Gamble, Douglas W.; Benedetti, Michael M.; Taylor, Audrey K.; Lane, Chad S.


    We conducted fossil pollen, charcoal, and geochemical analyses of sediment cores from Jones Lake and Singletary Lake spanning the last ∼50,000 cal yr B.P. to examine the linkages between climate, vegetation, and fire activity on the Atlantic Coastal Plain, and particularly emphasize changes since the Last Glacial Maximum. Application of the modern analog technique (MAT) to fossil pollen data allowed for quantitative estimates of Holocene climate, but Pleistocene assemblages had no modern analogues preempting their use for quantitative reconstructions. The MAT data indicate markedly lower mean annual precipitation and temperatures during the late Pleistocene relative to the Holocene. Increased charcoal accumulation during interstadials indicates increased fire activity during these warm intervals. Geochemical data (δ13C, δ15N, C:N) and pollen concentrations indicate a sparsely-vegetated Pleistocene landscape that produced few fires followed by an increase in biomass and fire activity around the lakes during the Holocene transition. A Quercus spp. maximum in the early Holocene is associated with low charcoal abundances, while increased dominance of Pinus spp. during the middle Holocene is associated with dramatic increases in charcoal. It is unclear if the Quercus-Pinus transition was the result of changing fire regimes or if the fire regime changed in response to vegetation. The regional asynchronicity of the Quercus-Pinus transition may indicate another forcing mechanism besides climate change, such as prehistoric human activity, is responsible for the ecological change. Macroscopic charcoal and C:N ratios reach unprecedented values during the late Holocene, possibly as a result of deforestation by both prehistoric Native Americans and later immigrant populations.

  14. Development and application of a pollen-based paleohydrologic reconstruction from the lower Roanoke River Basin, North Carolina, USA

    Willard, D.; Bernhardt, C.; Brown, R.; Landacre, B.; Townsend, P.


    We used pollen assemblages to reconstruct late-Holocene paleohydrologic patterns in floodplain deposits from the lower Roanoke River basin (North Carolina, southeastern USA). Using 120 surface samples from 38 transects, we documented statistical relationships between pollen assemblages, vegetation, and landforms. Backswamp pollen assemblages (long hydroperiods) are dominated by Nyssa (tupelo) and Taxodium (cypress) and have high pollen concentrations. Sediments from elevated levees and seasonally flooded forests (shorter hydroperiods) are characterized by dominant Pinus (pine) pollen, variable abundance of hardwood taxa, and low pollen concentrations. We apply the calibration data set to interpret past vegetation and paleohydrology. Pollen from a radiocarbon-dated sediment core collected in a tupelo-cypress backswamp indicates centennial-scale fluctuations in forest composition during the last 2400 years. Backswamp vegetation has occupied the site since land clearance began ~300 years ago. Recent dam emplacement affected sedimentation rates, but vegetation changes are small compared with those caused by pre-Colonial climate variability. The occurrence of wetter conditions from ~2200 to 1800 cal. yr BP, ~1100 to 750 cal. yr BP, and ~400 to 250 cal. yr BP may indicate changes in cyclonic circulation patterns related to shifts in the position of the Bermuda High and jet stream.

  15. Diet and habitat of the saiga antelope during the late Quaternary using stable carbon and nitrogen isotope ratios

    Jürgensen, Jonathan; Drucker, Dorothée G.; Stuart, Anthony J.; Schneider, Matthias; Buuveibaatar, Bayarbaatar; Bocherens, Hervé


    Saiga antelope (Saiga tatarica) is one of the typical late Pleistocene species of the cold and arid mammoth steppe that covered a large area of northern hemisphere. The species is currently endangered and persists only in small areas of Central Asian steppe and desert ecosystems. The investigation of the ecology of the Pleistocene saiga using stable isotope ratios (δ13C, δ15N) aimed to decipher how different their diet and habitat were from those observed nowadays in relict populations. Up to 76 samples of bone collagen of ancient saiga from Western Europe, Siberia and Eastern Beringia were analysed and compared with 52 samples of hair and bone collagen of modern specimens from Kazahkstan, Russia and Mongolia. The δ13C values of the ancient saiga do not exhibit a clear trend over time. They cover the same range of values as the modern ones, from a C3-dominated to a C3-C4-dominated mixed diet (including probably Chenopodiaceae). In contrast, the δ15N values of fossil saigas are more variable and lower on average than the extant ones. The lowest δ15N values of ancient saiga are found around the Last Glacial Maximum, reflecting the influence of the cold conditions at that time. On the other hand, fossil saiga occupying the same regions as the historical and modern populations exhibit high δ15N values similar to the modern ones, confirming ecological continuity over time. Modern saiga is thus occupying just one of its potential diverse habitats they used in the past. Therefore, the extant saiga is not a refugee species confined to a suboptimal habitat. During the late Pleistocene, the saiga occupied a separate niche compared with the other ungulates of the mammoth steppe. However, this species could also adapt to a lichen-dominated diet normally seen in reindeer, leading to an isotopic overlap between the two species in south-western France and Alaska around the Last Glacial Maximum. This adaptation allowed a geographical expansion that does not correspond to a

  16. Late Quaternary floods and droughts in the Nile valley, Sudan: new evidence from optically stimulated luminescence and AMS radiocarbon dating

    Williams, M. A. J.; Williams, F. M.; Duller, G. A. T.; Munro, R. N.; El Tom, O. A. M.; Barrows, T. T.; Macklin, M.; Woodward, J.; Talbot, M. R.; Haberlah, D.; Fluin, J.


    Our results show that the late Pleistocene Nile in northern Sudan was shifting position and actively aggrading at 145 ± 20 kyr, 83 ± 24 kyr, 32 ± 8 kyr and 20.7 ± 0.2 kyr and indicate, for the first time, a phase of high-energy flow in the White Nile at 27.8 ± 3.2 kyr, with still high but somewhat reduced flow in that river at 13.3 kyr, 10 kyr and 4.8-4.0 kyr. Beach ridges associated with a 386 m strandline of the White Nile have OSL ages of 27.5 ± 2.7 kyr and 14.5 ± 1.6 kyr. The Holocene terraces and former channels of the main Nile have ages of 11 kyr, 6.5-5.0 kyr and 4.8-4.0 kyr, after which there was a general decline in flood discharge. The now arid main Nile valley in northern Sudan was significantly wetter during the early to middle Holocene, with a lake up to 450 km 2 in area, fed by an overflow channel from the early Holocene Nile between 9.5 kyr and 7.5 kyr. Previously stable late Pleistocene dunes were reactivated at intervals during the Holocene, with five samples from the White Nile valley indicating brief phases of Holocene dune activity at 9.9 ± 2.0 kyr, 9.0 ± 2.8 kyr, 6.6 ± 0.9 kyr, 4.8 ± 0.9 kyr and 2.9 ± 0.5 kyr, the earliest of which occurred within periods of generally wetter climate and higher Nile flow. The youngest freshwater shells on the Khor Abu Habl alluvial fan west of the White Nile correspond to a time of regionally wetter climate between 1.7 and 1.0 kyr. Our results suggest that millennial scale climatic instability may have been characteristic of Holocene climates in this region.

  17. Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

    Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.


    Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22–21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12–9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

  18. Late neogene and early quaternary paleoenvironmental and paleoclimatic conditions in southwestern Europe: isotopic analyses on mammalian taxa.

    Domingo, Laura; Koch, Paul L; Hernández Fernández, Manuel; Fox, David L; Domingo, M Soledad; Alberdi, María Teresa


    Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ~11.1 to 0.8 Ma, late Miocene-middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ(13)C values (relative to VPDB, mean -10.3 ± 1.1‰; range -13.0 to -7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ(13)C values increase at ~9.5 Ma (MN9-MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ(13)C value drops significantly at ~4.2-3.7 Ma (MN14-MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ(13)C values from ~2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (~6.3-0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation.

  19. Late neogene and early quaternary paleoenvironmental and paleoclimatic conditions in southwestern Europe: isotopic analyses on mammalian taxa.

    Laura Domingo

    Full Text Available Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ~11.1 to 0.8 Ma, late Miocene-middle Pleistocene of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ(13C values (relative to VPDB, mean -10.3 ± 1.1‰; range -13.0 to -7.4‰ are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ(13C values increase at ~9.5 Ma (MN9-MN10, probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ(13C value drops significantly at ~4.2-3.7 Ma (MN14-MN15 during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ(13C values from ~2.6 Ma onwards (MN16, most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records is a gradual drop between MN13 and the middle Pleistocene (~6.3-0.8 Ma most likely due to cooling associated with Northern Hemisphere glaciation.

  20. Late Neogene and Early Quaternary Paleoenvironmental and Paleoclimatic Conditions in Southwestern Europe: Isotopic Analyses on Mammalian Taxa

    Domingo, Laura; Koch, Paul L.; Hernández Fernández, Manuel; Fox, David L.; Domingo, M. Soledad; Alberdi, María Teresa


    Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ∼11.1 to 0.8 Ma, late Miocene–middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ13C values (relative to VPDB, mean −10.3±1.1‰; range −13.0 to −7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ13C values increase at ∼9.5 Ma (MN9–MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ13C value drops significantly at ∼4.2−3.7 Ma (MN14–MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ13C values from ∼2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (∼6.3−0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation. PMID:23717470

  1. Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

    Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon A.; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.


    Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22-21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12-9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

  2. Late Quaternary environmental change in the interior South American tropics: new insight from leaf wax stable isotopes

    Fornace, Kyrstin L.; Whitney, Bronwen S.; Galy, Valier; Hughen, Konrad A.; Mayle, Francis E.


    Stable isotope analysis of leaf waxes in a sediment core from Laguna La Gaiba, a shallow lake located at the Bolivian margin of the Pantanal wetlands, provides new perspective on vegetation and climate change in the lowland interior tropics of South America over the past 40,000 years. The carbon isotopic compositions (δ13C) of long-chain n-alkanes reveal large shifts between C3- and C4-dominated vegetation communities since the last glacial period, consistent with landscape reconstructions generated with pollen data from the same sediment core. Leaf wax δ13C values during the last glacial period reflect an open landscape composed of C4 grasses and C3 herbs from 41-20 ka. A peak in C4 abundance during the Last Glacial Maximum (LGM, ∼21 ka) suggests drier or more seasonal conditions relative to the earlier glacial period, while the development of a C3-dominated forest community after 20 ka points to increased humidity during the last deglaciation. Within the Holocene, large changes in the abundance of C4 vegetation indicate a transition from drier or more seasonal conditions during the early/mid-Holocene to wetter conditions in the late Holocene coincident with increasing austral summer insolation. Strong negative correlations between leaf wax δ13C and δD values over the entire record indicate that the majority of variability in leaf wax δD at this site can be explained by variability in the magnitude of biosynthetic fractionation by different vegetation types rather than changes in meteoric water δD signatures. However, positive δD deviations from the observed δ13C- δD trends are consistent with more enriched source water and drier or more seasonal conditions during the early/mid-Holocene and LGM. Overall, our record adds to evidence of varying influence of glacial boundary conditions and orbital forcing on South American Summer Monsoon precipitation in different regions of the South American tropics. Moreover, the relationships between leaf wax stable

  3. Late Quaternary Activity and Seismogenic Potential of the Gonave Microplate: Plantain Garden Strike-Slip Fault Zone of Eastern Jamaica

    Mann, P.; Prentice, C.; King, W.; Demets, C.; Wiggins-Grandison, M.; Benford, B.


    At the longitude of Jamaica, Caribbean (Carib)-North America (Noam) plate motion of 19 ± 2 mm/a is carried by two parallel, left-lateral strike-slip faults, the Oriente fault zone, immediately south of Cuba, and the Enriquillo-Plantain Garden fault zone (EPGFZ), which lies 100-150 km further south. It has been postulated that the lithosphere between these faults constitutes an independent Gonave microplate that has formed in response to the ongoing collision between the leading edge of Carib in Hispaniola and the Bahama carbonate platform. GPS measurements in Jamaica and Hispanola is supportive of the microplate hypothesis and indicates that roughly half of Carib-Noam plate motion (8-14 mm/a) is carried by the EPGFZ of southern Hispaniola and eastern Jamaica. This study applies geomorphic and paleoseismic methods as a direct test of the activity and amount of microplate motion carried on the Plantain Garden fault segment of eastern Hispaniola and how this motion is distributed across a large restraining bend that has formed the island of Jamaica since the late Miocene. The EPFZ curves gently to the northeast and forming a steep mountain front to the Blue Mountains restraining bend with elevations up to 2200 m. Geomorphic fault-related features along the mountain front fault zone include left-laterally deflected rivers and streams, but no small scale features indicative of Holocene activity. River and stream deflections range from 0.1 to 0.5 km. We identified and trenched the most active trace of the mountain front fault at the Morant River where the fault is characterized by a 1.5-m-wide sub-vertical fault zone juxtaposing sheared alluvium and fault Cretaceous basement rocks This section is overlain by a 6-m-thick fluvial terrace. Trenching in the unfaulted terrace immediately overlying the fault trace revealed radiocarbon and OSL ages ranging from 20 to 21 ka that are consistent with a prominent unfaulted alluvial fan along the projection of this fault 1.5 km to

  4. Reconstructing late Quaternary palaeosol development and landscape connectivity from combined soil magnetic, geochemical and micromorphological analyses: insights from the Wilgerbosch River, Great Karoo, South Africa.

    Oldknow, Chris; Hooke, Janet; Oldfield, Frank


    The characteristics, spatial and temporal patterns and drivers of Quaternary climate change across South Africa remain contentious principally due to the paucity of dated proxy records. River and fan terrace palaeosols may offer an important addition to analysis of spatially pervasive geomorphological landforms (palaeolake shorelines, terraces, dunes) conventionally used to reconstruct patterns of palaeoenvironmental change. In the Great Karoo, alluvial and colluvial exposures in the Wilgerbosch River and several of its tributaries have revealed up to five late Quaternary terraces of varying thickness, extent and pedogenic overprinting which may be of palaeoenvironmental significance. A combination of geochronology (OSL and radiocarbon), soil micromorphology, geochemistry (XRF, XRD) and soil magnetic proxies on both bulk (0-63 μm) and particle size extracts (0-4 and 32-63 μm) from major terrace palaeosols was used in order to establish: 1) changing sediment fluxes and pathways; 2) the characteristics and drivers of palaeosol formation; and 3) evaluate the suitability of these terrace palaeosols as indicators of palaeoenvironmental change. The results are used to test a conceptual model of landscape connectivity. Colluvial (slopewash, head deposits) sedimentation on the valley floors occurred around the time of the LGM due to enhanced regolith production through physical weathering. Soils overprinting these deposits (T1) are goethite-rich attesting to reducing conditions. Incision into T1 resulted in an extensive channel network forming. High concentrations of mafic minerals (Fe, Cr, Ca, Ti) and enhanced ferrimagnetism (XLF > 80) in the 32-63 μm fraction indicated connectivity with slope colluvium proximal to weathering dolerite tors. Fluvial aggradation (T2) occurred as a complex response to this phase of connectivity and terminated in the Late Glacial period (around 17±2.5 ka). The development of a rhizogenic calcrete overprinting T2 indicated an elevated

  5. Climatic and topographic controls on the style and timing of Late Quaternary glaciation throughout Tibet and the Himalaya defined by 10Be cosmogenic radionuclide surface exposure dating

    Owen, L.A.; Finkel, R.C.; Barnard, P.L.; Haizhou, Ma; Asahi, K.; Caffee, M.W.; Derbyshire, E.


    Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10Be cosmogenic radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a-1) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500-600 mm a-1) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (???300 mm a -1) and the Tanggula Shan (400-700 mm a-1). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early-mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western

  6. Late Quaternary extraglacial cold-climate deposits in low and mid-altitude Tasmania and their climatic implications

    McIntosh, P. D.; Eberhard, R.; Slee, A.; Moss, P.; Price, D. M.; Donaldson, P.; Doyle, R.; Martins, J.


    dominated Tasmania's climate and rain-bearing depressions generally passed south of the land mass. However in the east prominent palaeosols in aeolian deposits, dated between 26.4 ka and 16 ka at different locations, and palaeosols with morphology indicating formation under humid conditions, indicate periods of wetter climate in eastern Tasmania during or close to the LGM, deduced to be the result of easterlies associated with near-coastal depressions in the western Tasman Sea. Such easterlies may also be responsible for short Last Glacial wet periods noted at mainland coastal sites. A plot of ages of all dated deposits reveals an increase of erosion and deposition between 35 and 20 ka, and greater prevalence of aeolian deposits in the 35-15 ka period than earlier in the Last Glacial. There are two possible explanations for this pattern: (1) that aeolian activity increased as the result of climatic effects (e.g. increased windiness); or (2) that shrubland biomass increased after the megafauna were hunted to extinction following human arrival c. 40 ka, causing increased fire frequency, and in the cold dry climate of the late Last Glacial such fires caused increased erosion and increased aeolian accumulation.

  7. Paleoclimate change recorded in the red earth and brown-yellow sediment of Late Quaternary for northeastern part of Guangdong Province, south to the Nanling Mountains, China

    LI BaoSheng; NIU DongFeng; YANG Yi; WEN XiaoHao; DAVID DianZhang; QIU ShiFan; DONG YüXiang; LI ZhiWen; DU ShuHuan; QIU XianJiao; LI HouXin


    The paleoenvironment indicated by the geochronology, major oxides-SiO2, AI203 and TOFE (Fe203 +FeO), and CIA (Chemical Index of Alteration) value of the red earth and brown-yellow silt primarily characterized by the Linjiang stratigraphic section, based on the geological investigation of Late Quaternary along the river banks of northeastern part of China's Guangdong Province, south to the Nanling Mountains, allow us to hypothesize that the red earth on the first terrace in northeastern part of Guangdong belongs to reticulated red clay developed in a hot-wet environment of the last interglacial period (132-73 ka BP), similar to the monsoon environment in the northern margin of modern tropical zone, while the overlying brown-yellow silt layer mainly accumulated in a monsoon environment of warm temperate zone in the last glacial period (73-11 ka BP), with the aeolian sand LJ3 representing an extreme period of worsening climate. Such a hypothesis corresponds well with predecessors' research on the paleoenvironment indicated by abundant fossils in both south and east to the Nanling Mountains. Hence, it follows that the bioclimatic zone did experience a large and rapid vicissitude in northeastern part of China's Guangdong Province, and even in the full extent of the region south to the Nanling Mountains from the last interglacial period to the last glacial period, with the red earth being replaced by the brown-yellow silty sediment, and even maybe with the Ailuropoda-Stegodon Fauna being replaced by the Penghu Fauna. This study may provide an important geological demonstration for the environmental response to global change in China's low latitudes on a 10 ka scale.

  8. Geomorphology of Late Quaternary Mass Movement Deposits using a Decimetre-Resolution 3D Seismic Volume: Case Studies from Windermere, UK, and Trondheimsfjorden, Norway

    Vardy, M. E.; Dix, J. K.; Henstock, T.; Bull, J. M.; Pinson, L.; L'Heureux, J.; Longva, O.; Hansen, L.; Chand, S.; Gutowski, M.


    We present results from decimetre resolution 3D seismic volumes acquired over Late Quaternary mass movement deposits in both Lake Windermere, UK, and the Trondheim Harbour area, central Norway. Both deposits were imaged using the 3D Chirp sub-bottom profiler, which combines the known, highly repeatable source waveform of Chirp profilers with the coherent processing and interpretation afforded by true 3D seismic volumes. Reflector morphology from these two volumes are used to identify and map structure on scales of 10s cm to 100s metres. This shows the applicability of the method for the interpretation of failure mechanism, flow morphology and depositional style in these two environments. In Windermere, Younger Dryas deposits have been substantially reworked by the episodic redistribution of sediment from the steep lakesides into the basin. Within the 100 x 400 m 3D seismic volume we identify two small debris flow deposits (1500 m3 and 60,000 m3) and one large (500,000 m3) erosive mass flow deposit. These two depositional mechanisms are distinct. The debris flows have high amplitude, chaotic internal reflections, with a high amplitude reflector representing a lower erosional boundary, discontinuous low amplitude top reflector, and thin out rapidly with distance from the lake margin. The thicker mass flow unit lacks internal structure, and has high amplitude top and base reflectors,. In the Trondheim Harbour we image the down-slope extent of three large slide blocks (which have a net volume > 1 x 106 m3), mobilised by a landslide in 1990, in the 100 x 450 m 3D seismic volume. The morphology of these mass movement deposits is distinct again; demonstrating translational failure along a clear slip plane, leaving well defined slide scars, and forming prominent compressional/extensional structures.

  9. Systematics and evolution of the Meriones shawii/grandis complex (Rodentia, Gerbillinae) during the Late Quaternary in northwestern Africa: Exploring the role of environmental and anthropogenic changes

    Stoetzel, Emmanuelle; Cornette, Raphaël; Lalis, Aude; Nicolas, Violaine; Cucchi, Thomas; Denys, Christiane


    Rodents of the Meriones shawii/grandis complex have been attested to in North Africa since the Middle Pleistocene and are abundant in archaeological sites. Today, they are widely spread and represent a major pest to local human populations. This complex, therefore, represents an accurate model for investigating the roles of climate change and human impact in shaping Quaternary faunal diversity and distribution. Many gray areas still exist regarding the systematics, ecology and geographical distribution of this complex, for both present and past populations. The purpose of this study is to compare modern genotyped and fossil Meriones specimens in order to 1) clarify the current systematics and distribution of the Meriones populations of the shawii/grandis complex, 2) document the taxonomic diversity in fossil Meriones from northwestern Africa, and 3) track their phenotypic and biogeographic evolution through time. To answer these questions we used geometric morphometrics on skulls (landmarks) and first upper molars (landmarks and sliding landmarks). We evidenced the existence of two morpho-groups within the M. shawii/grandis complex, with a clear geographic pattern (M. grandis in Morocco vs. M. shawii in Algeria and Tunisia). Currently only one morpho-group, attributed to M. grandis, seems to exist in Morocco, with a small overlap with M. shawii in the most eastern part of the country. However, according to fossil data, M. shawii was also present in Atlantic Morocco during the Late Pleistocene. We have also highlighted the impact of Holocene climate change and habitat anthropization on this arid adapted group. During the Middle Holocene, a major climatic event (last interglacial optimum) seems to have induced a demographic collapse in Moroccan populations and the disappearance of the shawii clade from Morocco (except in the most eastern areas). Both species then re-expanded, benefitting from the increasing aridity and the new ecological niche driven by agriculture

  10. Sedimentary ancient DNA and pollen reveal the composition of plant organic matter in Late Quaternary permafrost sediments of the Buor Khaya Peninsula (north-eastern Siberia)

    Hildegard Zimmermann, Heike; Raschke, Elena; Saskia Epp, Laura; Rosmarie Stoof-Leichsenring, Kathleen; Schwamborn, Georg; Schirrmeister, Lutz; Overduin, Pier Paul; Herzschuh, Ulrike


    Organic matter deposited in ancient, ice-rich permafrost sediments is vulnerable to climate change and may contribute to the future release of greenhouse gases; it is thus important to get a better characterization of the plant organic matter within such sediments. From a Late Quaternary permafrost sediment core from the Buor Khaya Peninsula, we analysed plant-derived sedimentary ancient DNA (sedaDNA) to identify the taxonomic composition of plant organic matter, and undertook palynological analysis to assess the environmental conditions during deposition. Using sedaDNA, we identified 154 taxa and from pollen and non-pollen palynomorphs we identified 83 taxa. In the deposits dated between 54 and 51 kyr BP, sedaDNA records a diverse low-centred polygon plant community including recurring aquatic pond vegetation while from the pollen record we infer terrestrial open-land vegetation with relatively dry environmental conditions at a regional scale. A fluctuating dominance of either terrestrial or swamp and aquatic taxa in both proxies allowed the local hydrological development of the polygon to be traced. In deposits dated between 11.4 and 9.7 kyr BP (13.4-11.1 cal kyr BP), sedaDNA shows a taxonomic turnover to moist shrub tundra and a lower taxonomic richness compared to the older samples. Pollen also records a shrub tundra community, mostly seen as changes in relative proportions of the most dominant taxa, while a decrease in taxonomic richness was less pronounced compared to sedaDNA. Our results show the advantages of using sedaDNA in combination with palynological analyses when macrofossils are rarely preserved. The high resolution of the sedaDNA record provides a detailed picture of the taxonomic composition of plant-derived organic matter throughout the core, and palynological analyses prove valuable by allowing for inferences of regional environmental conditions.

  11. Millennial-Scale Hydroclimate Variation in North America during the Late-Quaternary: Evidence from a Network of Lake-Level Reconstructions

    Shuman, B. N.


    The North American hydrologic cycle has undergone both long-term and abrupt changes during the late-Quaternary Period, and these changes have dramatically altered continental moisture gradients. A newly updated database of lake elevation data, based on geomorphic and sedimentological evidence, provides evidence that much of the United States and Canada is wetter today than during much of the last 15000 years. The number of lakes classified as low across the continent shows a strong correlation with summer insolation anomalies during this period. Multi-century episodes of aridity, however, are also evident and appear superimposed upon such orbitally-forced trends. For example, in the southern Rocky Mountains, geophysical surveys and transects of sediment cores collected from multiple lakes show a series of paleoshorelines submerged below the modern lake surfaces. One particularly prominent paleoshoreline, found at multiple sites, spans a 1500-yr period from 3700-1200 cal yr BP when dunes in the region are also active. An earlier paleoshoreline at these lakes spans the Younger Dryas interval (12,900-11700 cal yr BP). By linking data such as these across multiple regions, we show the spatial patterning of dry events for comparison with modern droughts and climate model output. Some dry episodes span sites from the northeast U.S. to the western Interior (e.g., just prior to 1200 cal yr BP), and are therefore similar in extent to the severe 1930s drought. Other episodes, such as the Younger Dry interval, show patterning similar to the common north-south dipole pattern of moisture availability documented historically in the western United States. These episodes require mechanistic explanation, which their spatial fingerprints may help to elucidate.

  12. Late Quaternary Glaciations in the Central Peruvian Andes (10°-11°S) and Evidence for a Link to Heinrich Events

    Smith, J. A.; Farber, D. L.; Finkel, R. C.; Rodbell, D. T.; Seltzer, G. O.


    Seven cosmogenic 10Be ages from a moraine in the Santuario Nacional Bosque de Piedras de Huayllay (BP) in the Western Cordillera of the central Peruvian Andes (10°59'S, 76°20'W, 4180-4200 masl) are consistent with 10Be ages on moraines in both the Eastern Cordillera (40-45 km to the east) and Nevado Jeulla Rajo (NJR) massif (10°00'S, 77°16'W) at the southern end of the Cordillera Blanca (150 km to the northwest). In the BP, 10Be ages are ~14-15 ka on four ignimbrite boulders, ~26 and ~20 ka on two quartz boulders, and ~45 ka on ignimbrite bedrock below the trimline in the valley wall. In the Eastern Cordillera bordering Lake Junin, the most extensive glaciations are >150 ka, but end moraines farther upvalley date to the local last glacial maximum (LLGM; 25-30 ka) and a late-glacial stillstand or readvance (14-18 ka). In NJR, 10Be ages indicate that the largest lateral moraines were deposited during similar intervals (27-32 ka and 14-18 ka). Avulsion of a glacial valley preserved an older, smaller pair of lateral moraines (56-65 ka) in NJR; correlative moraines were apparently not preserved in the Junin valleys. We have found no moraines in NJR that date to the global LGM (ca. 19-24 ka), but see some evidence for an advance ca. 40-48 ka. Outwash deposits (ca. 43-50 ka) located beyond the termini of NJR moraines are underlain by lodgement till that extends ca. 6 km across the Conococha Plain, suggesting that at least one older glaciation was far more extensive than any of the late Quaternary NJR advances dated by 10Be (ages calculated using CRONUS-Earth Online Calculator v. 2.2, Lal/Stone time-dependent scaling, and zero erosion). The timing of glacial advances in the central Peruvian Andes since 70 ka suggests a correlation to Heinrich events and associated southward shifts of the Intertropical Convergence Zone (ITCZ) in the Atlantic Ocean. We propose that Peruvian glaciers typically expanded when southward migration of the ITCZ resulted in increased

  13. Meteoric sphaerosiderite lines and their use for paleohydrology and paleoclimatology

    Ludvigson, Greg A.; Gonzalez, Luis A.; Metzger, R.A.; Witzke, B.J.; Brenner, Richard L.; Murillo, A.P.; White, T.S.


    Sphaerosiderite, a morphologically distinct millimeter-scale spherulitic siderite (FeCO3), forms predominantly in wetland soils and sediments, and is common in the geologic record. Ancient sphaerosiderites are found in paleosol horizons within coal-bearing stratigraphic intervals and, like their modern counterparts, are interpreted as having formed in water-saturated environments. Here we report on sphaerosiderites from four different stratigraphic units, each of which has highly variable 13C and relatively stable 18O compositions. The unique isotopic trends are analogous to well-documented meteoric calcite lines, which we define here as meteoric sphaerosiderite lines. Meteoric sphaerosiderite lines provide a new means of constraining ground-water ??18O and thus allow evaluation of paleohydrology and paleoclimate in humid continental settings.


    V. D. Mats


    Full Text Available The article reviews three typical concepts concerning the age of the Baikal rift (BR which development is still underway: 5 Ma (the BR development start in the Late Pliocene, 30 Ma (Miocene or Oligocene, and 60–70 Ma (the Late Cretaceous. Under the concept of the young BR age (Pliocene–Quaternary [Artyushkov, 1993; Nikolaev et al., 1985; Buslov, 2012], according to E.V. Artyushkov, BR is not a rift, but a graben due to the fact that the pre‐Pliocene structure of BR does not contain any elements that would be indicative of tensile stresses. However, field studies reported in [Lamakin, 1968; Ufimtsev, 1993; Zonenshain et al., 1995; Mats, 1993, 2012; Mats et al., 2001] have revealed that extension structures, such as tilted blocks and listric faults, are abundant in the Baikal basin (BB, and thus do not supportE.V. Artyushkov’s argumentation. The opinion that BR is young is shared by M.M. Buslov [2012]; he refers to studies of  Central Asia and states that only the Pliocene‐Quaternary structure of BB is a rift, while the oldest Cenozoic structures (Upper Cretaceous – Miocene are just fragments of the large Cenozoic Predbaikalsky submontane trough (PBT which are not related to the rift. However, the coeval Cenozoic lithological compositions, thicknesses of sediment layers and types of tectonic structures in PBT and BB have nothing in common. Across the area separating PBT and BB, there are no sediments or structures to justify a concept that BR and PBT may be viewed as composing a single region with uniform structures and formations. The idea of the Pliocene‐Quaternary age of BR should be rejected as it contradicts with the latest geological and geophysical data. Seismic profiling in BB has revealed the syn‐rift sedimentary bed which thickness exceeds 7.5 km. Results of drilling through the 600‐metre sedimentary sequence of Lake Baikal suggest the age of 8.4 Ma [Horiuchi et al., 2004], but M.M. Buslov believes

  15. Late Quaternary evolution of the East Asian summer monsoon: Clay and magnetic mineralogical records retrieved from the northern South China Sea

    Chen, Q.; Liu, Z.; Kissel, C.


    East Asian monsoon is a major component of global monsoon system. Acting as the largest marginal sea in the western Pacific, the South China Sea is a natural laboratory recording East Asian monsoon evolution. In order to reconstruct the late Quaternary evolution of the monsoon, we analyzed in details the 50.8-m-long Core MD12-3432 retrieved from the northern South China Sea at 2125 m water depth. Carbonate and magnetic stratigraphy indicates that Core MD12-3432 covers the last 400 ka. Clay mineralogical analysis was performed every 10 cm using XRD method. Bulk magnetic properties (susceptibility, NRM, ARM, and IRM) were measured on u-channel samples with a resolution of 2 cm. Cumulative log Gaussian decomposition analysis was performed on 33 high resolution IRM acquisition curves to evaluate the contribution of coercivity components. Three-axis thermal demagnetization was conducted on 14 samples to identify the nature of magnetic minerals. Clay mineral assemblage of Core MD12-3432 is dominated by smectite (23-59%) and illite (22-43%), with minor chlorite (13-27%) and kaolinite (4-13%). Because smectite is formed by rapid chemical weathering of volcanic rocks in Luzon, while illite and chlorite are primary minerals formed by physical erosion, smectite/(illite+chlorite) ratio constitutes a proxy of chemical weathering intensity. Magnetic fraction of Core MD12-3432 is composed by minerals with different coercivities, the relative proportion of which varies along the core. The high coercivity is carried by hematite and the low coercivity fraction is mainly composed by magnetite with some iron-sulphides. Luzon is the most efficient source of magnetite because of the rapid eluviation and weathering of volcanic rocks, while the Pearl River basin is the only source that produces hematite mainly through physical degradation of bedrocks. Thus, the bulk coercivity as indicated by S-ratio can serve as a proxy of chemical weathering. Both indicators, smectite

  16. Reconstruction of late Quaternary relative humidity changes on the southern slopes of Mt. Kilimanjaro, East Africa, using a coupled δ2H-δ18O biomarker paleohygrometer

    Hepp, Johannes; Zech, Roland; Rozanski, Kazimierz; Tuthorn, Mario; Glaser, Bruno; Greule, Markus; Keppler, Frank; Huang, Yongsong; Zech, Wolfgang; Zech, Michael


    Our understanding of African paleoclimate/-hydrological history is decisively based on lake level and lake sediment studies. It furthermore improved remarkably during the last decade thanks to emerging stable isotope techniques such as compound-specific deuterium analysis of sedimentary leaf wax biomarkers (δ2Hleaf wax). Here we present results from a multi-proxy biomarker study carried out on a ~100 ka paleosol sequence developed in the Maundi crater at ~2780 m a.s.l. on the southeastern slopes of Mt. Kilimanjaro in equatorial East Africa. The Maundi stable isotope records established for hemicellulose-derived sugars, lignin- and pectin-derived methoxyl groups and leaf wax-derived fatty acid and n-alkane biomarkers (δ18Osugars, δ2Hmethoxyl groups, δ2Hfatty acids and δ2Hn-alkanes) reveal differences but also similar patterns. Maxima characterize the period from 70 to 60 ka, the last glacial maximum (LGM) and the Younger Dryas (YD), whereas minima occur during the Holocene. The application of a 'coupled δ2Hn-alkane-δ18Osugar paleohygrometer' allows the reconstruction of the Late Quaternary relative humidity (RH) history of the Maundi study site. Accordingly, the reconstructed RH changes are well in agreement with the Maundi pollen results. Apart from the overall regional moisture availability, the intensification versus weakening of the trade wind inversion, which affects the diurnal montane atmospheric circulation on the slopes of Mt. Kilimanjaro, is suggested as local second important factor controlling the RH history at Maundi. Furthermore, the Maundi results of the coupled δ2Hn-alkane-δ18Osugar approach caution against interpreting δ2Hleaf wax (as well as δ18Osugar) records straight forwards in terms of reflecting δ2Hprec, because variably and primarily RH-dependent isotopic evapotranspirative enrichment of leaf water can mask δ2Hprec changes. Concerning the biomarker-based reconstructed Maundi δ2H/δ18Oprec record, the comparison with the

  17. Slip Rate on the Altyn Tagh Fault on the West of the Cherchen River (Between 85°~85°45′E) Since Late Quaternary

    Wang Feng; Li Ming; Xu Xiwei; Zheng Rongzhang; Chen Wenbin


    Because of the significance to the formation and evolution of the Tibetan plateau, the displacement and slip rate of the Altyn Tagh fault have been topics full of disputation.Scientists who hold different opinions on the evolution of Tibet insist on different slip rates and displacements of the fault zone.In the article, study is focused on the late Quaternary slip rate of the Altyn Tagh fault west of the Cherchen River (between 85°E and 85°45' E). On the basis of high resolution SPOT images of the region, three sites, namely Koramlik, Aqqan pasture and Dalakuansay, were chosen for field investigation. To calculate the slip rate of the fault, displacement of terraces was measured on SPOT satellite images or in situ during fieldwork and thermo-luminescence (TL) dating method was used. To get the ages of terraces, samples of sand were collected from the uppermost sand beds that lie just under loess. The method for calculating slip rate of fault is to divide the displacement of terrace risers by the age of its neighboring lower terrace. The displacement of rivers is not considered in this article because of its uncertainties.At Koramlik, the slip rate ofthe Altyn Tagh fault is 11.6 ± 2.6mm/a since 6.02 ± 0.47kaB.P and 9.6 ± 2.6mm/a since 15.76 ± 1.19ka B.P.At Aqqan pasture, about 30km west of Koramlik, the slip rate is 12.1 ± 1.9mm/a since2.06±0.16 ka B.P.At Dalakuansayi, the slip rate of the fault is 12.2 ± 3.0mm/a since 4.91 ± 0.39ka B.P.Hence, we get the average slip rate of 11.4 ± 2.5mm/a for the western part of the Altyn Tagh Fault since Holocene. This result is close to the latest results from GPS research .

  18. Reconciling late Quaternary transgressions in the Bohai Sea, China to the global sea level changes, and new linkage of sedimentary records to three astronomical rhythms

    Yi, Liang


    noticeable feature of these coastal sediment variations is the little internal similarity between records compared with high similarity with external forcing indicating that the coastal sediments in the south Bohai Sea integrate different influences from various environmental factors: (1) the grain-size variation represents Asian monsoon intensity which was dominated by both solar insolation (major) and global ice volume (minor) forcing; (2) the magnetic susceptibility indicates river incision processes which were sensitive to orbital tilt with influence from solar insolation; (3) the vegetation coverage responded to global ice volume coupled obliquity changes; and that (4) neither external nor internal factors could dominate the paleoenvironmental evolution on orbital timescales in an independent way, and they are both integrated in a complex pattern. Therefore, combining all of these results, we report those great similarities between regional and global sea-level patterns and the nonlinear interaction and the complex response to driving processes in a coastal evolution. However, all of these studies only used the upper part of cores within marine strata, and the rest containing lacustrine sediment is still in process. Sediment grain size, magnetic susceptibility, color reflectance were finished, and the magnetostratigraphic, environmental magnetism and element analysis are ongoing. More results about high-/low-latitude interaction and relative sea level will be released in three years, and anyone who has interests in cooperation will be welcome (Email: References Chappell, J., Omura, A., Esat, T., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth and Planetary Science Letters 141, 227-236. Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice Age

  19. Radiocarbon dates of late quaternary mammals in the Archangelsk Region and their contribution to reconstructions of the last glaciation in Eastern Europe

    Ponomarev, D. V.; Markova, A. K.; van Kolfschoten, T.; van der Plicht, J.; Yushkin, N.P.


    Twelve new AMS (Accelerator Mass Spectrometry) dates of large Quaternary mammal remains were reported: mammoth (Mammuthus primigenius, bison (Bison priscus), and musk ox (Ovibos pallantis) found in the Archangelsk Region. The absolute age of the identified samples varies from 46 000 to 22 000 calibr

  20. Late Quaternary Incisions and Related Shallow Subsurface Stratigraphy on the New Jersey Mid-Outer Shelf: Preliminary Results from Ultra-High Resolution Chirp Sonar Images - Part I

    Nordfjord, S.; Gulick, S. P.; Austin, J. A.; Goff, J. A.; Fulthorpe, C. S.


    dates), which show the age of "R" to be between ~43.1 kyr and 47.8 kyr. "R" appears at the base of the outer shelf sediment wedge as a high-amplitude, continuous reflection and shoals landward to the middle shelf, where it is in places truncated by the seafloor. While some channels are capped by and therefore older then "R", the majority of observed buried channels either incise "R" or lie stratigraphically above "R". The variety of buried channels on the New Jersey shelf suggest that late Quaternary channelized flow occurred over a large range of spatial scales, from widths of hundreds of meters and thicknesses of a few meters to widths of kilometers and thicknesses of tens of meters. Generally, trunk (main) channels have box-like cross-sections, with flat floors and high width/depth ratios. Smaller, tributary channels have v-shaped cross-sections with lower width/depth ratios. We believe that the observed range of channel types is likely influenced by both the magnitude of discharge and the character of the flow regime. The deepest channel fills have never been sampled, despite repeated attempts using both vibra- and piston coring. However, in September/October 2002, the GLAD-800 system, modified with heave compensation, was used aboard the R/V Knorr to determine lithologies and physical properties at depths previously unattainable.

  1. Southern Westerly Winds submit to the ENSO regime: A multiproxy paleohydrology record from Lake Dobson, Tasmania

    Rees, Andrew B. H.; Cwynar, Les C.; Fletcher, Michael-Shawn


    The El Niño-Southern Oscillation (ENSO) and Southern Westerly Winds (SWW) profoundly influence synoptic-scale climate in the Southern Hemisphere. Although many studies have invoked either phenomenon to explain trends in proxy data, few have demonstrated the transition from a climate dominated by SWW flow to one controlled by El Niño activity, which is postulated to have occurred after 5 cal ka BP in the mid-latitudes of the Southern Hemisphere. Tasmania, southeast Australia, is ideally situated to detect changes in both of these climatic controls. Currently, El Niño and La Niña events result in drier and wetter conditions island-wide, respectively, with the greatest impact in the north. Further, Tasmania houses north-south trending mountain ranges near its western coast. As a result, areas west of the mountains exhibit a positive correlation between SWW flow and precipitation, while eastern regions possess either no or a negative relationship. Here, we present data from chironomid remains, charcoal, and geochemical proxies to investigate the paleohydrological history of Lake Dobson, a site located in Mount Field National Park, Tasmania. The proxies revealed three broad periods: (1) an early Holocene (11.5-8.3 cal kyr BP) characterised by generally high rainfall, the occurrence of irregular fires, and elevated charcoal influx at 11.4 and 10.2 cal ka BP - conditions compatible with attenuated SWW flow over the site; (2) an ambiguous mid-Holocene (8.3-5 cal kyr BP) that marks the transition from a SWW- to ENSO-dominated climate; and (3) a relatively dry and stable late Holocene (5 cal kyr BP to present) that is consistent with the onset of a climate controlled by ENSO activity (i.e., characterised by a more mean El Niño climate state). The proxy record of Lake Dobson highlights the teleconnections between the equatorial Pacific and southern Australasia.

  2. Testate Amoebae as Paleohydrological Proxies in the Florida Everglades

    Andrews, T.; Booth, R.; Bernhardt, C. E.; Willard, D. A.


    The largest wetland restoration effort ever attempted, the Comprehensive Everglades Restoration Plan (CERP), is currently underway in the Florida Everglades, and a critical goal of CERP is reestablishment of the pre-drainage (pre-AD 1880) hydrology. Paleoecological research in the greater Everglades ecosystem is underway to reconstruct past water levels and variability throughout the system, providing a basis for restoration targets. Testate amoebae, a group of unicellular organisms that form decay-resistant tests, have been successfully used in northern-latitude bogs to reconstruct past wetland hydrology; however, their application in other peatland types, particularly at lower latitudes, has not been well studied. We assessed the potential use of testate amoebae as tools to reconstruct the past hydrology of the Everglades. Modern surface samples were collected from the Everglades National Park and Water Conservation Areas, across a water table gradient that included four vegetation types (tree island interior, tree island edge, sawgrass transition, slough). Community composition was quantified and compared to environmental conditions (water table, pH, vegetation) using ordination and gradient-analysis approaches. Results of nonmetric multidimensional scaling revealed that the most important pattern of community change, representing about 30% of the variance in the dataset, was related to water-table depth (r2=0.32). Jackknifed cross-validation of a transfer function for water table depth, based on a simple weighted average model, indicated the potential for testate amoebae in studies of past Everglades hydrology (RMSEP = 9 cm, r2=0.47). Although the performance of the transfer function was not as good as those from northern-latitude bogs, our results suggest that testate amoebae could be could be a valuable tool in paleohydrological studies of the Everglades, particularly when used with other hydrological proxies (e.g., pollen, plant macrofossils, diatoms).

  3. Geomorphic assessment of late Quaternary volcanism in the Yucca Mountain area, southern Nevada: Implications for the proposed high-level radioactive waste repository

    Wells, S. G.; McFadden, L. D.; Renault, C. E.; Crowe, B. M.


    Volcanic hazard studies for high-level radioactive waste isolation in the Yucca Mountain area, Nevada, require a detailed understanding of Quaternary volcanism to forecast rates of volcanic processes. Recent studies of the Quaternary Cima volcanic field in southern California have demonstrated that K-Ar dates of volcanic landforms are consistent with their geomorphic and pedologic properties. The systematic change of these properties with time may be used to provide age estimates of undated or questionably dated volcanic features. The reliability off radiometric age determinations of the youngest volcanic center, Lathrop Wells, near the proposed Yucca Mountain site in Nevada has been problematic. In this study, a comparison of morphometric, pedogenic, and stratigraphic data establishes that correlation of geomorphic and soil properties between the Cima volcanic field and the Yucca Mountain area is valid. Comparison of the Lathrop Wells cinder cone to a 15-20 ka cinder cone in California shows that their geomorphic-pedogenic properties are similar and implies that the two cones are of similar age. We conclude that previous determinations of ca. 0.27 Ma for the latest volcanic activity at Lathrop Wells, approximately 20 km from the proposed repository, may be in error by as much as an order of magnitude and that the most recent volcanic activity is no older than 20 ka.

  4. Evaluating the reliability of Late Quaternary landform ages: Integrating 10Be cosmogenic surface exposure dating with U-series dating of pedogenic carbonate on alluvial and fluvial deposits, Sonoran desert, California

    Blisniuk, K.; Sharp, W. D.


    To assess the reliability of Quaternary age determinations of alluvial and fluvial deposits across the Sonoran Desert (Coachella Valley and Anza Borrego) in southern California, we applied both 10Be exposure age dating of surface clasts and U-series dating of pedogenic carbonate from subsurface clast-coatings to the same deposits. We consider agreement between dates from the two techniques to indicate reliable age estimates because each technique is subject to distinct assumptions and therefore their systematic uncertainties are largely independent. 10Be exposure dates should yield maximum ages when no correction is made for inheritance and post-depositional erosion is negligible. U-series dating, in contrast, provides minimum dates because pedogenic carbonate forms after deposition. Our results show that: (1) For deposits ca. 70 ka or younger, 10Be and U-series dates were generally concordant. We note, however, that in most cases U-series soil dates exceed 10Be exposure dates that are corrected for inheritance when using 10Be in modern alluvium. This suggests that 10Be concentrations of modern alluvium may exceed the 10Be acquired by late Pleistocene deposits during fluvial transport and hillslope residence (i.e., Pleistocene inherited 10Be). (2) For deposits older than ~70 ka, U-series dates are significantly younger than the 10Be dates. This implies that U-series dates in this region may significantly underestimate the depositional age of older alluvium, probably because of delayed onset of deposition, slow accumulation, or poor preservation of secondary carbonate in response to climatic controls. Thus, whenever possible, multiple dating methods should be applied to obtain reliable ages for late Quaternary deposits.

  5. Signatures of Late Quaternary sea-level changes and Neo-tectonic activity over Visakhapatnam - Gopalpur shelf, east coast of India

    Rao, K.M.; Reddy, N.P.C.; PremKumar, M.K.; Raju, Y.S.N.; Venkateswarlu, K.; Murthy, K.S.R.

    representing still stands during the late Pleistocene to Holocene. Seismic records obtained off Visakhapatnam-Pudimadaka show two distinct sedimentary units bounded by erosional unconformities. Occurrence of palaeo-channel beneath the seabed in the inner shelf...

  6. Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: Implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

    Phillips, R.L.; Grantz, A.


    The composition and distribution of ice-rafted glacial erratics in late Quaternary sediments define the major current systems of the Arctic Ocean and identify two distinct continental sources for the erratics. In the southern Amerasia basin up to 70% of the erratics are dolostones and limestones (the Amerasia suite) that originated in the carbonate-rich Paleozoic terranes of the Canadian Arctic Islands. These clasts reached the Arctic Ocean in glaciers and were ice-rafted to the core sites in the clockwise Beaufort Gyre. The concentration of erratics decreases northward by 98% along the trend of the gyre from southeastern Canada basin to Makarov basin. The concentration of erratics then triples across the Makarov basin flank of Lomonosov Ridge and siltstone, sandstone and siliceous clasts become dominant in cores from the ridge and the Eurasia basin (the Eurasia suite). The bedrock source for the siltstone and sandstone clasts is uncertain, but bedrock distribution and the distribution of glaciation in northern Eurasia suggest the Taymyr Peninsula-Kara Sea regions. The pattern of clast distribution in the Arctic Ocean sediments and the sharp northward decrease in concentration of clasts of Canadian Arctic Island provenance in the Amerasia basin support the conclusion that the modem circulation pattern of the Arctic Ocean, with the Beaufort Gyre dominant in the Amerasia basin and the Transpolar drift dominant in the Eurasia basin, has controlled both sea-ice and glacial iceberg drift in the Arctic Ocean during interglacial intervals since at least the late Pleistocene. The abruptness of the change in both clast composition and concentration on the Makarov basin flank of Lomonosov Ridge also suggests that the boundary between the Beaufort Gyre and the Transpolar Drift has been relatively stable during interglacials since that time. Because the Beaufort Gyre is wind-driven our data, in conjunction with the westerly directed orientation of sand dunes that formed during

  7. An endemic rat species complex is evidence of moderate environmental changes in the terrestrial biodiversity centre of China through the late Quaternary

    Ge, Deyan; Lu, Liang; Cheng, Jilong; Xia, Lin; Chang, Yongbin; Wen, Zhixin; Lv, Xue; Du, Yuanbao; Liu, Qiyong; Yang, Qisen


    The underlying mechanisms that allow the Hengduan Mountains (HDM), the terrestrial biodiversity centre of China, to harbour high levels of species diversity remain poorly understood. Here, we sought to explore the biogeographic history of the endemic rat, Niviventer andersoni species complex (NASC), and to understand the long-term persistence of high species diversity in this region. In contrast to previous studies that have proposed regional refuges in eastern or southern of the HDM and emphasized the influence of climatic oscillations on local vertebrates, we found that HDM as a whole acted as refuge for the NASC and that the historical range shifts of NASC mainly occurred in the marginal regions. Demographic analyses revealed slight recent population decline in Yunnan and south-eastern Tibet, whereas of the populations in Sichuan and of the entire NASC were stable. This pattern differs greatly from classic paradigms of temperate or alpine and holarctic species. Interestingly, the mean elevation, area and climate of potential habitats of clade a (N. excelsior), an alpine inhabitant, showed larger variations than did those of clade b (N. andersoni), a middle-high altitude inhabitant. These species represent the evolutionary history of montane small mammals in regions that were less affected by the Quaternary climatic changes. PMID:28393882

  8. Predicting reach-specific properties of fluvial terraces to guide future fieldwork. A case study for the Late Quaternary River Allier (France) with the FLUVER2 model

    Veldkamp, Tom; Schoorl, Jeroen M.; Viveen, Willem


    Numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling. This paper explores the potential of the longitudinal profile model FLUVER2 to predict testable field properties of the relatively well-studied, Late Quat

  9. The influence of time on the magnetic properties of late Quaternary periglacial and alluvial surface and buried soils along the Delaware River, USA

    Gary E Stinchcomb


    Full Text Available Magnetic susceptibility of soils has been used as a proxy for rainfall, but other factors can contribute to magnetic enhancement in soils. Here we explore influence of century- to millennial-scale duration of soil formation on periglacial and alluvial soil magnetic properties by assessing three terraces with surface and buried soils ranging in exposure ages from <0.01 to ~16 kyrs along the Delaware River in northeastern USA. The A and B soil horizons have higher Xlf, Ms, and S-ratios compared to parent material, and these values increase in a non-linear fashion with increasing duration of soil formation. Magnetic remanence measurements show a mixed low- and high-coercivity mineral assemblage likely consisting of goethite, hematite and maghemite that contributes to the magnetic enhancement of the soil. Room-temperature and low-temperature field-cooled and zero field-cooled remanence curves confirm the presence of goethite and magnetite and show an increase in magnetization with increasing soil age. These data suggest that as the Delaware alluvial soils weather, the concentration of secondary ferrimagnetic minerals increase in the A and B soil horizons. We then compared the time-dependent Xlf from several age-constrained buried alluvial soils with known climate data for the region during the Quaternary. Contradictory to most studies that suggest a link between increases in magnetic susceptibility and high moisture, increased magnetic enhancement of Delaware alluvial soils coincides with dry climate intervals. Early Holocene enhanced soil Xlf (9.5 – 8.5 ka corresponds with a well-documented cool-dry climate episode. This relationship is probably related to less frequent flooding during dry intervals allowing more time for low-coercive pedogenic magnetic minerals to form and accumulate, which resulted in increased Xlf. Middle Holocene enhanced Xlf (6.1 – 4.3 ka corresponds with a transitional wet/dry phase and a previously documented incision

  10. The last interglacial period at Guantanamo Bay, Cuba and an estimate of late Quaternary tectonic uplift rate in a strike-slip regime

    Schweig, E. S.; Muhs, D. R.; Simmons, K. R.; Halley, R. B.


    Guantanamo Bay, Cuba is an area dominated by a strike-slip tectonic regime and is therefore expected to have very low Quaternary uplift rates. We tested this hypothesis by study of an unusually well preserved emergent reef terrace around the bay. Up to 12 m of unaltered, growth-position reef corals are exposed at about 40 sections examined around ˜40 km of coastline. Maximum reef elevations in the protected, inner part of the bay are ˜11-12 m, whereas outer-coast shoreline angles of wave-cut benches are as high as ˜14 m. Fifty uranium-series analyses of unrecrystallized corals from six localities yield ages ranging from ˜134 ka to ˜115 ka, when adjusted for small biases due to slightly elevated initial 234U/238U values. Thus, ages of corals correlate this reef to the peak of the last interglacial period, marine isotope stage (MIS) 5.5. Previously, we dated the Key Largo Limestone to the same high-sea stand in the tectonically stable Florida Keys. Estimates of paleo-sea level during MIS 5.5 in the Florida Keys are ~6.6 to 8.3 m above present. Assuming a similar paleo-sea level in Cuba, this yields a long-term tectonic uplift rate of 0.04-0.06 m/ka over the past ~120 ka. This estimate supports the hypothesis that the tectonic uplift rate should be low in this strike-slip regime. Nevertheless, on the southeast coast of Cuba, east of our study area, we have observed flights of multiple marine terraces, suggesting either (1) a higher uplift rate or (2) an unusually well-preserved record of pre-MIS 5.5 terraces not observed at Guantanamo Bay.

  11. Cenozoic ecological history of South East Asian peat mires based on the comparison of coals with present day and Late Quaternary peats

    Robert J. Morley


    Full Text Available Tropical peat swamps are more widespread in Sundaland than in any other equatorial region. Also, Cenozoic deposits from the area are rich in coals. The developmental pattern of present day peat swamps from the region has often been used to help clarify that of coals in the geological record. This paper initially reviews the ecology of present day ombrotrophic, rheotrophic and brackish mangrove peat swamps, and their pattern and timing of development during the Holocene and latest Pleistocene based on palynological studies. Then, it attempts to examine the developmental pattern of the peats which led to the formation of Cenozoic coals across the region, based on both published and unpublished datasets generated during the course of hydrocarbon exploration programmes. It is concluded that Cenozoic coals reflect a greater variety of peat forming settings than occurs in the region today. Extensive brackish water peats formed during the Middle and Late Eocene and Middle and Late Miocene, these often being laterally very extensive. Rheotrophic peats also formed widely through most of the Cenozoic. Ombrotrophic kerapah type peats are first recognised in the Late Oligocene, based on their content of common Casuarina type and Dacrydium pollen, and were particularly common during the Early and Late Miocene in the Sunda shelf region. Kerapah peats sometimes developed great thickness. Basinal peats, on the other hand, increased in representation during the course of the Miocene. No convincing evidence for doming in Cenozoic peats has yet been noted, but on the other hand, no really thick coals, which may have been formed from basinal peats, have so far been studied. As a consequence, examples of doming in the rock record from this area are probably yet to be found.

  12. Copper-bearing encrustations: a tool for age dating and constraining the physical-chemical regime during the late Quaternary in the Wadi Araba, southern Jordan

    Dill, H. G.; Techmer, A.; Botz, R.


    The alluvial-fluvial drainage system in the Wadi Araba, southern Jordan, incised into Cambrian clastic sedimentary and felsic igneous rocks giving rise to a disseminated Cu-(Mn) mineralization of diagenetic and epigenetic origin along the southern branch of the Dead Sea Transform Fault (=DSTF). During the Late Pleistocene and Holocene, the primary Cu sulfides were replaced by secondary minerals giving rise to hypogene to supergene encrustations, bearing Cu silicates, Cu carbonates, Cu oxychlorides and cupriferous vanadates. They occur in fissures, coat walls and developed even-rim/meniscus and blocky cements in the arenites near the surface. The first generation cement has been interpreted in terms of freshwater vadose hydraulic conditions, while the second-generation blocky cement of chrysocolla and malachite evolved as late cement. The Cu-Si-C fluid system within the Wadi Araba drainage system is the on-shore or subaerial facies of a regressive lacustrine regime called the "Lake Lisan Stage", a precursor of the present-day Dead Sea. Radiocarbon dating (younger than 27,740 ± 1,570 years), oxygen-isotope-based temperature determination (hot brine-related mineralization at 60-80 °C, climate-driven mineralization at 25-30 °C) and thermodynamical calculations let to the subdivision of this secondary Cu mineralization into four stages, whose chemical and mineralogical composition was controlled by the variation of the anion complexes of silica and carbonate and the chlorine contents. The acidity of the pore water positively correlates with the degree of oxidation. The highest aridity and most intensive evaporation deduced from the thermodynamical calculations were achieved during stage 3, which is coeval with late Lake Lisan. Geogene processes causing Cu-enriched encrustations overlap with man-made manganiferous slags. The smelter feed has been derived mainly from Cu ore which developed during Late Pleistocene in the region.

  13. Timing and development of Late Quaternary fluvial terraces of the lower course of Kızılırmak River (Northern Turkey)

    Berndt, Christopher; Yıldırım, Cengiz; Çiner, Attila; Ertunç, Gülgün; Akif Sarıkaya, M.; Özcan, Orkan; Güneç Kıyak, Nafiye; Öztürk, Tuǧba


    The Kızılırmak River (1355 km) is the longest river of Anatolia. It traverses the Central Pontides and forms deep bedrock gorges, fluvial and deltaic terraces along its lower stream and a large delta into the Black Sea. The Central Pontides is an actively deforming and uplifting mountain range located at the northern margin of the Central Anatolian Plateau (CAP). The presence of strath terraces and uplifted paleo-delta levels along the lower course of the river indicates a response of Kızılırmak to active uplift of the Central Pontides and sea-level fluctuations of the Black Sea. To understand the Quaternary tectonic, climatic and sea level impacts on the lower stream and delta of the Kızılırmak River, we carried out geologic and geomorphic mapping of several fluvial and deltaic terraces in order to date 5 levels by optically stimulated luminescence dating (OSL) method. Our results indicate accelerated regional uplift since Middle Pleistocene in the eastern part of the Central Pontides with uplift rates varying between about 0.07 and 0.3 m/ka. The delta terraces at 103 and 123 m above mean river level on the western side of Kızılırmak River uplifted presumably faster than the terraces at 58 and 87 m above mean river level on the eastern side by 0.2-0.3 m/ka. Since MIS 9 the western and eastern delta platforms uplift coherently with 0.2 m/ka or less. The southern part of the delta is delimited by Alaçam Segment of the Erikli Fault. The area south of the Alaçam segment of the Erikli Fault is uplifting faster than the region to the north of it (0.07 m/ka) since Middle Pleistocene. This indicates a tectonic interaction between the positive flower structure of the North Anatolian Fault Zone and an active rifting of the Sinop Graben over the Erikli Fault system.

  14. Climate and tectonic variability during Late Quaternary in western fringe of Tibetan Plateau: case study from Trans-Himalayan ranges of Ladakh, NW India

    Phartiyal, B.


    The climate system plays an important role in the geomorphological dynamics of a region. The cold, arid, high altitude, tectonically active areas of Ladakh (India) in Trans Himalaya, western Tibetan Plateau is none exception. Noticeable change in the landscape with a shift from fluvial to lacustrine regime at 10000 yrs BP forming big open valley lakes occupying the present day river valleys is attributed to the early Holocene northward advancement of the mean latitudinal position of the summer ITCZ causing wetter conditions in this dry area. The glaciers of the Ladakh range are almost depleted and the northern range glaciers show andrastic retreat in the Quaternary time. Lakes were studied using multi-proxies, to record centennial and decadal scale climatic variability. Spatial and temporal setting of Spituk palaeolake (12600-240 cal yrs BP) along Indus River, was analyzed using multi proxies. The lake that extended for 40-50 km covering an area of 106 km2, was formed after Older Dryas as a result of river blockage by precipitation induced debris flow and seismicity. Two lake phases between 12600-9000 and 5500-3200 cal yrs BP show stable lake conditions and have synchronous relationship between high variation in monsoon intensity, high δ18O values in the Guliya core, rise in temperature and high solar insolation. High magnetic susceptibility and clay content along with diversified diatom and other freshwater algae and land derived organic matter are indicative of fresh water supply leading to high lake level from 4700 yr BP onwards in the present pro-glacial lakes studied. The multi-proxy data provides evidence of much higher and stable lake level during 3700 yr BP and 3000 yr BP onwards due to high water supply in these lake. It is in contrast to the records of weak ISM conditions and low lake level in rest of the part of Indian peninsula during the period. The study also suggests strong western disturbance activity during 4800-3000 yr BP leading to high lake

  15. On the Reconstruction of Paleo-hydrology: a Foundation for More Reliable Water Resources Management

    Razavi, Saman; Elshorbagy, Amin; Wheater, Howard; Sauchyn, David


    The design and management of water resource infrastructure have been generally based on the information available in the periods of observational record with the central, default assumption of stationarity. It is well known that this assumption is not true in general and the common practice of relying on the periods of observational record for the analysis of water resources is flawed. To understand and address the climate-driven non-stationarities in hydrologic variables in a region, one approach, which is still largely unexplored in many regions, is to analyse natural proxy records of hydroclimatic behaviour (such as tree-ring chronologies) over the past several centuries or millennia. There have been research activities in this "paleo-hydrology" field across the world demonstrating the existence of significant non-stationarities and extreme behaviours in climate and hydrology over the past couple of centuries, in the absence of greenhouse gas emissions. On the basis of the science of dendrohydrology, which mainly aims to reconstruct paleo-hydrology, this study follows three objectives: (1) the identification of non-stationarities in different statistical properties of paleo-hydrologic time series, mainly the mean and covariance, (2) more effective quantification of uncertainties associated with the reconstructions of streamflow time series based on tree-ring chronologies, and (3) the generation of an ensemble of basin-wide paleo-hydrologic time series data. The Alberta portion of the Saskatchewan River basin (SRB), Canada, is used as a case study. Results indicate that the statistical properties of annual paleo-hydrologic time series in the basin, particularly the covariance structure, have undergone significant changes at different points in the history. The results also demonstrate that the reliability of tree-ring chronologies as proxies for hydrologic variables in the basin differs for different periods in time, as the range of uncertainty produced based on

  16. Reply to Discussion: a critique of Possible waterways between the Marmara Sea and the Black Sea in the late Quaternary: evidence from ostracod and foraminifer assemblages in lakes İznik and Sapanca, Turkey, Geo-Marine Letters, 2011

    Nazik, Atike; Meriç, Engin; Avşar, Niyazi


    In their discussion of our 2011 paper dealing with possible waterways between the Marmara Sea and the Black Sea in the "late" Quaternary, based on data from ostracod and foraminifer assemblages in lakes İznik and Sapanca, Turkey, Yaltırak et al. (Geo-Mar Lett 32:267-274, 2012) essentially reject the idea of any links whatsoever, be they between the Marmara Sea and the lakes İznik and Sapanca, or further to the Black Sea via the valley of the Sakarya River. The evidence they provide in support of their view, however, is essentially circumstantial, in part conjectural, and also inconclusive considering the findings in favour of linkage between the Marmara Sea and the lakes at the very least, while the proposed connection with the Sakarya River valley remains speculative because of the lack of unambiguous data. On the other hand, Yaltırak et al. (Geo-Mar Lett 32:267-274, 2012) do raise valid points of concern which deserve careful future investigation, the most important being the possibility of sample contamination from dumped marine sediment used for construction purposes along some parts of the shore of Lake İznik. We agree that a concerted multidisciplinary effort is required to address the many unresolved issues in connection with the potential waterways proposed by us and others before us.


    刘俊英; 王海雷


    The materials in this paper come from a natural section of 3. 69 m depth and 32. 6-4. 5 ka B. P. In the Taicuo ancient lake, western Qiangtang Plateau, Tibet. From 156 samples obtained there abundant microfossils have been found such as charophyte, ostracod, gastropod and foraminifera. Based on the shape, apical structure and spiral calcification of the gyrogonites, the charophytes from the section all belong to Chara. During a period of 28 ka in the Taicuo ancient lake there occurred 22 species of charophytes among which are 8 new types including 4 new species: Chara platea , Ch. Gemma, Ch. Subnana and Ch. Taicuoensis and one variety- Chara convex var. Zangbeiensis. The rest are Quaternary Chara members seen worldwide, including 5 new combination species: Chara alba (Madler et Staesche), Ch. Daqaidamensis, Ch. Quartjiensis, Ch. Longistipitata and Ch. Tartensis. The multi-kind microfossils such as charophyte, ostracod and gastropod closely coexist there, which shows important significance in the ecological study of the charophyte flora.%本文的研究材料来自西藏羌塘高原西部台错古湖一个3.69 m的天然剖面,其地层测年为32.6-4.5ka.从其156个样品中获取大量的轮藻类、介形类和腹足类及少量有孔虫等微体化石.据轮藻类藏卵器外形,顶部结构、螺旋细胞钙化式样等特征,该剖面的轮藻类应归属于轮藻科Characeae之轮藻属Chara.经研究得知,台错古湖在大约28 ka的时期内,曾生长过22种轮藻,其中新类型7个,包括新种4个:Chara platea,Ch.gemma,Ch.subnana和Ch.taicuoensis;新型2个:Chara latispiralis f.stipiata,Ch.specialis f.major;新变种1个:Chara convex var.zangbeiensis.其余是曾产于国内外第四系的Chara其它分子.其中有5个新联合种:Chara alba (M(a)dler et Staesche),Ch.daqaidamensis(Tang et Di),Ch.quanjiensis(Tang et Di),Ch.longistipitata(Tang et Di)和Ch.tartensis.该剖面轮藻类、介形类、腹足类等多门类微体化石的紧密共生,对

  18. How Sensitive is the Asian Monsoon System to Remote Forcing?: A Perspective from the late Quaternary Bay of Bengal and Arabian Sea Regions

    Stoll, H. M.; Vance, D.; Arevalos, A.; Shimizu, N.; Burke, A.; Ziveri, P.


    Over the Quaternary has the Asian monsoon system responded predominantly to regional climate drivers such as orbital changes in summer insolation and the land-sea pressure gradient, or global climate boundary conditions such as the extent of northern hemisphere(NH) ice sheets and snow cover? Our paleorecords from the Bay of Bengal and Arabian Sea reveal contrasting influence of the NH ice sheets. Seawater Nd isotopic ratios in the northern Bay of Bengal, reconstructed from planktic foraminifera, are sensitive to the degree of northward penetration of the Asian summer monsoon precipitation into the nonradiogenic terranes of the Himalayas. Shifts in river sources from the more northerly Ganges-Brahmaputra watershed to the more southerly Arakan coastal river systems respond dominantly to ITCZ movement driven by Northern Hemisphere cooling during 100 ky glacial-interglacial cycles. A nonlinear correlation of epsilon Nd with ice volume suggests that ITCZ movement responds to aerial coverage of ice sheets and snow rather than to ice thickness and volume as expected from albedo forcing. These data add support to recent general circulation models of which in this region show strong ITCZ response to Northern Hemisphere ice coverage. A small component of Nd isotopic variation on precessional timescales corresponds to ITCZ movement within the southern Irrawaddy and Arakan coastal systems. There is a strong connection between ITCZ movement and productivity even in a non-upwelling system such as the Bay of Bengal. In the northernmost Bay of Bengal, productivity indicators from Sr-Ca ratios in coccoliths and from Ba-Ti ratios of sediments exhibit principally glacial-interglacial variability consistent with the epsilon Nd record. Higher productivity during interglacials may reflect either higher riverine nutrient sources or stronger wind- driven eddy pumping. In the more southerly Andaman Sea, Sr-Ca ratios in coccoliths reveal productivity variations dominantly on precessional

  19. Pedogeochemistry and micromorphology of oxisols - A basis for understanding etchplanation in the Araucárias Plateau (Southern Brazil) in the Late Quaternary

    Paisani, Julio Cesar; Pontelli, Marga Eliz; de Barros Corrêa, Antônio Carlos; Rech Rodrigues, Rafaela Ana


    Approximately five years ago, the Working Group on Ancient Surfaces and Long-Term Landscape Evolution was created to raise planed surfaces in Brazil, Argentina, Uruguay and Paraguay with the aim of establishing regional correlations of planed surfaces after the formation of the Gondwanan rocks in South America. In Brazil, planed surfaces were recognized and classified between 1940 and 1960 and were given various designations and different age estimates based on regional morphostratigraphic correlation attempts. In the last twenty years, the assumptions of those attempts began to be questioned on a large scale by studies in which empirical observations, mediated by the use of new methodologies, did not indicate such a direct relationship between the paleosurfaces and their long-term erosive origin. We identified eight staggered surfaces in the Araucárias Plateau, Southern Brazil, between the Iguazu and Uruguay Rivers. Initially, we attempted to understand the planed surfaces as classic pediplains, but we found weathering profiles of different thicknesses with oxisols downstream of the knickpoints, instead of correlative deposits. We understand these surfaces as planed surfaces or paleosurfaces without erosive interrelation between them, resulting from the action of etchplanation processes. This idea contradicts the classical perspective of Brazilian geomorphology that attributes the cyclical alternation of Quaternary paleoclimates to the evolution of the model of the subtropical landscapes. The hypothesis begins from the assumption that the model evolved from the binomial morphogenesis/pedogenesis in phase with the glacial/interglacial cycles. In this study, we attempt to demonstrate that the climactic controls on morphogenesis/pedogenesis are mediated by the responses of the weathered mantle on the scale of its chemical and microstructural organization, which does not always validate previous theoretical assumptions. In this article, we use the chemical

  20. Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel)

    Lisker, Sorin; Porat, Roi; Davidovich, Uri; Eshel, Hanan; Lauritzen, Stein-Erik; Frumkin, Amos


    The Moringa Cave within Pleistocene sediments in the En Gedi area of the Dead Sea Fault Escarpment contains a sequence of various Pleistocene lacustrine deposits associated with higher-than-today lake levels at the Dead Sea basin. In addition it contains Chalcolithic remains and 5th century BC burials attributed to the Persian period, cemented and covered by Late Holocene travertine flowstone. These deposits represent a chain of Late Pleistocene and Holocene interconnected environmental and human events, echoing broader scale regional and global climate events. A major shift between depositional environments is associated with the rapid fall of Lake Lisan level during the latest Pleistocene. This exposed the sediments, providing for cave formation processes sometime between the latest Pleistocene (ca. 15 ka) and the Middle Holocene (ca. 4500 BC), eventually leading to human use of the cave. The Chalcolithic use of the cave can be related to a relatively moist desert environment, probably related to a shift in the location of the northern boundary of the Saharo-Arabian desert belt. The travertine layer was U-Th dated 2.46 ± 0.10 to 2.10 ± 0.04 ka, in agreement with the archaeological finds from the Persian period. Together with the inner consistency of the dating results, this strongly supports the reliability of the radiometric ages. The 2.46-2.10 ka travertine deposition within the presently dry cave suggests a higher recharge of the Judean Desert aquifer, correlative to a rising Dead Sea towards the end of the 1st millennium BC. This suggests a relatively moist local and regional climate facilitating human habitation of the desert.

  1. A record of Late Quaternary continental weathering in the sediment of the Caspian Sea: evidence from U-Th, Sr isotopes, trace element and palynological data

    Pierret, M. C.; Chabaux, F.; Leroy, S. A. G.; Causse, C.


    This study presents combined mineralogical, chemical, isotopic (87Sr/86Sr and U-Th disequilibria series) and palynological analyses on bulk sediments and on distinct mineral phases (carbonates and clays) from a 10-m-long core drilled in the southern Caspian Sea and containing a Late Pleistocene and Early Holocene record. The data allowed identifying 1) the main variations in sedimentation, 2) the processes causing these variations, 3) the modification of erosion vs weathering, and 4) the influence of climatic and/or Caspian Sea level changes in the region since the Late Pleistocene. The chemical and mineralogical results allowed the division of the sedimentary sequence into three main units and a transition zone. The lower unit (unit U1) primarily consists of silicate and carbonate-rich detritus. Sedimentation characteristics, including observation of detritus in secular equilibrium, are relatively constant within this unit and reflect mechanical erosion in a cold climate. Unit U1 probably corresponds to a glacial period when the vegetation cover was sparse and wind and river transport of pollen were strong. Subsequently, global increase in temperatures has greatly modified the sedimentation in the Caspian Sea south basin. Biogenic sedimentation is higher in units U2 and U3, and detrital inputs varied from unit U1. Variations in detrital input are likely to be caused by decreasing aeolian contribution and by relative changes in river volumes and origins. The study of the bulk sediments, clays and carbonates reflects an increase in chemical weathering since about 10 14C ka BP ago (base of unit U2), in line with an increase in the vegetation cover. Our results suggest an evolution of continental weathering conditions in the catchment area of the Caspian Sea, from dominantly mechanical/physical erosion during the cold period to a continuous increase in weathering since the Lateglacial period, as climate improved, which illustrates the strong relation between climate

  2. Late Quaternary developments of Mediterranean oaks in the Atlantic domain of the Iberian Peninsula: The case of the Cantabrian region (N Spain)

    Uzquiano, P.; Ruiz-Zapata, MaB.; Gil-Garcia, MaJ.; Fernández, S.; Carrión, J. S.


    A synthesis of the occurrence of the evergreen oak (Quercus ilex-type) in the Cantabrian region (northern Spain) is presented on the basis of integrated charcoal and pollen analyses. Archaeological charcoal comes largely from sites along the littoral and pre-littoral territories of the Basque Country, Cantabria and Asturias dated from 45 to 3.7 Kyr cal BP, and culturally ranging from Mousterian to Iron Age. Pollen information is produced from a few archaeological sites but mainly from peats and lake sediments. Q. ilex-type is observed as early as at 45-30 Kyr cal BP, with sporadic occurrences in vegetation contexts dominated by Pinus sylvestris-type, which was widely exploited by Mousterian and Aurignacian inhabitants. Afterwards, during the Upper Palaeolithic, there is an important decline, and Q. ilex-type is hardly present between 29 and 15 Kyr cal BP, with open environments dominated by heathland shrubs. From Late Magdalenian onwards, Q. ilex-type expanded again, remaining in the landscape of the Cantabrian region throughout the Holocene, although subordinated in deciduous oak forests under the influence of oceanic climate conditions. Q. ilex-type had a more favourable position than deciduous Quercus across the Cantabrian southern slopes and northwest of the adjacent Iberian Cordillera, where oceanic influences have become attenuated by summer drought and continentality.

  3. Impacts of climate change on the formation and stability of late Quaternary sand sheets and falling dunes, Black Mesa region, southern Colorado Plateau, USA

    Ellwein, Amy L.; Mahan, Shannon; McFadden, Leslie D.


    Detailed geomorphic mapping and analysis of soil-stratigraphy and optically stimulated luminescence (OSL) dating of eolian sand dunes on Black Mesa, Arizona, reveal eolian sediment deposition occurred from 30 to 16 ka, followed by a period of widespread dune stabilization from 12 to 8 ka. Localized reactivation of the previously stabilized dune forms or local changes in sediment supply have occurred in the middle to late Holocene in this region. Cooler, wetter, and more variable climatic conditions during MIS 3 and 2 led to increased channel and floodplain sediment supply. Eolian sediment derived from these sources was transported up to 60 km. Deposition of this material has reduced regional topographic roughness by filling tributary canyon ‘traps’ oriented perpendicular to the dominant wind and sediment transport direction. Topographically controlled falling dunes and sand ramps in this region are preserved because of their geomorphic position and provide evidence of the paleoenvironmental state of the fluvial and eolian systems before, during, and immediately after the last glacial maximum on the southern Colorado Plateau.

  4. Variable scale channel avulsion history using fan architecture and stratigraphy, and sediment provenance of Sutlej-Yamuna fans in northwest Gangetic plains during Late Quaternary

    Singh, Ajit; Gupta, Sanjeev; Sinha, Rajiv; Densmore, Alexander; Buylaert, Jan-Pieter; Carter, Andrew; Van-Dijk, Wout M.; Joshi, Suneel; Nayak, Nibedita; Mason, Philippa J.; Kumar, Dewashish; Mondal, Setbandhu; Murray, Andrew; Rai, Shiv P.; Shekhar, Shashank


    Channel avulsion during fan development controls distribution and deposition of channel sandbodies and hence alluvial architecture of a fan system. Variable scale spatio-temporal information of fluvial responses to past climate changes is stored in these channel sandbodies. Further these channel sandbodies form fluvial aquifers in alluvial fans and therefore understanding of alluvial architecture and stratigraphy of a fan is crucial for development of groundwater management strategies. In this study we used multiple approaches to map subsurface fluvial aquifer architecture and alluvial stratigraphy, and to estimate sediment provenance using U-Pb dating of detrital zircon grains of Sutlej-Yamuna fan system in northwest India. Satellite imagery based geomorphic mapping shows two large fan system with interfan area. The fan surfaces show presence of major and minor paleochannels. 2D resistivity tomography along several transects across fan surfaces shows distinct layers with contrasting resistivity values. These geo-electric facies corresponds to presence of channel sandbodies beneath surface signature of paleochannels and finer floodplain deposits useful to demarcate lateral extent of subsurface channel sandbodies. A more detailed subsurface stratigraphy using ~50m deep sediment cores and their luminescence ages from across fan surface shows presence of multi-storey sandbodies (MSB) separated by floodplain fines. Within the MSB, individual channel deposits are identified by presence of channel scour surfaces located at coarse sand overlying fine sand layer. Depositional ages of MSB's ranges from ~81 ka (late MIS5) to ~15 ka (MIS2) with major depositional break during MIS3 in parts of the fans. Sediment aggradation rate varies laterally across fan surface as well as vertically down the depth with an average rate of 0.54 mm/year. Fluvial channel persistence for studied time interval (about last 81 ka BP) shows major depositional breaks (and possible incision) at ~41 ka

  5. Vertebrate paleontology, stratigraphy, and paleohydrology of Tule Springs Fossil Beds National Monument, Nevada (USA)

    Springer, Kathleen; Pigati, Jeffery S.; Scott, Eric


    Tule Springs Fossil Beds National Monument (TUSK) preserves 22,650 acres of the upper Las Vegas Wash in the northern Las Vegas Valley (Nevada, USA). TUSK is home to extensive and stratigraphically complex groundwater discharge (GWD) deposits, called the Las Vegas Formation, which represent springs and desert wetlands that covered much of the valley during the late Quaternary. The GWD deposits record hydrologic changes that occurred here in a dynamic and temporally congruent response to abrupt climatic oscillations over the last ~300 ka (thousands of years). The deposits also entomb the Tule Springs Local Fauna (TSLF), one of the most significant late Pleistocene (Rancholabrean) vertebrate assemblages in the American Southwest. The TSLF is both prolific and diverse, and includes a large mammal assemblage dominated by Mammuthus columbi and Camelops hesternus. Two (and possibly three) distinct species of Equus, two species of Bison, Panthera atrox, Smilodon fatalis, Canis dirus, Megalonyx jeffersonii, and Nothrotheriops shastensis are also present, and newly recognized faunal components include micromammals, amphibians, snakes, and birds. Invertebrates, plant macrofossils, and pollen also occur in the deposits and provide important and complementary paleoenvironmental information. This field compendium highlights the faunal assemblage in the classic stratigraphic sequences of the Las Vegas Formation within TUSK, emphasizes the significant hydrologic changes that occurred in the area during the recent geologic past, and examines the subsequent and repeated effect of rapid climate change on the local desert wetland ecosystem.

  6. Holocene Paleohydrology of the tropical andes from lake records

    Abbott, M. B., LLNL


    Two century-scale time series in northern Bolivia constrain the ages of abrupt changes in the physical, geochemical, and biological characteristics of sediments obtained from lakes that formed during deglaciation from the late Pleistocene glacial maximum. The watersheds of Laguna Viscachani (16{degrees}12`S, 68{degrees}07`W, 3780m) and Lago Taypi Chaka Kkota (16{degrees}13`S, 68{degrees}21`W, 4300m), located on the eastern and western slopes of the Cordillera Real, respectively, contain small cirque glaciers. A high-resolution chronology of the lake sediments is provided by 23 AMS {sup 14}C dates of discrete macro-fossils. Late Pleistocene glaciers retreated rapidly, exposing the lake basins between 10,700 and 9700 {sup 14}C yr B.P. The sedimentary facies suggest that after 8900 {sup 14}C B.P. glaciers were absent from the watersheds and remained so during the middle Holocene. An increase in the precipitation-evaporation balance is indicated above unconformities dated to about 2300 {sup 14}C yr B.P. in both Lago Taypi Chaka Kkota and Laguna Viscachani. An abrupt increase in sediment accumulation rated after 1400 {sup 14}C yr B.P. signals the onset of Neoglaciation. A possible link exists between the observed millennial-scale shifts in the regional precipitation- evaporation balance and seasonal shifts in tropical insolation.

  7. Late Quaternary drainage dynamics in northern Brazil based on the study of a large paleochannel from southwestern Marajó Island

    Dilce F. Rossetti


    Full Text Available Marajó Island shows an abundance of paleochannels easily mapped in its eastern portion, where vegetation consists mostly of savannas. SRTM data make possible to recognize paleochannels also in western Marajó, even considering the dense forest cover. A well preserved paleodrainage network from the adjacency of the town of Breves (southwestern Marajó Island was investigated in this work combining remote sensing and sedimentological studies. The palimpsest drainage system consists of a large meander connected to narrower tributaries. Sedimentological studies revealed mostly sharp-based, fining upward sands for the channelized features, and interbedded muds and sands for floodplain areas. The sedimentary structures and facies successions are in perfect agreement with deposition in channelized and floodplain environments, as suggested by remote sensing mapping. The present study shows that this paleodrainage was abandoned during Late Pleistocene, slightly earlier than the Holocene paleochannel systems from the east part of the island. Integration of previous studies with the data available herein supports a tectonic origin, related to the opening of the Pará River along fault lineaments. This would explain the disappearance of large, north to northeastward migrating channel systems in southwestern Marajó Island, which were replaced by the much narrower, south to southeastward flowing modern channels.A Ilha do Marajó mostra uma abundância de paleocanais que são facilmente mapeáveis em sua porção leste, onde a vegetação consiste principalmente em savanas. Dados SRTM possibilitam reconhecer paleocanais também na porção oeste do Marajó, mesmo considerando a cobertura vegetal de floresta densa. Uma rede de paleodrenagem bem preservada nas adjacências da cidade de Breves (sudoeste da Ilha do Marajó foi investigada neste trabalho combinando-se sensoriamento remoto e estudos sedimentológicos. O sistema de drenagem palimpséstico consiste

  8. Effects of a regional décollement level for gravity tectonics on late Neogene-Quaternary deep-sea clastic sedimentation in the Foz do Amazonas Basin, Brazil

    Cruz, A. M.; Gorini, C.


    Sets of 2D multi-channel seismic and chronostratigraphic data allowed us to undertake analyses of source to sink processes and triggering mechanisms of the gigantic megaslides previously documented off the NW and SE steep slope settings of the Foz do Amazonas basin. These megaslides comprise two sets of stacked allochthonous masses within the Upper Miocene-Quaternary sedimentary record, now described as Mass-Transport Complexes (MTCs): the Amapá Megaslide Complex (AMC) and the Pará-Maranhão Megaslide Complex (PMMC). Individual megaslides of both MTCs can mobilize to deep waters up to kilometer thick sedimentary series as allochthonous masses with different flow directions, degrees of sediment disruption and internal coherence. Megaslides spread downslope over areas as large as thousands of km2, attaining dimensions comparable to the world's largest mass-transport deposits. The basal and largest megaslide of the AMC (AM1 megaslide) is a quite unique example of mass-transport deposit, since it is interpreted as a dominant carbonate allochthonous mass sourced from a mixed carbonate-siliciclastic platform. According to stratigraphic correlations with global sea-level positions, platform instability would have been triggered between the late Miocene and the end of the Early Pliocene by gravitational collapse of the mixed platform under its own weight, after successive subaerial exposures which were able to generate karstification processes. Siliciclastic-type megaslides, on the other hand, are all sourced from large upslope slide and/or rotated blocks (up to 60 km large in the case of the PMMC).Stratigraphic correlations evidenced that horizon equally acts as the upper décollement level for the gravity tectonic system that operates in the regional scale of the Foz do Amazonas basin. In such a context, results of this work evidence complex links between variable modes of gravity deformation (gravity tectonics and mass wasting), all induced by instability created from

  9. Along-fault migration of the Mount McKinley restraining bend of the Denali fault defined by late Quaternary fault patterns and seismicity, Denali National Park & Preserve, Alaska

    Burkett, Corey A.; Bemis, Sean P.; Benowitz, Jeff A.


    The tallest mountain in North America, Denali (formerly Mount McKinley, 6,190 m), is situated inside an abrupt bend in the right-lateral strike-slip Denali fault. This anomalous topography is clearly associated with the complex geometry of the Denali fault, but how this restraining bend has evolved in conjunction with the regional topography is unknown. To constrain how this bend in the Denali fault is deforming, we document the Quaternary fault-related deformation north of the Denali fault through combined geologic mapping, active fault characterization, and analysis of background seismicity. Our mapping illustrates an east-west change in faulting style where normal faults occur east of the fault bend and thrust faults predominate to the west. The complex and elevated regional seismicity corroborates the style of faulting adjacent to the fault bend and provides additional insight into the change in local stress field in the crust adjacent to the bend. The style of active faulting and seismicity patterns define a deforming zone that accommodates the southwestward migration of this restraining bend. Fault slip rates for the active faults north of the Denali fault, derived from offset glacial outwash surfaces, indicate that the Mount McKinley restraining bend is migrating along the Denali fault at a late Pleistocene/Holocene rate of 2-6 mm/yr. Ongoing thermochronologic and structural studies of the Mount McKinley restraining bend will extend these constraints on the migration and evolution of the restraining bend deeper in time and to the south of the Denali fault.

  10. Late-Quaternary variation in C3 and C4 grass abundance in southeastern Australia as inferred from δ13C analysis: Assessing the roles of climate, pCO2, and fire

    Nelson, David M.; Urban, Michael A.; Kershaw, A. Peter; Hu, Feng Sheng


    Climate, atmospheric pCO2, and fire all may exert major influences on the relative abundance of C3 and C4 grasses in the present-day vegetation. However, the relative role of these factors in driving variation in C3 and C4 grass abundances in the paleorecord is uncertain, and C4 abundance is often interpreted narrowly as a proxy indicator of aridity or pCO2. We measured δ13C values of individual grains of grass (Poaceae) pollen in the sediments of two sites in southeastern Australia to assess changes in the proportions of C3 and C4 grasses during the past 25,000 years. These data were compared with shifts in pCO2, temperature, moisture balance, and fire to assess how these factors were related to long-term variation of C4 grass abundance during the late Quaternary. At Caledonia Fen, a high-elevation site in the Snowy Mountains, C4 grass abundance decreased from an average of 66% during the glacial period to 11% during the Holocene, primarily in response to increased pCO2 and temperature. In contrast, this pattern did not exist in low-elevation savannah woodlands around Tower Hill Northwest Crater, where C4 grass abundance instead varied in response to shifts in regional aridity. Fire did not appear to have strongly influenced the proportions of C3 and C4 grasses on the landscape at millennial timescales at either site. These patterns are similar to those of a recent study in East Africa, suggesting that elevation-related climatic differences influence how the abundance of C3 and C4 grasses responds to shifts in climate and pCO2. These results caution against using C4 plant abundance as a proxy indicator of either climate or pCO2 without an adequate understanding of key controlling factors.

  11. Morphometry and distribution of isolated caves as a guide for phreatic and confined paleohydrological conditions

    Frumkin, Amos; Fischhendler, Itay


    Isolated caves are a special cave type common in most karst terrains, formed by prolonged slow water flow where aggressivity is locally boosted. The morphometry and distribution of isolated caves are used here to reconstruct the paleohydrology of a karstic mountain range. Within a homogenous karstic rock sequence, two main types of isolated caves are distinguished, and each is associated with a special hydrogeologic setting: maze caves form by rising water in the confined zone of the aquifer, under the Mt. Scopus Group (Israel) confinement, while chamber caves are formed in phreatic conditions, apparently by lateral flow mixing with a vadose input from above.

  12. Preliminary Study on the Late Quaternary Activity Characteristics of the Menglian Fault in Southwest Yunnan%滇西南地区孟连断裂晚第四纪新活动特征初步研究

    何文贵; 刘兴旺; 袁道阳; 张波; 吴明


    Because it is located in an area of extensive collision between the Indian Plate and the Eurasian Plate,the Sichuan- Yunnan rhombic block in southwest Yunnan at the southeastern margin of the Tibetan Plateau is one of the regions with the highest concentration and frequency of strong earthquakes in China.Due to compression of this block in the SE direction,the region developed two groups of active transverse faults in NE and NNW directions.Both groups are in-volved in the process of rupture and the occurrence of earthquakes of above M7. 0.In this area, the main feature of the late Quaternary activity of these faults is strike-slip.The NW-trending faults have right-lateral strike-slip characteristics,whereas the NE-trending faults have left-later-al strike-slip characteristics.The Menglian fault is located in the boundary zone between south-west Yunnan and Myanmar.It is a large active fault in the south of the Sichuan-Yunnan rhom-bic block and its late Quaternary activity is intense.This fault has the main characteristics of left-lateral strike-slip with dip-slip.However,there are few research data on this fault and the extent of study has been low. There are no records of earthquakes on the Menglian fault.However,in the southwest of the fault,a MS 7.3 earthquake occurred in the territory of Myanmar on July 12,1995,which may be related to its activity.The linear structure of the fault in satellite images and landforms is very clear.The stream and water system are obviously offset to the left side along the fault.According to scanning electron microscopy results of the characteristics of the surface of quartz fragments in gravel from a fault gouge and research into active faults,Weixian et al.(2002)believed that the Menglian fault was formed before the Pliocene,displayed a high frequency of activity in the late Pleistocene,and has been active since then. Through an investigation of the active characteristics of the Menglian fault in the late Qua-ternary,this study

  13. Possible paleohydrologic and paleoclimatic effects on hominin migration and occupation of the Levantine Middle Paleolithic.

    Frumkin, Amos; Bar-Yosef, Ofer; Schwarcz, Henry P


    This paper explores the impact of major glacial/interglacial paleohydrologic variations in the Middle-Paleolithic Levant on hominin migration and occupation. The climatic reconstruction is based primarily on the most straight-forward paleohydrologic records recently published. These terrestrial proxies convey direct paleoenvironmental signals of effective precipitation and aquifer recharge. The two main proxies are temporal changes of terminal lake levels in the Dead Sea basin and periods of deposition or non-deposition of speleothems. Other records, such as stable isotopes, if interpreted correctly, correspond well with these two direct proxies. All the records consistently indicate that the last two glacial periods in the central Levant were generally wet and cool, while the last two interglacials were dry and warm, so more water was available for the ecosystem and thus hominins during glacial periods than during interglacials. Some proxies indicate that the higher precipitation/evaporation ratio during glacial periods involved higher precipitation rather than only reduced evaporation. Beyond the general mean glacial/interglacial climate suggested here, variations occurred at all temporal scales throughout glacial or interglacial periods. In the Sahara-Negev arid barrier, moister conditions occurred during Marine Isotope Stage (MIS) 6a-5e, when Anatomically Modern Humans apparently migrated out of Africa. We suggest that this migration, as well as the later Neanderthal expansion from Southeast Europe or the Anatolian plateau into the Levant during early MIS 4, could be facilitated by the observed major climatic variations.

  14. Paleohydrologic controls on methanogenesis in organic-rich saline aquifers

    McIntosh, J.; Petsch, S.; Schlegel, M.; Osborn, S.


    , respectively), where the permeable aquifers are a relatively open system, rapidly flushed by modern recharge. In contrast, the deep Upper Devonian shales have relatively positive d13C values for CO2 and CH4 (6 to 20 per mil, -56 to -50 per mil, respectively), indicating that methane has been generated over relatively long time scales (at least since the Late Pleistocene) in a closed system. The Pennsylvanian coal beds have intermediary d13C values for CO2 and CH4 (-8 to 11 per mil, -66 to -56 per mil, respectively), and contain Holocene groundwaters. Understanding the hydrobiogeochemical processes active within fractured shales and coal beds is important for energy resources, as well as CO2 sequestration.

  15. Late Quaternary climate change shapes island biodiversity

    Weigelt, Patrick; Steinbauer, Manuel; Cabral, Juliano


    Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration–extinction dynamics1, or as geologically dynamic with biodiversity resulting from immigration–speciation–extinction dynamics influenced by changes in island...... sea levels3, 4 and caused massive changes in island area, isolation and connectivity5, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory2, 6. Consequences of these oscillations for present biodiversity remain unassessed5, 7...

  16. Late Quaternary evolution of Lago Castor (Chile, 45.6°S): Timing of the deglaciation in northern Patagonia and evolution of the southern westerlies during the last 17 kyr

    Van Daele, Maarten; Bertrand, Sébastien; Meyer, Inka; Moernaut, Jasper; Vandoorne, Willem; Siani, Giuseppe; Tanghe, Niels; Ghazoui, Zakaria; Pino, Mario; Urrutia, Roberto; De Batist, Marc


    Even though Patagonia is ideally located to study climate of the southern mid-latitudes, many questions on the late Quaternary climate evolution remain unresolved. The timing of maximum glacier extent is still uncertain in vast areas, and the postglacial evolution of the Southern Westerly Wind Belt (SWWB) remains highly debated. Here, we study the sedimentary infill of a glacigenic lake (Lago Castor; 45.6°S, 71.8°W) located at the leeside of the Andes in Chilean Patagonia to i) reconstruct the deglacial evolution of the eastern flank of the Patagonian Ice Sheet (PIS), and ii) discuss postglacial changes in wind strength at a critical location where westerly wind records are critically lacking. A dense grid of high-resolution reflection-seismic data was used to reconstruct the large-scale infill history of the lake, and a radiocarbon dated sediment core penetrating all lacustrine seismic units, was retrieved. Results indicate that the deglaciation of the lake basin and its catchment occurred no later than ∼28 cal kyr BP (i.e. an early LGM), but possibly even already after MIS 4. Afterwards, the Lago Castor area was covered by a large proglacial lake that drained - possibly through an outburst flood - when the PIS outlet glaciers retreated to a critical location. Subsequently, very dry conditions caused the lake to desiccate, as evidenced by an unconformity visible on the seismic profiles and in the sediment core. This dry period likely resulted from the increased orographic effect of the PIS-covered Andes, accompanied by weaker westerlies. From ∼20 kyr BP onwards, the combination of a shrinking PIS and a southward shift of the SWWB resulted in increased precipitation, which caused the lake level to rise. After ∼17 cal kyr BP, lake sedimentation was more directly influenced by the southern westerlies, with the formation of sediment drifts resulting from strong bottom current during periods of intense westerly winds. Our results suggest a progressive increase

  17. Extensive Quaternary glaciations in eastern Turkey

    Yeşilyurt, Serdar; Akçar, Naki; Doǧan, Uǧur; Yavuz, Vural; Ivy-Ochs, Susan; Vockenhuber, Christof; Schlunegger, Fritz; Schlüchter, Christian


    During cold periods in the Quaternary, global ice volume increased and as a result valley glaciers advanced and the vice versa occurred during the warm periods. Quaternary glacier fluctuations had been also recorded in the Turkish mountains. Recently, the chronology of Late Quaternary advances in the northern and western Turkish mountains was reconstructed by surface exposure dating. However, these advances in the eastern Turkey are not dated yet. In this study, we investigated paleoglaciations in Kavuşşahap Mountains, which is located to the south of Lake Van in eastern Turkey. These mountains are one of the extensively glaciated areas in Turkey. Glacial activity is evidenced by more than 20 U-shaped valleys. For instance, one of the prominent and well-preserved glacial landscapes of Turkey is situated in the Narlıca valley system. Lateral and terminal moraines in the valley system indicate more than 10 glacial advances. To build their chronology, 39 erratic carbonaceous boulders were sampled for surface exposure dating with cosmogenic 36Cl. We also reconstructed the ice margin reconstruction of the Narlıca paleoglacier using the accumulation area ratio and area-altitude balance ratio approaches. We estimated an equilibrium line altitude (ELA) of ca. 2900 m above sea level based on the maximum ice extend, which implied ca. 800 m decrease in the ELA during the Late Quaternary in comparison to the lower bound of the modern ELA estimate. The first results of the surface exposure dating will be presented.



    <正>20112526Bai Daoyuan (Hunan Institute of Geology Survey,Changsha 410011,China); Liu Bo Quaternary Tectonic-Sedimentary Characteristics and Environmental Evolution of Linli Sag,Dongting Basin (Journal of



    <正>20111129 Bai Daoyuan(Hunan Institute of Geological Survey,Changsha 410011,China);Li Chang’an Quaternary Tectonic-Sedimentary Characteristics and Environmental Evolution of Anxiang Sag in Dongting Basin and Its West Periphery(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,32(2),2010,p.120-129,6 illus.,1 table,48 refs.)Key words:Quaternary,sedimentary environment,structural evolution,Dongtinghu Basin Detailed geologic mapping and bore data was conducted to study on the Quaternary tectonic and sedimentary characteristics and environmental evolution of Anxiang Sag and its west periphery of Dongting Basin,which provided new materials for Quaternary geology of Jianghan-Dongting Basin.The sag trends north-south direction and is surrounded by normal faults.The thickness of Quaternary deposits in the sag is commonly 100~220 m with maximun thickness of 300 m,and from lower to upper,the Quaternary strata is composed of Early Pleistocene Huatian Formation and Miluo Formation,Middle Pleistocene Dongtinghu Formation

  20. Evolution of mangroves in the Late Quaternary in the Pearl River Delta and its environmental significance%珠江三角洲晚第四纪红树林的演化及其环境意义

    翁毅; 张伟强


    广州番禺东涌剖面样品的AMS(磁谱仪)年龄及红树林孢粉分析结果表明,珠江三角洲存在晚更新世和全新世的红树林,红树林是海侵的标志之一.按照检出红树属花粉的9个剖面的分布以及5处埋藏红树林腐木的分布,可以描绘出全新世海侵的边界.根据东涌剖面的沉积旋回、样品年龄、红树林花粉含量曲线、半咸水-淡水硅藻及热性-温性硅藻含量曲线的综合分析,可将沉积环境的变迁分为4个阶段.第一阶段和第三阶段的海侵有利于红树林的发展,第二阶段不利于红树林的发展,第四阶段的晚全新世,红树林的生长频繁.显示人为因素的影响.%The depositional environment of the Pearl River Delta in the Late Quaternary and the spatio-temporal change in the climate are discussed on the basis of serial sampling and the results of sporo-pollen analysis of mangroves and accelerator mass spectrometry dating of samples. The profile of Dongchong in Panyu, Guangzhou is taken as a representative and associated with-correlative profiles. The research results show that there were mangroves during the Late Pleistocene and Holocene in the Pearl River Delta. The mangroves are an indicator of transgression. The boundary of Holocene transgression can be traced according to the distribution of nine profiles for which the content of Rhizophora sporo-pollen is observed and five locations of buried rotted mangrove wood. Changes in the depositional environment can be divided into four stages on the basis of comprehensive analysis of the sedimentary cycle, dating of samples and the three curves of the contents of mangrove sporo-pollen, brackish fresh water diatom and hot warm species diatom in the Dongchong profile. The first stage was the Last Subinterglacial Period of MIS3, before 25 000 aB. P. , and the lithology was a coarse bottom grain layer of the sedimentary cycle with depth from 24.8 to 29.8 m. The mangroves flourished, with the

  1. Paleohydrologic change across the Paleocene-Eocene Thermal Maximum, Bighorn Basin, WY

    Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.


    One of the uncertainties in accurately predicting future climate change involves how the hydrologic cycle will respond to increasing pCO2 and temperature. Quantifying the relationship between carbon cycle perturbations and the hydrologic cycle in the geologic past is crucial to understanding and accurately modeling how anthropogenic carbon emissions will affect future changes in the hydrologic cycle. Records of paleohydrologic response to global warming in the geologic past are rare, particularly for continental interiors, where climate model projections of precipitation are highly uncertain. Here we examine hydrogen isotope ratios of leaf waxes as a tool for reconstructing paleohydrologic change in the continental interior of North America across the Paleocene-Eocene Thermal Maximum (PETM), an abrupt, transient episode of extreme global warming ~56 Ma. New hydrogen isotope measurements of leaf-wax n-alkanes from the southeastern Bighorn Basin, Wyoming record two positive shifts during the PETM. n-Alkane δD values first shift to more positive values just after the onset of the carbon isotope excursion and then again higher up in the body of the carbon isotope excursion, with a return to slightly more negative δD values in between. Paleobotanical, paleopedologic, and isotope data from the same field area have suggested that the Bighorn Basin may have experienced a drier or more seasonally dry climate during the PETM. Mean annual precipitation estimates based on paleosol major oxides, soil wetness assessed using the soil morphology index, and an aridity proxy based on differences in δ18O values of tooth enamel in aridity-sensitive and aridity-insensitive mammals each independently suggest a potential two-phase drying within the PETM interval. Similarly, the hydrogen isotope record could reflect two periods of drying, with a return to slightly wetter conditions in between. However, leaf-wax hydrogen isotope ratios reflect not only source water hydrogen isotope

  2. Paleohydrology reconstruction and Holocene climate variability in the South Adriatic Sea

    G. Siani


    Full Text Available Holocene paleohydrology reconstruction is derived combining planktonic and benthic stable oxygen and carbon isotopes, sea surface temperatures (SSTs and oxygen isotope composition of seawater (δ18Ow from a high sedimentation core collected in the South Adriatic Sea (SAS. Core chronology is based on 10 AMS 14C measures on planktonic foraminifera and tephra layers. Results reveal two contrasted paleohydrological periods that reflect (i a marked lowering of δ18Ow/salinity during the early to mid-Holocene (11.5 ka to 6.3 ka, including the two-step sapropel S1 deposition, followed during the mid- to upper Holocene by (ii a prevailing period of increased salinity and enhanced arid conditions in the South Adriatic Basin. Superimposed on these trends, short-term centennial-scale hydrological events punctuated the Holocene period in the SAS. During the early to mid-Holocene, two main SST coolings together with prominent δ18Ow/salinity lowering delineate the sapropel S1 interruption and the post-sapropel phase between 7.3 to 6.3 ka. After 6 ka, centennial-scale δ18Ow and G. bulloides δ13C lowering, mostly centered between 3 to 0.6 ka, reflect short-term hydrological changes related to more intensive runoff of the Po and/or Apennine rivers. These short-term events, even of lesser amplitude compared to the early to mid-Holocene period, may have induced a lowering of sea surface density and consequently reduced and/or inhibited the formation of deep bottom waters in the SAS. Comparison of the emerging centennial- to millennial-scale hydrological record with previous climatic records from the central Mediterranean area and north of the Alps reveal possible synchronicities (within the radiocarbon-dating uncertainty between phases of lower salinity in the SAS and periods of wetter climatic conditions around the north-central Adriatic Sea. Finally, wavelet analyses provide new clues about the potential origin of climate variability in the SAS, confirming

  3. Reconstruction of paleohydrology in semi-arid regions for water resources management: Opportunities and challenges

    Elshorbagy, Amin; Wagener, Thorsten; Razavi, Saman; Sauchyn, David


    Tree-ring based reconstruction of paleohydrology can be a valuable and important means to extend the available hydrological records for several centuries. Such record extension, when properly done, can improve water resources management and planning by making available realistic long records that reflect past short- and long-term hydrometeorological variabilities. This research highlights some of the important, and perhaps unresolved, issues in tree-ring based reconstruction of paleohydrology, especially in semi-arid regions. The relationships between tree growth, as represented by tree-ring chronologies (TRCs), runoff (Q), precipitation (P), and evapotranspiration (ET) are discussed within both statistical and hydrological contexts. The Oldman River Basin (OMRB), Alberta, Canada, is presented as a case study, with TRCs and hydrometeorological data used to demonstrate the relevant issues. Runoff and precipitation data were available through measurements, and actual evapotranspiration was estimated using a lumped conceptual hydrological model developed in this study for the OMRB. Correlation analysis was conducted to explore the relationships between TRCs and each of Q, P, and ET over the entire historical record (globally) as well as locally within the wet and dry subperiods. Global and local correlation strengths and linear relationships appear to be significantly different, particularly affecting tree-ring based inferences about the hydrology and wet and dry episodes from reconstructions made using regression models. This finding is not typically highlighted in the available literature. Reconstruction of paleoQ may also not be as credible as paleoP and paleoET. This is discussed within the context of the watershed storage and release functions. It was also found that a moving average window, of more than one year, of P and ET time series might be necessary for reconstruction of these variables using tree-ring chronologies. This study improves our understanding of

  4. Second Quaternary dating workshop



    The second Quaternary dating methods workshop was held at Lucas Heights and sponsored by ANSTO and AINSE. Topics covered include, isotope and thermoluminescence dating, usage of accelerator and thermal ionisation mass spectrometry in environmental studies emphasizing on the methodologies used and sample preparation

  5. Correlation and causation in tree-ring-based reconstruction of paleohydrology in cold semiarid regions

    Elshorbagy, Amin; Wagener, Thorsten; Razavi, Saman; Sauchyn, David


    This paper discusses ways in which the tree-ring-based reconstruction of paleohydrology can be better understood and better utilized to support water resource management, especially in cold semiarid regions. The relationships between tree growth as represented by tree ring chronologies (TRCs), runoff (Q), precipitation (P), and evapotranspiration (ET) are discussed and analyzed within both statistical and hydrological contexts. Data from the Oldman River Basin (OMRB), Alberta, Canada, are used to demonstrate the relevant issues. Instrumental records of Q and P data were available while actual ET was estimated using a lumped conceptual hydrological model developed in this study. Correlation analysis was conducted to explore the relationships between TRCs and each of Q, P, and ET over the entire historical record (globally) as well as locally in time within the wet and dry subperiods. Global and local correlation strengths and linear relationships appear to be substantially different. This outcome particularly affects tree-ring-based inferences about the hydrology of wet and dry episodes when reconstructions are made using regression models. Important findings include (i) reconstruction of paleo-runoff may not be as credible as paleo-precipitation and paleo-evapotranspiration; (ii) a moving average window of P and ET larger than 1 year might be necessary for reconstruction of these variables; and (iii) the long-term mean of reconstructed P, Q, and ET leads us to conclude that there is uncertainty about the past climate. Finally, we suggest using the topographic index to prejudge side suitability for dendrohydrological analysis.



    <正>20050939 An Chengbang (Key Lab. of Western Chinese Environment System, Ministry of Education, Lanzhou University, Lanzhou, Gansu 730000, China); Feng Zhaodong Humid Climate During 9-3. 8 KaBP in the Western Part of Chinese Loess Plateau (Marine Geology & Quaternary Geology, ISSN0256-1492, CN37-1117/P, 24 (3), 2004, p. 111-116, 3 illus. , 1 table, 40 refs. , with English abstract)

  7. Partitioning the Quaternary

    Gibbard, Philip L.; Lewin, John


    We review the historical purposes and procedures for stratigraphical division and naming within the Quaternary, and summarize the current requirements for formal partitioning through the International Commission on Stratigraphy (ICS). A raft of new data and evidence has impacted traditional approaches: quasi-continuous records from ocean sediments and ice cores, new numerical dating techniques, and alternative macro-models, such as those provided through Sequence Stratigraphy and Earth-System Science. The practical usefulness of division remains, but there is now greater appreciation of complex Quaternary detail and the modelling of time continua, the latter also extending into the future. There are problems both of commission (what is done, but could be done better) and of omission (what gets left out) in partitioning the Quaternary. These include the challenge set by the use of unconformities as stage boundaries, how to deal with multiphase records in ocean and terrestrial sediments, what happened at the 'Early-Mid- (Middle) Pleistocene Transition', dealing with trends that cross phase boundaries, and the current controversial focus on how to subdivide the Holocene and formally define an 'Anthropocene'.

  8. Paleohydrology Workshops for Water Resource Managers Using an Iterative Evaluation Process

    Woodhouse, C.; Lukas, J.


    Workshops can be an effective avenue for the exchange of information and ideas between scientists and decision-makers. The interactive aspects of workshops promote more active participation and interactions between the two groups. In 2006, at the suggestion of water resource managers, we began presenting a series of small workshops (10-25 participants) on the use and application of tree-ring data in water resource management. The one-day workshops cover the basic science behind tree-ring reconstructions of hydrology, resources available, and applications of the data to resource management, with presentations by both tree-ring scientists and water resource professionals. They also include plenty of time for informal discussion. We have now held ten workshops across the western U.S., and several more are planned. We use pre-workshop surveys to tailor the workshop to the needs of the participants, and we assess the workshop's effectiveness through participant evaluations completed at the end of the workshop. We also receive post-workshop feedback in the form of follow-up emails or via word of mouth. This iterative process of evaluation, with each workshop, has enabled us to fine-tune the format and content of the workshops and respond to additional needs such as data, web resources, online tools for using paleodata, as well as follow-up workshops. This approach has resulted in an improvement in the credibility, acceptance, and use of tree-ring data in water resource applications, as evidenced by an independent survey of workshop participants. Although the focus of these workshops has been on paleohydrologic data, this approach would be applicable to other climate-stakeholder issues as well.

  9. Cyanines Bearing Quaternary Azaaromatic Moieties

    Sbliwa, Wanda; Matusiak, Grazyna; Bachowska, Barbara


    Selected cyanines bearing quaternary azaaromatic moieties are presented, showing their monomers, dimers and polymers, as well as their possible applications. Cyanines having NLO properties are also briefly described.

  10. 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

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


    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

  11. Magnetism of quaternary sediments

    Heller, Friedrich

    Magnetism of Quaternary sediments was the topic of a well-attended symposium held during the 13th INQUA (International Union of Quaternary Research) congress in Beijing, China, August 2-9. More than 40 papers were delivered by scientists from Belgium, England, France, Germany, Japan, New Zealand, Sweden, Switzerland, Taiwan, the United States, the Soviet Union, Yugoslavia, and other countries. The host country contributed to a productive session that was part of the first large scientific meeting to take place in Beijing after the June 4, 1989, upheaval.Nearly half of the studies focused on paleomagnetic and rock magnetic properties of loess in Alaska, Central Asia, China, and New Zealand. Magnetostratigraphic polarity dating was done at some sections in the western (Shaw et al.) and central Chinese loess plateau (Bai and Hus; Wang and Evans; Yue). The interpretation of the polarity pattern found in the western loess plateau still is not unambiguous. In the central part, certain polarity boundaries, such as the Brunhes/Matuyama (B/M) boundary, are found in slightly different stratigraphic positions (Hus et al.; Yue). In deep-sea sediments the lock-in depth of natural remanent magnetization (NRM) at the B/M boundary seems to be a linear function of sedimentation rate (de Menocal et al.). Although the magnetization process in the Chinese loess is not well understood, detailed records of polarity transitions have been reported for the B/M and the Jaramillo R→N transition (Ma et al.; Rolph).

  12. Paleohydrologic controls on soft-sediment deformation in the Navajo Sandstone

    Bryant, Gerald; Cushman, Robert; Nick, Kevin; Miall, Andrew


    Many workers have noted the presence of contorted cross-strata in the Navajo Sandstone and other ancient eolianites, and have recognized their significance as indicators of sediment saturation during the accumulation history. Horowitz (1982) proposed a general model for the production of such features in ancient ergs by episodic, seismically induced liquefaction of accumulated sand. A key feature of that popular model is the prevalence of a flat water table, characteristic of a hyper-arid climatic regime, during deformation. Under arid climatic conditions, the water table is established by regional flow and liquefaction is limited to the saturated regions below the level of interdune troughs. However, various paleohydrological indicators from Navajo Sandstone outcrops point toward a broader range of water table configurations during the deformation history of that eolianite. Some outcrops reveal extensive deformation complexes that do not appear to have extended to the contemporary depositional surface. These km-scale zones of deformation, affecting multiple sets of cross-strata, and grading upward into undeformed crossbeds may represent deep water table conditions, coupled with high intensity triggers, which produced exclusively intrastratal deformation. Such occurrences contrast with smaller-scale complexes formed within the zone of interaction between the products of soft-sediment deformation and surface processes of deposition and erosion. The Horowitz model targets the smaller-scale deformation morphologies produced in this near-surface environment. This study examines the implications of a wet climatic regime for the Horowitz deformation model. It demonstrates how a contoured water table, characteristic of humid climates, may have facilitated deformation within active bedforms, as well as in the accumulation. Intra-dune deformation would enable deflation of deformation features during the normal course of dune migration, more parsimoniously accounting for

  13. Assessment Of A Groundwater Flow Model Of The Bangkok Basin, Thailand, Using Carbon-14-Based Ages And Paleohydrology

    Sanford, Ward E.; Buapeng, Somkid


    A study was undertaken to understand the groundwater flow conditions in the Bangkok Basin, Thailand, by comparing 14C-based and simulated groundwater ages. 14C measurements were made on about 50 water samples taken from wells throughout the basin. Simulated ages were obtained using 1) backward-pathline tracking based on the well locations, and 2) results from a three-dimensional groundwater flow model. Comparisons of ages at these locations reveal a large difference between 14C-based ages and ages predicted by the steady-state groundwater flow model. Mainly, 14C and 13C analyses indicate that groundwater in the Bangkok area is about 20,000 years old, whereas steady-state flow and transport simulations imply that groundwater in the Bangkok area is 50,000-100,000 years old. One potential reason for the discrepancy between simulated and 14C-based ages is the assumption in the model of steady-state flow. Groundwater velocities were probably greater in the region before about 10,000 years ago, during the last glacial maximum, because of the lower position of sea level and the absence of the surficial Bangkok Clay. Paleoflow conditions were estimated and then incorporated into a second set of simulations. The new assumption was that current steady-state flow conditions existed for the last 8,000 years but were preceded by steady-state conditions representative of flow during the last glacial maximum. This "transient" paleohydrologic simulation yielded a mean simulated age that more closely agrees with the mean 14C-based age, especially if the 14C-based age corrected for diffusion into clay layers. Although the uncertainties in both the simulated and 14C-based ages are nontrivial, the magnitude of the improved match in the mean age using a paleohydrologic simulation instead of a steady-state simulation suggests that flow conditions in the basin have changed significantly over the last 10,000-20,000 years. Given that the valid age range of 14C-dating methods and the timing

  14. Occurrence of volcanic ash in the Quaternary alluvial deposits, lower Narmada basin, western India

    Rachna Raj


    This communication reports the occurrence of an ash layer intercalated within the late Quaternary alluvial succession of the Madhumati River, a tributary of the lower Narmada River. Petrographic, morphological and chemical details of glass shards and pumice fragments have formed the basis of this study. The ash has been correlated with the Youngest Toba Tuff. The finding of ash layer interbedded in Quaternary alluvial sequences of western Indian continental margin is significant, as ash being datable material, a near precise time-controlled stratigraphy can be interpreted for the Quaternary sediments of western India. The distant volcanic source of this ash requires a fresh re-assessment of ash volume and palaeoclimatic interpretations.

  15. Paleohydrology of meandering systems: a new approach for the reconstruction of ancient drainage areas and the quantification of the controlling factors

    Held, A.; Cojan, I.


    In meandering system fluvial sedimentology, studying infill geometries and sedimentary structures of channelized sandstone bodies, gives information about the sedimentary dynamic and the depositional environment. Associated with such a sedimentary approach, paleohydrology enables the reconstruction of hydrological parameters such as discharge, drainage area or stream length. Although fluvial systems are known to be influenced by allogenic and/or autogenic processes, climate or structural evolution were not taken into account in previous paleohydrological studies. Therefore, the present study attempts to develop a new method of paleohydrological reconstitution, based on the geometry of fluvial sandstone bodies and constrained by the controlling factors (climate and tectonic). We selected two meandering systems of the same age, developed under different climatic setting: the first one is located in the Alpine Foreland Basin (SE France) and was associated to a subtropical humid realm; the second one is situated in the Loranca Basin (Central Spain) and was related to subtropical semi-arid conditions. Dealing with the uniformitarianism concept, we developed a new method to determine the paleohydrological parameters of the two different systems. For each of these two climatic setting we have constructed an equivalent modern rivers database taking into account their respective climatic conditions. By defining empirical relations, we translated the point-bar thickness (the only data available in the field) into paleohydrological parameters, such as channel geometry, water discharge and basin geometry. Because fluvial members studied are composed of several channelized sequences; each of them gives a specific drainage area depending on discharge value and climatic coefficient. But assuming a constant basin area all along the river evolution, we can quantify the spatiotemporal impact of the climate on the development of an alluvial system. Furthermore, granulometry

  16. Uranium-series dating of travertine from Soda Dam, New Mexico: Constructing a history of deposition, with implications for landscape evolution, paleohydrology and paleoclimatology

    Tafoya, A. J.; Crossey, L. J.; Karlstrom, K. E.; Kolomaznik, M.; Polyak, V. J.; Asmerom, Y.; Cox, C. J.


    We apply high precision uranium series geochronology to decipher rates of change in travertine growth at Soda Dam, New Mexico which preserve a paleohydrology record for parts of the last 500 ka. Travertine-depositing springs occur along the intersection of the Soda Dam fault, part of the Jemez fault zone, and the Jemez River. Modern travertine-depositing hot springs are part of the Valles geothermal system, which has been active throughout the Quaternary. Previous U-series dates (Goff et al., 1987) on the Soda Dam travertines were: Soda Dam = 4.8±0.2 ka; Deposit A (west side) = 215±40 ka and >350 ka; Deposit B (east side) = 98±7 ka near top and 58±3 ka in the core; Deposit C (southeast side) = 107±5 ka near base. New dates provide improved geochronologic and geologic context with respect to timing of movement in the western side of the Rio Grande Rift and the Pajarito fault, incision rates of the Jemez River, and timing of travertine accumulation. Large volumes of travertine preserved high in the landscape yield an age of 560.3 ± 324 ka. Inset into this deposit are Jemez River gravels that are 30 m above the modern river with travertine coating on cobbles giving an age of 200.6±2.1 ka and gravels cut by sparite sills of 109 ± 1.5 ka. These ages give river incision rates of 150 m/Ma over the last 200 ka. Deposit B is a mound accumulation on the east side of the river that developed on a banded central fissure ridge, much like the modern Soda Dam. The mound accumulation is 138.4 ± 1.1 ka near the base and 78.2 ± 1.6 ka at the top; the central fissure has a 20 cm thick vein system a portion of which yields a more restricted age range from 133.9±11 ka toward the walls to 95.8±1.0 ka toward the center. The combined data indicate the fissure/mound system was active from 138-78 ka, a 60,000 yr interval that spans the transition from glacial marine isotope stage 6 into interglacial marine isotope stage 5. Accumulation rates on the vein system of deposit B are 2

  17. 中国庐山晚第四纪沉积岩系的石英形貌显微结构及环境过程%Microstructure and Morphology of Quartz from Late Quaternary Sedimentary Rocks in Lushan Mts. China, and Its Environment Process

    胡东生; 李小豫; 熊卫强; 张华京; 弓虎军; 胡文瑄; 张国伟


    During systematic investigation on the typical profiles of the Late Quaternary in the Lushan region, the authors collected quartz samples from the profiles. The samples were sieved into particles with quartz particle size of Θ= l~3mm. Observation under electronic microscope reveals quartz microstructures such as morphology, deformation, and dynamic chemical effect. Key events taking place in the process were analyzed to understand environmental response of strata profiles. Through comprehensive index which reflects earth surface process and environmental response, four paleo-climate environmental stages were determined from bottom to top: glacier environment, inter glacier environment, ice margin environment to post glacier environment. The research results provide new evidence for further study and understanding of evolution and global change of the Quaternary environment in the Lushan region.%基于庐山山地晚第四纪地层典型断面的系统调查,从地层剖面层序中筛选的微粒(θ=1~3mm)石英颗粒进行环境电子显微镜观测研究,辨认出显微结构-颗粒形态-变形构造-动力化学作用等特征,运用系统过程发展中的节点事件进行层型剖面的环境响应分析,采取综合指标表征地球表层过程及环境响应情景,明确划分出四个古气候环境发展阶段,由下往上分别表现为冰期环境-间冰期环境-冰缘环境-冰后期环境,为深入研究及科学认识庐山第四纪环境演化过程及全球变化提供了新的基础依据.

  18. Geochemistry, age and strontium isotope composition of late tertiary and quaternary basalts and andesites in western Nevada and their relation to geothermal potential. Final report, October 1, 1982-December 31, 1983

    Fultz, L.A.; Bell, E.J.; Trexler, D.T.


    This research was undertaken to characterize the late Cenozoic volcanic rocks associated with active geothermal systems in west-central Nevada. Petrographic and microprobe, geochemical and isotopic analysis and age dating techniques were used to characterize these young volcanic rocks. These data were combined with the limited data previously reported in the literature on these same volcanic areas to interpret their petrogenesis. The overall characterization resulted from integrating the petrogenesis with a structural-tectonic model of the region. Potassium-argon isotopic ages ranging up to 14 million years were determined for eight localities within the Reno 1 x 2/sup 0/ study region. These ages are consistent with the morphology of the volcanic landforms, the active geothermal systems associated with them, and with other isotopic ages reported in the literature for these and similar rocks within the study region. Petrographic analysis of hand specimens and thin-sections indicated mineralogic assemblages of the respective rock types and specific mineral textures and phenocryst compositions and characteristics. These identifications were further substantiated by microprobe analysis of selected phenocrysts and groundmass phases. Classification of the respective rock types was also based on chemical composition and normative calculations using the program PETCAL. Basaltic andesites are identified and described for Steamboat Hills, Table Mountain, Silver Springs, Churchill Butte, Cleaver Peak, Desert Peak and Carson City sites.

  19. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    Søager, Nina

    The extensive Quaternary volcanism in the Payenia volcanic province, Mendoza, Argentina, is investigated in this study by major and trace element analyses, Sr, Nd, Hf and Pb-isotopic analyses and Zr-Hf isotope dilution data on samples from almost the entire province. The samples are mainly...... in basalts from all the studied volcanic fields in Payenia is signs of lower crustal contamination indicating assimilation of, in some cases, large amounts of trace element depleted, mafic, plagioclase-bearing rocks. The northern Payenia is dominated by backarc basalts erupted between late Pliocene to late...

  20. Late Quaternary hydroclimatology of a hyper-arid Andean watershed: Climate change, floods, and hydrologic responses to the El Niño-Southern Oscillation in the Atacama Desert

    Magilligan, F. J.; Goldstein, P. S.; Fisher, G. B.; Bostick, B. C.; Manners, R. B.


    Although certain characteristics of the El Niño-Southern Oscillation (ENSO) are well known on contemporary timescales, less is known about the magnitude-frequency relationships of this atmospheric phenomenon on longer timescales or its relationship to widespread flooding, especially in its core zone along the sub-tropical Andes where La Niña or El Niño episodes control regional hydroclimatology. Using a combination of stratigraphic evidence, geochronologic dating ( 14C and OSL), stable isotope analyses, and water geochemistry along the Rio Moquegua in the northern fringes of the Atacama Desert, we assemble a paleoflood chronology for mainstem and tributary sections for the past ca. 20 ka and ascertain the variation in ENSO frequency and magnitude. Because of the inherent watershed structure and regional hydroclimatology, mid-valley tributaries of the Rio Moquegua only flood during El Niño episodes and thus provide an important proxy of extreme El Niños while mainstem stratigraphy records both La Niña and El Niño episodes. El Niño floods appear to have been pronounced during the Late Pleistocene and up to at least the Younger Dryas (~ 12,000 cal yr BP) while stratigraphic evidence of large El Niño floods is lacking in tributary systems during the Mid-Holocene. Flood stratigraphy in a ~ 2 ka 7 m high terrace along the mainstem indicates an increased frequency and magnitude of large floods between ca. 700 and 1610 AD as compared to the period from ca. 160 BCE to 700 AD with "mega-Niños" occurring ca. 1330 AD and ca. 1650 AD. Water geochemistry and radiocarbon dating indicate that at least two major aquifers exist, with wells and springs in the mid-valley dating to 710 and 3100 14C yr BP, respectively, while water from a spring in the headwaters dates to 10,320 14C yr BP. This range in dates suggests that groundwater flow in the mid-valley is neither fossil water nor exclusively recharged from local precipitation while the older date for headwater sections


    张梦莹; 范代读; 吴国瑄; 尚帅; 陈玲玲


    YQ0902孔位于瓯江三角洲南翼的海岸平原上,沉积相与AMS14C测年分析表明,钻孔底部为MIS 3阶段的河湖相沉积,之上为形成于MIS 2的硬粘土层.约在10cal.kaB.P.海侵到达本区,沉积了一套厚约29m的海侵-海退沉积旋回.古气候重建表明,50 ~ 35cal.kaB.P.凉爽干燥,35 ~ 25cal.kaB.P.温和湿润,25~ 10cal.kaB.P.寒冷干燥,10 ~ 9cal.kaB.P.凉爽偏干,9.0~6.5cal.kaB.P.暖热潮湿,6.5 ~ 4.8cal.kaB.P.温凉偏干,4.8~1.8cal.kaB.P.温暖潮湿,1.8cal.kaB.P.之后趋同于现代气候.受中全新世东亚夏季风减弱影响,研究区降雨减弱始于6.5cal.kaB.P.,这与前人研究认为季风区降雨减弱年限随纬度增加有时滞的观点相一致.孢粉记录的两次百年尺度(6.9 ~7.3cal.kaB.P.和5.0 ~5.5cal.kaB.P.)降温事件,与全球性强降温事件(7.3cal.kaB.P.和5.5cal.kaB.P.)有较好的对应关系.%Borehole YQ0902( 27°55'N, 120°51'E) was drilled from the southern coastal plain of Oujiang River delta, with a total length of 41. 9m. Sediment cores were split and described in detail,including color,sedimentary texture and structure, and stratigraphical boundaries before sampling. Fourteen AMS14C dating samples were collected and sent to Beta Analytic Company for dating. Forty-five samples were collected with roughly 1 -m sampling interval for palynological studies. Facies analysis together with AMS C age data showed that the lower section of the core was deposited during MIS 3 in a fluvial-lacustrine environment, topped by the paleosol formed during the MIS 2 low sea-level stage. A complete transgressive-regressive succession of 29m thick overlying the paleosol, was presumed to deposit after 10cal. kaB. P. when the transgression reached the area. Pollen-spore analysis suggested that the Late Quaternary paleoenvironmental evolution can be divided into eight stages. 1 ) Between 50cal. kaB. P. and 35cal. kaB. P. , the climate was cool and dry, and the sea-level was at least

  2. Quaternary stratigraphy and palaeogeography of Poland

    Marks, Leszek; Dzierżek, Jan; Janiszewski, Robert; Kaczorowski, Jarosław; Lindner, Leszek; Majecka, Aleksandra; Makos, Michał; Szymanek, Marcin; Tołoczko-Pasek, Anna; Woronko, Barbara


    Though the stratigraphical and palaeogeographical framework of the Quaternary in Poland is still to be completed, several crucial points have been confirmed recently. The preglacial series, accepted for years as belonging to the Lower Pleistocene, is undoubtedly of Early Pliocene age, with a huge hiatus above almost until the uppermost Lower Pleistocene. The earliest glaciation in Poland (Nidanian) occurred at about 900 ka BP when the ice sheet reached the mid-southern part of the country. The following Podlasian Interglacial embraced the Brunhes/Matuyama boundary in the middle, in a similar fashion to the corresponding Cromerian Complex in Western Europe. The late Early and early Middle Pleistocene interglacials in Poland comprised 2-3 optima each, whereas every one of the younger interglacials was characterised by a single optimum only. The Late Vistulian ice sheet was most extensive in the western part of Poland (Leszno Phase) whereas the younger Poznań Phase was more extensive in the central and eastern part of the country. This was due to the varied distance from the glaciation center in Scandinavia, making the ice sheet margin reach a terminal position in different times. Palaeoclimatological research in the Tatra Mountains has provided new evidence for the atmospheric circulation over Europe. During cold phases of the Pleistocene in Poland a continental climate extended further westwards, quite the opposite that occurring during warmer intervals.

  3. Proposal to redefine the Quaternary



    The following proposal has been circulated, via the Executive of the International Union for Quaternary Research (INQUA), to all INQUA members for discussion. It also appears on the ICS web site ( Comments may be sent to John Clague, President of INQUA (, and Brad Pillans(

  4. Using historic aerial photography and paleohydrologic techniques to assess long-term ecological response to two Montana dam removals.

    Schmitz, Denine; Blank, Matt; Ammondt, Selita; Patten, Duncan T


    The restorative potential of dam removal on ecosystem function depends on the reversibility of dam effects and its operations. While dam removal is an established engineering practice, the need for an understanding of the ecological response remains. We used paleoflood hydrology, hydrologic modeling, and aerial photo interpretation to investigate the long-term ecologic responses to dam failure and breach. We investigated downstream geomorphic and vegetation responses to a dam failure (Pattengail Dam in 1927) and a controlled dam breach, which used natural sediment removal (Mystic Lake Dam in 1985). Our data showed vegetation responses indicative of channel and floodplain evolution at Pattengail. The size of the flood following the Pattengail dam failure initiated a series of channel adjustments and reworked over 19ha of floodplain downstream of the dam. In Mystic, we observed few flood stage indicators and a slight response in floodplain vegetation. We made several findings. (1) Dam removal effects on channel evolution and floodplain development depend on reach types and their responsiveness to flow regime change. (2) Ecologic response to dam removal depends on the sizes and timing of high flow events during and following removal. (3) Paleohydrology can be used to assess historic floods (>20 years). We see the utility of assessing the ecological responsiveness of a system to previous fluvial events or changes in flow regime. Informed about the character of a system based on its history, dam removal scientists can use these tools to set realistic restoration goals for removing a dam.

  5. Late Quaternary faunal change in coastal Arabian sea sediments

    Borole, D.V.; Rao, K.K.; Krishnamurthy, R.V.; Somayajulu, B.L.K.

    Carbonate content and faunal composition of two gravity cores from the coastal Arabian Sea provide evidence of a major environmental change in surface ocean waters about 13,000 yr B.P. Radiocarbon dating indicates that deposition rates ranged from 1...

  6. Millennial-scale ocean acidification and late Quaternary

    Riding, Dr Robert E [University of Tennessee (UT); Liang, Liyuan [ORNL; Braga, Dr Juan Carlos [Universidad de Granada, Departamento de Estratigrafıa y Paleontologıa, Granada, Spain


    Ocean acidification by atmospheric carbon dioxide has increased almost continuously since the last glacial maximum (LGM), 21 000 years ago. It is expected to impair tropical reef development, but effects on reefs at the present day and in the recent past have proved difficult to evaluate. We present evidence that acidification has already significantly reduced the formation of calcified bacterial crusts in tropical reefs. Unlike major reef builders such as coralline algae and corals that more closely control their calcification, bacterial calcification is very sensitive to ambient changes in carbonate chemistry. Bacterial crusts in reef cavities have declined in thickness over the past 14 000 years with largest reduction occurring 12 000 10 000 years ago. We interpret this as an early effect of deglacial ocean acidification on reef calcification and infer that similar crusts were likely to have been thicker when seawater carbonate saturation was increased during earlier glacial intervals, and thinner during interglacials. These changes in crust thickness could have substantially affected reef development over glacial cycles, as rigid crusts significantly strengthen framework and their reduction would have increased the susceptibility of reefs to biological and physical erosion. Bacterial crust decline reveals previously unrecognized millennial-scale acidification effects on tropical reefs. This directs attention to the role of crusts in reef formation and the ability of bioinduced calcification to reflect changes in seawater chemistry. It also provides a long-term context for assessing anticipated anthropogenic effects.

  7. Luminescence dating of Late Quaternary sediments from East Greenland

    Mejdahl, V.; Funder, Svend Visby


    Luminescence dating based on K-feldspars and using both TL and OSL methods have been performed on 94 sediment samples from East Greenland. The ages go back more than 380 ka, but are mainly from the last interglaciation and the subsequent period and include both shallow-marine/coastal-fluvial and ......Luminescence dating based on K-feldspars and using both TL and OSL methods have been performed on 94 sediment samples from East Greenland. The ages go back more than 380 ka, but are mainly from the last interglaciation and the subsequent period and include both shallow...

  8. Quantifying bioturbation and soil thickening over the late Quaternary

    Wilkinson, M. T.; Pietsch, T.; Fox, J. F.


    We present geochemistry and biochemistry data to explore how bioturbation has operated in a residual sandstone-derived soil that thickened during the Holocene following aeolian deflation during the Last Glacial Maximum. Our site is located on a plateau cut into Triassic sandstones in humid Blue Mountains, SE Australia, where precipitation is ~1100 mm/a, and the mean annual maximum and minimum temperatures are 17°C and 5°C, respectively. Vegetation cover increase occurred ~13 ka, based on nearby palaeodune activity and pollen data from other highland sites. Our interpretation of terrestrial cosmogenic radionuclides (TCN) data suggests that ~30 cm of soil thickening has taken place since 13 ka, which includes 16 cm of bedrock lowering. Biofabrics preserve a short-term picture of biotically-displaced soil. In general, bioturbation decreases exponentially with increasing soil depth. The upper 21 cm of the profile is ~95% bioturbated; the middle 13 cm is 13 - 32% bioturbated; and the lowest 52 cm is 1 - 6% bioturbated. Tree roots penetrate weakness in the sandstone below this depth. Fallout radionuclides (7Be, 210Pb, and 137Cs) in the profile also suggest that vertical mixing in the upper 20 - 40 cm occurs over short—decadal—timescales. Optically stimulated luminescene (OSL) data records the time that quartz grains were last at the surface, and are used here to demonstrate vertical mixing of the profile over tens of thousands of years. OSL data indicates that some soil grains at all burial depths were once at the surface, consistent with modern process observations. Carbon and nitrogen isotopic values (delta 13C and delta 15N) of soil organic matter support the existence of soil organic matter turnover in the upper 30 cm of the soil column when regressed with log(SOC) and log(TN). Our carbon isotope data defy typical trends below ~30 cm for residual, undisturbed soils. We suggest this may reflect the absence of bioturbation during the LGM when the climate was cold and dry, and soil was deflated. Since ~13 ka, we believe the vegetation cover increased and bioturbation became affective, resulting in mixing of organic and mineral material, and concurrent soil thickening.

  9. Late quaternary environmental history of Lake Valencia, Venezuela

    Platt, Bradbury J.; Leyden, B.; Salgado-Labouriau, M.; Lewis, W.M.; Schubert, C.; Binford, M.W.; Frey, D.G.; Whitehead, D.R.; Weibezahn, F.H.


    Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed. Copyright ?? 1981 AAAS.

  10. Late Quaternary sedimentation in eastern Bay of Bengal

    Chauhan, O; Mascarenhas, A; Paropkari, A; Rao, Ch.M.

    This study presents variations in various size measures, calcium carbonate, organic carbon, clay mineralogy and major and trace elements in a core (5.40 m long, 2713 m depth) from the eastern Bay of Bengal. On a CM diagram, the sediments of the core...

  11. Luminescence dating of Late Quaternary sediments from East Greenland

    Mejdahl, V.; Funder, Svend Visby


    Luminescence dating based on K-feldspars and using both TL and OSL methods have been performed on 94 sediment samples from East Greenland. The ages go back more than 380 ka, but are mainly from the last interglaciation and the subsequent period and include both shallow-marine/coastal-fluvial and ......Luminescence dating based on K-feldspars and using both TL and OSL methods have been performed on 94 sediment samples from East Greenland. The ages go back more than 380 ka, but are mainly from the last interglaciation and the subsequent period and include both shallow...

  12. Eagel Hill: A Late Quaternary Upland Site in Western Louisiana.


    rather than filed in card boxes. Geo-environmental Samples During the summer, incoming constant volume samples (CVS), soil, phytolith / pollen, and HREC...seasaw battle between tall and short grass prairies. Phytoliths from mesic tall grasses appeared with evidence of human occupation and radiocarbon

  13. The Late Quaternary Oxygen Isotope Composition of Lake Michigan

    MacDonald, R. A.; Longstaffe, F. J.; Crowe, A. S.


    We present stable isotope records for porewater (oxygen, hydrogen) and biogenic carbonates (oxygen, carbon; ostracode and clam shells) in sediment cores from the Chippewa, Milwaukee and South Chippewa Basins of Lake Michigan. The oxygen and hydrogen isotope compositions of porewater from the South Chippewa Basin core showed very little variation with depth. At the maximum depth of 16.6m, δ18O values were within 2‰ and δD values were within 12‰ of modern Lake Michigan water (average δ18O = -5.9‰; average δD = -45‰); original porewater compositions have not been preserved. The oxygen isotope results for the biogenic carbonates, by comparison, provide a record of the isotopic composition of Lake Michigan over the last ~11,000 years, including significant incursions of very low-18O water, as first reported by Colman et al. (1990) and Forester et al. (1994). The low-18O waters originated from the retreating Laurentide ice sheet and may have been routed through Lakes Agassiz and Superior and discharged as large volumes over very short intervals of time. Periods characterized by much higher oxygen isotope compositions likely record the isotopic composition of regional precipitation over the catchment area. In summary, the large variations in the oxygen isotope composition of early Lake Michigan water arose from regional climate change and changing water sources during the times of ice-sheet retreat.

  14. Late Quaternary carbonate accumulation along eastern South Atlantic Ocean

    Crabill, K.; Slowey, N. C.; Foreman, A. D.; Charles, C.


    Water masses originating from both the North Atlantic Ocean and the Southern Ocean intersect the Walvis Ridge and Namibian margin of southwest Africa. Changes in the distribution and properties of these water masses through time are reflected by variations in the nature of the sediments accumulating along this margin. A suite of piston and gravity cores that possess sediment records corresponding to the most recent glacial-interglacial cycles were collected from the water depth range of 550 to 3700 meters. Sediment dry bulk density, XRF analyses and the concentration of CaCO3 were precisely determined at regular depth intervals in these cores. Foraminiferal δ18O along with XRF Fe/Ca data provide an age-depth model for key cores. The age-depth model and dry bulk density will be used with the calcium carbonate contents to calculate the accumulation rates of CaCO3 during each MIS 1-5e. The spatial and temporal variability in both the CaCO3 content and the CaCO3 mass accumulation rates along the Namibian continental slope will be described. Based on comparisons of these two parameters, inferences will be made about how variations of CaCO3 production, dilution of by non-CaCO3 sediment components, and dissolution of CaCO3 due to changes in ocean circulation/climate have occurred during intervals of the last glacial-interglacial cycle.

  15. Late quaternary environmental history of lake valencia, Venezuela.

    Bradbury, J P; Leyden, B; Salgado-Labouriau, M; Lewis, W M; Schubert, C; Binford, M W; Frey, D G; Whitehead, D R; Weibezahn, F H


    Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed.

  16. Late Quaternary palaeoenvironmental reconstruction from Lake Ohrid using stable isotopes

    Lacey, Jack H.; Leng, Melanie J.; Francke, Alexander; Vogel, Hendrik; Zanchetta, Giovanni; Wagner, Bernd


    Lake Ohrid is a large, deep lake located on the Balkan Peninsula at the border between Macedonia and Albania, and is considered the oldest extant lake in Europe. An International Continental scientific Drilling Program (ICDP) deep drilling campaign was carried out in 2013 as part of the interdisciplinary Scientific Collaboration On Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. Over 1500 m of sediment were recovered from six coring locations at the main target site in the central basin, where the maximum drill depth reached 569 m below the lake floor. Initial results indicate continuous lacustrine conditions over the past >1.2 Ma (Wagner et al., 2014). Here, we present oxygen and carbon isotope data (δ18O and δ13C) from carbonate from the upper 248 m of the SCOPSCO succession, which covers the last 640 ka, spanning marine isotope stages 15-1, according to an age model based on tephra and orbital tuning (Francke et al., 2015). Modern monitoring data show Lake Ohrid to be an evaporative system, where variations in δ18O of endogenic carbonate are primarily a function of changes in water balance, and δ13C largely reflects fluctuations in the amount of soil-derived CO2 and organic matter recycling. Our results indicate a trend from wetter to drier conditions through the Holocene, which is consistent with regional and hemispheric processes related to changes in insolation and progressive aridification. Over the last 640 ka, relatively stable climate conditions are inferred before ca. 450 ka, a transition to a wetter climate between ca. 400-250 ka, and a trend to drier climate after ca. 250 ka. Higher frequency, multi-millennial-scale oscillations observed during warm stages are most likely associated with regional climate change as a function of orbital forcing. This record is one of the most extensive and highly-resolved continental isotope records available, and emphasises the potential of Lake Ohrid as a valuable archive of long-term palaeoclimate and palaeoenvironmental change in the northern Mediterranean region. Francke, A., Wagner, B., Just, J., Leicher, N., Gromig, R., Baumgarten, H., Vogel, H., Lacey, J. H., Sadori, L., Wonik, T., Leng, M. J., Zanchetta, G., Sulpizio, R., and Giaccio, B. (2015). Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 640 ka and present day. Biogeosciences Discussions 12, 15111-15156. Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., Leng, M. J., Grazhdani, A., Trajanovski, S., Francke, A., Lindhorst, K., Levkov, Z., Cvetkoska, A., Reed, J. M., Zhang, X., Lacey, J. H., Wonik, T., Baumgarten, H., and Vogel, H. (2014). The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid. Scientific Drilling 17, 19-29.

  17. Recent and late quaternary changes in water level

    Walcott, R. I.


    Water level changes of both the Great Lakes and the sea are described along with methods of analyzing water level data. The influence of elastic deformation of the earth and viscosity is discussed. Causes of water level changes reviewed include: earth movements, geoid changes, storm surges or meteorological phenomena, and melting ice in Antarctica, Greenland, and the mountain glaciers.

  18. Synthesis of Chitosan Quaternary Ammonium Salts


    A series of N-alkyl or N-aryl chitosan quaternary ammonium salts were prepared via Schiffs base intermediates. Quaternization of N-substituted chitosan derivatives was carried out using methyl iodide to produce water-soluble cationic chitosan quaternary ammonium salt. The products were characterized by IR, 1HNMR and elemental analysis. The degree of substitution of chitosan quaternary ammonium salt was calculated by elemental analysis.

  19. 南海北部有孔虫碳氧同位素特征与晚第四纪水合物分解的响应关系%Respondence Between Carbon and Oxygen Isotopic Characteristics of Foraminifera from the Northern South China Sea and Late Quaternary Hydrate Released

    曹超; 雷怀彦


    为探寻晚第四纪以来水合物分解事件在南海北部甲烷渗漏环境下有孔虫中的记录,对南海北部陆坡2个区块的沉积柱状样有孔虫碳氧同位素组成和测年分析发现,底栖有孔虫Uvigerina spp.碳同位素值为-2.12‰~-0.21‰,浮游有孔虫Globigerinoides ruber.氧同位素值为-3.11‰ ~-0.60‰,ZD3、ZS5 2个柱状样孔底年龄分别为26616、64090 a,对应了氧同位素Ⅲ、Ⅳ期末期,有孔虫碳同位素负偏的层位与氧同位素Ⅱ、Ⅳ期(冷期)层位相对应,负偏程度达到了-2‰,与布莱克海台和墨西哥湾等地区晚第四纪沉积层中有孔虫碳氧同位素组成相似.分析认为:研究区是典型的甲烷渗漏环境,该区在氧同位素Ⅱ、Ⅳ期,由于全球海平面下降,导致海底压力减小,天然气水合物分解释放,具轻碳同位素的大量甲烷释放进入海底溶解无机碳(DIC)池并记录在有孔虫壳体内,造成有孔虫碳同位素负偏;同时在有孔虫负偏层位黄铁矿和自生碳酸盐较发育,进一步证实了有孔虫碳同位素受甲烷影响较大,而海洋生产力的降低和早期成岩作用对有孔虫碳同位素负偏的影响较小.%To search the records of the gas hydrate decomposition events under methane seepage condition since the late Quaternary, carbon and oxygen isotopes analysis and radiometric dating of foraminifera from sediment cores collected from three different blocks of the northern slope of the South China Sea are carried out. The results show:l) the carbon isotope value of benthic foraminifera Uvigerina spp. is -2. 12 ‰ to -0. 21 ‰ and oxygen isotope value of planktonic foraminifera Globigerinoides ruber is -3. 11 ‰ to -0. 60 ‰; 2) the age of the two cores at the bottom of ZD3 and ZS5 drills are 26 616 a and 64 090 a respectively, corresponding to the early oxygen isotope stage DI and the end of IV; 3) negative -skewed layer of carbon isotope (up to -2 ‰) corresponds to that of oxygen

  20. Towards dating Quaternary sediments using the quartz Violet Stimulated Luminescence (VSL) signal

    Ankjærgaard, C.; Jain, Mayank; Wallinga, J.


    Quartz optically stimulated luminescence (OSL) dating is widely used to determine the time of deposition and burial of Late Quaternary sediments. Application of the method is usually limited to the past 150,000 years due to early saturation of the OSL signal. Here we explore the potential to date...... Quaternary sediments using the violet (402 nm) stimulated luminescence (VSL) signal of quartz.We develop and test a new post-blue VSL single aliquot regenerative dose dating protocol, and demonstrate that the VSL signal originates from a deep trap at about 1.9 eV with a thermal lifetime of 1011 years at 10...

  1. A new concept for paleohydrological evolution of the Younger Dryas in NE Brazil

    Bouimetarhan, Ilham; Prange, Matthias; Gonzalez, Catalina; Dupont, Lydie


    The late deglacial interval from approximately 13 to 11 kyr BP contains some of the best documented abrupt climate changes in the Past, the Younger Dryas (YD). It is also an interval when the bipolar climatic signature of millennial-scale changes in the Atlantic meridional overturning circulation (AMOC) is well expressed. Here we present a high-resolution palynological record from core GeoB16205-4 (1°21.11'N, 43°05.80'W), retrieved off the Parnaíba River mouth, southeast of the Amazon River (~1955 m water depth). Pollen and organic-walled dinoflagellate cyst assemblages indicate a predominantly wet climate during the YD in the nowadays semi-arid Nordeste, whereby a second phase between ~12.3 and 11.7 kyr BP is wetter than the period before. This is recorded by a strong increase in the concentrations of river plume dinoflagellate cyst assemblages indicative of a stratified surface water column and reduced salinity environments, as well as a drop in grass pollen and microcharcoal particle concentrations along with strong fluctuations in the representation of rain forest, gallery forest and tree ferns suggesting year-round humid conditions. This shift from a relatively wet first phase to a much wetter second phase is in agreement with the transient TRACE-21k coupled climate model simulation which shows a first pluvial Parnaíba stage from ~12.8 to 12.3 kyr BP and a second stronger pluvial stage between ~12.3 and 11.7 kyr BP to be related to a very weak AMOC due to meltwater pulses in the North Atlantic. The AMOC variation induces a steep temperature gradient between the Southern and the Northern Hemisphere which forces a southward shift of the Intertropical Convergence Zone (ITCZ) and its associated rainfall. The two-step hydroclimatic and environmental evolution during the Younger Dryas has not been documented previously in this region.

  2. Salinity proxy comparison in four tropical biogenic carbonates for suitability in paleohydrologic reconstruction

    Broach, K.; Paytan, A.; Street, J. H.


    Climate change is expected to increasingly stress water resources in drought-prone areas such as the American Southwest or Central America. Understanding patterns in precipitation frequency and intensity in the recent past are critical to accurately modeling groundwater recharge potential and managing diminishing resources in conjunction with rapid urbanization (e.g. Yucatan, Mexico). Wet and dry seasons on the Yucatan Peninsula are affected by the Intertropical Convergence Zone (ITCZ) which can exacerbate drought as the climate warms. This study focuses on precipitation patterns during the late Holocene recorded in foraminifera (Ammonia beccarii, Elphidium sp., Quinqueloculina sp.) and ostracods (suspected Hemicyprideis nichuptensis) along a transect in Celestun Lagoon near Merida, Yucatan, Mexico. Submarine groundwater springs feed the north terminus of the lagoon resulting in δ18O and Mg gradients toward the ocean which oscillate in response to increased or decreased precipitation. Mg/Ca ratios from the north (4.59) and south (3.08) lagoon suggest warmer waters in the shallow northern end, resulting in evaporation and confounding the δ18O values there (upper lagoon = 2.1‰, middle lagoon = 0.3‰, lower lagoon = 1.5‰). B/Ca ratios remain fairly constant (average range 27.3-33.2) despite increasing B concentrations toward the southern mouth, suggesting a concurrent increase in dissolved calcium down the lagoon and thus a lower Ca signal in spite of the karst source of springs. Of the four species tested, A. beccarii and H. nichuptensis yielded the most similar results ([Ca] ~ 150 ppm). Replicate analyses are needed for Elphidium sp. and Quinqueloculina sp. due to their low sample size and signal variability which suggests they may not be ideal candidates for paleoenvironmental reconstruction in Celestun Lagoon and possible other marginal environments around the Yucatan Peninsula.

  3. Quaternary evolution of the Southern Apennines coastal plains: a review

    Santangelo, Nicoletta; Romano, Paola; Ascione, Alessandra; Russo Ermolli, Elda


    The Quaternary evolution of the main coastal basins located along the southwestern margin of the Southern Apennines has been reconstructed by integrating the huge amount of existing stratigraphical and geomorphological data. The information produced in the last twenty years has shed new light on the recent (late Middle Pleistocene to Present) history of the Campanian and Sele plains or basins. During the early Quaternary, the analysed coastal basins originated as half-grabens in response to opening processes active since the late Tortonian in the southern Tyrrhenian back-arc basin. In some of these basins (e.g. the Campanian Plain), volcanism has also played an important role. In the inner sectors of the coastal basins, the complex interplay between block faulting, sedimentary inputs and glacioeustatic fluctuations gave rise to relative sea-level change and related coastline migrations, leading to the formation of the present-day coastal plains. In the Sele Plain basin, the construction of the present-day landscape mainly resulted from the substantial ceasing of subsidence in the final part of the Middle Pleistocene. Conversely, a strong contribution to the recent evolution of the Campanian Plain has been provided by abundant volcaniclastic aggradation, able to hinder the effect of the vertical motions that occurred in the last 100 ka.

  4. Quaternary evolution of the Southern Apennines coastal plains: a review

    Santangelo Nicoletta


    Full Text Available The Quaternary evolution of the main coastal basins located along the southwestern margin of the Southern Apennines has been reconstructed by integrating the huge amount of existing stratigraphical and geomorphological data. The information produced in the last twenty years has shed new light on the recent (late Middle Pleistocene to Present history of the Campanian and Sele plains or basins. During the early Quaternary, the analysed coastal basins originated as half-grabens in response to opening processes active since the late Tortonian in the southern Tyrrhenian back-arc basin. In some of these basins (e.g. the Campanian Plain, volcanism has also played an important role. In the inner sectors of the coastal basins, the complex interplay between block faulting, sedimentary inputs and glacioeustatic fluctuations gave rise to relative sea-level change and related coastline migrations, leading to the formation of the present-day coastal plains. In the Sele Plain basin, the construction of the present-day landscape mainly resulted from the substantial ceasing of subsidence in the final part of the Middle Pleistocene. Conversely, a strong contribution to the recent evolution of the Campanian Plain has been provided by abundant volcaniclastic aggradation, able to hinder the effect of the vertical motions that occurred in the last 100 ka.

  5. Book Review: Quaternary Environmental Change in Southern Africa: Physical and Human Dimensions

    Murray-Wallace, Colin V.


    This attractively presented book examines the legacy of a diverse range of Quaternary environmental processes in the fashioning of Southern African landscapes and their ultimate interconnection with human evolution, technological developments and subsistence in dynamically changing environments. In its 25 chapters the book reviews different elements of Southern African landscapes and emphasizes their diversity, from classical desert dune environments to glacial, periglacial, fluvial, karst, wetlands, estuaries and sandy coastal landscapes. In addition, the soils and duricrusts that are so distinctive to these landscapes (Runge) and colluvial deposits and slope instability (Botha et al.) are also reviewed. Evidence for Quaternary environmental change is also examined in terms of pollen, charcoal and plant macrofossil records (Bamford et al.), minerogenic microfossil records (Fitchett et al.) and terrestrial ecosystem changes in the late Quaternary (Meadows and Quick). The archaeological records of the Earlier Stone Age (Kuman), Middle Stone Age, and Later Stone Age (Mitchell) are also comprehensively reviewed.

  6. Rare earth element records from core sediments of southern Pearl River Delta: Geochemical response to palaeoenvironmental changes during the Late Quaternary%珠江三角洲南部晚第四纪环境变化的稀土元素记录

    刘春莲; 吴洁; 杨婷婷; Franz T Fürsich; 张素青


    The rare earth element (BEE) distribution in Core PRD05 is closely related to sedimentary environmental changes during the Late Quaternary in the southern Pearl River Delta. Before approximately 31 000 cai a BP, a fluvial setting developed in the study area. The sediments have a lower ∑REE concentration and show HREE enrichment, which are effects of grain size and heavy mineral concentration. The sediments dated to 31 000 to 16 600 cai a BP were possibly deposited in a brackish-water environment, with a high ∑REE and a clear enrichment of LREE relative to HREE. The upper part of these sediments underwent subaerial weathering and erosion during the last glacial maximum. Their REE pattern is subparallel to that of the lower part of sediments, with a slightly higher enrichment of LREE. During the first phase of the postglacial sea-level rise (from around 16600 to 10300 cal a BP), a swamp environment developed in the study area. Organic-rich conditions resulted in high ∑REE concentrations.Since 10 300 cai a BP, an estuarine environment with short-term fluctuations developed and persisted until 5600 cai a BP. Correspondingly, the sediments generally exhibit an enrichment of ∑REE, particularly LREE. A fluvial environment developed at around 5600 cai a BP, and was succeeded by an alluvial plain setting with occasional tidal influence. REE concentrations strikingly decreased and frequently fluctuated.%珠江三角洲南部平原PRD05孔稀土元素(REE)的分布特征与晚第四纪沉积环境变化密切相关.随着不同时期沉积环境的波动,稀土元素分布也发生相应的变化.约31 000 cal a BP以前,研究区发育河流环境,受矿物组成和沉积物粒度的影响,∑REE含量偏低,且重稀土元素(HREE)相对富集.31 000-16600cal a BP期间,∑REE含量明显高于前一阶段,并显示轻稀土元素(LREE)富集;稀土元素分布模式表现为河口半咸水环境特征;其上部沉积物经历了末次冰盛期的风化作用,稀

  7. 西北冰洋阿尔法脊晚第四纪的陆源沉积物记录及其古环境意义%Late Quaternary Terrigenous Sedimentation in the Western Arctic Ocean as Exemplified by a Sedimentary Record from the Alpha Ridge

    刘伟男; 王汝建; 陈建芳; 程振波; 陈志华; 孙烨忱


    通过西北冰洋阿尔法脊B84A孔中—晚第四纪以来的沉积物颜色旋回,Mn、Ca元素相对含量、颜色反射率、有孔虫丰度、冰筏碎屑(IRD)含量、粒度组分及其敏感性分析的综合研究,建立了B84A孔的地层年代框架,其沉积物被划分为MIS 12~MIS 1的沉积序列。阿尔法脊B84A孔可以识别出12个IRD事件,它们大多出现在冰消期,并认为其源区为加拿大北极群岛地区。这些IRD事件反映了加拿大北极冰盖的崩塌和气候变化。阿尔法脊B84A孔沉积物的环境敏感组分分别为细组分(4~9μm)和粗组分(19~53μm),两者的变化趋势相反,主要由海冰和洋流进行搬运,指示了洋流的强度变化。B84A孔的平均沉积速率约为0.4 cm/ka,与阿尔法脊周围地区沉积速率相近。相比于近岸的高沉积速率,其限制因素主要为大面积海冰覆盖造成的较低的生产力和由于长距离搬运造成的较低的陆源输入量。%Terrigenous components in sediment core B84A from the Alpha Ridge,western Arctic Ocean,have been investigated to reconstruct the Mid to Late Quaternary variations in sedimentation,source regions,and related climate changes.The core stratigraphy,evaluated by a combination of variations in Mn content,color cycles,foraminiferal abundance,and lithological correlation,extends back to estimated Marine Isotope Stage(MIS) 12.Twelve ice rafted detritus(IRD,〉250 μm) events were identified and interpreted to mostly occur during the deglacial periods.The Canadian Arctic covered by ice sheets during glacial periods is suggested to be the major source region.The IRD events likely indicate the collapses of ice sheets,possibly in relation to abrupt climate changes.Grain size analysis of B84A indicates sedimentologically sensitive components in core B84A in the silt subfractions 4~9 μm and 19~53 μm,which are inferred to be mainly transported by currents and sea ice


    金海燕; 翦知湣; 谢昕; 田军


    选取大洋钻探ODP 184航次在南海北部钻取的1144站(20°3.18'N,117°25.14'E;水深2037m)上部岩芯为研究材料.通过X荧光光谱(XRF)岩芯扫描仪获取晚第四纪100ka以来时间分辨率高达10年的元素记录,并与德国"太阳号"95航次在同一站位获得的17940-2柱状样(20°07.0'N,117°23.0'E;水深1728m)的相关数据(包括底栖有孔虫Uvigerina+Bulimina的丰度、有机碳通量和粘土含量)进行比较,发现Ba/Ti和K/Al比值可以分别反映表层生产力和陆地化学风化的变化,且都具有明显的岁差和半岁差周期,呈现典型的热带气候特征,可能与东亚夏季风的变化有关.特别是,Ba/Ti和K/Al比值还具有类似D/O事件的千年尺度(1.4~2.0ka)周期和与太阳活动相关的百年尺度(约200a和500a)变化周期,且其千年尺度的变化特征在形态上更接近于南极冰芯中的氧同位素记录,反映了低纬海区与南半球高纬区的古气候联系.%The Ocean Drilling Program Site 1144 ( 20°3. 18'N. 117°25. 14'E; water depth 2037m) from the Northern South China Sea was selected for the measurements on elemental contents in deep-sea sediments of the last lOOkaB. P. ,by using a nondestructive X-ray fluorescence ( XRF ) core scanner with an interval of 1cm ( time resolution ca. lOa) . Compared with the relevant data ( benthic foraminifera Uvigerina+Bulimina abundance , organic carbon flux and clay percentage) from Core 17940 -2 ( 20°07. O'N . 117°23. O'E ; water depth 1728m ) recovered during the German SONNE Cruise 95 at almost the same position , our data demonstrated that the elemental ratios such as Ba/Ti and K/Al could be used to indicate the Late Quaternary changes in surface paleoproductivity and chemical weathering ,respectively, and hence to reflect the variations of the East Asian summer monsoon. On the orbital time-scale , the changes of Ba/Ti and K/Al ratios showed remarkable ca. 19. 5ka processional and obvious ca. 10. 9ka semi

  9. Novel Quaternary Quantum Decoder, Multiplexer and Demultiplexer Circuits

    Haghparast, Majid; Monfared, Asma Taheri


    Multiple valued logic is a promising approach to reduce the width of the reversible or quantum circuits, moreover, quaternary logic is considered as being a good choice for future quantum computing technology hence it is very suitable for the encoded realization of binary logic functions through its grouping of 2-bits together into quaternary values. The Quaternary decoder, multiplexer, and demultiplexer are essential units of quaternary digital systems. In this paper, we have initially designed a quantum realization of the quaternary decoder circuit using quaternary 1-qudit gates and quaternary Muthukrishnan-Stroud gates. Then we have presented quantum realization of quaternary multiplexer and demultiplexer circuits using the constructed quaternary decoder circuit and quaternary controlled Feynman gates. The suggested circuits in this paper have a lower quantum cost and hardware complexity than the existing designs that are currently used in quaternary digital systems. All the scales applied in this paper are based on Nanometric area.

  10. Novel Quaternary Quantum Decoder, Multiplexer and Demultiplexer Circuits

    Haghparast, Majid; Monfared, Asma Taheri


    Multiple valued logic is a promising approach to reduce the width of the reversible or quantum circuits, moreover, quaternary logic is considered as being a good choice for future quantum computing technology hence it is very suitable for the encoded realization of binary logic functions through its grouping of 2-bits together into quaternary values. The Quaternary decoder, multiplexer, and demultiplexer are essential units of quaternary digital systems. In this paper, we have initially designed a quantum realization of the quaternary decoder circuit using quaternary 1-qudit gates and quaternary Muthukrishnan-Stroud gates. Then we have presented quantum realization of quaternary multiplexer and demultiplexer circuits using the constructed quaternary decoder circuit and quaternary controlled Feynman gates. The suggested circuits in this paper have a lower quantum cost and hardware complexity than the existing designs that are currently used in quaternary digital systems. All the scales applied in this paper are based on Nanometric area.

  11. Characteristics of Quaternary deposits near Songjianghe Town on west slope of Changbai Mountain

    WANG Xi-kui; LI Jun-min; ZHANG Hong-yan


    On the basis of field survey, microscope sighting, TL dating and scanning electron microscope analysis, the characteristics of Quaternary deposits near Songjianghe Town on the west slope of Changbai Mountain are analyzed and described. There were two phases of volcanism during Mid-Late Quaternary. One occurred before 15.22 × 104 aB.P. and the other happened between 14.27 × 104 aB.P. and 1.41 × 104 aB.P. Volcanism is a landform-making process which makes the rough relief in the studied area become higher and higher. Flow water is a main erosion agency and it cuts into the basalts making river valleys. The Quaternary fluvial deposits distributed on terraces first come from the weathered debris of basement rocks, then they are transported and deposited by flow water. After 1.41 × 104 aB.P, the river water quickly cuts into the newly formed basalts making a deep valley. Volcanism in the studied area is a main landform-making event in Mid-Late Quaternary.


    董艺辛; 刘春莲; 陈木宏; 曲日涛; 吴土荣; 赵飞


    Delta during the Late Quaternary. Totally 34 species from 17 genus of foraminifers and 59 species from 34 genus ostracods were identified in the cores. According to distribution of water depth, microfaunas are divided into two groups (Group I,20m) to discuss environmental changes. Microfaunal characteristics especially foraminifers allow refining paleoenvironmental interpretation. Detailed correlation of cores PRD01 ~ 05 allow to depict the Late Quaternary paleogeographic evolution of the study area. The vertical stacking of seven units depicts the paleoenvironmental evolution of the study area from the Last Glacial Maximum to present. Unit A corresponds to base rock and its weathered residue. Unit B shows fluvial environment deposited during last glacial period. Unit C ( 14340 ~ 6480cal. aB. P. ) generally marks a back-barrier environment. Unit D(6480 ~ 2860cal. aB. P. ) primarily represents an estuary environment over the study area, corresponding to the Holocene transgression, while Unit E ( 2860 ~ 230cal. aB. P. ) represents sand barrier deposition in the west part of the study area, suggesting a continuous regression. Unit F(230cal. aB. P. ~ 0 ) equals to present overbank delta plain deposit in all cores. These units are considered to be 3 periods: Lowstand deposits ( Unit A and B ) , Transgression deposits ( Unit C and D ) and Highstand deposits( Unit E and F). Therefore Unit C ~ F corresponds to the post-Last Glacial Maximum deposition. Division of microfauna into two groups allow prodelta ( esturine) environment differentiating into six subunits which represent different sea-level fluctuations. Subunit D1 (6480~ 6340cal. aB. P. ) : sea-level rose rapidly; Subunit D2(6340 ~6120cal. aB. P. ) : sea-level rise slowed down;Subunit D3(6120 ~5670cal. aB. P. ) : sea-level rose rapidly again; Subunit D4 (5670 ~ 4950eal. aB. P. ) : largest extension of transgression was reach and then sea-level fell gradually; Subunit D5 (4950 ~ 4140cal. aB. P. ) : sea-level fell greatly

  13. 206Pb-230Th-234U-238U and 207Pb-235U geochronology of Quaternary opal, Yucca Mountain, Nevada

    Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.


    U–Th–Pb isotopic systems have been studied in submillimeter-thick outermost layers of Quaternary opal occurring in calcite–silica fracture and cavity coatings within Tertiary tuffs at Yucca Mountain, Nevada, USA. These coatings preserve a record of paleohydrologic conditions at this site, which is being evaluated as a potential high-level nuclear waste repository. The opal precipitated from groundwater is variably enriched in 234U (measured 234U/238U activity ratio 1.124–6.179) and has high U (30–313 ppm), low Th (0.008–3.7 ppm), and low common Pb concentrations (measured 206Pb/204Pb up to 11,370). It has been demonstrated that the laboratory acid treatment used in this study to clean sample surfaces and to remove adherent calcite, did not disturb U–Th–Pb isotopic systems in opal. The opal ages calculated from 206Pb∗/238U and 207Pb∗/235U ratios display strong reverse discordance because of excess radiogenic 206Pb∗ derived from the elevated initial 234U. The data are best interpreted using projections of a new four-dimensional concordia diagram defined by 206Pb∗/238U, 207Pb∗/235U, 234U/238Uactivity, and 230Th/238Uactivity. Ages and initial 234U/238U activity ratios have been calculated using different projections of this diagram and tested for concordance. The data are discordant, that is observed 207Pb∗/235U ages of 170 ± 32 (2σ) to 1772 ± 40 ka are systematically older than 230Th/U ages of 34.1 ± 0.6 to 452 ± 32 ka. The age discordance is not a result of migration of uranium and its decay products under the open system conditions, but a consequence of noninstantaneous growth of opal. Combined U–Pb and 230Th/U ages support the model of slow mineral deposition at the rates of millimeters per million years resulting in layering on a scale too fine for mechanical sampling. In this case, U–Pb ages provide more accurate estimates of the average age for mixed multiage samples than 230Th/U ages, because ages based on shorter


    李艳丽; 林春明; 张霞; 周健; 曲长伟; 潘峰; 姚玉来


    In 2009, a 51. 5-m-long core SE2 was drilled at 120°21'57" E, 30°12'38" N, from the Kanshan town, Hangzhou city, in the south bank of the Qiantang River. The ground surface elevation of the core is 6. Om above mean sea level. Core SE2,10. 8cm in diameter,was obtained by rotary drilling with a 96% recovery. A total of 294 samples were collected at 10 ~20cm intervals along the cored succession for grain size analysis,93 samples at 20 ~ 80cm intervals for foraminifera identification, and 27 samples at 200cm intervals for rare earth elements analysis. The lithology, grain size, sedimentary structure, foraminifera, and rare earth elements of Late Quaternary sediments in the borehole SE2 were analyzed to research the sedimentary environment evolution, and the associated distribution variation of rare earth elements in the Qiantang River mouth area. The results indicate that five sedimentary facies, including fluvial channel,floodplain,tidal flat,shallow marine,and estuarine sand bar,can be distinguished,and the rare earth elements distribution is closely related to sedimentary environment. Fluvial channel facies consists of sandy gravel,gravelly sand, and fine sand, with high content of rolling and saltation population. Foraminifera are absent. The sediments have the lowest total rare earth elements content in all sedimentary facies,and high light rare earth elements concentration. The fractionation degree of light and heavy rare earth elements, and fractionation degree of heavy rare earth elements are positively related with the total rare earth elements content. The fractionation of light rare earth elements shows negative correlation with the total rare earth elements content, heavy rare earth elements concentration, the fractionation of light and heavy rare earth elements, and fractionation in heavy rare earth elements. Floodplain facies are dominated by clay, with foraminifera and rolling population absent. Total rare earth elements content is the highest. The

  15. Quaternary Magmatism in the Cascades - Geologic Perspectives

    Hildreth, Wes


    Foreward The Cascade magmatic arc is a belt of Quaternary volcanoes that extends 1,250 km from Lassen Peak in northern California to Meager Mountain in Canada, above the subduction zone where the Juan de Fuca Plate plunges beneath the North American Plate. This Professional Paper presents a synthesis of the entire volcanic arc, addressing all 2,300 known Quaternary volcanoes, not just the 30 or so visually prominent peaks that comprise the volcanic skyline. Study of Cascade volcanoes goes back to the geological explorers of the late 19th century and the seminal investigations of Howel Williams in the 1920s and 1930s. However, major progress and application of modern scientific methods and instrumentation began only in the 1970s with the advent of systematic geological, geophysical, and geochemical studies of the entire arc. Initial stimulus from the USGS Geothermal Research Program was enhanced by the USGS Volcano Hazards Program following the 1980 eruption of Mount St. Helens. Together, these two USGS Programs have provided more than three decades of stable funding, staffing, and analytical support. This Professional Paper summarizes the resultant USGS data sets and integrates them with the parallel contributions of other investigators. The product is based upon an all-encompassing and definitive geological database, including chemical and isotopic analyses to characterize the rocks and geochronology to provide the critical time constraints. Until now, this massive amount of data has not been summarized, and a systematic and uniform interpretation firmly grounded in geological fact has been lacking. Herein lies the primary utility of this Cascade volume. It not only will be the mandatory starting point for new workers, but also will provide essential geological context to broaden the perspectives of current investigators of specific Cascade volcanoes. Wes Hildreth's insightful understanding of volcanic processes and his uncompromising scientific integrity make him

  16. A rhinoceros from the late miocene of Fort Ternan, Kenya

    Hooijer, D.A.


    SYNOPSIS A rhinoceros from the Fort Ternan site, Kenya, Late Miocene in age, represents a form distinctly more advanced than the genera and species known from the Early Miocene although it is not directly ancestral to the Quaternary forms. It is a collaterally developed tuskless, two-horned, browsin

  17. A New Quaternary Strand of the Karakoram Fault System, Ladakh Himalayas

    Bohon, W.; Hodges, K.; Arrowsmith, R.; Tripathy, A.


    The NW-SE striking, dextral Karakoram fault system stretches for more than 1200 km from the Pamirs of Central Asia at least as far southeast as the Kailas area of Tibet. Estimates for the total lateral displacement along the fault system range from 150-1000 km, and estimated Quaternary rates of slip range from 1 to 30 mm/yr. In the Ladakh region of NW India (~ 33°28’N, 78°45’E), the fault system expresses as northern and southern strands bounding the Pangong Range. Studies of ductile deformation fabrics along these strands suggest that slip began in the Miocene, and Brown et al. (2002) documented Quaternary right-lateral slip along the northern strand at ~4 mm/yr on the basis of offset geomorphic features. The lack of documented Quaternary offset along the southern strand has led most researchers to assume that Quaternary slip on the Karakoram fault system in this region was partitioned exclusively to the northern strand. Our summer 2009 field work in the Pangong Range and adjacent Nubra Valley provides the first documentation of significant Quaternary activity along the southern strand. In the valley between the villages of Tangste (34°01’ N, 78°10’ E) and Durbuk (34°06’ N, 78°07’), the fault is visible high on the northeastern mountain side as a break in slope with offset Quaternary paleosurfaces and beheaded and offset stream channels, the largest of which have been displaced by as much as 250 m. Field mapping north of Durbuk, near the town of Tangyar (34°15’N, 77°52’E), shows that the southern strand continues northwest and cuts across the landscape as a sinuous, continuous trace with shutter ridges, offset alluvial fan surfaces, and sag ponds developed along its length. In this region, the northern and southern strands are linked by a Quaternary, E-directed thrust fault that places high-grade metamorphic rocks over poorly consolidated Quaternary alluvium. The partitioning of dextral slip between two strands of the Karakoram system

  18. PRN 88-2: Clustering of Quaternary Ammonium Compounds

    This Notice announces that EPA has clustered the Quaternary Ammonium Compounds into four groups for the purpose of testing chemicals to build a database that will support continued registration of the entire family of quaternary ammonium compounds

  19. On the use of Historic Atmosphere-Lake-Level Relationships for Reconstructing Stable Oxygen Isotope-Based Paleohydrology in Southern CA.

    Kirby, M. E.; Lund, S.; Poulsen, C.; Patterson, W.; Burnett, A.


    Understanding the future of Southern California's present freshwater crisis is dependent on past knowledge of the region's hydrological system. Unfortunately, with the exception of a few short dendroclimatological records and a low-resolution palynological record, there are no terrestrially-based long-term (i.e., Holocene), continuous, high-resolution (i.e., decadal-to-centennial) paleohydrological records for Southern California. Here, we present initial sedimentological and geochemical findings from sediments extracted from one of Southern California's only natural lakes, Lake Elsinore (located 75km southeast of Los Angeles). These results link historically-based meteorological data with lake-level variations, and associated proxies, thus providing a template for geological interpretation of Southern California's paleohydrology. A comparison of lake-level variations at Lake Elsinore to regional winter season (Dec. through Feb.) precipitation amount and latitude of the 500-hPa geopotential height (5460m; i.e., the polar front jet stream) indicate a strong linkage between atmospheric processes and the lake's hydrological budget. Higher lake-levels are related to a migration of the polar front jet stream to lower latitudes which increases the advection of moisture-rich air masses from the sub-tropical and equatorial Pacific regions, and vice versa. Both the environmental magnetic measurement CHI and the value of d18O from calcite precipitated in the lake's water column show a strong correspondence with the historical records of lake-level and winter season precipitation amount. As a result, these initial proxies provide a collaborative method for interpreting past hydrological conditions at Lake Elsinore (i.e., Southern CA). Interestingly, these proxies indicate that the past 150-200 years have been relatively wet when compared to the preceeding 500 years (i.e., possibly the Little Ice Age). On a hemispheric scale, lake-level variations at Lake Elsinore are linked


    LU Rui-jie; CHEN Yuan; HASI Eerdun; YUE Xing-ling


    Quaternary aeolian environment researches were mainly conducted by analyzing the information carri-ers, extracting valuable evidences about aeolian environment changes, so to presume and reconstruct paleoenviron-ments. This paper formulated progress in Quaternary aeolian environment research using dune-morphological records,sedimentological records and bio-fossils records, as well as advances about chronology; presented that people shouldpay more attention to further synthetic study of multi-types of records including dune morphology, size, formationtime, sediment supply, and their relations with wind regime in future, especially the research on dating method.

  1. Catalytic enantioselective synthesis of quaternary carbon stereocentres

    Quasdorf, Kyle W.; Overman, Larry E.


    Quaternary carbon stereocentres--carbon atoms to which four distinct carbon substituents are attached--are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials.

  2. Quaternary Geology and Geomorphology of Terna River Basin in West Central India

    Mohammad Babar


    Full Text Available This paper presents the morphostratigraphy, lithostratigraphy and sedimentary structures of Terna River basin in the Deccan Basaltic Province (DBP of West Central India. These Quaternary deposits have been divided into three informal formations (i dark grey silt formation – Late Holocene, (ii Light grey silt formations – Early Holocene, (iii Dark grayish brown silt formation – Late Pleistocene with the older Quaternary Alluvial deposits of Upper Pleistocene age. The fine clay and silt formations in the lower reaches reflect that the streams are of low gradient and more sinuous. The river shows evidences of channel movement by avulsion, largely controlled by lineaments. Palaeo-levees, in the form 4–5 m high ridges exist along the Terna River floodplain, specifically in the Ter, Killari, Sastur, Dhuta and Makni villages. Several lineaments occur along NE-SW, NW-SE, E-W and WNW-ESE directions, which control the basement structure in the study area. The values of the Topographic Sinuosity Index (TSI indicate rejuvenation of the area leading to the dominance of topography on the sinuosity of the river channels. The break in slope in the long profile is also indication of the Quaternary tectonic uplift of the area. Radiocarbon dating of some charcoal fragments collected from folded beddings indicates that paleoseismic activity might have taken place along the basin between AD 120 and AD 1671.

  3. 21 CFR 172.165 - Quaternary ammonium chloride combination.


    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  4. Summary of Quaternary geology of the Municipality of Anchorage, Alaska

    Schmoll, H.R.; Yehle, L.A.; Updike, R.G.


    Quaternary geology of the Upper Cook Inlet region is dominated by deposits of glacier retreats that followed repeated advances from both adjacent and more distant mountains. At several levels high on the mountains, there are remnant glacial deposits and other features of middle or older Pleistocene age. Late Pleistocene lateral moraines along the Chugach Mountain front represent successively younger positions of ice retreat from the last glacial maximum. As the trunk glacier retreated northeastward up the Anchorage lowland, Cook Inlet transgressed the area, depositing the Bootlegger Cove Formation and Tudor Road deposits. The glacier then readvanced to form the latest Pleistocene Elmendorf Moraine, a prominent feature that trends across the Anchorage lowland. Extensive alluvium was deposited both concurrently and somewhat later as Cook Inlet regressed. Mountain valleys contain (1) locally preserved moraines possibly of early Holocene age; (2) poorly preserved moraine remnants of older late Holocene age; and (3) well-preserved moraines formed mainly during the Little Ice Age. Glaciers still occupy large parts of the mountains, the upper ends of some mountain valleys, and small cirques. Holocene landslide deposits, including those formed during the great Alaska earthquake of 1964, occur throughout the area, especially along bluffs containing the Bootlegger Cove Formation.

  5. Palladium-Catalyzed Asymmetric Quaternary Stereocenter Formation

    Gottumukkala, Aditya L.; Matcha, Kiran; Lutz, Martin; de Vries, Johannes G.; Minnaard, Adriaan J.


    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of beta,beta-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF6, and pr

  6. Palladium-catalyzed asymmetric quaternary stereocenter formation

    Gottumukkala, A.L.; Matcha, K.; Lutz, M.; de Vries, J.G.; Minnaard, A.J.


    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of β,β-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF6, and provides

  7. Palladium-catalyzed asymmetric quaternary stereocenter formation

    Gottumukkala, A.L.; Matcha, K.; Lutz, M.|info:eu-repo/dai/nl/304828971; de Vries, J.G.; Minnaard, A.J.


    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of β,β-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF6, and provides

  8. Palladium-Catalyzed Asymmetric Quaternary Stereocenter Formation

    Gottumukkala, Aditya L.; Matcha, Kiran; Lutz, Martin; de Vries, Johannes G.; Minnaard, Adriaan J.


    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of beta,beta-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF6, and pr

  9. Late Budgets

    Andersen, Asger Lau; Lassen, David Dreyer; Nielsen, Lasse Holbøll Westh

    The budget forms the legal basis of government spending. If a budget is not in place at the beginning of the fiscal year, planning as well as current spending are jeopardized and government shutdown may result. This paper develops a continuous-time war-of-attrition model of budgeting...... in a presidential style-democracy to explain the duration of budget negotiations. We build our model around budget baselines as reference points for loss averse negotiators. We derive three testable hypotheses: there are more late budgets, and they are more late, when fiscal circumstances change; when such changes...... are negative rather than positive; and when there is divided government. We test the hypotheses of the model using a unique data set of late budgets for US state governments, based on dates of budget approval collected from news reports and a survey of state budget o¢ cers for the period 1988...

  10. Late Budgets

    Andersen, Asger Lau; Lassen, David Dreyer; Nielsen, Lasse Holbøll Westh

    are negative rather than positive; and when there is divided government. We test the hypotheses of the model using a unique data set of late budgets for US state governments, based on dates of budget approval collected from news reports and a survey of state budget o¢ cers for the period 1988......The budget forms the legal basis of government spending. If a budget is not in place at the beginning of the fiscal year, planning as well as current spending are jeopardized and government shutdown may result. This paper develops a continuous-time war-of-attrition model of budgeting...... in a presidential style-democracy to explain the duration of budget negotiations. We build our model around budget baselines as reference points for loss averse negotiators. We derive three testable hypotheses: there are more late budgets, and they are more late, when fiscal circumstances change; when such changes...

  11. Book Review: The history of the Quaternary Research Association

    Bowen, D. Q.


    This is a book that should be in the library of every member of the QRA as well as their institutions. This volume is a celebration of 50 years of the Quaternary Studies Field Group (1964), which was renamed the Quaternary Research Association (QRA) in 1969. What follows is a combination of a review with some further information based on the recollection of someone who was there. In examining the origins of the QSFG due credit is paid to Richard Hey and Richard West, but an inexplicable omission is the earlier discussion between Hey, Allan Straw and others during the field meeting of the Yorkshire Geological Society in September 1962 (Worsley, 2014). It is said that history is always written by the victors, or in modern parlance by those who write the minutes! But, in the writing of history there are only degrees of unsuccess. In Chapter 2 John Catt comments on the less than perfect early archival records of the QRA. So it is to his credit that 50 years of archival material has been diligently sifted and edited. In this he was assisted by memories of some named QRA members who are thanked. Wider consultation may have filled some of the gaps. At earlier meetings it was always a pleasure to greet long retired colleagues, such as Archie Lamont at the Carlops glacial drainage system when being demonstrated by Brian Sissons in 1966, or Tony Farringdon at Ballycotton Bay in 1968, or Hallam Movius in 1971 at a London discussion meeting. Similarly, who can forget the field meeting at Canterbury in 1967 when Alec Skempton demonstrated the Sevenoaks by-pass late-glacial slope failures, and John Hutchinson's use of Pomatias elegans for dating the Folkestone Warren landslips? Jan Mangerud's first QRA meeting on the Isle of Man (1971) was notable for his prescient recognition of glaciomarine deposits.

  12. Quaternary fossil fish from the Kibish Formation, Omo Valley, Ethiopia.

    Trapani, Josh


    The late Quaternary Kibish Formation of the Omo Valley, southwestern Ethiopia, preserves environments reflecting a history of fluctuations in the level of nearby Lake Turkana over the past 200,000 years. The Kibish Formation has yielded a diverse mammalian fauna (as well as birds and crocodiles), stone tools, and the oldest anatomically modern Homo sapiens. Fish, the most common vertebrate fossils in this unit, are reported in this study. Catfish (especially clariids and Synodontis) and Nile perch (Lates niloticus) predominate, but the gymnarchid Gymnarchus, a cyprinid (Barbus), tigerfish (Hydrocynus), pufferfish (Tetraodon), and other catfish are also present. In total, nine teleost genera are found in the Kibish Formation, representing a subset of the 37 genera that constitute the modern Omo-Turkana ichthyofauna. Several taxa present in the modern fauna, including Polypterus and members of the family Cichlidae, are not found in the Kibish deposits. Most specimens are preserved as disarticulated or broken skeletal elements, but some preservation of articulated elements (e.g., sets of vertebrae, crania with lower jaws or cleithra) also occurs. Many of the catfish and Nile perch specimens are larger than the largest reported from the modern river or lake. Faunas of Kibish Members I and III closely resemble one another; the fauna from Member IV contains only the three most common taxa (Clarias, Synodontis, Lates), though this may result from insufficient sampling. Barbed bone points have been collected from the upper part of the formation, indicating a long association between the human inhabitants and the fish fauna of the Omo Valley.

  13. [Quaternary prevention: containment as an ethical necessity].

    Martínez González, C; Riaño Galán, I; Sánchez Jacob, M; González de Dios, J


    The growing capacity of medicine to generate more iatrogenic events than ever, and the risk of unsustainability of health systems have led to new prevention concept: quaternary prevention aimed at restraining medicalization. Quaternary prevention is essential in the phenomenon called disease mongering, which could be translated as commercialization of disease. Encouraging this sort of prevention and halting the consequences of disease mongering requires the development of all the institutional potential for prevention, as well as all the personal willingness for restraint; it involves separating us from the unnecessary auspices of industry, being critical of our work, not being maleficent, respecting the principle of justice as managers of the limited public resources and making ourselves feel responsible for the social cost resulting from medical decisions. From this point of view, this work analyses neonatal screening, developments in the area of neonatology and primary health care.

  14. Quaternary Tipping Points in Tropical Northern Australia

    Moss, Patrick; Dunbar, Gavin; Croke, Jacky; Katunar, Rosie


    Tropical northern Queensland, particularly the volcanic Atherton Tableland, contains some of the most detailed and longest terrestrial palaeoenvironmental archives in Australia and when combined with adjacent marine sediment records provides key insight into potential environmental 'tipping points' for the entire Quaternary period and beyond. This presentation will provide an overview of some of the key tipping points (i.e. significant landscape transformation) that have occurred within the tropical northern Australian region over the Quaternary, as well as discussing potential causes and subsequent impacts of these transformation episodes. These events include the development of the Great Barrier Reef, transition from obliquity to eccentricity dominated glacial-interglacial cycles, the Mid-Brunhes event, the Oxygen Isotope Stage 6 episode, the arrival of people into the region, Last Glacial-Interglacial Transition and European settlement.

  15. Efficient cellulose solvent: quaternary ammonium chlorides.

    Kostag, Marc; Liebert, Tim; El Seoud, Omar A; Heinze, Thomas


    Pure quaternary tetraalkylammonium chlorides with one long alkyl chain dissolved in various organic solvents constitute a new class of cellulose solvents. The electrolytes are prepared in high yields and purity by Menshutkin quaternization, an inexpensive and easy synthesis route. The pure molten tetraalkylammonium chlorides dissolve up to 15 wt% of cellulose. Cosolvents, including N,N-dimethylacetamide (DMA), may be added in large excess, leading to a system of decreased viscosity. Contrary to the well-established solvent DMA/LiCl, cellulose dissolves in DMA/quaternary ammonium chlorides without any pretreatment. Thus, the use of the new solvent avoids some disadvantages of DMA/LiCl and ionic liquids, the most extensively employed solvents for homogeneous cellulose chemistry.

  16. PCA for predicting quaternary structure of protein

    Tong WANG; Hongbin SHEN; Lixiu YAO; Jie YANG; Kuochen CHOU


    The number and arrangement of subunits that form a protein are referred to as quaternary structure. Knowing the quaternary structure of an uncharacterized protein provides clues to finding its biological function and interaction process with other molecules in a biological system. With the explosion of protein sequences generated in the Post-Genomic Age, it is vital to develop an automated method to deal with such a challenge. To explore this prob-lem, we adopted an approach based on the pseudo position-specific score matrix (Pse-PSSM) descriptor, proposed by Chou and Shen, representing a protein sample. The Pse-PSSM descriptor is advantageous in that it can combine the evolution information and sequence-correlated informa-tion. However, incorporating all these effects into a descriptor may cause 'high dimension disaster'. To over-come such a problem, the fusion approach was adopted by Chou and Shen. A completely different approach, linear dimensionality reduction algorithm principal component analysis (PCA) is introduced to extract key features from the high-dimensional Pse-PSSM space. The obtained dimension-reduced descriptor vector is a compact repre-sentation of the original high dimensional vector. The jack-knife test results indicate that the dimensionality reduction approach is efficient in coping with complicated problems in biological systems, such as predicting the quaternary struc-ture of proteins.

  17. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  18. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  19. Monsoon triggered formation of Quaternary alluvial megafans in the interior of Oman

    Blechschmidt, Ingo; Matter, Albert; Preusser, Frank; Rieke-Zapp, Dirk


    A vast bajada consisting of coalescing low-gradient (veneer of weakly cemented Quaternary gravels. A combination of remote sensing, lithological analyses and luminescence dating is used to interpret the complex aggradation history of the Quaternary alluvial fans from the interior of Oman in the context of independent regional climate records. From satellite imagery and clast analysis four fans can be discerned in the study area. While two early periods of fan formation are tentatively correlated to the Miocene-Pliocene and the Early Pleistocene, luminescence dating allows the distinction of five phases of fan aggradation during the Middle-Late Pleistocene. These phases are correlated with pluvial periods from Marine Isotope Stage (MIS) 11 through 3, when southern Arabia was affected by monsoonal precipitation. It is concluded that the aggradation of the alluvial fans was triggered by the interplay of increased sediment production during arid periods and high rainfall with enhanced erosion of hillslopes and transport rates during strong monsoon phases. However, the lack of fine-grained sediments, bioturbation and organic material implies that although the Quaternary fans are sourced by monsoonal rains they formed in a semi-arid environment. Thus, it appears that, in contrast to the Oman Mountains, the interior was not directly affected by monsoonal precipitation.

  20. Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.


    water currents. This has strong implications for both the Quaternary climate archive and petroleum systems in the North Sea. Key Words: base-Quaternary; chronostratigraphy: seismic interpretation; paleoenvironments References Buckley, F.A., (2012) 'An Early Pleistocene grounded ice sheet in the Central North Sea' From: Huuse, M., Redfern, J., Le Heron, D.P., Dixon, R.J., Moscariello, A., Craig, J. (eds) 'Glaciogenic reservoirs and Hydrocarbon Systems' Geological Society, London, Special Publications, 368 Cameron, T.D.J., Stoker, M.S., Long, D., (1987) 'The history of Quaternary sedimentation in the UK sector of the North Sea Basin' Journal of the Geological Society, 144, 43-58 Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kulhmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

  1. The pragmatic roots of American Quaternary geology and geomorphology

    Baker, Victor R.


    H.L. Fairchild's words from the 1904 Geological Society of America Bulletin remain appropriate today: "Geologists have been too generous in allowing other people to make their philosophy for them". Geologists have quietly followed a methodological trinity involving (1) inspiration by analogy, (2) impartial and critical assessment of hypotheses, and (3) skepticism of authority (prevailing theoretical constraints or paradigms). These methods are described in classical papers by Quaternary geologists and geomorphologists, mostly written a century ago. In recent years these papers have all been criticized in modern philosophical terms with little appreciation for the late 19th century American philosophical tradition from which they arose. Recent scholarly research, however, has revealed some important aspects of that tradition, giving it a coherence that has largely been underappreciated as 20th century philosophy of science pursued its successive fads of logical positivism, critical rationalism, relativism, and deconstructivism — for all of which "science" is synonymous with "physics". Nearly all this ideology is geologically irrelevant. As philosophy of science in the late 20th century has come to be identical with philosophy of analytical physics, focused on explanations via ideal truths, much of geology has remained true to its classical doctrines of commonsensism, fallibilism, and realism. In contrast to the conceptualism and the reductionism of the analytical sciences, geology has emphasized synthetic thinking: the continuous activity of comparing, connecting, and putting together thoughts and perceptions. The classical methodological studies of geological reasoning all concern the formulation and testing of hypotheses. Analysis does not serve to provide the ultimate answers for intellectual puzzles predefined by limiting assumptions imposed on the real world. Rather, analysis in geology allows the investigator to consider the consequential effects of

  2. Synthesis of novel quaternary ammonium surfactants containing adamantane

    Jian Wei Guo; Xing Zhong; Hua Zhu; Li Juan Feng; Ying De Cui


    A series of novel quaternary ammonium surfactants containing adamantane were designed and synthesized from 1-adamantanecarboxylic acid.The structures of target surfactants were confirmed by 1H NMR,elements analysis and FTIR.Surface properties of these surfactants were investigated.Due to the lipophilicity of adamantane,the critical micelle concentration (CMC) and C20 values of the synthesized quaternary ammonium surfactants are lower than that of conventional quaternary ammonium surfactants.

  3. Quaternary Geochronology, Paleontology, and Archaeology of the Upper San Pedro River Valley, Sonora, Mexico

    Gaines, E. P.


    This poster presents the results of multi-disciplinary investigations of the preservation and extent of Quaternary fossil-bearing strata in the San Pedro River Valley in Sonora, Mexico. Geologic deposits in the portions of the San Pedro Valley in southern Arizona contain one of the best late Cenozoic fossil records known in North America and the best record of early humans and extinct mammals on the continent. The basin in the U.S. is one of the type locations for the Blancan Land Mammal Age. Hemiphilian and Irvingtonian fossils are common. Rancholabrean remains are widespread. Strata in the valley adjacent to the international border with Mexico have yielded the densest concentration of archaeological mammoth-kill sites known in the western hemisphere. Despite more than 60 years of research in the U.S., however, and the fact that over one third of the San Pedro River lies south of the international boundary, little has been known about the late Cenozoic geology of the valley in Mexico. The study reported here utilized extensive field survey, archaeological documentation, paleontological excavations, stratigraphic mapping and alluvial geochronology to determine the nature and extent of Quaternary fossil-bearing deposits in the portions of the San Pedro Valley in Sonora, Mexico. The results demonstrate that the Plio-Pleistocene fossil -bearing formations known from the valley in Arizona extend into the uppermost reaches of the valley in Mexico. Several new fossil sites were discovered that yielded the remains of Camelids, Equus, Mammuthus, and other Proboscidean species. Late Pleistocene archaeological remains were found on the surface of the surrounding uplands. AMS radiocarbon dating demonstrates the widespread preservation of middle- to late- Holocene deposits. However, the late Pleistocene deposits that contain the archaeological mammoth-kill sites in Arizona are absent in the valley in Mexico, and are now known to be restricted to relatively small portions of

  4. Quaternary geologic map of the Winnipeg 4 degrees x 6 degrees quadrangle, United States and Canada

    Fullerton, D. S.; Ringrose, S.M.; Clayton, Lee; Schreiner, B.T.; Goebel, J.E.


    The Quaternary Geologic Map of the Winnipeg 4? ? 6? Quadrangle, United States and Canada, is a component of the U.S. Geological Survey Quaternary Geologic Atlas of the United States map series (Miscellaneous Investigations Series I-1420), an effort to produce 4? ? 6? Quaternary geologic maps, at 1:1 million scale, of the entire conterminous United States and adjacent Canada. The map and the accompanying text and supplemental illustrations provide a regional overview of the areal distributions and characteristics of surficial deposits and materials of Quaternary age (~1.8 Ma to present) in parts of North Dakota, Minnesota, Manitoba, and Saskatchewan. The map is not a map of soils as soils are recognized in agriculture. Rather, it is a map of soils as recognized in engineering geology, or of substrata or parent materials in which agricultural soils are formed. The map units are distinguished chiefly on the basis of (1)genesis (processes of origin) or environments of deposition: for example, sediments deposited primarily by glacial ice (glacial deposits or till), sediments deposited in lakes (lacustrine deposits), or sediments deposited by wind (eolian deposits); (2) age: for example, how long ago the deposits accumulated; (3) texture (grain size)of the deposits or materials; (4) composition (particle lithology) of the deposits or materials; (5) thickness; and (6) other physical, chemical, and engineering properties. Supplemental illustrations show (1) temporal correlation of the map units, (2) the areal relationships of late Wisconsin glacial ice lobes and sublobes, (3) temporal and spatial correlation of late Wisconsin glacial phases, readvance limits, and ice margin stillstands, (4) temporal and stratigraphic correlation of surface and subsurface glacial deposits in the Winnipeg quadrangle and in adjacent 4? ? 6? quadrangles, and (5) responsibility for state and province compilations. The database provides information related to geologic hazards (for example

  5. A model of the 4000-year paleohydrology (δ18O) record from Lake Salpetén, Guatemala

    Rosenmeier, Michael F.; Brenner, Mark; Hodell, David A.; Martin, Jonathan B.; Curtis, Jason H.; Binford, Michael W.


    A simple mass-balance model provides insights into the influence of catchment vegetation changes and climate variability on the hydrologic and stable oxygen isotope (δ18O) evolution of Lake Salpetén, in the Maya Lowlands of northern Guatemala. Model simulations for the last 4000 years incorporate pollen-inferred changes in vegetation cover and account for 75% of the variance observed in the biogenic carbonate δ18O record from a long lake sediment core. Vegetation-driven hydrologic changes, however, failed to capture the full range of late Holocene sediment core δ18O variability. The model requires incorporation of additional shifts in catchment vegetation cover, inclusion of regional precipitation changes, or likely both, to explain the fluctuations observed in the lake core oxygen isotope record. Climatic interpretation of the model results suggests that there was relatively greater moisture availability between about 2400 and 1800 years ago, but increased δ18O values centered at ~ 3300, 2900, 500, and 200 calendar years before present (cal yr BP) indicate abrupt precipitation decreases. There is evidence for protracted aridity between 1500 and 800 cal yr BP.

  6. The grain-size characteristics of Quaternary deposits at Xingshan near Siping in Jilin province, China

    Maxwell A Boateng; Xikui Wang


    This research paper analyses the grain-size characteristics of the Quaternary deposits at Xingshan near Siping, Jilin province in China by employing graphic measures to study the grain size distribution and its mode of transport and deposition. The Quaternary deposits at Xingshan lie unconformable on Cretaceous rocks made of siltstone, mudstone and sandstone. The average grain size is between 8.06 to 8.55Φ (0.002 6 ~0.003 7 mm). The Quaternary deposits at Xingshan mainly compose of very fine silt to clay. The compositions of the grade are clay 63% and silt 37%. The clay size components are weathered debris transported and deposited by flowing water from the SE highlands or hills to the low lying NW Xingshan plains whereas the silty components accumulated by aoelian process. The Quaternary deposits at Xingshan accumulated in the middle and late Pleistocene interglacial periods from (459.12~39.03) ka to (88.92~7.56) ka. The standard deviation ranged from 0.96 to 1.36Φ, indicating that the sediments are moderately to poorly sorted, Coefficient of skewness ranged from 0.16~0.31 with an average skewness of 0.218, (Positively skewed towards fine). Kurtosis values (0.84~1.05) from the grain size distribution and visual inspection of the frequency curves indicate platykurtic to mesokurtic curves and unimodal to bimodal grain-size distribution. The type of deposit formation is sand dune and the source is at a distal from its provenance.

  7. An Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient

    Jakobsson, M.; Dowdeswell, J. A.; Canals, M.; Todd, B. J.; Dowdeswell, E. K.; Hogan, K. A.


    In the past two decades there have been several advances that make the production of an atlas of submarine glacial landforms timely. First is the development of high-resolution imaging technologies; multi-beam echo-sounding or swath bathymetry that allows the detailed mapping of the sea floor at water depths of tens to thousands of metres across continental margins, and 3-D seismic methods that enable the visualisation of palaeo-continental shelves in Quaternary sediments and ancient palaeo-glacial rocks (e.g. Late Ordovician of Northern Africa). A second technological development is that of ice-breaking or ice-strengthened ships that can penetrate deep into the ice-infested waters of the Arctic and Antarctic, to deploy the multibeam systems. A third component is that of relevance - through both the recognition that the polar regions, and especially the Arctic, are particularly sensitive parts of the global environmental system and that these high-latitude margins (both modern and ancient) are likely to contain significant hydrocarbon resources. An enhanced understanding of the sediments and landforms of these fjord-shelf-slope systems is, therefore, of increasing importance to both academics and industry. We are editing an Atlas of Submarine Glacial Landforms that presents a series of individual contributions that describe, discuss and illustrate features on the high-latitude, glacier-influenced sea floor. Contributions are organised in two ways: first, by position on a continental margin - from fjords, through continental shelves to the continental slope and rise; secondly, by scale - as individual landforms and assemblages of landforms. A final section provides discussion of integrated fjord-shelf-slope systems. Over 100 contributions by scientists from many countries contain descriptions and interpretation of swath-bathymetric data from both Arctic and Antarctic margins and use 3D seismic data to investigate ancient glacial landforms. The Atlas will be

  8. Study on the Late Quaternary Incised-valley Sequence Feature of the Changjiang Delta Estuary and Favorable Geological Conditions for Biogas Reservoir Formation%长江三角洲河口地区晚第四纪下切河谷层序特征与生物气成藏有利地质条件研究

    徐振宇; 方朝刚; 殷启春; 滕龙


    依据对江苏省启东市和海门市钻孔地层岩心沉积特征的研究,结合两个钻孔83个有机碳含量样品、28个渗透率样品的测试值和钻孔周边18个静力触探孔试气效果统计,讨论了晚第四纪以来长江三角洲河口地区的层序地层特征及生物气的勘探前景。研究表明,晚第四纪以来长江三角洲河口地区LG海侵旋回只保留了底部的河流相沉积,PG海侵旋回自下而上依次发育河流相、浅海相、三角洲相和河流相、强潮河口湾相两套不同的沉积组合。亚间冰期( LG)海侵旋回只保留了底部侵蚀面,冰后期( PG)海侵旋回发育一套完整的海侵-海退旋回,底部侵蚀面为该层序的底界面,最大海泛面则发育在浅海相中沉积物最细、海相性最强的淤泥质黏土层中。研究区生物气的生储盖条件优越、试气效果好,为后期的生物气勘探与开发提供了优越的条件。%On the basis of analysis on the sedimentary characteristics of drilling cores located in Qidong city and Haimen city of Jiangsu province and test values of 83 organic carbon content samples and 28 permeability samples and gas production test effect statistics of 18 cone penetration test holes, the Changjiang delta estuary sequence stra-tigraphic character and the biogenic gas exploration prospect in later Quaternary are discussed.The research shows that only fluvial deposition reserved at the progressive cycle telophase of subinterglaciation( LG) , while the regres-sive cycle postglacial period( PG) contains two sets of depositional combination including fluvial facies, shallow se-aphase, delta phase and fluvial facies, strong tide estuarine facies from top to bottom.The erosion surface at the bottom is reserved only in the progressive cycle telophase of subinterglaciation( LG) while a set of complete trans-gression-regression cycle is developed in the regressive cycle postglacial period(PG).The erosion

  9. The impact of the Quaternary glaciations on the Durmitor mountains (Montenegro) as understood from detailed geomorphological mapping

    Frankl, Amaury; Annys, Klaas; Spalević, Velibor; Čurović, Milic; Borota, Dragan; Nyssen, Jan


    In the Balkans, few studies exist that highlight the impact of the Quaternary glaciations on the landscape. However, the impact of the Quaternary glaciations was important and the glacial imprint remains well preserved in the limestone massifs where karst hydrology prevails. This study presents a detailed geomorphological map at scale 1:10,000 that was prepared of the northeastern Durmitor mountains (2523 m a.s.l.) and the plateau Jezerska Površ (47 km², Dinaric Alps, Montenegro). Mapping occurred from an intensive fieldwork campaign and remote sensing analysis, and was finalized in a GIS environment. The basic components of the legend are (i) processes/genesis, (ii) materials, (iii) morphometry/morphography, (iv) hydrography, (v) vegetation and (vi) anthropogenic features, that are organized as a box-of-bricks type of legend (AGRG-system). The geomorphological setting of the area consists of Mesozoic limestones which were eroded physically by Quaternary glacial and periglacial activity and chemically during interglacials. Glacial deposits of three Middle to Late Pleistocene glacial phases exist on the plateau, only scarcely dissected by meltwater channels. In the mountains, Holocene glacier retreat left behind a series of well-preserved recessional moraines and a static glacier remains in the cirque head. The presented map serves as a valuable tool for Quaternary research in the Durmitor Mountains, and serves as an example on the interaction between glacial and karst processes. Keywords: Debeli Namet glacier, Dinaric Alps, Geographic Information System (GIS), Glacial landforms, Karst.

  10. Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A.

    Culver, Stephen J.; Farrell, Kathleen M.; Mallinson, David J.; Willard, Debra A.; Horton, Benjamin P.; Riggs, Stanley R.; Thieler, E. Robert; Wehmiller, John F.; Parham, Peter; Snyder, Scott W.; Hillier, Caroline


    To understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio-hydro-isostacy, tectonics, subsidence, geologic environments and sedimentation patterns for the Quaternary of a passive continental margin, a nearly complete stratigraphic record that is fully integrated with a three dimensional chronostratigraphic framework, and paleoenvironmental information are necessary. The Albemarle Embayment, a Cenozoic regional depositional basin in eastern North Carolina located on the southeast Atlantic coast of the USA, is an ideal setting to unravel these dynamic, interrelated processes.Micropaleontological data, coupled with sedimentologic, chronostratigraphic and seismic data provide the bases for detailed interpretations of paleoenvironmental evolution and paleoclimates in the 90. m thick Quaternary record of the Albemarle Embayment. The data presented here come from a transect of cores drilled through a barrier island complex in the central Albemarle Embayment. This area sits in a ramp-like setting between late Pleistocene incised valleys.The data document the episodic infilling of the Albemarle Embayment throughout the Quaternary as a series of transgressive-regressive (T-R) cycles, characterized by inner shelf, midshelf, and shoreface assemblages, that overlie remnants of fluvial to estuarine valley-fill. Barrier island and marginal marine deposits have a low preservation potential. Inner to mid-shelf deposits of the early Pleistocene are overlain by similar middle Pleistocene shelf sediments in the south of the study area but entirely by inner shelf deposits in the north. Late Pleistocene marine sediments are of inner shelf origin and Holocene deposits are marginal marine in nature. Pleistocene marine sediments are incised, particularly in the northern half of the embayment by lowstand paleovalleys, partly filled by fluvial/floodplain deposits and in some cases, overlain by remnants of transgressive estuarine sediments. The shallowing

  11. Palladium-catalyzed asymmetric quaternary stereocenter formation.

    Gottumukkala, Aditya L; Matcha, Kiran; Lutz, Martin; de Vries, Johannes G; Minnaard, Adriaan J


    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of β,β-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl(2), PhBOX, and AgSbF(6), and provides products in up to 99% enantiomeric excess, with good yields. Based on this strategy, (-)-α-cuparenone has been prepared in only two steps. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A“Yellow Cap” on Quaternary Red Clay in Jiujiang,Jiangxi Province


    A thin layer of yellow-brown-colored earth was generally found on Quaternary red clay in Jiujing,Jiangxi Province,A typical profile was established.Both particle size distribution and REE(rare earth elements)characteristics of the yellow-brown-colored earth of the profile fully suggested its aeolian origin and close similarity of Nanjing Xiashu Loess.The study also implied aeolian origin of the underlying Quaternary red clay,Compared with the red clay,the yellow-brown-colored earth was less weathered because of its lower content of free iron and higher mole ratios of SiO2/Al2O3 and SiO2(Fe2O3+Al2O3) as well as its less developed chemical microtextures of quartz grains.In order to study the ages of the two deposits comparatively,the thermoluminescent dating method was used.As a result,the bottom of the yellow-brown-colored earth was dated to 60±5 ka B.P.and the upper part of the red clay 388±54 ka B.P.It was suggested that the yellow-brown-colored earth earth was formed in the Late Pleistocene and was probably the aeolian deposit of the Last Glacial,which corresponded with the Malan Loess in the Loess Plateau of the northwestern part of China,while the underlying red clay was formed in the Middle Pleistocene.A“yellow cap” on Quaternary red clay in Jiujiang implied a great climatic and environmental variation in the beginning of the Late Pleistocene in the southern part of China,especially in the middle and lower reaches of the Yangtze River,The event not only halted the rubification,once dominating the region but also produced a widespread covering of aeolian deposit,as only occurred in the cold and dry environment.

  13. Mapping process and age of Quaternary deposits on Santa Rosa Island, Channel Islands National Park, California

    Schmidt, K. M.; Minor, S. A.; Bedford, D.


    Employing a geomorphic process-age classification scheme, we mapped the Quaternary surficial geology of Santa Rosa (SRI) within the Channel Islands National Park. This detailed (1:12,000 scale) map represents upland erosional transport processes and alluvial, fluvial, eolian, beach, marine terrace, mass wasting, and mixed depositional processes. Mapping was motivated through an agreement with the National Park Service and is intended to aid natural resource assessments, including post-grazing disturbance recovery and identification of mass wasting and tectonic hazards. We obtained numerous detailed geologic field observations, fossils for faunal identification as age control, and materials for numeric dating. This GPS-located field information provides ground truth for delineating map units and faults using GIS-based datasets- high-resolution (sub-meter) aerial imagery, LiDAR-based DEMs and derivative raster products. Mapped geologic units denote surface processes and Quaternary faults constrain deformation kinematics and rates, which inform models of landscape change. Significant findings include: 1) Flights of older Pleistocene (>120 ka) and possibly Pliocene marine terraces were identified beneath younger alluvial and eolian deposits at elevations as much as 275 m above modern sea level. Such elevated terraces suggest that SRI was a smaller, more submerged island in the late Neogene and (or) early Pleistocene prior to tectonic uplift. 2) Structural and geomorphic observations made along the potentially seismogenic SRI fault indicate a protracted slip history during the late Neogene and Quaternary involving early normal slip, later strike slip, and recent reverse slip. These changes in slip mode explain a marked contrast in island physiography across the fault. 3) Many of the steeper slopes are dramatically stripped of regolith, with exposed bedrock and deeply incised gullies, presumably due effects related to past grazing practices. 4) Surface water presence is

  14. Quaternary continetal back-arc evolution from southern Mendoza, Argentina

    Espanon, Venera; Chivas, Allan; Dosseto, Anthony; Honda, Masahiko; Phillips, David; Matchan, Erin; Price, David


    The Quaternary evolution of the Payenia Basaltic Province (PBP) in southern Mendoza, Argentina has been investigated using a multi-dating approach in combination with pre-exiting geochemical data. This basaltic province covers an area of approximately 40000 km2 and is mainly characterised by backarc volcanism. In the current investigation nine new radiometric ages obtained using surface exposure, 40Ar/39Ar and thermoluminescence dating are presented. Six ages correspond to the late Pleistocene and three to the Holocene. The surface exposure ages obtained using cosmogenic 3He and 21Ne are in good agreement with previous publications and confidently suggest that part of this basaltic province was active at least 4000 years ago (taking a conservative approach). In addition, we combined the available geochronological and geochemical data to reconstruct the Quaternary evolution of this basaltic province. This approach was used to create maps of geospatial distribution of trace-element ratios to determine geochemical changes during the Pleistocene. Employing this method it is evident that two geochemical distinct types of magma were erupting at the same time interval within the PBP. In the north eastern part (Nevado volcanic field) of the PBP an arc-like signature is evident, while in the southern part (Río Colorado volcanic field) of the same basaltic province an Ocean Island Basalt (OIB) signature is evident. The arc-like signature in the north eastern part of the PBP, decreased during the Pleistocene in a north-west direction indicated by a reduction in Ba/La and La/Ta in the Nevado and Llancanelo volcanic field. The Holocene volcanism is restricted to the western side of the Payún Matrú volcanic field and is dominated by OIB-like signatures such as high Ta/Hf and low Ba/La and La/Ta. This contribution presents new geochronology for the PBP and confirms that two different types of volcanism occurred simultaneously during the Pleistocene, while the Holocene

  15. Quaternary Deformation of Sumba, Indonesia: Evidence from Carbonate Terraces

    Dahlquist, M. P.; West, A. J.; Dolan, J. F.


    The Banda Arc of Indonesia remains one of the least understood tectonic domains on the modern Earth. The island of Sumba, located approximately 50 km south of Flores and 120 km north of the Java Trench, northwest of where it transitions into the Timor Trough, lies in a region of tectonic transition and potentially offers insights into regional dynamics. The Banda Arc is volcanically active, but Sumba itself is not volcanic. The northern coast of Sumba is covered in Quaternary coral terraces, with the rest of the island's surface geology composed of Mio-pliocene carbonates and uplifted Late Cretaceous-Oligocene forearc basin and volcanic rocks. The purpose of this study is to remotely map the topographic expression of the coral terraces and use the information gained to better understand deformation on Sumba since their deposition. The ages of the coral terraces, of which many platforms are exposed over significant areas of the island, have been constrained at Cape Luandi in north central Sumba, but uplift rates calculated from those ages may not be representative of the island as a whole. The lateral continuity of these dated terraces can help constrain the extent to which uplift of Sumba is spatially variable. Analysis of the terraces using SRTM digital elevation data with ArcGIS software makes it possible to trace the same terrace platforms over large distances, and shows that the north central part of the island has experienced the most uplift since the deposition of the terraces, forming an anticline with the east limb dipping more steeply than the west. The terraces are not well preserved on the southern half of the island. Exposure of older rocks and lack of terrace preservation, as well as a south-skewed drainage divide suggests the southern half of the island experiences greater exhumation, but this could be driven by climate or other factors and does not necessarily indicate more rapid uplift. Study of Quaternary deformation of Sumba can offer greater




    The 2-adic representations of codewords of the dual of quaternary Goethals code are given. By the 2-adic representations, the binary image of the dual of quaternary Goethals code under the Gray map is proved to be the nonlinear code constructed by Goethals in 1976.

  17. The Quaternary Silver Creek Fault Beneath the Santa Clara Valley, California

    Wentworth, Carl M.; Williams, Robert A.; Jachens, Robert C.; Graymer, Russell W.; Stephenson, William J.


    The northwest-trending Silver Creek Fault is a 40-km-long strike-slip fault in the eastern Santa Clara Valley, California, that has exhibited different behaviors within a changing San Andreas Fault system over the past 10-15 Ma. Quaternary alluvium several hundred meters thick that buries the northern half of the Silver Creek Fault, and that has been sampled by drilling and imaged in a detailed seismic reflection profile, provides a record of the Quaternary history of the fault. We assemble evidence from areal geology, stratigraphy, paleomagnetics, ground-water hydrology, potential-field geophysics, and reflection and earthquake seismology to determine the long history of the fault in order to evaluate its current behavior. The fault formed in the Miocene more than 100 km to the southeast, as the southwestern fault in a 5-km-wide right step to the Hayward Fault, within which the 40-km-long Evergreen pull-apart basin formed. Later, this basin was obliquely cut by the newly recognized Mt. Misery Fault to form a more direct connection to the Hayward Fault, although continued growth of the basin was sufficient to accommodate at least some late Pliocene alluvium. Large offset along the San Andreas-Calaveras-Mt Misery-Hayward Faults carried the basin northwestward almost to its present position when, about 2 Ma, the fault system was reorganized. This led to near abandonment of the faults bounding the pull-apart basin in favor of right slip extending the Calaveras Fault farther north before stepping west to the Hayward Fault, as it does today. Despite these changes, the Silver Creek Fault experienced a further 200 m of dip slip in the early Quaternary, from which we infer an associated 1.6 km or so of right slip, based on the ratio of the 40-km length of the strike-slip fault to a 5-km depth of the Evergreen Basin. This dip slip ends at a mid-Quaternary unconformity, above which the upper 300 m of alluvial cover exhibits a structural sag at the fault that we interpret as

  18. New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.


    report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kuhlmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

  19. A Late Younger Dryas-Early Holocene tephrostratigraphy for Fosen, Central Norway

    Lind, Ewa M.; Wastegard, Stefan; Larsen, Jeppe J.


    a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash approximate to 10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras...

  20. Ancient DNA reveals late survival of mammoth and horse in interior Alaska

    Haile, James; Froese, Duane G; Macphee, Ross D E


    Causes of late Quaternary extinctions of large mammals ("megafauna") continue to be debated, especially for continental losses, because spatial and temporal patterns of extinction are poorly known. Accurate latest appearance dates (LADs) for such taxa are critical for interpreting the process of ...

  1. Quaternary nanofossils on the Brazilian continental shelf; Nanofosseis calcarios do quaternario da margem continental brasileira

    Antunes, Rogerio Loureiro [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Gerencia de Bioestratigrafia e Paleoecologia], E-mail:


    The study of calcareous nanofossils occurring in the deposits on the Brazilian continental margin began in the late 1960s, undertaken solely by PETROBRAS. Instead of presenting an academic outlook, the purpose of these investigations is first to formulate a biostratigraphic framework to apply to oil well samples. The initial result was the first zoning for the Brazilian continental margin, which considered the deposits formed between the Aptian and Miocene series. Since the 1960s to date, many papers have been written either with details of that original zoning or applying nanofossil biostratigraphy to solve stratigraphic problems. Regardless of all the papers and studies undertaken, little attention has been paid to the Quaternary, since these deposits are normally of no interest to petroleum geology stricto sensu, especially in a large part of the Brazilian margin. On the other hand, there are a few articles and some Master's dissertations and PhD theses that were written and/or are in progress in Brazilian universities. On the other hand, elsewhere in the world, Quaternary nanofossils have been thoroughly investigated in terms of biostratigraphy and paleoceanography. It is, therefore, very clear that there is a gap between what is being done elsewhere in the world and what has been done in Brazil. In fact, this gap is not larger simply because of a few researchers in Brazilian universities who are studying this topic. The intention of this paper is to contribute toward a richer study of Quaternary nanofossils. It, therefore, contains illustrations and taxonomic descriptions of many species observed in the younger strata of the Brazilian margin basins. This article not only aspires to portray and disseminate the potential of nanofossils for the marine Quaternary study but is also an invitation to students (under and post-graduates) and university researchers - an invitation to learn a little more about the subject and spend some time studying these real gems

  2. Studies of Quaternary deformation zones through geomorphic and geophysical evidence: A case in the Precordillera Sur, Central Andes of Argentina

    Terrizzano, Carla M.; Fazzito, Sabrina Y.; Cortés, José M.; Rapalini, Augusto E.


    At the northern sector of the Precordillera Sur (31° 50'-32° 40' SL/68° 45'-69° 20' WL), Central Andes of Argentina, NW-trending sinistral transpressive shear zones at different scales, product of the Late Cenozoic Andean deformation, are recognized. The most significant of them is the 120 km long Barreal-Las Peñas Belt and within it, a small-scale (7 km long) Quaternary sinistral transpressive shear zone, called Los Avestruces, has been detected from geomorphological and geophysical analysis (32° SL/69° 21 WL). Geophysical techniques were applied to better characterize the shallow structure and kinematics of some representative structures in this shear zone. In particular, the use of tomography of electrical resistivity methods allowed characterizing the subsurface geometry of some areas of interest, enabling the recognition of Quaternary layers against their original slope, the geometry of the reverse fault which uplifted the Pleistocene deposits of one of the highs, the geometry of a likely previous extensional fault reactivated and inverted during the Quaternary as well as the presence of a reverse blind fault, which has uplifted the Quaternary deposits of the Los Avestruces bog. The location of the above mentioned shear zones coincides with the northern branch of the NW-trending extensional Triassic Cuyana basin. Thus, their presence appears to be related to Andean reactivation of older (Triassic), mainly NW-trending, structures. In the northern area of the Precordillera Sur, as well as in other places of the world here discussed, these kinds of paleotectonic oblique features play a major role in defining the geometry and kinematics of Late Cenozoic deformation.

  3. Absolute age determination of quaternary faults

    Cheong, Chang Sik; Lee, Seok Hoon; Choi, Man Sik [Korea Basic Science Institute, Seoul (Korea, Republic of)] (and others)


    To constrain the age of neotectonic fault movement, Rb-Sr, K-Ar, U-series disequilibrium, C-14 and Be-10 methods were applied to the fault gouges, fracture infillings and sediments from the Malbang, Ipsil, Wonwonsa faults faults in the Ulsan fault zone, Yangsan fault in the Yeongdeog area and southeastern coastal area. Rb-Sr and K-Ar data imply that the fault movement of the Ulan fault zone initiated at around 30 Ma and preliminary dating result for the Yang san fault is around 70 Ma in the Yeongdeog area. K-Ar and U-series disequilibrium dating results for fracture infillings in the Ipsil fault are consistent with reported ESR ages. Radiocarbon ages of quaternary sediments from the Jeongjari area are discordant with stratigraphic sequence. Carbon isotope data indicate a difference of sedimentry environment for those samples. Be-10 dating results for the Suryum fault area are consistent with reported OSL results.

  4. Paleomagnetic research on Black Sea Quaternary sediments

    Kalcheva, V.; Nozharov, P.; Kovacheva, M.; Shopov, V.


    The paper reports the first paleomagnetic study of a Black Sea Quaternary sediment core made by a Bulgarian research group. The experimental results show an important difference in magnetic behaviour between the samples from the Holocene part and those from the Pleistocene part of the core. Suggestions are made for the character of the remanent magnetization and the main carriers of it. The presence of greigite (Fe 3S 4) and pyrite (FeS 2) is discussed. A rough correlation is established between the variation of inclination for the Holocene part of the sediment and for the Bulgarian archeomagnetic curve. On the basis of the comparison of inclination data obtained from the Pleistocene part of the core and previously studied Black Sea core (related to the absolute time scale), it is suggested that the lower boundary of the Pleistocene part is ˜ 16000 years old (BP).

  5. Suggested terminology for Quaternary dating methods

    Colman, Steven M.; Pierce, K.L.; Birkeland, P.W.


    Classification of Quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods. We recommend the use of the terms numerical-age, calibrated-age, relative-age, and correlated-age to describe these levels. We also classify dating methods by type into sideral, isotopic, radiogenic, chemical and biological, geomorphic, and correlation methods. The use of "absolute" is inappropriate for most dating methods, and should be replaced by "numerical." The use of "date" should be minimized in favor of "age" or "age estimate." We recommend use of the abbreviations ka and Ma for most ages; calender dates can be used where appropriate and yr B.P. can be used for radiocarbon ages. ?? 1987.

  6. Quaternary ammonium compounds – New occupational hazards

    Agnieszka Lipińska-Ojrzanowska


    Full Text Available Quaternary ammonium compounds (QACs, quats belong to organic ionic chemical agents which display unique properties of both surfactants and disinfectants. Their wide distribution in the work environment and also in private households brings about new occupational hazards. This paper reviews reports about the health effects of QACs. QACs could play a role of sensitizers and irritants to the skin and mucous membranes. It is suspected that particular QACs can display an immunologic crossreactivity between each other and with other chemical compounds containing ammonium ion, such as muscle relaxants widely used in anesthesia. They may promote the development of airway allergy, however, the background mechanisms are still unclear and need to be further investigated. Until now, a few cases of occupational asthma induced by QACs have been described and their involvement in contact dermatitis has been documented. The possibility of anaphylaxis due to QACs cannot be excluded as well. Med Pr 2014;65(5:675–682

  7. Biosedimentology of Quaternary stromatolites in intertropical Africa

    Casanova, J.

    Mineralizations of microbial origin constitute a non-negligeable part of Quaternary limestones in intertropical Africa. Stromatolites have colonized a wide range of environments corresponding to different hydroclimatic situations: travertines in fluviatile environments, oncolites in flood plains, encrustations in sebkha areas and shorelines of deep, fresh water lakes. The developed morphologies represent a complete catalogue of the microbial carbonated mineralizations: oncolites, chemneys, pool-rim dams, biocherms, planar or cylindrical encrustations. The building organisms may be either pure bacterial colonies (hydrothermal and lacustrine environments), cyanophyte associations (fluviatile and lacustrine environments) or complex microbial biocoenoses. Stromatolites have recorded the hydrologic, climatic and sedimentologic evolution of the continental environment in intertropical Africa for the past 240 000 years.

  8. Hydration Structure of the Quaternary Ammonium Cations

    Babiaczyk, Wojtek Iwo


    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  9. Energy consumption maps for quaternary distillation sequences

    Gomez-Castro, F.I.; Ramírez-Vallejo, N.E.; Segovia-Hernandez, J.G.


    of the solutions space. For the separation of ternary mixtures, Tedder and Rudd (1978) presented a composition map for which thermally coupled systems allowed energy savings. However, the scenario is different for quaternary mixtures, since no similar information is available. Therefore, in this work, energy...... be generated for the separation of multicomponent mixtures. This fact is an advantage, since a wide portfolio of alternatives can be used to separate a specific mixture; however, this is also a disadvantage since a lot of alternatives must be explored in order to find the optimal one. The optimal configuration......, for a given mixture, depends on the nature of the mixture, usually quantified for ternary mixtures through the ease of separation index (ESI), and also on the feed composition. As can be noticed, the size of the design and optimization problem increases when these variables are considered in the generation...

  10. Quaternary glacial stratigraphy and chronology of Mexico

    White, Sidney E.

    The volcano Iztaccihuatl in central Mexico was glaciated twice during the middle Pleistocene, once probably in pre-Illinoian (or pre-Bull Lake) time, and once in late Illinoian (or Bull Lake) time. Glaciation during the late Pleistocene was restricted to the late Wisconsin (or Pinedale). A maximum advance and one readvance are recorded in the early part, and one readvance in the latter part. Three or four small neoglacial advances occurred during the Holocene. Two other volcanoes nearby, Ajusco and Malinche, have a partial record of late Pleistocene and Holocene glaciations. Three others, Popocatépetl, Pico de Orizaba, and Nevado de Toluca, have a full Holocene record of three to five glacial advances during Neoglaciation.

  11. Quaternary Tectonism in a Collision Zone, Northwest Washington

    McCrory, P. A.; Wolf, S. C.; Intelmann, S. S.; Danforth, W. W.; Weldon, R. J.; Blair, J. L.


    Kinematic, geodetic, and geologic observations define a region with 6-8 mm/y of north-south contraction between the Columbia River and Vancouver Island. We attribute this contraction to differential forearc-block motion within the Cascadia subduction system where the Oregon Coast Range block is moving northward relative to Vancouver Island. The contraction is accommodated by a combination of distributed uplift in the Olympic Mountains, and faulting along the margins of the Coast Range and Vancouver Island blocks. The tide gauge at Neah Bay, which records one of the highest rates of uplift anywhere along the Cascadia subduction margin, suggests that a significant portion of this north-south contraction occurs between the northern Olympic Peninsula and Vancouver Island. The northwest-trending Calawah fault, extending from Makah Bay eastward to near Lake Crescent, appears to mark the modern boundary between the Olympic Mountains block and the Vancouver Island block in northwestern Washington. Onshore, the 80+ km-long Calawah fault displaces late Quaternary glacial sediments and geodetic uplift rates increase abruptly across the fault zone. Offshore in Makah Bay, new multibeam, sidescan-sonar, and high-resolution seismic reflection data image a complex, multi-strand fault zone that offsets the seafloor and moves Cape Flattery rocks seaward. Two parallel, northwest-trending fault strands bound a down-dropped block that in turn terminates along a northward-trending anticlinal fold and thrust fault. These data suggest that the Calawah fault zone currently accommodates contraction both by uplift and by seaward translation of rocks north of the forearc-block boundary. Our geologic mapping in the Cape Flattery area indicates that differential block motion is accommodated by a combination of crustal uplift, folding, and left-lateral, strike-slip faulting.

  12. Quaternary deformation around the Palo Negro area, Pampa Norte, Argentina

    Brunetto, E.; Iriondo, M.; Zamboni, L.; Gottardi, G.


    The Pampa Norte region is a great plain characterized by low slopes and accumulation of hundreds of meters of thick loose sediments. A high morphostructure denominated San Guillermo block stands out in the central plain, the Tostado-Selva scarp forming its western boundary. It is located in an intraplate setting characterized by low tectonic activity. However recent uplift can be inferred by means of terrain analysis and the sedimentology of the Palo Negro Fm. Pond deposits (Palo Negro Fm.) observed in the scarp suggest topographic inversion during the Late Quaternary in the Palo Negro area. The morphology indicates that the deformation was widely distributed, forming a gentle (ca. 5 m amplitude and 13 km wavelength) asymmetric fold. Low sinuosity lineaments located in the base of the scarp, coincident with knick points in the topographic profile, can be interpreted as the projection of tip-lines by high-angle fault-propagation. This geometry is compatible with reverse kinematics on blind faults. A deformation style with reactivation of pre-existing faults is consistent with structural observations. Seismic reflectors suggest the presence of Cretaceous high-angle normal faults, and the orientation of lineaments is similar to the orientation of the graben systems and transverse accommodation zones originated during the opening of the South Atlantic Ocean. One OSL dating of 67.4 ± 5.1 kyr B.P (from Palo Negro Fm. supposed as deposited on a flat plain floor) and a height difference of 9.5 m measured in the Tostado-Selva scarp account for an averaged uplift rate of 0.14 mm/year.

  13. Quaternary Logic and Applications Using Multiple Quantum Well Based SWSFETs

    P. Gogna


    Full Text Available This paper presents Spatial Wavefunction-Switched Field-Effect Transistors (SWSFET to implement efficient quaternary logic and arithmetic functions. Various quaternary logic gates and digital building blocks are presented using SWSFETs. In addition, arithmetic operation with full adder using novel logic algebra is also presented. The SWSFET based implementation of digital logic, cache and arithmetic block results in up to 75% reduction in transistor count and up to 50% reduction in data interconnect densities. Simulations of quaternary logic gates using the BSIM equivalent models for SWSFET channels are also described.

  14. Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

    Yan Xue


    Full Text Available Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers.


    梅静; 王汝建; 陈建芳; 程振波; 陈志华; 孙烨忱


    Stage (MIS) 3. A total of five IRD events were distinguished during the late MIS 1, MIS 2 and early to mid MIS 3. These IRD, transported by sea ice and icebergs, and brought to the Chukchi Plateau, by the Beaufort Gyre, might be exported from the M'Clure Strait Ice Stream, Canadian Arctic Archipelago. They are indicators of the collapse events of North American Ice Sheet (NAIS) and the evolutionary history of the Beaufort Gyre since MIS 3. Grain size components changes show that the sand components, which correspond to the high IRD size fraction, might be transported by icebergs: but the silt components might be mainly transported by sea ice, and the clay component was probably mainly carried by the Beaufort Gyre. The variation of two sensitive components (5-13 μm and 110-176 μm) present clear symmetric distribution, the coarser component corresponds to the IRD, and the finer may indicate the source region and the influence of deposition. During MIS 3, MIS 2 and MIS 1, the sedimentation rates of core P31 are 2. 2 cm/ka, 0. 16 cm/ka and 1. 6 cm/ka, respectively. The average sedimentation rate is about 1. 2 cm/ka. The overall picture of the western Arctic Ocean shows high sedimentation rates in the ice edge, and low sedimentation rates in areas with permanent sea ice cover. High sedimentation rates occur in areas of shallow water depth, and close to the terrigenous source regions, and low sedimentation rates in the high latitude area of Mendeleev-alpha ridge and Canada Basin area.

  16. Origin, Extent, and Thickness of Quaternary Geologic Units in the Willamette Valley, Oregon

    O'Connor, Jim E.; Sarna-Wojcicki, Andrei M.; Wozniak, Karl C.; Polette, Danial J.; Fleck, Robert J.


    Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic, pedogenic, and hydrogeologic properties. In summation, these units reflect four distinct episodes in the Quaternary geologic development of the Willamette Valley: 1) Fluvial sands and gravels that underlie terraces flanking lowland margins and tributary valleys were probably deposited between 2.5 and 0.5 million years ago. They are the oldest widespread surficial Quaternary deposits in the valley. Their present positions and preservation are undoubtedly due to postdepositional tectonic deformation - either by direct tectonic uplift of valley margins, or by regional tectonic controls on local base level. 2) Tertiary and Quaternary excavation or tectonic lowering of the Willamette Valley accommodated as much as 500 m (meters) of lacustrine and fluvial fill. Beneath the lowland floor, much of the upper 10 to 50 m of fill is Quaternary sand and gravel deposited by braided channel systems in subhorizontal sheets 2 to 10 m thick. These deposits grade to gravel fans 40 to 100 m thick where major Cascade Range rivers enter the valley and are traced farther upstream as much thinner valley trains of coarse gravel. The sand and gravel deposits have ages that range from greater than 420,000 to about 12,000 years old. A widely distributed layer of sand and gravel deposited at about 12 ka (kiloannum, thousands of years before the present) is looser and probably more permeable than older sand and gravel. Stratigraphic exposures and drillers' logs indicate that this late Pleistocene unit is mostly between 5 and 20 m thick where it has not been subsequently eroded by the Willamette River and its

  17. Significance of Quaternary and Experimental Fluvial Systems to Interpretation of the Stratigraphic Record

    Blum, M. D.; Martin, J. M.


    subsurface data, the sequence boundary is most commonly defined by the base of fluvial incision, which demarcates a significant basinward shift of facies, and is assumed to be an unconformity that everywhere separates younger strata above from older strata below. This classical interpretation is derived from a model for fluvial incision and sediment bypass during relative sea-level fall: fluvial deposits that rest on the sequence boundary are commonly assumed to represent filling of an empty container during late lowstand or early transgression. However, the model of fluvial incision and sediment bypass during relative sea-level fall has never been verified and does not stand up to scrutiny in Quaternary systems or experiments. Moreover, sediment bypass and deposition within incised valleys are not mutually exclusive: a large proportion of fluvial sediment is in transit over the duration of a base-level cycle, even though erosion and channel-belt deposition continuously redefines the valley shape, and at any one point the basal valley-fill surface is the same age as fluvial deposits that rest on top of it. Last, extension of valleys across a newly emergent shelf is accompanied by linked channel-belt deposition and delta progradation, such that the base of fluvial incision does not qualify as an unconformity or meet traditional criteria for a sequence boundary.

  18. Exploring Late Globalization

    Turcan, Romeo V.


    The purpose of this viewpoint paper is to motivate a program of research on late globalization, a program that could eventually lead to one or more significant theories of late globalization. The paper explores the phenomenon of late globalization as well as the idea of “late” by drawing on sparse...... literature on late globalization from sociocultural and economic perspectives. It illustrates in a vignette the character and features of late globalization observable in the withdrawal from foreign locations or deinternationalization of universities, as late globalizing entitis. The paper discusses...... the range of constructs around the core idea of late globalization, generating questions for future work in a late globalization research program....

  19. Quaternary Fault and Fold Database of the United States

    U.S. Geological Survey, Department of the Interior — The Quaternary Fault and Fold Database contains the results of thousands of scientific assessments of faults and associated folds in the United States that...

  20. Quaternary phosphorites off the southeast coast of India

    Rao, V.P.; Michard, A.; Naqvi, S.W.A.; Boettcher, M.E.; Krishnaswamy, R.; Thamban, M.; Natarajan, R.; Borole, D.V.

    Detailed petrological, mineralogical, geochemical and radiogenic (U, Sr, Nd) and stable isotope (C, O, S) studies have been carried out on the Quaternary phosphorites of the continental margin off Chennai, southeast coast of India...

  1. Quaternary alluvial stratigraphy and palaeoclimatic reconstruction at the Thar margin

    Jain, M.; Tandon, S.K.


    Quaternary alluvial record at the Thar desert margin has been examined using the exposed succession along Mahudi, Sabarmati river, Western India. Different alluvial facies, their associations and granulometry have been studied for palaeoenvironmental reconstruction. Clay mineral indices smectite/...




    Full Text Available The objective of this study was to answer the following question: are quaternary ammonium antibacterials suitable for dental materials? Reviewing the literature on quaternary ammonium compounds evidenced that this type of compounds is soluble in water. Our own findings also showed that they are well soluble in water and that their application as dental composites requires to check their solubility level in water.

  3. A Quaternary Geomagnetic Instability Time Scale

    Singer, B. S.


    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought

  4. A kinematic model for the Plio-Quaternary evolution of the Tyrrhenian Apenninic system: implications for rifting processes and volcanism

    Turco, E.; Zuppetta, A.


    During the frontal accretion due to the Late Miocene-Quaternary thrusting, the interior of the Apenninic chain underwent large-scale extension which produced the opening of the Tyrrhenian Oceanic Basin, a back-arc basin in respect to the late Cenozoic Apenninic chain, and the onset of the Quaternary volcanic activity in the Campanian Plain and more generally in the Tyrrhenian area. To outline the space/time distribution and the geotectonic setting of the Tyrrhenian volcanics we approached the problem from a kinematic point of view. A synthesis of the available geological and geophysical data leads us to suggest that the progressive migration of the Apenninic Arcs is responsible for the extension phenomena which took place during the last 5 Ma. At first, the extension resulted from the kinematic interaction between the Northern Apenninic Arc and the Southern Apenninic Arc during the Late Pliocene. Then, from the Early Pleistocene the extension was controlled by the SE migration of the Southern arc only, and therefore it can be regarded as part of the general Southern Tyrrhenian extension phenomenon. Due to the intense thinning, the isotherms migrated upward very rapidly within the Toscana, Latium and Campania lithosphere where the melting point was reached, giving rise to the onset of volcanic activity at the end of the Early Pleistocene.

  5. Known and suggested quaternary faulting in the midcontinent United States

    Wheeler, R.L.; Crone, A.J.


    The midcontinent United States between the Appalachian and Rocky Mountains contains 40 known faults or other potentially tectonic features for which published geologic information shows or suggests Quaternary tectonic faulting. We report results of a systematic evaluation of published and other publicly available geologic evidence of Quaternary faulting. These results benefit seismic-hazard assessments by (1) providing some constraints on the recurrence intervals and magnitudes of large, prehistoric earthquakes, and (2) identifying features that warrant additional study. For some features, suggested Quaternary tectonic faulting has been disproved, whereas, for others, the suggested faulting remains questionable. Of the 40 features, nine have clear geologic evidence of Quaternary tectonic faulting associated with prehistoric earthquakes, and another six features have evidence of nontectonic origins. An additional 12 faults, uplifts, or historical seismic zones lack reported paleoseismological evidence of large. Quaternary earthquakes. The remaining 13 features require further paleoseismological study to determine if they have had Quaternary earthquakes that were larger than any known from local historical records; seven of these 13 features are in or near urbanized areas where their study could affect urban hazard estimates. These seven are: (1) the belt of normal faults that rings the Gulf of Mexico from Florida to Texas. (2) the Northeast Ohio seismic zone, (3) the Valmont and (4) Goodpasture faults of Colorado. (5) the Champlain lowlands normal faults of New York State and Vermont, and (6) the Lexington and (7) Kentucky River fault systems of eastern Kentucky. Published by Elsevier Science B.V.

  6. Mutagenicity of quaternary ammonium salts containing carbohydrate moieties

    Dmochowska, Barbara [Department of Carbohydrate Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Piosik, Jacek; Woziwodzka, Anna [Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk (Poland); Sikora, Karol; Wisniewski, Andrzej [Department of Carbohydrate Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Wegrzyn, Grzegorz, E-mail: [Department of Molecular Biology, University of Gdansk, Kladki 24, 80-822 Gdansk (Poland)


    Highlights: {yields} A series of quaternary ammonium salts containing carbohydrate moieties, with configuration D-galacto, D-gluco and D-manno, was synthesized and characterized. {yields} The quaternary ammonium salts containing carbohydrate moieties revealed potent mutagenic activities, as assessed by using the Vibrio harveyi bioluminescence mutagenicity test. {yields} The N-[2-(D-glycopyranosyloxy)ethyl]-N,N,N-trimethylaminium salts were of the highest activity in the mutagenicity assay. {yields} We suggest that quaternary ammonium salts may be more hazardous than previously supposed. - Abstract: Quaternary ammonium salts are widely used in industrial, agricultural, healthcare and domestic applications. They are believed to be safe compounds, with little or no health hazard to humans. However, in this report, we demonstrate that a series of newly synthesized quaternary ammonium salts containing carbohydrate moieties reveal potent mutagenic activities, as assessed by using the Vibrio harveyi bioluminescence mutagenicity test. D-Gluco- and D-galacto-derivatives were found to have a higher mutagenic potential than D-manno-derivatives. Among the former groups of compounds, the N-[2-(D-glycopyranosyloxy)ethyl]-N,N,N-trimethylaminium salts were of the highest activity in the mutagenicity assay. These results suggest that the safety of quaternary ammonium salts may be lower than previously supposed, indicating a need for testing such compounds for their mutagenicity.

  7. Interseismic Coupling, Quaternary Uplift Rates, and Fore arc Deformation Along the Costa Rican Segment of the Middle American Trench

    Sak, P. B.; Fisher, D. M.; Gardner, T. W.; La Femina, P.; Marshall, J. S.


    Late Quaternary uplift recorded by marine and fluvial terraces is broadly consistent with geodetically constrained measurements of locking across the Costa Rican segment of the Middle American Trench (MAT), implying potential linkages between rough crust subduction and seismogenesis. Fifty nine published and seven unpublished radiocarbon dated marine samples constrain variations in Late Quaternary surface uplift rates across a ~300 km long segment of the Pacific coast of Costa Rica between the central Nicoya Peninsula and the Osa Peninsula. All sixty six samples are analyzed using the most recent (IntCal04) calibration and recent sea level curves to constrain late Quaternary uplift rates. Regions characterized by the fastest (> 6 m k.y.-1) long-term uplift rates map to geodetically defined regions of elevated interseismic locking along the Nicoya and Osa Peninsulas. Kinematic analysis of > 40 mesoscale fault populations from along the Costa Rican fore arc provide additional evidence of long-term patterns of upper plate deformation. Mesoscale fault populations suggest that the fore arc can be subdivided into three domains that correlate to the geometry and morphology of the subducting plate. Across the Nicoya Peninsula, where the crust currently entering the MAT is smooth and the Benioff zone defines a steeply dipping slab, mesoscale fault populations are consistent with margin parallel extension and strike-slip motion. Along the central Pacific coast, steeply dipping northeast striking nodal planes accommodate differential uplift associated with ongoing seamount subduction. Further south, inboard of where the aseismic Cocos ridge is under thrust along a subhorizontal Benioff zone, mesoscale fault populations record active shortening related to an extensive thrust belt. Rates of vertical tectonism across the fore arc provide a first order estimate of elastic strain accumulation within the subjacent seismogenic zone. Permanent deformation and permanent shortening

  8. IODP Expeditions 303 and 306 Monitor Miocene- Quaternary Climate in the North Atlantic

    Carlos Alvarez-Zarikian


    Full Text Available Introduction The IODP Expeditions 303 and 306 drilling sites were chosen for two reasons: (1 to capture Miocene-Quaternary millennial-scale climate variability in sensitive regions at the mouth of the Labrador Sea and in the North Atlantic icerafted debris (IRD belt (Ruddiman et al., 1977, and (2 to provide the sedimentary and paleomagnetic attributes, including adequate sedimentation rates, for constructinghigh-resolution isotopic and magnetic stratigraphies.High accumulation rates, reaching 20 cm ky-1, permit the study of millennial-scale variations in climate and in the Earth's magnetic fi eld over the past several million years, when the amplitude and frequency of climate variability changed substantially. Shipboard logging and scanning data (magnetic susceptibility and remanence, density, natural gamma radiation, digital images and color refl ectance and post-expedition x-ray fl uorescence (XRF scanning datahave revealed that the sediment cores recovered on Expeditions 303 and 306 contain detailed histories of millennial-scale climate and geomagnetic fi eld variability throughout the late Miocene to Quaternary epochs. The climate proxies will be integrated with paleomagnetic data to place the records of millennial-scale climate change into a high resolution stratigraphy based on oxygen isotope andrelative paleomagnetic intensity (RPI. The paleomagnetic record of polarity reversals, excursions and RPI in these cores is central to the construction of the stratigraphic template and will provide detailed documentation of geomagnetic fi eld behavior.

  9. Active Faulting and Quaternary Landforms Deformation Related to the Nain Fault

    Abolghasem Gourabi


    Full Text Available Problem statement: Landforms developed across terrain defining boundary the Nain fault have imprints of recent tectonic activity in the west region of Central Iran. Depositional landforms such as alluvial fans bear signatures of later phases of tectonic activity in the form of faulting of alluvial fan deposits and development of fault traces and scarps within 100 km long and a NW-SE-trending zone, 1000-2000 m wide. Approach: We are addressing the neotectonic landforms based on detailed field work carried out in the Nain exposed active fault segments which brought forward some outstanding morphtectonic evidence of quaternary tectonically activities. Tectonic geomorphology applied to the Nain fault suggests recent subsurface activity along the Nain fault and an interconnecting faulting network of roughly NW-SE-trending, right-lateral, strike-slip segments and mostly NW-SE-oriented, transtensional to normal faults. Results: Evidence for recent activity is provided by faulted Pleistocene-Holocene deposits, fresh scarps in Late Quaternary deposits, 8-15 m lateral offsets locally affecting the drainage pattern of the area, ground creeping, aligning of series of spring faults, deflected streams and fault trace over recent alluvial fans. The existences of strike-slip faults system in the Nain area can be implications for seismic hazard. Conclusion: Motion along these structures suggests, in fact, that cumulative displacements include normal, transtensional and strike-slip components. Based on all evidence of active tectonics, earthquake risk and occurrence area is significant.

  10. A Quaternary Fault Database for Central Asia

    S. Mohadjer


    Full Text Available Earthquakes represent the highest risk in terms of potential loss of lives and economic damage for Central Asian countries. Knowledge of fault location and behavior is essential in calculating and mapping seismic hazard. Previous efforts in compiling fault information for Central Asia have generated a large amount of data that are published in limited-access journals with no digital maps publicly available, or are limited in their description of important fault parameters such as slip rates. This study builds on previous work by improving access to fault information through a web-based interactive map and an online database with search capabilities that allow users to organize data by different fields. The data presented in this compilation include fault location, its geographic, seismic and structural characteristics, short descriptions, narrative comments and references to peer-reviewed publications. The interactive map displays 1196 fault segments and 34 000 earthquake locations on a shaded-relief map. The online database contains attributes for 122 faults mentioned in the literature, with Quaternary and geodetic slip rates reported for 38 and 26 faults respectively, and earthquake history reported for 39 faults. This work has implications for seismic hazard studies in Central Asia as it summarizes important fault parameters, and can reduce earthquake risk by enhancing public access to information. It also allows scientists and hazard assessment teams to identify structures and regions where data gaps exist and future investigations are needed.

  11. A Quaternary Fault Database for Central Asia

    Mohadjer, S.; Ehlers, T. A.; Bendick, R.; Stübner, K.; Strube, T.


    Earthquakes represent the highest risk in terms of potential loss of lives and economic damage for Central Asian countries. Knowledge of fault location and behavior is essential in calculating and mapping seismic hazard. Previous efforts in compiling fault information for Central Asia have generated a large amount of data that are published in limited-access journals with no digital maps publicly available, or are limited in their description of important fault parameters such as slip rates. This study builds on previous work by improving access to fault information through a web-based interactive map and an online database with search capabilities that allow users to organize data by different fields. The data presented in this compilation include fault location, its geographic, seismic and structural characteristics, short descriptions, narrative comments and references to peer-reviewed publications. The interactive map displays 1196 fault segments and 34 000 earthquake locations on a shaded-relief map. The online database contains attributes for 122 faults mentioned in the literature, with Quaternary and geodetic slip rates reported for 38 and 26 faults respectively, and earthquake history reported for 39 faults. This work has implications for seismic hazard studies in Central Asia as it summarizes important fault parameters, and can reduce earthquake risk by enhancing public access to information. It also allows scientists and hazard assessment teams to identify structures and regions where data gaps exist and future investigations are needed.

  12. A Quaternary fault database for central Asia

    Mohadjer, Solmaz; Ehlers, Todd Alan; Bendick, Rebecca; Stübner, Konstanze; Strube, Timo


    Earthquakes represent the highest risk in terms of potential loss of lives and economic damage for central Asian countries. Knowledge of fault location and behavior is essential in calculating and mapping seismic hazard. Previous efforts in compiling fault information for central Asia have generated a large amount of data that are published in limited-access journals with no digital maps publicly available, or are limited in their description of important fault parameters such as slip rates. This study builds on previous work by improving access to fault information through a web-based interactive map and an online database with search capabilities that allow users to organize data by different fields. The data presented in this compilation include fault location, its geographic, seismic, and structural characteristics, short descriptions, narrative comments, and references to peer-reviewed publications. The interactive map displays 1196 fault traces and 34 000 earthquake locations on a shaded-relief map. The online database contains attributes for 123 faults mentioned in the literature, with Quaternary and geodetic slip rates reported for 38 and 26 faults respectively, and earthquake history reported for 39 faults. All data are accessible for viewing and download via This work has implications for seismic hazard studies in central Asia as it summarizes important fault parameters, and can reduce earthquake risk by enhancing public access to information. It also allows scientists and hazard assessment teams to identify structures and regions where data gaps exist and future investigations are needed.

  13. Paleovalley systems: Insights from Quaternary analogs and experiments

    Blum, M.; Martin, J.; Milliken, K.; Garvin, M.


    between the river mouth and the shelf margin likely occurs for different periods of time depending on gradient of the river and shelf, as well as amplitude of high-frequency sea-level changes. Late Quaternary analogs and experimental studies provide an alternative sequence-stratigraphic interpretation for paleovalley systems. In coastal-plain paleovalleys, basal valley-fill surfaces meet criteria for an unconformity and a classically-defined sequence boundary: however, this surface is mostly everywhere of the same age as overlying fluvial deposits, and does not correspond to a long period of incision and sediment bypass. In cross-shelf paleovalleys, the basal contact between fluvial and deltaic or shoreface deposits is commonly interpreted as a sequence boundary, but is not an unconformity characterized by incision and sediment bypass. Instead, this surface is a facies contact that separates genetically-related fluvial and deltaic strata: the surface that correlates to the basal valley-fill surface within the coastal-plain paleovalley dips below cross-shelf prograding deltaic and/or shoreface strata, which are fed by deposition within the evolving valley itself, and should be the downlap surface. Many issues deserve attention in the future. We have stressed understanding the inherent scales and physical processes that operate during the formation and evolution of paleovalley systems. We also suggest the relative roles of allogenic forcing vs. autogenic dynamics, and the potential significance of high-frequency isostatic adjustments should be topics for future discussion.

  14. Europe's Neogene and Quaternary lake gastropod diversity - a statistical approach

    Neubauer, Thomas A.; Georgopoulou, Elisavet; Harzhauser, Mathias; Mandic, Oleg; Kroh, Andreas


    During the Neogene Europe's geodynamic history gave rise to several long-lived lakes with conspicuous endemic radiations. However, such lacustrine systems are rare today as well as in the past compared to the enormous numbers of "normal" lakes. Most extant European lakes are mainly results of the Ice Ages and are due to their (geologically) temporary nature largely confined to the Pleistocene-Holocene. As glacial lakes are also geographically restricted to glacial regions (and their catchment areas) their preservation potential is fairly low. Also deposits of streams, springs, and groundwater, which today are inhabited by species-rich gastropod assemblages, are rarely preserved. Thus, the pre-Quaternary lacustrine record is biased towards long-lived systems, such as the Late Miocene Lake Pannon, the Early to Middle Miocene Dinaride Lake System, the Middle Miocene Lake Steinheim and several others. All these systems have been studied for more than 150 years concerning their mollusk inventories and the taxonomic literature is formidable. However, apart from few general overviews precise studies on the γ-diversities of the post-Oligocene European lake systems and the shifting biodiversity in European freshwater systems through space and time are entirely missing. Even for the modern faunas, literature on large-scale freshwater gastropod diversity in extant lakes is scarce and lacks a statistical approach. Our preliminary data suggest fundamental differences between modern and pre-Pleistocene freshwater biogeography in central Europe. A rather homogenous central European Pleistocene and Holocene lake fauna is contrasted by considerable provincialism during the early Middle Miocene. Aside from the ancient Dessaretes lakes of the Balkan Peninsula, Holocene lake faunas are dominated by planorbids and lymnaeids in species numbers. This composition differs considerably from many Miocene and Pliocene lake faunas, which comprise pyrgulid-, hydrobiid-, viviparid-, melanopsid

  15. South Texas Quaternary karst: Paleoclimatic implications

    Prouty, J.S. (Corpus Christi State Univ., TX (United States)); Lovejoy, D.W. (W. Palm Beach Atlantic Coll., FL (United States))


    A beachrock correlative with the Ingleside complex of the late Pleistocene Beaumont Formation crops out discontinuously along the mainland shore of Laguna Madre, extending approximately 10 km southward from Baffin Bay, Texas. Carbon-14 dating yields ages of 23, 430 to 33,390 yrs. B.P.; the beachrock formed along a Gulf shoreline in a zone of converging longshore currents during the last sea level highstand of the late Wisconsinan. The beachrock shows intense karstification. Vertical, steep-walled solution pipes penetrate the outcrops, and reddish-brown laminated caliche crusts coat outcrop surfaces and solution-pipe walls in many places. These karst features probably formed by subaerial exposure and weathering of the beachrock during the latest sea level lowstand. Today in semiarid South Texas, rainfall averages only 28 inches per year. Local features of late Pleistocene age include river gravels coarser than modern loads of those same rivers, and relict drainage networks far denser than modern ones. Such features indicate that during the late Pleistocene this region was more humid than now. Karst is typical of humid to subhumid climates, also suggesting that during karstification of the beachrock wetter climates prevailed.

  16. The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia

    Maddy, D.; Veldkamp, A.; Demir, T.; van Gorp, W.; Wijbrans, J. R.; van Hinsbergen, D. J. J.; Dekkers, M. J.; Schreve, D.; Schoorl, J. M.; Scaife, R.; Stemerdink, C.; van der Schriek, T.; Bridgland, D. R.; Aytaç, A. S.


    match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruptions and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lava-dammed lake drainage. Establishing a firm stratigraphy and geochronology for the Early Pleistocene archive provides a secure framework for future exploitation of this part of the archive and sets the standard as we begin our work on the Middle-Late Pleistocene sequence. We believe this work forms a benchmark study for detailed Quaternary research in Turkey.

  17. Quaternary geology of the Bellevue area in Blaine and Camas Counties, Idaho

    Schmidt, Dwight Lyman


    The Bellevue area covers about 350 square miles of a foothill belt between the Rocky Mountains to the north and the Snake River plains to the south. Complexly deformed impure quartzites and limestones of the Mississippian Milligen and Pennsylvanian-Permian Wood River formations were intruded by large bodies of quartz diorite and granodiorite along regional structures trending northwesterly; the intrusions are part of the Cretaceous Idaho batholith. Erosional remnants of the Challis volcanics, dominantly latitic to andesitic in composition and early(?) to middle Tertiary in age, rest unconformably on the older rocks. A sequence of Pliocene Rhyolitic ash flows and basaltic lava flows unconformably overlies the Challis and older rocks and is in turn unconformably overlain by olivine basalt of late Pliocene or early Quaternary age. The main valleys of the area, partly Erosional and partly structural in origin, are underlaind by late Quaternary olivine basalt flows (Snake River basalt) and intercalated lacustrine, fluvial, proglacial sediments. The Big Wood River, the master stream of the area, flows southward through a narrow steep-sided valley in the mountainous country north of the Bellevue area and debouches into a broad alluvial valley, the Wood River Valley, in the foothill belt. The valley has the shape of an isosceles triangle with a ten mile long, east-west base consisting of a ridge of Pliocene volcanics which separates the valley from the Snake River Plains to the south. The river now flows through a narrow gap in the southwest corner of the triangle. A similar, but wider, gap around the east end of the ridge was formerly occupied by the river. The river has been shifted back and forth between these two gaps at least four times during an interval in which six late Quaternary basalt flows erupted in the Bellevue area. Two of the flows caused direct diversion of the river and another was influential in bringing about a diversion on an aggradational fan upstream

  18. Abrupt response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa

    Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie


    Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth’s climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related climatic evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to abrupt hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region. PMID:28290474

  19. Soil development on Late Quaternary river terraces in a high montane valley in Bhutan, Eastern Himalayas

    Tshering Dorji,; Caspari, T.; Bäumler, R.; Veldkamp, A.; Jongmans, A.G.; Kado Tshering,; Tsheten Dorji,; Baillie, I.


    We examined the geochemistry and micromorphology of the soils on a suite of morphologically well-defined and visually distinct fluvial terraces, up to 40 m elevation above the current riverbed, at Thangbi in the upper Bumthang Valley, Bhutan. The alluvia forming each of the terraces are lithological

  20. Late Quaternary glaciation history of northernmost Greenland - Evidence of shelf-based ice

    Larsen, Nicolaj; Kjær, Kurt H.; Funder, Svend Visby;


    to retreat ca 16 ka to 10.3 cal ka BP before the final break-up, which took place ca 10.1 cal ka BP probably as a combined result of increased inflow of warm Atlantic water through the Fram Strait, a shallower halocline and higher summer temperatures, corresponding to orbital maximum solar insolation...... at this time. The existence of extensive shelf-based ice north of Greenland provides an important contribution to the understanding of the LGM glaciation history of the Arctic Ocean....

  1. Lake-System Response to Late Quaternary Environmental Dynamics on the northeastern Tibetan Plateau

    Diekmann, Bernhard; Hartmann, Kai; Herzschuh, Ulrike; Lehmkuhl, Frank; Mischke, Steffen; Stauch, Georg; Wünnemann, Bernd; Zhang, Yongshan


    Palaeoclimatic reconstructions in central China often rely on proxy information, obtained from single palaeoenvironmental archives at a distinct study site, such as lake sediments. Although they provide a high temporal resolution of information, their context within the acting depositional and geomorphological processes in a distinct landscape unit often is difficult to ascertain. The nature of lake systems strongly depends on catchment processes in addition to direct responses to climate forcing. In the scope of palaeoclimatic studies on the northern Tibetan Plateau and its foreland, we investigate the complex interaction of landscape evolution in response to monsoon dynamics. Our approach follows a source-to-sink approach along sediment cascades, to infer palaeoclimatic responses and to decipher internal non-climatic dynamics of the landscape system. Lake sediments represent the final and mostly complete sedimentary products, while adjacent landforms and offshore deposits provide insights into the spatial dimension of palaeoenvironmental change. The approach of concerted geomorphological and limnogeological research was successfully demonstrated at Lake Donggi Cona on the NE Tibetan Plateau at 4,090 m elevation. The 30 km long, 8 km wide, and 90 m deep lake occupies a pull-apart basin. Sub-bottom profiling revealed the presence of tectonic structures as well as subaquatic terraces and ancient fan systems from former low lake stands, draped by younger lake sediments. A prominent moraine arc in the vicinity of the lake can be attributed to a glacial advance during an early stage of the last glacial cycle. Several terrace levels and fossil lake sediments of early to mid-Holocene age around the lake shore document former stages of higher lake level of about 10 m above present level. In addition to alluvial processes, dunes and loess-like sediments in the catchment of the lake give evidence of differing stages in the intensity of aeolian sediment mobilisation or fixation. Lake development is documented by multi-proxy data in a series of sediment cores across the lake basin. The oldest recovered sediments, younger than 18 ka BP, comprise siliciclastic laminates and lateglacial saline shallow-lake sediments, overlying basal sands. The deposition of fine-grained marls and enhanced biological production characterized the deep lacustrine environment of the Holocene. A switch from a closed lake basin with brackish conditions towards an open oligotrophic fresh-water basin after 6.8 ka BP is indicated by ostracod assemblages and changes in carbonate chemistry. This change in hydrology likely was triggered by tectonic pulses along the Kunlun Fault, an area with severe earthquake activity. Pollen records exhibit climate signals and indicate moist conditions in the early Holocene. During the same time, loess sediments have been preserved from a period from 10.5 to 7.5 ka BP, related to the strengthening of the insolation-driven Asian summer monsoons. This time was characterized by wetter and warmer climate and supported the trapping of dust. A dry and cooler climate resulted in the reactivation of dune sands from 3 ka to present, possibly in combination with stronger human influence.

  2. Evidence of Late Quaternary seismicity from Yunam Tso, Lahaul and Spiti, NW Himalaya, India

    Archna Bohra; B S Kotlia; Amzad H Laskar; M G Yadava


    A relict fluvio-lacustrine sediment of an 8 m thick section exposed at Kilang Sarai along Yunam river, near Baralacha La shows presence of cycloids or pseudonodules, ball and pillow structures, flame-like and pocket structures, sand dyke injections, bed dislocation/faulting and flow folds. Within this section four deformed levels of soft sediment structures have been identified which were dated ca. 25 ka BP at level 1 (∼0.4 m from the modern river level (mrl), 20.1 ka BP at level 2 (∼1.8 m mrl), 17.7 ka BP at level 3 (∼2.56 m mrl) and 12.2 ka BP at level 4 (∼4.25 m mrl)). Detailed study of these soft sediment structures allow us to demonstrate that deformation level 3 is not related to seismic trigger, but remaining three deformation levels (1, 2 and 4) are ascribed to seismic origin. From compilation of earlier palaeoseismological studies using soft sediment deformational structures (SSDS) in the palaeolake deposits in the adjoining area, suggest that the deformational events identified in the present study are regional in nature and thus tectonic process plays an important role in the evolution of landform in the Spiti region.

  3. Species-specific responses of Late Quaternary megafauna to climate and humans

    Lorenzen, Eline D; Nogués-Bravo, David; Orlando, Ludovic


    the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human...... signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change....

  4. Full-Vector Geomagnetic Field Records for the Late Quaternary from El Hierro and the Eifel

    Monster, M.; de Groot, L. V.; Dekkers, M. J.; van Galen, J. P.; Kuiper, K.; Langemeijer, J.; Wiarda, L. R.


    Twenty-eight flows in the age range of c. 100 to c. 500 ka were sampled on the island of El Hierro (Canary Islands, Spain) and twelve in the Eifel (Germany). All sites from the Eifel had been previously dated, whereas the ages of the El Hierro flows were approximated by stratigraphic and directional coherency with a dated section c. 4 km to the north-east. Additionally, seven flows were dated using the ThermoFisher Helix multi-collector mass spectrometer at VU University Amsterdam (the Netherlands). The rocks were subjected to standard rock magnetic and palaeomagnetic experiments. Palaeodirections were obtained using both thermal and alternating-field demagnetisation techniques. Apart from two sites that appear to have been struck by lightning, all sites yielded reliable palaeodirections. Absolute palaeointensities were obtained using three different methods: IZZI-Thellier, the multispecimen protocol and the calibrated pseudo-Thellier technique. Nineteen sites from El Hierro and all twelve sites from the Eifel passed the selection criteria for one or more of these methods, with the pseudo-Thellier technique having the highest success rate (c. 35% for El Hierro and 55% for the Eifel). The palaeointensities obtained for El Hierro were mostly between 20 and 40 μT and for the Eifel between 20 and 50 μT, both with a tendency to be somewhat low compared to the present-day field of c. 39 μT and c. 49 μT, respectively. The pseudo-Thellier and multispecimen methods generally yielded lower palaeointensities than IZZI-Thellier, but no clear trend was visible.

  5. Seismic and sequence stratigraphy of the central western continental margin of India: late-Quaternary evolution

    Karisiddaiah, S.M.; Veerayya, M.; Vora, K.H.

    Seismic and sequence stratigraphic architecture of the central western continental margin of India (between Coondapur and south of Mangalore) has been investigated with shallow seismic data. Seismic stratigraphic analysis defined nine seismic units...

  6. Multiple ash layers in late Quaternary sediments from the Central Indian Basin

    Mascarenhas-Pereira, M.B.L.; Nath, B.N.; Iyer, S.D.; Borole, D.V.; Parthiban, G.; Jijin, R.; Khedekar, V.D.

    and dispersed shards. Rhyolitic glass shards of bubble wall, platy, angular and blocky types were retrieved from various stratigraphic horizons in the cores. The abundance of glass shards, composition of bulk sediments, and 230Thexcess ages of the host sediments...

  7. Late quaternary fluctuations in carbonate and carbonate ion content in the northern Indian ocean

    Naik, S.S.

    cores. Marine Isotpe Stages bounaies are markd with orizotal ines and MIS stage numbers are labeld. 8048926% CO3 0.1Age (Ma) 1345678910R24-16506708901 a30.20.1Age (Ma) 234567 8V30-4 405607809% CO3 0.4Age (Ma)12345 6V25-9 Chapter I... 506708901% CaO3 0.20.1Age(Ma)2345678910123415DSP-72 406801% aO3 0.60.4 0.2Age (Ma)2345678910123415RC-20 20460810% aO3 (Ma) 1345678910 2134516SDE 0 20460810% CaO3 0.60.4 0.2Age (ma)2345678910123415V28-79 20460810% CaO3 0.60.4 0.2Age...

  8. Changing sedimentary environment during the late Quaternary: Sedimentological and isotopic evidence from the distal Bengal Fan

    Kessarkar, P.M.; Rao, V.P.; Ahmad, S.M.; Patil, S.K.; AnilKumar, A.; AnilBabu, G.; Chakraborty, S.; SounderRajan, R.

    of the sediment was separated by settling velocity principle and or- iented clay slides were prepared by pipetting 1ml clay solution onto glass slides and allowing them to dry in air. The remaining clay sample (o2mm fraction) was dried, powdered and used for Sr... on duplicate analysis is as follows: Rb70.73ppm, Sr71.02ppm, Sm70.4ppm, Nd70.21ppm. The powdered o2mm fractions of the clay samples were digested with HF–HNO 3 acid mixture. The Sr and REE were then separated using columns packed with cation exchange resin...

  9. Lime muds and their genesis off-Northwestern India during the late Quaternary

    Rao, V.P.; AnilKumar, A.; Naqvi, S.W.A.; Chivas, A.R.; Sekar, B.; Kessarkar, P.M.

    millennial to cen- tennial carbonate cyclicity recorded in slope sediments of the Great Bahama Bank and its climatic implications; Sedimentology 52 161–181. Shinn E A, Steinen R P, Lidz B H and Swart P K 1989 Whitings: A sedimentological dilemma; J. Sedim...

  10. Late Quaternary changes in depositional processes along the western margin of the Indus Fan

    Govil, P.; Naidu, P.D.

    Malvern laser particle size analyser (Master-Sizer 2000). Size classification is according to the Wentworth scale (Folk 1968). Calcium carbonate contents were estimated by using the gasometric technique. Aluminium (Al) and titanium (Ti) were analysed... mbsf, the reconstructed chronology being based on the isotope stage boundaries up to 11 described in Bassinot et al. (1994). Oxygen isotopic analyses were not carried out below 18 mbsf, due to insufficient number of Foraminifera specimens. Therefore...

  11. Late Quaternary seismic sequence stratigraphy of the Gulf of Kachchh, northwest of India

    Michael, L.; Rao, D.G.; Krishna, K.S.; Vora, K.H.

    along the northwest coast of India), lies between the mainland of Kachchh in the north and the Saurashtra/Kathiawar peninsula in the south and is open to the Arabian Sea in the west (Figure 1). The nonhostile conditions, high 3-6 knots tidal currents... (Figure 2) and the macrotidal (semidiurnal with ~ 6 m maximum wave heights) regime of the gulf are unfavourable for conducting any underwater investigations in the area, and thus understanding of the geologic structure and origin of the gulf is elusive...

  12. Late-Quaternary biogeographic scenarios for the brown bear ( Ursus arctos), a wild mammal model species

    Davison, John; Ho, Simon Y. W.; Bray, Sarah C.; Korsten, Marju; Tammeleht, Egle; Hindrikson, Maris; Østbye, Kjartan; Østbye, Eivind; Lauritzen, Stein-Erik; Austin, Jeremy; Cooper, Alan; Saarma, Urmas


    This review provides an up-to-date synthesis of the matrilineal phylogeography of a uniquely well-studied Holarctic mammal, the brown bear. We extend current knowledge by presenting a DNA sequence derived from one of the earliest known fossils of a polar bear (dated to 115 000 years before present), a species that shares a paraphyletic mitochondrial association with brown bears. A molecular clock analysis of 140 mitochondrial DNA sequences, including our new polar bear sequence, provides novel insights into the times of origin for different brown bear clades. We propose a number of regional biogeographic scenarios based on genetic data, divergence time estimates and paleontological records. The case of the brown bear provides an example for researchers working with less well-studied taxa: it shows clearly that phylogeographic models based on patterns of modern genetic variation alone can be substantially improved by including data on historical patterns of genetic diversity in the form of ancient DNA sequences derived from accurately dated samples and by using an approach to divergence-time estimation that suits the data under analysis. Using such approaches it has been possible to (i) establish that the processes shaping modern genetic diversity in brown bears acted recently, within the last three glacial cycles; (ii) distinguish among hypotheses concerning species' responses to climatic oscillations in accordance with the lack of phylogeographic structure that existed in brown bears prior to the last glacial maximum (LGM); (iii) reassess theories linking monophyletic brown bear populations to particular LGM refuge areas; and (iv) identify vicariance events and track analogous patterns of migration by brown bears out of Eurasia to North America and Japan.

  13. Late Quaternary glaciation history of northernmost Greenland - Evidence of shelf-based ice

    Larsen, Nicolaj Krog; Kjær, Kurt H; Funder, Svend


    to retreat ca 16 ka to 10.3 cal ka BP before the final break-up, which took place ca 10.1 cal ka BP probably as a combined result of increased inflow of warm Atlantic water through the Fram Strait, a shallower halocline and higher summer temperatures, corresponding to orbital maximum solar insolation...

  14. Ocean dominated expansion and contraction of the late Quaternary tropical rainbelt.

    Singarayer, Joy S; Valdes, Paul J; Roberts, William H G


    The latitude of the tropical rainbelt oscillates seasonally but has also varied on millennial time-scales in response to changes in the seasonal distribution of insolation due to Earth's orbital configuration, as well as climate change initiated at high latitudes. Interpretations of palaeoclimate proxy archives often suggest hemispherically coherent variations, some proposing meridional shifts in global rainbelt position and the 'global monsoon', while others propose interhemispherically symmetric expansion and contraction. Here, we use a unique set of climate model simulations of the last glacial cycle (120 kyr), that compares well against a compilation of precipitation proxy data, to demonstrate that while asymmetric extratropical forcings (icesheets, freshwater hosing) generally produce meridional shifts in the zonal mean rainbelt, orbital variations produce expansion/contractions in terms of the global zonal mean. This is primarily a dynamic response of the rainbelt over the oceans to regional interhemispheric temperature gradients, which is opposite to the largely local thermodynamic terrestrial response to insolation. The mode of rainbelt variation is regionally variable, depending on surface type (land or ocean) and surrounding continental configuration. This makes interpretation of precipitation-proxy records as large-scale rainbelt movement challenging, requiring regional or global data syntheses.

  15. Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere.

    Vandergoes, Marcus J; Newnham, Rewi M; Preusser, Frank; Hendy, Chris H; Lowell, Thomas V; Fitzsimons, Sean J; Hogg, Alan G; Kasper, Haino Uwe; Schlüchter, Christian


    In agreement with the Milankovitch orbital forcing hypothesis it is often assumed that glacial-interglacial climate transitions occurred synchronously in the Northern and Southern hemispheres of the Earth. It is difficult to test this assumption, because of the paucity of long, continuous climate records from the Southern Hemisphere that have not been dated by tuning them to the presumed Northern Hemisphere signals. Here we present an independently dated terrestrial pollen record from a peat bog on South Island, New Zealand, to investigate global and local factors in Southern Hemisphere climate changes during the last two glacial-interglacial cycles. Our record largely corroborates the Milankovitch model of orbital forcing but also exhibits some differences: in particular, an earlier onset and longer duration of the Last Glacial Maximum. Our results suggest that Southern Hemisphere insolation may have been responsible for these differences in timing. Our findings question the validity of applying orbital tuning to Southern Hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change.

  16. Cytherellid species (Ostracoda) and their significance to the Late Quaternary events in the Santos Basin, Brazil

    Bergue, C.T.; Coimbra, J.C.; Cronin, T. M.


    Four autochthonous cytherellid species (Cytherella serratula (BRADY, 1880), C. hermargentina WHATLEY et al. 1998, C. pleistocenica sp. nov. and C. santosensis sp. nov.) have been identified from two offshore cores (44 samples) within the Santos Basin. The distribution of these ostracodes is controlled by local hydrological conditions such as the temperature and, possibly, the oxygen minimum zone (OMZ). However, these factors cannot explain completely the species occurrence in the analysed cores, and relative sea level changes and productivity variation driven by climatic changes are proposed as additional explanations for the faunal distribution pattern. ?? E. Schweizerbart'sche Verlagsbuchhandlung (Na??gele u. Obermiller), 2007.

  17. Lime muds and their genesis off-Northwestern India during the late Quaternary

    V Purnachandra Rao; A Anil Kumar; S W A Naqvi; Allan R Chivas; B Sekar; Pratima M Kessarkar


    Two sediment types were found in five gravity cores collected from water depths between 56 m and 121 m along the northwestern continental margin of India: lime muds were abundant in the lower section while siliciclastic sediments dominated the upper section. Lime mud-dominated sediments in shelf cores contained 60%–75% carbonate, 0.3%–0.6% Sr and terrigenous minerals, whereas those at the shelf break were found to have < 90% carbonate, 0.6%–0.8% Sr and traces of terrigenous minerals. Aragonite needles showing blunt edges, jointed needles and needles wrapped in smooth aragonite cement were found to be common. Stable (O and C) isotopes of lime mud indicate a potentially freshwater contribution for shelf cores and purely marine contribution for those at the shelf break. Calibrated radiocarbon ages of the lime muds ranged from 17.6–11.9 ka in different cores. The results reported here suggest that the lime muds in the shallow shelf are probably reworked from the Gulf of Kachchh, whereas those at the shelf break were biodetrital, initially formed on the carbonate platform during low stands of sea level and then exported. The change in lime mud-dominated to siliciclastic-dominated sediments in the cores may be due to climate change and rapid rise in sea level during the early Holocene.

  18. Influence of monsoon upwelling on the planktonic foraminifera off Oman during Late Quaternary

    Naidu, P.D.

    foraminifer species mass accumulation rates (flux), coiling direction, test size and isotopic values primarily based on the results from the Ocean Drilling Program (ODP) Site 723A (18°03N, 57°37E, water depth 808m) from the Oman Margin, Arabian Sea... Drilling Program (ODP) Site 723A from the Oman Margin, Arabian Sea. Neogloboquadrina pachyderma Fluctuations of the sinistral morphotype fluxes of Neogloboquadrina pachyderma follow closely the variation in the upwelling index in being higher...

  19. Late Quaternary upper-water column structure in upwelling areas of the South China Sea


    Based on a quantitative analysis of planktonic foraminifera in two gravity cores (17928 and 17954), the history of the upper-water structure of the eastern and western slopes of the South China Sea (SCS) over the last 220 Ka was reconstructed using the transfer function technique. Our results show that lower sea surface temperature (SST) and shallower depth of thermocline (DOT) exist at Core 17928, off Luzon, in the glacial periods; on the contrary, the same situation turned up in the interglacial at Core 17954, off Vietnam. These changes of the upper-water column structure in the two areas are induced by coastal upwelling, which in turn is driven by monsoons, namely, winter monsoon leads to upwelling at the eastern slope, and summer monsoon gives birth to upwelling on the western slope. Moreover, the intensity of upwellings is also closely related to the evolution of the East Asian monsoon. Therefore, we assume that the changes of the upwelling in the two sites indicate strengthenning of winter and su mmer monsoon during the glacial and interglacial periods, respectively.

  20. Late Quaternary glacier sensitivity to temperature and precipitation distribution in the Southern Alps of New Zealand

    Ann V. Rowan; Simon H. Brocklehurst; David M. Schultz; Mitchell A. Plummer; Leif S. Anderson; Neil F. Glasser


    Glaciers respond to climate variations and leave geomorphic evidence that represents an important terrestrial paleoclimate record. However, the accuracy of paleoclimate reconstructions from glacial geology is limited by the challenge of representing mountain meteorology in numerical models. Precipitation is usually treated in a simple manner and yet represents difficult-to-characterize variables such as amount, distribution, and phase. Furthermore, precipitation distributions during a glacial probably differed from present-day interglacial patterns. We applied two models to investigate glacier sensitivity to temperature and precipitation in the eastern Southern Alps of New Zealand. A 2-D model was used to quantify variations in the length of the reconstructed glaciers resulting from plausible precipitation distributions compared to variations in length resulting from change in mean annual air temperature and precipitation amount. A 1-D model was used to quantify variations in length resulting from interannual climate variability. Assuming that present-day interglacial values represent precipitation distributions during the last glacial, a range of plausible present-day precipitation distributions resulted in uncertainty in the Last Glacial Maximum length of the Pukaki Glacier of 17.1?km (24%) and the Rakaia Glacier of 9.3?km (25%), corresponding to a 0.5°C difference in temperature. Smaller changes in glacier length resulted from a 50% decrease in precipitation amount from present-day values (-14% and -18%) and from a 50% increase in precipitation amount (5% and 9%). Our results demonstrate that precipitation distribution can produce considerable variation in simulated glacier extents and that reconstructions of paleoglaciers should include this uncertainty.

  1. Late Quaternary development of the Storfjorden and Kveithola Trough Mouth Fans, northwestern Barents Sea

    Llopart, Jaume; Urgeles, Roger; Camerlenghi, Angelo; Lucchi, Renata; Rebesco, Michele


    The development of two Arctic Trough Mouth Fans (TMFs), the Storfjorden and Kveithola TMFs, is investigated by means of sub-bottom and seismic reflection profiles, multibeam bathymetry and sediment samples allowing their detailed stratigraphic architecture to be defined. We find that the TMFs mainly consist of an alternation of rapidly deposited glacigenic debris flows during glacial maxima and a sequence of well-layered plumites and hemipelagic sediments, which were mainly deposited during the deglaciation phase of the adjacent glacial trough. We have identified eight units above regional reflector R1, which indicate that the ice sheet reached the shelf edge within the Storfjorden Trough on at least three occasions during the last ~200 ka. A shallow subsurface unit of glacigenic debris flows suggests that the ice sheet had a short re-advance over the northern and central part of Storfjorden after the Last Glacial Maximum. From stratigraphy, core and literature data, we estimate that ice sheets reached the shelf edge between 19.5 to 22.5 ka, 61 to 65 ka and 135 to 167 ka. Detailed seismic imaging allows us to refine the sedimentary model of Arctic TMFs. The main differences to previous models involve gully formation during not only the deglaciation phase, but also during interglacials by dense shelf water cascading, and a specific timing for the occurrence of slope failures (i.e., shortly after the deglaciation phase). High mean sedimentation rates during glacial maxima of up to 18 kg m-2 yr-1 likely allow excess pore pressure to develop in the water rich plumites and hemipelagic sediments deposited in the previous deglacial period, particularly where such plumites attain a significant thickness. The position of the submarine landslides in the stratigraphic record suggest that such excess pore pressure is not enough to trigger the slope failures and suggests that earthquakes related to isostatic rebound are likely involved in the final activation.

  2. Dynamics of Late Quaternary sapropel periods documented by micropaleontological and sedimentological data from North Aegean Sea

    Gkaniatsa, Georgia; Kontakiotis, George; Antonarakou, Assimina; Drinia, Hara; Anastasakis, George


    Located at the interface of the mid/high latitude climate system and affected by the North Atlantic Oscillation and the monsoonal system over Africa, the Mediterranean Sea has a unique potential to record the occurrence and phasing of climatic changes in both systems. In particular, the eastern Mediterranean Sea is more sensitive and faster responding to external forcing than the open ocean due to smaller size and partial isolation. A manifestation of the high sensitivity of the eastern Mediterranean sedimentary environment to climatic forcing is the periodic deposition of dark colored and organic matter rich sediments, termed "sapropels". In particular their formation is closely correlated with the reduction in ventilation, due to low salinity surface water layer, leading to anoxia at the bottom and preservation of organic matter, and/or the increase in primary productivity in the photic zone. To address which factor is more responsible for the sapropel's formation, a high-resolution study of planktonic foraminiferal abundances in two cores from North Aegean was carried out. Their response reflects the essential information about the paleoceanographic evolution in the water column in terms of stratification and productivity during the different sapropel events covering the last 90 kyrs. Cores M 22-67 and M22-68 were recovered from the water depths of 175 and 305 m respectively in the Chios Basin (North Aegean Sea). Both cores approximately span the last 90 ka, exposing the most recent S1 and the older S3 sapropels. They particularly exposed at very high resolution compared to most occurrences throughout the eastern Mediterranean, because of the highest sediment accumulation rates occurred in the study basin. Application of this information to the study hemipelagic sediment cores, through the planktonic foraminiferal analyses, suggests that we further contribute to existing evidence of climatic instability during sapropel deposition in eastern Mediterranean Sea. Moreover, using sedimentological observations, we aim to determine the dynamics of sediment delivery, redox conditions and preservation during the formation of these sapropel events.

  3. The lost Adventure Archipelago (Sicilian Channel, Mediterranean Sea): Morpho-bathymetry and Late Quaternary palaeogeographic evolution

    Civile, Dario; Lodolo, Emanuele; Zecchin, Massimo; Ben-Avraham, Zvi; Baradello, Luca; Accettella, Daniela; Cova, Andrea; Caffau, Mauro


    The rise in sea level following the Last Glacial Maximum (LGM) radically altered pre-existing geography, pushing back the former shorelines. The effect of this eustatic change was particularly intense and dramatic in flat lands and shelves, such as the Sicilian Channel. High-resolution bathymetric maps and Chirp seismic profiles analyzed in this study show that the Sicilian Channel, now lying at depths rarely exceeding 150 m, has emerged several times during its geological history. The last emergence was during the Early Holocene, when kilometre-sized islands punctuated the north-western sector of the Sicilian Channel, the Adventure Plateau, forming a broad archipelago. Many of these islands, now located in water ranging in depth from - 10 to - 40 m, are composed of highly deformed Neogene sedimentary rocks (Talbot, Ante-Talbot, Nereo, and Pantelleria Vecchia banks), while others represent submarine Pleistocene volcanic edifices (Galatea, Anfitrite and Tetide banks). Sedimentary cover in all of these banks is virtually absent. High-resolution seismic profiles allowed the identification of post-LGM morphological markers associated with the marine transgression, some of which are characterized by melt water-pulses, as demonstrated by the presence of specific and distinct erosional features. Combining swath bathymetric data with the seismic profiles, we have generated two palaeogeographic maps of the former Adventure Archipelago at two specific time frames: (1) at the end of the Younger Dryas stadial (11,500 yr B.P., corresponding to a former sea level of - 60 m), and (2) at the end of the melt-water pulse 1B (11,200 yr B.P., corresponding to a former sea level of - 42 m). Maps clearly show that in just 300 years the geography of the archipelago has changed dramatically, so much so that some islands have disappeared and some have decreased by more than 80% of their pre-Younger Dryas size.

  4. Late quaternary variability of the Arabian Sea monsoon and oxygen minimum zone

    Reichart, Gert-Jan


    The Monsoon Among the first Europeans observing the Asiatic monsoon was Alexander the Great during his campaign to the mouth of the Indus (325 B.C.). The oldest known records of the Arabian Sea monsoonal climate, however, are shipping documents, dated about 2300 B.C., which refer to the use of the s

  5. Late quaternary climate, precipitation δ18O, and Indian monsoon variations over the Tibetan Plateau

    Li, Jingmin; Ehlers, Todd A.; Werner, Martin; Mutz, Sebastian G.; Steger, Christian; Paeth, Heiko


    The Himalaya-Tibet orogen contains one of the largest modern topographic and climate gradients on Earth. Proxy data from the region provide a basis for understanding Tibetan Plateau paleo climate and paleo elevation reconstructions. Paleo climate model comparisons to proxy data compliment sparsely located data and can improve climate reconstructions. This study investigates temporal changes in precipitation, temperature and precipitation δ18O (δO18p) over the Himalaya-Tibet from the Last Glacial Maximum (LGM) to present. We conduct a series of atmospheric General Circulation Model (GCM, ECHAM5-wiso) experiments at discrete time slices including a Pre-industrial (PI, Pre-1850 AD), Mid Holocene (MH, 6 ka BP) and LGM (21 ka BP) simulations. Model predictions are compared with existing proxy records. Model results show muted climate changes across the plateau during the MH and larger changes occurring during the LGM. During the LGM surface temperatures are ∼ 2.0- 4.0 °C lower across the Himalaya and Tibet, and >5.0 °C lower at the northwest and northeast edge of the Tibetan Plateau. LGM mean annual precipitation is 200-600 mm/yr lower over on the Tibetan Plateau. Model and proxy data comparison shows a good agreement for the LGM, but large differences for the MH. Large differences are also present between MH proxy studies near each other. The precipitation weighted annual mean δ18Op lapse rate at the Himalaya is about 0.4 ‰ /km larger during the MH and 0.2 ‰ /km smaller during the LGM than during the PI. Finally, rainfall associated with the continental Indian monsoon (between 70°E-110°E and 10°N-30°N) is about 44% less in the LGM than during PI times. The LGM monsoon period is about one month shorter than in PI times. Taken together, these results document significant spatial and temporal changes in temperature, precipitation, and δ18Op over the last ∼21 ka. These changes are large enough to impact interpretations of proxy data and the intensity of the Indian monsoon.

  6. Abrupt response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa

    Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie


    Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth’s climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related climatic evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to abrupt hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region.

  7. Abundance and size variation of Globorotalia menardii in the Northeastern Indian Ocean during the Late Quaternary

    Bhonsale, S.; Saraswat, R.

    . 3). The radiocarbon dates for the upper portion of the cores were obtained from Leibniz Labor für Altersbestimmung und Isotopenforschung, Christian-Albrechts-Universität, Kiel. The radiocarbon dates were calibrated using CalPal version quickcal...

  8. Geochemical characteristics of late Quaternary sediments from the southern Aegean Sea (Eastern Mediterranean)



    Ten cores from the southern Aegean Sea have been logged for their lithological composition and seventy-three sub-samples were analysed for the determination of major and trace elements concentrations. Four lithological units were identified, namely, mud, volcanic, turbidite and sapropel. On the basis of the “Z-2” Minoan ash layer radiocarbon age sedimentation rates for the southern Aegean Sea were estimated at 3.26 to 4.15 cm kyr -1. Simple correlation analysis revealed three groups of elemen...

  9. Late Quaternary palaeoenvironmental reconstruction from Lakes Ohrid and Prespa (Macedonia/Albania border using stable isotopes

    M. J. Leng


    Full Text Available Here we present stable isotope data from three sediment records from lakes that lie along the Macedonian-Albanian border (Lake Prespa: 1 core, and Lake Ohrid: 2 cores. The records only overlap for the last 40 kyr, although the longest record contains the MIS 5/6 transition (Lake Ohrid. The sedimentary characteristics of both lakes differ significantly between the glacial and interglacial phases. At the end of MIS 6 Lake Ohrid's water level was low (high δ18Ocalcite and, although productivity was increasing (high calcite content, the carbon supply was mainly from inorganic catchment rock sources (high δ13Ccarb. During the last interglacial, calcite and TOC production and preservation increased, progressively lower δ18Ocalcite suggest increase in humidity and lake levels till around 115 ka. During ca. 80 ka to 11 ka the lake records suggest cold conditions as indicated by negligible calcite precipitation and low organic matter content. In Lake Ohrid δ13Corg are complacent, in contrast Lake Prespa shows consistently higher δ13Corg suggesting a low oxidation of 13C-depleted organic matter in agreement with a general deterioration of climate conditions during the glacial. From 15 ka to the onset of the Holocene, calcite and TOC begin to increase, suggesting lake levels were probably low (high δ18Ocalcite. In the Holocene (11 ka to present enhanced productivity is manifested by high calcite and organic matter content. All three cores show an early Holocene characterised by low δ18Ocalcite, apart from the very early Holocene phase in Prespa where the lowest δ18Ocalcite occurs at ca. 7.5 ka, suggesting a phase of higher lake level only in (the more sensitive Lake Prespa. From 6 ka δ18Ocalcite suggest progressive aridification, in agreement with many other records in the Mediterranean, although the uppermost sediments in one core records low δ18Ocalcite which we interpret as a result of human activity. Overall, the isotope data present here confirm that these two big lakes have captured the large scale, low frequency palaeoclimate variation that is seen in Mediterranean lakes, although in detail there is much palaeoclimate information that could be gained, especially small scale, high frequency differences between this region and the Mediterranean.

  10. Late Quaternary climatic history of NW Romania: results from Th/U dating of speleothems

    Tudor TĂMAȘ


    Full Text Available Speleothems are secondary minerals that precipitate in caves, most commonly as stalagmites, stalactites and flowstones. They are primarily composed of calcium carbonate, precipitated by slow degassing of carbon dioxide from supersaturated waters entering the cave gallery. Trace elements may be transported in solution and co-precipitated in calcite. One of these, uranium, when in concentration that exceeds 0.01 ppm allows precise age determination by U-series dating methods. Speleothem growth is a sensitive indicator of both temperature and humidity, and changes in either one or both of these can cause periods of enhanced or reduced growth. Furthermore, the worldwide karst landscape distribution and the study of speleothems growth interval enable regional chronologies to be drawn up. Uranium concentration in speleothems depends on several factors: uranium content of the host rock, residence time in the underground water, HCO3- availability etc., and thus is highly variable from one speleothem to another or even in the same speleothem

  11. Late Quaternary relative sea-level changes and vertical movements at Lipari (Aeolian Islands)

    Calanchi, N.; Lucchi, F.; Pirazzoli, P. A.; Romagnoli, C.; Tranne, C. A.; Radtke, U.; Reyss, J. L.; Rossi, P. L.


    Indicators of former sea-levels are recognised on the emergent portion of Lipari, Aeolian Islands. They correlate with three raised shorelines, located at elevations of 43-45 m above present sea-level (I), 23-27 m (II) and about 12 m (III). According to stratigraphical constraints, these shorelines correlate with the sea-level highstands corresponding to marine oxygen isotope substages 5e (124 ka), 5c (100 ka) and 5a (81 ka), respectively. The correlation of the shoreline I with substage 5e is supported by a U/Th age (119 +/- 6 ka) obtained from corals. Chronological and height data relevant to the fossil shorelines indicate that Lipari was affected by uplift with an average rate of 0.34 mm yr-1 during the past 125 ka. This uplift rate accords with the average uplift rates obtained, during the same time period, from the nearby islands of Filicudi (0.31 mm yr-1) and Salina (0.36 mm yr-1). Combined, these data suggest a similar uplift trend related to regional tectonic processes.In contrast to the long-term uplift, a localised submergence trend, documented especially for the last century, affects the eastern coast of Lipari. This subsidence is related to neo- and/or volcano-tectonic processes.

  12. Late