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Sample records for late quaternary glaciation

  1. Late Quaternary glaciation in the Kyrgyz Tien Shan

    NASA Astrophysics Data System (ADS)

    Koppes, Michéle; Gillespie, Alan R.; Burke, Raymond M.; Thompson, Stephen C.; Stone, John

    2008-04-01

    The Tien Shan of Kyrgyzstan contains multiple moraines and drift from late Quaternary glaciations. The spatial/temporal distribution of the glaciers inferred from the moraines suggests that the main factor controlling glacier advance here was the availability of moisture. The dominant modern climatic signatures in northern Central Asia include orographic thunderstorms in summer, cold and dry Siberian high-pressure cells in winter, and westerly cyclonic storms from the North Atlantic and eastern Mediterranean in spring and fall. Changes in any of these systems during the late Quaternary would have varied precipitation delivery to, and glacier growth in the Kyrgyz Tien Shan. Geomorphic mapping and reconnaissance-level 10Be cosmic-ray exposure dating of moraine sequences in six drainages indicate that there were multiple "maximum" advances of similar extents and equilibrium-line depressions across the range. Glaciers in the north and east of the Kyrgyz Tien Shan last advanced to their maximum positions during marine oxygen isotope stage (MIS) 5 and again during MIS 4, while in the south and west of the range advance occurred during MIS 3. In contrast to maritime Europe and North America, there is no evidence of a major glacial advance during MIS 2. Glacier advances during MIS 2 and since were restricted to the vicinity of modern glaciers, allowing the older glacial record to be preserved well.

  2. Minimal erosion of Arctic alpine topography during late Quaternary glaciation

    NASA Astrophysics Data System (ADS)

    Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne

    2015-10-01

    The alpine topography observed in many mountainous regions is thought to have formed during repeated glaciations of the Quaternary period. Before this time, landscapes had much less relief. However, the spatial patterns and rates of Quaternary exhumation at high latitudes--where cold-based glaciers may protect rather than erode landscapes--are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5° N) using analyses of 10Be and 26Al concentrations. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley, which suggests that both mountain summits and low-elevation landscapes experienced very low erosion rates over the past million years. Our findings support the establishment of northwestern Svalbard’s alpine topography during the early Quaternary. We suggest that, as the Quaternary ice age progressed, glacial erosion in the Arctic became inefficient and confined to ice streams, and high-relief alpine landscapes were preserved by minimally erosive glacier armour.

  3. Styles of glaciation on Kilimanjaro, Tanzania, in response to late Quaternary climate change

    NASA Astrophysics Data System (ADS)

    Boston, Clare; Lovell, Harold; Mills, Stephanie; Cullen, Nicolas; Sirguey, Pascal

    2016-04-01

    The recognition of geomorphological evidence for more extensive ice masses in a number of areas near the equator provides a direct link to climate change in the tropics. Kilimanjaro in Tanzania consists of the highest elevations in Africa, and sets of moraines document that ice was significantly more extensive in the past. The most extensive moraines around Kibo, the highest peak, suggest that glaciers may have extended down to around 3800 m at the Last Glacial Maximum (LGM). A more recent set of moraines, at 4600-4800 m on the western side of the peak, document the maximum position that ice reached during the Little Ice Age (LIA). Both of these sets of moraines indicate significant recession has occurred throughout the late Quaternary, and particularly during the 20th century. Present-day ice is restricted to rapidly-receding glaciers and icefields on the uppermost flanks and summit of Kibo, between ~5000-5800 m. The area is therefore important for understanding the timing, magnitude and style of glacier response to changes in climate in the tropics in the late Quaternary. This research presents the results of new field and remotely-sensed mapping of moraines relating to the Late Pleistocene and LIA, providing greater detail on the glacial geomorphology of the area than in previous mapping. This allows an assessment of the styles of glaciation, and particularly the role of topography and aspect on influencing response to climate and patterns of glacier recession.

  4. Chronology of late Quaternary glaciation and landform evolution in the upper Dhauliganga valley, (Trans Himalaya), Uttarakhand, India

    NASA Astrophysics Data System (ADS)

    Bisht, Pinkey; Ali, S. Nawaz; Shukla, Anil D.; Negi, Sunil; Sundriyal, Y. P.; Yadava, M. G.; Juyal, Navin

    2015-12-01

    Detailed field mapping of glacial and paraglacial landforms supported by optical and radiocarbon dating is used to reconstruct the history of late Quaternary glaciation and landform evolution in the Trans Himalayan region of the upper Dhauliganga valley. The study identifies four events of glaciations with decreasing magnitude which are termed as Purvi Kamet Stage -Ia (PKS-Ia), PKS-Ib, PKS-II, PKS-III and PKS-IV respectively. The oldest PKS-Ia and Ib are assigned the Marine Isotopic Stgae-3 (MIS-3), the PKS-II to the Last Glacial Maximum (MIS-2), PKS-III dated to 7.9 ± 0.7 ka, and the PKS-IV is dated to 3.4 ± 0.3 ka and 1.9 ± 0.2 ka respectively. The largest valley glaciations viz. the (PKS-Ia) occurred during the strengthened summer monsoon corresponding to the MIS-3, following this, the recessional moraines (PKS-Ib) represent the gradual decline in summer monsoon towards the later part of MIS-3. The valley responded to the global Last Glacial Maximum (LGM), which is represented by the PKS-II moraine implying the influence of strengthened mid-latitude westerlies during the LGM. The post-LGM deglaciation was associated with the onset of summer monsoon and is represented by the deposition of four distinct outwash gravel terraces. The early Holocene PKS-III glaciation occurred around 7.9 ± 0.7 ka and broadly coincides with the early Holocene cooling event (8.2 ka). This was followed by the deposition of stratified scree deposits and the alluvial fan (between 5.5 ka and 3 ka) during the mid to late Holocene aridity. This was followed by marginal re-advancement of the valley glacier (viz. PKS-IV) during the late Holocene cool and moist climate. Although glaciers respond to a combination of temperature and precipitation changes, however during the Holocene it seems that temperature played a major role in driving the glaciation.

  5. Chronology and climatic implications of Late Quaternary glaciations in the Goriganga valley, central Himalaya, India

    NASA Astrophysics Data System (ADS)

    Nawaz Ali, S.; Biswas, R. H.; Shukla, A. D.; Juyal, N.

    2013-08-01

    Goriganga valley, which is located in the transition zone between the dry steppe of the Tibetan plateau in the north and the sub-humid Himalayan climate in the south, has preserved four events of glaciation with decreasing magnitude. The oldest Stage-I glaciation is represented by a ˜12.5 km long discontinuous diamictite ridge which terminates north of Rilkot (˜3100 m asl). The Stage-II glaciation is represented by sub-rounded and partially eroded lateral moraines and terminates around Martoli village (˜3240 m asl). The Stage-III and IV glacial moraines are sharp crested, unstable and terminate proximal to the present day glacier at ˜3640 m asl and ˜3740 m asl respectively. The Stage-II moraines have been optically dated between 25 ± 2 ka and 22 ± 1 ka implying that glacier expanded during the global Last Glacial Maximum (LGM). This is contrary to the suggestion that during Last Glacial maximum (LGM) glaciation was limited in extent due to weak Indian Summer Monsoon (ISM) in the monsoon dominated regions of the Himalaya. We ascribe the LGM glaciations to a combination of the lowered temperature and enhanced mid-latitude westerlies. Following the LGM glaciation, Goriganga valley experienced two major pulses of deglaciation. The older event is dated between 16 and 12 ka and is coeval with the initiation of the ISM whereas the younger events (10-8 ka) represent the early to mid-Holocene strengthened ISM. The Stage-III and IV glaciations which terminated proximal to the modern glacier are speculated to occur during the mid-Holocene and Little Ice Age (LIA) respectively.

  6. Late Quaternary Glaciation of the Naches River Drainage Basin, Washington Cascades

    NASA Astrophysics Data System (ADS)

    Sheffer, H. B.; Goss, L.; Shimer, G.; Carson, R. J.

    2014-12-01

    The Naches River drainage basin east of Mount Rainer includes tributary valleys of the Little Naches, American, Bumping, and Tieton rivers. An investigation of surface boulder frequency, weathering rind thicknesses, and soil development on moraines in these valleys identified two stages of Pleistocene glaciations in the American, Bumping, and Tieton drainages, followed by Neoglaciation. These stages include a more extensive early glaciation (Hayden Creek?), and the later Evans Creek Glaciation (25-15 ka). Thick forest cover, limited road cuts, and widespread post-glacial mass wasting hamper efforts to determine the maximum extent of glaciation. However, glacial striations at Chinook Pass, moraine complexes in the vicinity of Goose Egg Mountain, ice-transported boulders and striations on Pinegrass Ridge, and a boulder field possibly derived from an Evans Creek jökulhaup in the Tieton River valley, all point to extensive Pleistocene ice in the central tributaries of the Naches River. Lowest observed ice elevations in the Tieton (780 m), Bumping (850 m), and American (920 m) drainages increase towards the north, while glacial lengths decrease from 40 to 28 km. The Little Naches is the northernmost drainage in the study, but despite a maximum elevation (1810 m) that exceeds the floor of ice caps to the south, glacially-derived sediments are not evident and the surrounding peaks lack cirques. The absence of ice in the Little Naches drainage, along with the systematic northward change in glacial length and lowest observed ice elevations in the other drainages, are likely due to a precipitation shadow northeast of Mount Rainier. In contrast, the source of glacial ice in the Tieton drainage to the southeast was the Goat Rocks peaks. Ground-based study of neoglacial moraines and analysis of 112 years of topographic maps and satellite imagery point to rapid retreat of the remaining Goat Rocks glaciers following the Little Ice Age.

  7. Late Quaternary History of River Discharge and Glaciation in the Southern Kara Sea, Arctic Ocean: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Stein, R.; Niessen, F.; Dittmers, K.; Levitan, M.; Levitan, M.; Schoster, F.; Simstich, J.; Steinke, T.; Stepanets, O.

    2001-12-01

    Within the framework of the joint German-Russian project on "The Nature of Continental Run-Off from the Siberian Rivers and its Behavior in the Adjacent Arctic Basin (Siberian River Run-Off-SIRRO)", a multidisciplinary expedition with RV "Akademik Boris Petrov" was carried out in the Ob and Yenisei estuaries and the southern Kara Sea in August-September 2001. From the geological point of view, the variability of river discharge in relationship to climate change and the reconstruction of extent and history of glaciation in the southern Kara Sea during Late Quaternary times are major foci of interest. To reach these goals, an intensive sediment ecosounding (2-12 kHz) survey and sediment coring program has been performed. Based on profiling and sediment core data, the following preliminary statements can be given: (1) The extent of the eastern margin of the Barents Sea LGM Ice Sheet between 74 and 78oN can be mapped in detail. Different types of glacial to nonglacial facies can be distinguished. This ice barrier should have strongly influenced river discharge, diverted towards the NE probably into the Voronin Trough. (2) The local LGM (?) ice sheet on Taymyr Peninsula seems to be not connected with the Barents Sea Ice Sheet. (3) Siberian river discharge reached maximum values during the last deglaciation and displays distinct (cyclic) variability during Holocene times. Further detailed evaluation of the sediment echograph profiles as well as detailed sedimentological studies and AMS 14C datings will follow to support these ideas.

  8. Modeling late Paleozoic glaciation

    SciTech Connect

    Crowley, T.J.; Baum, S.K. )

    1992-06-01

    Late Paleozoic glaciation on Gondwana is associated with changes in geography, solar luminosity, and estimated CO{sub 2} levels. To assess the relative importance of these boundary conditions, the authors conducted a suite of climate model simulations for the periods before, during, and after peak mid-Carboniferous ({approximately}300 Ma) glaciation (340, 300, and 255 and 225 Ma, respectively). Orbital insolation values favorable for glaciation and interglaciation were used for each time interval. Results indicate that changes in geography cause significant changes in snow area, but the temporal trend is not consistent with the geologic record for glaciation. Combined CO{sub 2}-plus-geography changes yield the best agreement with observations. In addition, interglacial orbital configurations result in almost ice-free conditions for the glacial interval at 300 Ma, at a time of low CO{sub 2}. The large simulated glacial-interglacial snowline fluctuations for Permian-Carboniferous time may explain cyclothem fluctuations at these times. Overall, results support the importance of the CO{sub 2} paradigm, but also indicate that a fuller understanding of past climate change requires consideration of paleogeographic, luminosity, and orbital insolation changes.

  9. Late Quaternary glaciation history of Isla de los Estados, southeasternmost South America

    NASA Astrophysics Data System (ADS)

    Möller, Per; Hjort, Christian; Björck, Svante; Rabassa, Jorge; Ponce, Juan Federico

    2010-05-01

    Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400-450 m a.s.l., and above that trimline a distinct sharp-edged nunatak derived landscape is present. The westernmost part of the island has a lower, more subdued topography, reflecting its "softer" geology but possibly also over-running and erosion by mainland-derived ice streams. The present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs. A combination of OSL and 14C datings show that these sediments mostly date from the latest (Wisconsinan/Weichselian) glacial cycle, i.e. from the last ca. 100 ka with the oldest (glaciolacustrine) deposits possibly as old as 90-80 ka. The upper parts of overlying tills, with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island, date from the last global glacial maximum (LGM). Radiocarbon ages of peat and lake sediments indicate that deglaciation began 17-16 cal ka BP.

  10. Extensive Quaternary glaciations in eastern Turkey

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  11. Quaternary glaciation of Mount Everest

    NASA Astrophysics Data System (ADS)

    Owen, Lewis A.; Robinson, Ruth; Benn, Douglas I.; Finkel, Robert C.; Davis, Nicole K.; Yi, Chaolu; Putkonen, Jaakko; Li, Dewen; Murray, Andrew S.

    2009-07-01

    The Quaternary glacial history of the Rongbuk valley on the northern slopes of Mount Everest is examined using field mapping, geomorphic and sedimentological methods, and optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) dating. Six major sets of moraines are present representing significant glacier advances or still-stands. These date to >330 ka (Tingri moraine), >41 ka (Dzakar moraine), 24-27 ka (Jilong moraine), 14-17 ka (Rongbuk moraine), 8-2 ka (Samdupo moraines) and ˜1.6 ka (Xarlungnama moraine), and each is assigned to a distinct glacial stage named after the moraine. The Samdupo glacial stage is subdivided into Samdupo I (6.8-7.7 ka) and Samdupo II (˜2.4 ka). Comparison with OSL and TCN defined ages on moraines on the southern slopes of Mount Everest in the Khumbu Himal show that glaciations across the Everest massif were broadly synchronous. However, unlike the Khumbu Himal, no early Holocene glacier advance is recognized in the Rongbuk valley. This suggests that the Khumbu Himal may have received increased monsoon precipitation in the early Holocene to help increase positive glacier mass balances, while the Rongbuk valley was too sheltered to receive monsoon moisture during this time and glaciers could not advance. Comparison of equilibrium-line altitude depressions for glacial stages across Mount Everest reveals asymmetric patterns of glacier retreat that likely reflects greater glacier sensitivity to climate change on the northern slopes, possibly due to precipitation starvation.

  12. Reconstruction of the Late Quaternary Glaciation of the Macha Khola valley (Gorkha Himal, Nepal) using relative and absolute ( 14C, 10Be, dendrochronology) dating techniques

    NASA Astrophysics Data System (ADS)

    Zech, W.; Glaser, B.; Abramowski, U.; Dittmar, C.; Kubik, P. W.

    2003-11-01

    Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (<1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3-4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3-4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3-4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries.

  13. 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

    USGS Publications Warehouse

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

    2005-01-01

    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

  14. Quaternary glaciations in the Northern Hemisphere

    SciTech Connect

    Sibrava, V.; Bowen, D.Q.; Richmond, G.M.

    1987-01-01

    This volume presents the final report of Project 24 of the International Geological Correlation Programme. The publication is drawn from the contributions of leading individual scientist as well as from scientific research teams. It reflects the present state of knowledge of the Quaternary Glaciations in the Northern Hemisphere and their correlation in space and time, as well as providing a unique summary of climatic change.

  15. On Quaternary glaciations, observations and theories

    NASA Astrophysics Data System (ADS)

    Paillard, D.

    2015-07-01

    In a recent paper, Paillard (2015) presents a rapid overview of both major theoretical and empirical studies of Pleistocene glaciations. In particular, it is explained how, over the last 150 years, astronomical theories were confronted to observational constraints and why the "100-kyr problem" is still the major unsolved issue of Quaternary ice ages. This paper also discusses the main alternative theory, which involves changes in atmospheric carbon dioxide concentration. It is then argued that a synthesis of both theories would better account for empirical evidences, as well as for our current knowledge of climate physics. Indeed, if there is no doubt that ice ages are "paced" by the astronomy as evidenced in Hays et al. (1976), the cause of terminations, and therefore the dynamics of the 100-kyr cycles, appears to be closely linked to Southern Ocean climate and atmospheric pCO2.

  16. Late Quaternary landscape evolution in the Kunlun Mountains and Qaidam Basin, Northern Tibet: A framework for examining the links between glaciation, lake level changes and alluvial fan formation

    USGS Publications Warehouse

    Owen, L.A.; Finkel, R.C.; Haizhou, M.; Barnard, P.L.

    2006-01-01

    The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent-continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial cosmogenic radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of

  17. Late Amazonian Glaciations in Utopia Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Capitan, R. D.; Kerrigan, M.; Barry, N.; Blain, S.

    2012-03-01

    We present evidence from western Utopia Planitia, including lineated valley fill and lobate debris aprons, for widespread glaciations over a large expanse of the northern plains and dichotomy boundary during Late Amazonian times.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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 calibrated years ago. These data suggest that a substantial part of the Archangelsk Region was not covered by ice during the indicated time interval.

  19. A critical examination of evidence for a Quaternary glaciation in Mt. Laoshan, Eastern China

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy; Guo, Liang; Xiang, Shibao; Guo, Xiaoyu; Xu, Xingyong

    2011-01-01

    Accurately determining how far south Quaternary glaciers existed in eastern China has important implications for understanding global Quaternary climate. In this study, we provide evidence for a colder paleoclimate in the late Pleistocene of the Laoshan range on the eastern Shandong Peninsula at 36°05'-36°19'N latitude, through documentation of erosional and depositional landforms that were possibly formed by glaciation. We integrate field observations documenting and mapping the existence of typical glacial cirques, glacial horns, moraines, arêtes, tarn lakes, and other paleoglacial features in Mt. Laoshan, with a detailed digital elevation model (DEM) created in an ArcGIS environment, merged with Landsat ETM + imagery to document the spatial relations of these features. Other features that may or may not be glacial in origin include large boulder fields (that could be moraines or debris avalanches), and potholes (that could have formed beneath glaciers or in river systems). Additionally, some features previously interpreted as glacial features are here re-interpreted as weathering-related phenomena. Although some of these features alone provide only weak to moderate evidence for glaciation, together the suite of indicators provides strong evidence for sea-level glaciation at 36°N in the late Pleistocene of eastern China. We further integrate the evidence of glaciation with the late Pleistocene paleogeography and climate, and suggest that the glaciers formed as a result of orographic effects from moist monsoonal breezes crossing a paleolake developed in North China then rising over Mt. Laoshan and dropping their moisture there, with a wide desert formed on the leeward side of the mountains.

  20. The impact of the Quaternary glaciations on the Durmitor mountains (Montenegro) as understood from detailed geomorphological mapping

    NASA Astrophysics Data System (ADS)

    Frankl, Amaury; Annys, Klaas; Spalević, Velibor; Čurović, Milic; Borota, Dragan; Nyssen, Jan

    2014-05-01

    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.

  1. Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia

    NASA Astrophysics Data System (ADS)

    Stauch, Georg; Lehmkuhl, Frank

    2010-07-01

    Geomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50 ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90 ka, moraine IV is 100 to 120 ka, and the outermost moraine V was deposited around 135 ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets.

  2. Geochronology of Quaternary glaciations from the tropical Cordillera Huayhuash, Peru

    NASA Astrophysics Data System (ADS)

    Hall, Sarah R.; Farber, Daniel L.; Ramage, Joan M.; Rodbell, Donald T.; Finkel, Robert C.; Smith, Jacqueline A.; Mark, Bryan G.; Kassel, Christopher

    2009-12-01

    The Cordillera Huayhuash in the central Peruvian Andes (10.3°S, 76.9°W) is an ideal mountain range in which to study regional climate through variations in paleoglacier extents. The range trends nearly north-south with modern glaciers confined to peaks >4800 m a.s.l. Geomorphology and geochronology in the nearby Cordillera Blanca and Junin Plain reveal that the Peruvian Andes preserve a detailed record of tropical glaciation. Here, we use ASTER imagery, aerial photographs, and GPS to map and date glacial features in both the western and eastern drainages of the Cordillera Huayhuash. We have used in situ produced cosmogenic 10Be concentrations in quartz bearing erratics on moraine crests and ice-polished bedrock surfaces to develop an exposure age chronology for Pleistocene glaciation within the range. We have also collected sediment cores from moraine-dammed lakes and bogs to provide limiting 14C ages for glacial deposits. In contrast to the ranges to the north and south, most glacial features within the Cordillera Huayhuash are Lateglacial in age, however we have identified features with ages that span ˜0.2 to ˜38 ka with moraine sets marking the onset of glacier retreat at ˜0.3 ka, ˜9-10 ka, ˜13-14 ka, ˜20-22 ka, and >26 ka. The range displays a pronounced east-west variation in maximum down-valley distance from the headwall of moraine crests with considerably longer paleoglaciers in the eastern drainages. Importantly, Lateglacial paleoglaciers reached a terminal elevation of ˜4000 m a.s.l. on both sides of the Cordillera Huayhuash; suggesting that temperature may have been a dominant factor in controlling the maximum glacier extent. We suggest that valley morphology, specifically valley slope, strongly influences down-valley distance to the maximum glacier extent and potential for moraine preservation. While regionally there is an extensive record of older (>50 ka) advances to the north (Cordillera Blanca) and to the south (Junin region), the apparent

  3. Northern hemisphere glaciation during the globally warm early Late Pliocene.

    PubMed

    De Schepper, Stijn; Groeneveld, Jeroen; Naafs, B David A; Van Renterghem, Cédéric; Hennissen, Jan; Head, Martin J; Louwye, Stephen; Fabian, Karl

    2013-01-01

    The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream-North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century. PMID:24349081

  4. Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene

    PubMed Central

    De Schepper, Stijn; Groeneveld, Jeroen; Naafs, B. David A; Van Renterghem, Cédéric; Hennissen, Jan; Head, Martin J.; Louwye, Stephen; Fabian, Karl

    2013-01-01

    The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream–North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century. PMID:24349081

  5. New data on the most ancient early quaternary glaciation in Gornyi Altai

    NASA Astrophysics Data System (ADS)

    Zykin, V. S.; Zykina, V. S.; Smolyaninova, L. G.

    2016-01-01

    The data presented in this work introduce substantial corrections into the Upper Cenozoic stratigraphy and geological history of Gornyi Altai. They provide evidence for the most ancient Early Pleistocene glaciation in this region. This follows from finds of faceted boulders buried in the Bashkaus Formation. Pale-omagnetic investigations revealed in the latter a wide zone of negative polarity corresponding to the Matuyama Chron in the magnetostratigraphic scale and made it possible to correlate the formation with the Lower Pleistocene in the standard stratigraphic scale. It is shown that global cooling at the beginning of the Quaternary Period stimulated development of glaciation on the southern slope of the Kuraiskii Range exceeding in size its present-day scale.

  6. Late Quaternary sedimentation on the North Aegean continental margin, Greece

    SciTech Connect

    Piper, D.J.W. ); Perissoratis, C. )

    1991-01-01

    The late Quaternary seismic stratigraphy of the North Aegean continental shelf and adjacent basins has been interpreted from boomer and 3.5-kHz seismic profiles. Ages derived from shallow cores and offshore wells, and relative offsets on small synsedimentary faults, provide chronological control. Sea level history inferred from seismic stratigraphy correlates with the global eustatic sea level record based on oxygen isotopic curves. The present depth of the delta plain formed on the outer shelf during the late stage 6 lowstand provides a dated and originally horizontal marker for estimating rates of tectonic subsidence. Gross distribution of sediment facies is similar in both tectonically stable and active areas. The shell break formed by delta progradation, but is marked by faults in most places because of the accommodation provided by graben subsidence rates of 0.3-1.5 mm/yr. Standard sequence stratigraphic analysis can be applied to these sediments deposited during high-amplitude Quaternary sea level oscillations. High rates of subsidence result in the preservation an unusually complete record of sea level change. Major lowstand progradation is dependent on the duration, rather than the magnitude, of sea level lowstand. The long glaciations in isotopic stages 6, 12, 16, and 22 resulted in the most prominent seaward progradation on the margin. Sandy lowstand turbidite deposits formed only when there was rapid fall in sea level; otherwise sand was trapped on delta tops and silty muds were deposited in deep water.

  7. Chronology of late wisconsinan glaciation in middle North America

    NASA Astrophysics Data System (ADS)

    Clayton, Lee; Moran, Stephen R.

    We propose a chronology of late Wisconsinan glacial fluctuations in middle North America, from Alberta to Wisconsin, based on radiocarbon dates derived solely from wood. Previous chronologies of the southwestern margin of the North American Continental Ice Sheet have depended to a considerable degree on radiocarbon dates from fine-grained organic sediment. This material is commonly contaminated with older carbon, resulting in chronologic confusion. By using only dates from wood, much of the confusion disappears. However, because of the scarcity of wood dates, only four of the sixteen identified fluctuations are accurately dated: an advance into Iowa about 14,000 to 13,500 BP, an advance into South Dakota and Iowa about 12,300 BP, an advance into the Lake Michigan basin about 11,700 BP, and an advance into the Lake Superior basin about 9900 BP. In addition, the beginning of late Wisconsinan glaciation, before 20,000 BP, is fairly well documented. None of the fluctuations in the western part of the region are accurately dated.

  8. Chronology of late wisconsinan glaciation in middle North America

    USGS Publications Warehouse

    Clayton, L.; Moran, S.R.

    1982-01-01

    We propose a chronology of late Wisconsinan glacial fluctuations in middle North America, from Alberta to Wisconsin, based on radiocarbon dates derived solely from wood. Previous chronologies of the southwestern margin of the North American Continental Ice Sheet have depended to a considerable degree on radiocarbon dates from fine-grained organic sediment. This material is commonly contaminated with older carbon, resulting in chronologic confusion. By using only dates from wood, much of the confusion disappears. However, because of the scarcity of wood dates, only four of the sixteen identified fluctuations are accurately dated: an advance into Iowa about 14,000 to 13,500 BP, an advance into South Dakota and Iowa about 12,300 BP, an advance into the Lake Michigan basin about 11,700 BP, and an advance into the Lake Superior basin about 9900 BP. In addition, the beginning of late Wisconsinan glaciation, before 20,000 BP, is fairly well documented. None of the fluctuations in the western part of the region are accurately dated. ?? 1982.

  9. Late quaternary sequence stratigraphy, South Florida margin

    SciTech Connect

    Locker, S.D.; Hine, A.C.

    1995-12-01

    Late Quaternary sea-level change and the Florida Current have combined to produce a progradational shelf-slope margin along the western portion of the south Florida Platform facing the Straits of Florida. Analysis of high resolution seismic reflection profiles suggest at least eight 5th order late Quaternary sequences downlap onto the Pourtales Terrace at 250 m water depth. Along most of the south Florida margin, this Late Quaternary section is very thin, and only where significant accumulations occur can the stratigraphic patterns produced by sea-level change be clearly observed. Recognition of systems tracts and their boundaries from high-resolution seismic data is important for prediction of sedimentary facies and stratigraphic development of margins. Many south Florida seismic boundaries can be fit to the Exxon sequence stratigraphy model. Others appear to reflect the added effect of bottom-current erosion that complicates the signal produced by sea-level change. Overall, the sea-level signal appears to dominate the stratigraphic record, especially from the 2-dimensional perspective of dip-oriented seismic profiles. However, the 3-dimensional geometry of deposits are strongly influenced by along slope accumulation patterns controlled by the Florida Current. This study provides new insight on the importance of both geostrophic boundary currents and sea-level change in controlling stratigraphic development of a carbonate platform margin. Similar anomalously thick slope deposits in ancient sequences may indicate similar controls on accumulation and could lend to predictions of related paleo-platform configurations.

  10. Isotopic interrogation of a suspected late Eocene glaciation

    NASA Astrophysics Data System (ADS)

    Scher, Howie D.; Bohaty, Steven M.; Smith, Brian W.; Munn, Gabrielle H.

    2014-06-01

    Ephemeral polar glaciations during the middle-to-late Eocene (48-34 Ma) have been proposed based on far-field ice volume proxy records and near-field glacigenic sediments, although the scale, timing, and duration of these events are poorly constrained. Here we confirm the existence of a transient cool event within a new high-resolution benthic foraminiferal δ18O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the Priabonian oxygen isotope maximum (PrOM) Event, lasted ~140 kyr and is tentatively placed within magnetochron C17n.1n (~37.3 Ma) based on the correlation to ODP Site 689 (Maud Rise, Southern Ocean). A contemporaneous change in the provenance of sediments delivered to the Kerguelen Plateau occurs at the study site, determined from the <63 µm fraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth ɛNd, were less pronounced and slower relative to the benthic δ18O and terrigenous ɛNd changes. Terrigenous sediment ɛNd values rapidly shifted to less radiogenic signatures at the onset of the PrOM Event, indicating an abrupt change in provenance favoring ancient sources such as the Paleoproterozoic East Antarctic craton. Bottom water ɛNd reached a minimum value during the PrOM Event, although the shift begins much earlier than the terrigenous ɛNd excursion. The origin of the abrupt change in terrigenous sediment provenance is compatible with a change in Antarctic terrigenous sediment flux and/or source as opposed to a reorganization of ocean currents. A change in terrigenous flux and/or source of Antarctic sediments during the oxygen isotope maximum suggests a combination of cooling and ice growth in East Antarctica during the early late Eocene.

  11. North atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles

    USGS Publications Warehouse

    Dwyer, G.S.; Cronin, T. M.; Baker, P.A.; Raymo, M.E.; Buzas, Jeffrey S.; Correge, T.

    1995-01-01

    Variations in the ratio of magnesium to calcium (Mg/Ca) in fossil ostracodes from Deep Sea Drilling Project Site 607 in the deep North Atlantic show that the change in bottom water temperature during late Pliocene 41,000-year obliquity cycles averaged 1.5??C between 3.2 and 2.8 million years ago (Ma) and increased to 2.3??C between 2.8 and 2.3 Ma, coincidentally with the intensification of Northern Hemisphere glaciation. During the last two 100,000-year glacial-to-interglacial climatic cycles of the Quaternary, bottom water temperatures changed by 4.5??C. These results show that glacial deepwater cooling has intensified since 3.2 Ma, most likely as the result of progressively diminished deep-water production in the North Atlantic and of the greater influence of Antarctic bottom water in the North Atlantic during glacial periods. The ostracode Mg/Ca data also allow the direct determination of the temperature component of the benthic foraminiferal oxygen isotope record from Site 607, as well as derivation of a hypothetical sea-level curve for the late Pliocene and late Quaternary. The effects of dissolution on the Mg/Ca ratios of ostracode shells appear to have been minimal.

  12. Late Quaternary climate change shapes island biodiversity.

    PubMed

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

    2016-04-01

    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. PMID:27027291

  13. Late Quaternary carbonate deposition at the bottom of the world

    NASA Astrophysics Data System (ADS)

    Frank, Tracy D.; James, Noel P.; Bone, Yvonne; Malcolm, Isabelle; Bobak, Lindsey E.

    2014-05-01

    Carbonate sediments on polar shelves hold great potential for improving understanding of climate and oceanography in regions of the globe that are particularly sensitive to global change. Such deposits have, however, not received much attention from sedimentologists and thus remain poorly understood. This study investigates the distribution, composition, diagenesis, and stratigraphic context of Late Quaternary calcareous sediments recovered in 15 piston cores from the Ross Sea shelf, Antarctica. Results are used to develop a depositional model for carbonate deposition on glaciated, polar shelves. The utility of the deposits as analogs for the ancient record is explored. In the Ross Sea, carbonate-rich lithofacies, consisting of poorly sorted skeletal sand and gravel, are concentrated in the west and along the outer reaches of the continental shelf and upper slope. Analysis of fossil assemblages shows that deposits were produced by numerous low-diversity benthic communities dominated locally by stylasterine hydrocorals, barnacles, or bryozoans. Radiocarbon dating indicates that carbonate sedimentation was episodic, corresponding to times of reduced siliciclastic deposition. Most accumulation occurred during a time of glacial expansion in the lead-up to the Last Glacial Maximum. A more recent interval of carbonate accumulation postdates the early Holocene sea level rise and the establishment of the modern grounding line for the Ross Ice Shelf. When carbonate factories were inactive, fossil debris was subjected to infestation by bioeroders, dissolution, fragmentation, and physical reworking. This study reveals the episodic nature of carbonate deposition in polar settings and a reciprocal relationship with processes that deliver and redistribute siliciclastic debris. Carbonate production is most active during colder periods of the glacial-interglacial cycle, a potential new sedimentological paradigm for polar carbonate systems. Low accumulation rates and long residence

  14. Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels.

    PubMed

    Lunt, Daniel J; Foster, Gavin L; Haywood, Alan M; Stone, Emma J

    2008-08-28

    It is thought that the Northern Hemisphere experienced only ephemeral glaciations from the Late Eocene to the Early Pliocene epochs (about 38 to 4 million years ago), and that the onset of extensive glaciations did not occur until about 3 million years ago. Several hypotheses have been proposed to explain this increase in Northern Hemisphere glaciation during the Late Pliocene. Here we use a fully coupled atmosphere-ocean general circulation model and an ice-sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the Greenland ice sheet in particular. We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene. By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway, with the termination of a permanent El Niño state or with tectonic uplift are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth's orbit. PMID:18756254

  15. (Model) Peatlands in late Quaternary interglacials

    NASA Astrophysics Data System (ADS)

    Kleinen, Thomas; Brovkin, Victor

    2016-04-01

    Peatlands have accumulated a substantial amount of carbon, roughly 600 PgC, during the Holocene. Prior to the Holocene, there is relatively little direct evidence of peatlands, though coal deposits bear witness to a long history of peat-forming ecosystems going back to the Carboniferous. We therefore need to rely on models to investigate peatlands in times prior to the Holocene. We have developed a dynamical model of wetland extent and peat accumulation, integrated in the coupled climate carbon cycle model of intermediate complexity CLIMBER2-LPJ, in order to mechanistically model interglacial carbon cycle dynamics. This model consists of the climate model of intermediate complexity CLIMBER2 and the dynamic global vegetation model LPJ, which we have extended with modules to determine peatland extent and carbon accumulation. The model compares reasonably well to Holocene peat data. We have used this model to investigate the dynamics of atmospheric CO2 in the Holocene and two other late Quaternary interglacials, namely the Eemian, which is interesting due to its warmth, and Marine Isotope Stage 11 (MIS11), which is the longest interglacial during the last 500ka. We will also present model results of peatland extent and carbon accumulation for these interglacials. We will discuss model shortcomings and knowledge gaps currently preventing an application of the model to full glacial-interglacial cycles.

  16. Foraminiferal biostratigraphy of the shelf edge: a key to late Quaternary paleoenvironments

    USGS Publications Warehouse

    Poag, C. Wylie; Sidner, B.R.

    1976-01-01

    Foraminiferal assemblages in eight piston cores from West Flower Garden Bank at the edge of the Texas continental shelf contain a nearly complete record of late Quaternary paleoclimatic and geologic events. The faunas are divisible into three distinct successive biofacies on the basis of both planktonic and benthic foraminifers: the basal Inflata Facies accumulated in cool shallow waters during late Pleistocene glaciation; the middle Crassaformis Facies represents a deepening sea that had warming surface waters; the upper Cultrata Facies is characteristic of the Holocene outer-shelf environment. Sea level was at -73 m and -53 m at the end of deposition of the Inflata and Crassaformis Facies, respectively. The biostratigraphic events at West Flower Garden Bank can be accurately correlated with those recorded in the middle and inner shelf and in deep-sea cores. The sequence of late Quaternary sea level and paleotemperature changes in the northern Gulf of Mexico can thereby be reconstructed. Eventually, this knowledge can be integrated with similar data from the shelf edge in other parts of the world to help bridge the gap between the known Quaternary record of the deep sea and that of the continents. ?? 1976.

  17. Late glacial 10Be ages for glacial landforms in the upper region of the Taibai glaciation in the Qinling Mountain range, China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Liang; Chen, Yixin; Liu, Beibei; Harbor, Jonathan M.; Cui, Zhijiu; Liu, Rui; Liu, Xiao; Zhao, Xu

    2016-01-01

    Glacial landforms are well preserved on Taibai Mountain (3767 m), the main peak of the Qinling mountain range located south of the Loess Plateau and east of the Qinghai-Tibet Plateau. The timing and extent of Quaternary glaciation in the study area is important for reconstructing Quaternary environmental change however numerical ages for glaciation in this study area have not previously been well resolved. Using terrestrial in situ cosmogenic nuclides we dated four samples collected from two glacially eroded rock steps in the upper part of a valley near the main peak, in an area previously identified as having been occupied by ice during the Taibai glaciation. The 10Be results are all late glacial in age: 18.6 ± 1.1 ka, 16.9 ± 1.0 ka, 16.9 ± 1.1 ka and 15.1 ± 1.0 ka. The spatial pattern of ages in the valley suggests fast retreat, with horizontal and vertical retreat rates estimated to be on the order of 0.4 and 0.09 m a-1, respectively. A simple extrapolation of these retreat rates from the ages at the two sample sites suggests that the glacier retreat began during Last Glacial Maximum and that glaciers disappeared from the main peak by about 15 ka.

  18. Quaternary fluvial history of the Delaware River, New Jersey and Pennsylvania, USA: The effects of glaciation, glacioisostasy, and eustasy on a proglacial river system

    NASA Astrophysics Data System (ADS)

    Stanford, Scott D.; Witte, Ron W.; Braun, Duane D.; Ridge, John C.

    2016-07-01

    Fluvial, glacial, and estuarine deposits in the Delaware Valley record the response of the Delaware River to glaciation, sea-level change, and glacioisostasy during the Quaternary. Incision following an early Pleistocene glaciation created the present valley, which is inset into a Pliocene strath and fluvial plain. Middle and upper Pleistocene and Holocene deposits were laid down in this inset valley. Estuarine terraces in the lower valley and bayshore at + 20 m (probably Marine Isotope Stage [MIS] 11), + 8 m (MIS 5e), and + 3 m (MIS 5a or c), and a fluvial deposit that correlates to offshore MIS 3 marine deposits at - 20 m are at elevations consistent with glacioisostatic models. Successive incisions during lowstands in the middle and late Pleistocene lengthened, deepened, and narrowed the channel in the lower valley and shifted the channel westward in Delaware Bay. During MIS 2 glaciation, from 25 to 18 ka, the Delaware was diverted to the Hudson Shelf Valley by glacioisostatic tilting. Most glacial sediment was trapped in fluvial-lacustrine valley fills north of the terminal moraine. Incision of the valley fill was accomplished during the early stage of rebound, between 17 and 12 ka. Drainage to the Delaware shelf was restored between 15 and 13 ka as the forebulge collapsed. During incision, multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward; and a single terrace formed where the valley paralleled the contours, and there was no differential elevation or steepening. About 65% of the original volume of MIS 2 glacial sediment remains in the main valley, and most of the eroded volume is in the channel in the lower valley beneath Holocene estuarine fill. Little glacial sediment reached the Delaware or Hudson shelf. Overbank deposition on the lower postglacial terrace and modern floodplain spans the Holocene. The volume of Holocene sediment in the estuary and bay yields a basinwide

  19. Genetic footprints of demographic expansion in North America, but not Amazonia, during the Late Quaternary.

    PubMed

    Lessa, Enrique P; Cook, Joseph A; Patton, James L

    2003-09-01

    The biotic consequences of climate change have attracted considerable attention. In particular, the "refugial debate" centers on the possible retraction of habitats to limited areas that may have served as refuges for many associated species, especially during glaciations of the Quaternary. One prediction of such scenarios is that populations must have experienced substantial growth accompanying climatic amelioration and the occupation of newly expanded habitats. We used coalescence theory to examine the genetic evidence, or lack thereof, for late Pleistocene refugia of boreal North American and tropical Amazonian mammals. We found substantial and concordant evidence of demographic expansion in North American mammals, particularly at higher latitudes. In contrast, small mammals from western Amazonia appear to have experienced limited or no demographic expansion after the Late Pleistocene. Thus, demographic responses to climate change can be tracked genetically and appear to vary substantially across the latitudinal gradient of biotic diversity. PMID:12913123

  20. Evidence for Late Ordovician glaciation of Al Kufrah Basin, Libya

    NASA Astrophysics Data System (ADS)

    Le Heron, Daniel Paul; Howard, James

    2010-09-01

    Fieldwork at the flanks of Al Kufrah Basin, Libya, reveals that Late Ordovician ice sheets were present in the eastern Sahara and that they extended northeastward toward Egypt. Evidence for grounded ice sheets is preserved at the both the southeastern (Jabal Azbah) and northern (Jabal az-Zalmah) basin margins. Characteristic soft-sediment deformation structures, including soft-sediment folds, small-scale faults and striated pavements indicate subglacial shearing and the formation of glacial erosion surfaces. These findings support the presence of a Late Ordovician ice margin in the eastern Sahara and add vital new constraints to reconstructions of the morphology of North African grounded ice sheets. Prior to our study, there existed two plausible models on ice sheet geometry. The first was that separate ice sheets - namely a north and west African ice sheet and an Arabian ice sheet - extended over this part of western North Gondwana. The second was that ice cover was continuous. The presence of a suite of subglacially-generated deformation structures adds considerable credence to the latter interpretation.

  1. Genetic and morphological consequences of Quaternary glaciations: A relic barbel lineage (Luciobarbus pallaryi, Cyprinidae) of Guir Basin (Algeria).

    PubMed

    Brahimi, Amina; Tarai, Nacer; Benhassane, Abdelkrim; Henrard, Arnaud; Libois, Roland

    2016-02-01

    Climatic variations during the Quaternary period had a considerable impact on landscapes and habitat fragmentation (rivers) in North Africa. These historical events can have significant consequences on the genetic structure of the populations. Indeed, geographically separated and genetically isolated populations tend to differentiate themselves through time, eventually becoming distinct lineages, allowing new species to emerge in later generations. The aim of the present study is to use genetic and morphological techniques to evaluate the major role of the Saalian glaciation (Middle Quaternary) in the establishment of the geographic space and in the evolution of the intraspecific genetic diversity, by tracing the demographic history of barbels belonging to the Luciobarbus pallaryi (Cyprinidae) species in the Guir Basin (Algeria). In this context, two populations, from two distinct and isolated sites, were studied. Analysis of the cytochrome b (cyt b) mitochondrial markers and of the "D-loop" control region has shown that the "upstream" and "downstream" Guir populations are genetically differentiated. The molecular analyses suggest that the upstream population was disconnected from this hydrographic system during the Saalian glaciation period of the Quaternary. Subsequently, it was isolated in the foggaras underground waters in the Great Western Erg, at approximately 320 000 years BP, creating, through a bottleneck effect, a new allopatric lineage referred to as "Adrar". Conversely, the high genetic diversity in the upstream Guir (Bechar) population suggests that the stock is globally in expansion. These barbels (n=52) were also examined with meristic, morphometric, osteological, and biological features. These data also reveal a complete discrimination between the two populations, with a remarkable and distinctive behavioural adaptation for the Adrar specimens: neoteny. PMID:26874458

  2. Spatial Response of Mammals to Late Quaternary Environmental Fluctuations

    PubMed

    Graham; Lundelius; Graham; Schroeder; Toomey; Anderson; Barnosky; Burns; Churcher; Grayson; Guthrie; Harington; Jefferson; Martin; McDonald; Morlan; Semken; Webb; Werdelin; Wilson

    1996-06-14

    Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene. PMID:8662471

  3. Ice Age Earth: Late Quaternary geology and climate

    SciTech Connect

    Dawson, A.G.

    1992-01-01

    This book is a concise and readable account of the most important geologic records of the late Quaternary. It provides a synopsis of the major environmental changes that took place from approximately 13,000 to 7,000 years ago, highlighting the complexity and rapidity of past climate changes and the environmental responses they produced. The text is well illustrated, though some figures are rough and need more explanation. Also needed is a critical appraisal of the geochronology which places the paleoenvironmental records into the temporal domain. However, as a whole the book reaches its objective of summarizing the most important scientific findings about the nature of the late Quaternary climate changes.

  4. Rock varnish microlamination dating of late Quaternary geomorphic features in the drylands of western USA

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo; Broecker, Wallace S.

    2008-01-01

    Varnish microlamination (VML) dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts. In this study, we establish a generalized late Quaternary (i.e., 0-300 ka) varnish layering sequence for the drylands of western USA and tentatively correlate it with the SPECMAP oxygen isotope record. We then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late Quaternary geomorphic features in the study region. VML dating of alluvial fan deposits in Death Valley of eastern California indicates that, during the mid to late Pleistocene, 5-15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation. During the Holocene interglacial time, however, 0.5-1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate. VML dating of alluvial desert pavements in Death Valley and the Mojave Desert reveals that pavements can be developed rapidly (< 10 ky) during the Holocene (and probably late Pleistocene) in the arid lowlands (< 800 m msl) of these regions; but once formed, they may survive for 74-85 ky or even longer without being significantly disturbed by geomorphic processes operative at the pavement surface. Data from this study also support the currently accepted, "being born at the surface" model of desert pavement formation. VML dating of colluvial boulder deposits on the west slope of Yucca Mountain, southern Nevada, yields a minimum age of 46 ka for the emplacement of these deposits on the slope, suggesting that they were probably formed during the early phase of the last glaciation or before. These results, combined with those from our previous studies, demonstrate that VML dating has great potential to yield numerical age

  5. Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

    NASA Astrophysics Data System (ADS)

    Krabbendam, Maarten; Bradwell, Tom

    2014-07-01

    Vast areas previously covered by Pleistocene ice sheets consist of rugged bedrock-dominated terrain of innumerable knolls and lake-filled rock basins - the ‘cnoc-and-lochan' landscape or ‘landscape of areal scour'. These landscapes typically form on gneissose or granitic lithologies and are interpreted (1) either to be the result of strong and widespread glacial erosion over numerous glacial cycles; or (2) formed by stripping of a saprolitic weathering mantle from an older, deeply weathered landscape. We analyse bedrock structure, erosional landforms and weathering remnants and within the ‘cnoc-and-lochan' gneiss terrain of a rough peneplain in NW Scotland and compare this with a geomorphologically similar gneiss terrain in a non-glacial, arid setting (Namaqualand, South Africa). We find that the topography of the gneiss landscapes in NW Scotland and Namaqualand closely follows the old bedrock-saprolite contact (weathering front). The roughness of the weathering front is caused by deep fracture zones providing a highly irregular surface area for weathering to proceed. The weathering front represents a significant change in bedrock physical properties. Glacial erosion (and aeolian erosion in Namaqualand) is an efficient way of stripping saprolite, but is far less effective in eroding hard, unweathered bedrock. Significant glacial erosion of hard gneiss probably only occurs beneath palaeo-ice streams. We conclude that the rough topography of glaciated ‘cnoc-and-lochan' gneiss terrains is formed by a multistage process: 1) Long-term, pre-glacial chemical weathering, forming deep saprolite with an irregular weathering front; 2) Stripping of weak saprolite by glacial erosion during the first glaciation(s), resulting in a rough land surface, broadly conforming to the pre-existing weathering front (‘etch surface'); 3) Further modification of exposed hard bedrock by glacial erosion. In most areas, glacial erosion is limited, but can be significant beneath palaeo

  6. Stratigraphic evidence for late Quaternary dune activity near Hudson on the Piedmont of northern Colorado

    SciTech Connect

    Forman, S.L.; Maat, P. )

    1990-08-01

    Stabilized dune fields are common features near Hudson, on the Piedmont of northern Colorado. Exposures in dune and interdune sites expose a sequence of eolian sediments and paleosols that record a complex history of eolian activity during the late Quaternary. Radiocarbon and thermoluminescence age estimates on A horizons buried by eolian sand indicate that dunes were reactivated sometime between 7 and 9 ka. On the basis of morphology of surface soils, the dunes were most recently stabilized <3 ka. At present that are no data to indicate if there were multiple periods of dune movement and stabilization during the Holocene. The penultimate pre-Holocene dune-forming episode probably terminated ca. 13 ka and may be coincident with the Pinedale glaciation. The stratigraphy at interdune sites shows at least two eolian depositional events prior to the penultimate event; they were separated by periods of pedogenesis, one of which may have exceeded 40 ka. This analysis indicates that dunes in northern Colorado were active during both cold-arid and warn-arid periods in the late Quaternary.

  7. Late Quaternary history of the Atacama Desert

    USGS Publications Warehouse

    Latorre, Claudio; Betancourt, Julio L.; Rech, Jason A.; Quade, Jay; Holmgren, Camille; Placzek, Christa; Maldonado, Antonio; Vuille, Mathias; Rylander, Kate A.

    2005-01-01

    Of the major subtropical deserts found in the Southern Hemisphere, the Atacama Desert is the driest. Throughout the Quaternary, the most pervasive climatic influence on the desert has been millennial-scale changes in the frequency and seasonality of the scant rainfall, and associated shifts in plant and animal distributions with elevation along the eastern margin of the desert. Over the past six years, we have mapped modern vegetation gradients and developed a number of palaeoenvironmental records, including vegetation histories from fossil rodent middens, groundwater levels from wetland (spring) deposits, and lake levels from shoreline evidence, along a 1200-kilometre transect (16–26°S) in the Atacama Desert. A strength of this palaeoclimate transect has been the ability to apply the same methodologies across broad elevational, latitudinal, climatic, vegetation and hydrological gradients. We are using this transect to reconstruct the histories of key components of the South American tropical (summer) and extratropical (winter) rainfall belts, precisely at those elevations where average annual rainfall wanes to zero. The focus has been on the transition from sparse, shrubby vegetation (known as the prepuna) into absolute desert, an expansive hyperarid terrain that extends from just above the coastal fog zone (approximately 800 metres) to more than 3500 metres in the most arid sectors in the southern Atacama.

  8. The timing of Late Pleistocene glaciation at Mount Wilhelm, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Mills, Stephanie; Barrows, Timothy; Hope, Geoff; Pillans, Brad; Fifield, Keith

    2016-04-01

    The highlands of New Guinea were the most extensively glaciated area in the Asian tropical region during the Late Pleistocene. Evidence for glaciation is widespread on most of the mountain peaks above ~3500 m. Glacial landforms include both valley and ice cap forms, but the timing of glaciation remains constrained to only a few local areas. This paper focuses on Mount Wilhelm, which is situated in the central southern region of Papua New Guinea at 5.78°S and is the highest peak (4510 m a.s.l.) We focus on a south easterly valley (Pindaunde Valley) emanating from the peak, where large moraines indicate the maximum ice extent of a valley glacier ~5 km long. Within this extensive moraine complex, recessional moraines document the retreat of the glacier towards the summit region. In order to determine the timing of deglaciation, we collected samples for surface exposure dating using 36Cl and 10Be from diorite boulders positioned on moraine crests. The ages indicate that maximum ice extent was attained during the last glacial maximum (LGM) and that ice remained near its maximum extent until after 15 ka but persisted at higher elevations almost until the Holocene. These results are similar to those described from Mt Giluwe to the northwest of Mount Wilhelm, where an ice cap reached its maximum extent at the LGM and remained there for around 3-4,000 years. This indicates that full glacial conditions were only brief in this region of the tropics.

  9. Ecological impacts of the late Quaternary megaherbivore extinctions.

    PubMed

    Gill, Jacquelyn L

    2014-03-01

    As a result of the late Quaternary megafaunal extinctions (50,000-10,000 before present (BP)), most continents today are depauperate of megaherbivores. These extinctions were time-transgressive, size- and taxonomically selective, and were caused by climate change, human hunting, or both. The surviving megaherbivores often act as ecological keystones, which was likely true in the past. In spite of this and extensive research on the causes of the Late Quaternary Extinctions, the long-term ecological consequences of the loss of the Pleistocene megafauna remained unknown until recently, due to difficulties in linking changes in flora and fauna in paleorecords. The quantification of Sporormiella and other dung fungi have recently allowed for explicit tests of the ecological consequences of megafaunal extirpations in the fossil pollen record. In this paper, I review the impacts of the loss of keystone megaherbivores on vegetation in several paleorecords. A growing number of studies support the hypothesis that the loss of the Pleistocene megafauna resulted in cascading effects on plant community composition, vegetation structure and ecosystem function, including increased fire activity, novel communities and shifts in biomes. Holocene biota thus exist outside the broader evolutionary context of the Cenozoic, and the Late Quaternary Extinctions represent a regime shift for surviving plant and animal species. PMID:24649488

  10. Late Quaternary environments in Ruby Valley, Nevada

    USGS Publications Warehouse

    Thompson, R.S.

    1992-01-01

    Palynological data from sediment cores from the Ruby Marshes provide a record of environmental and climatic changes over the last 40,000 yr. The modern marsh waters are fresh, but no deeper than ???3 m. A shallow saline lake occupied this basin during the middle Wisconsin, followed by fresh and perhaps deep waters by 18,000 to 15,000 yr B.P. No sediments were recovered for the period between 15,000 and 11,000 yr B.P., possibly due to lake desiccation. By 10,800 yr B.P. a fresh-water lake was again present, and deeper-than-modern conditions lasted until 6800 yr B.P. The middle Holocene was characterized by very shallow water, and perhaps complete desiccation. The marsh system deepened after 4700 yr B.P., and fresh-water conditions persisted until modern times. Vegetation changes in Ruby Valley were more gradual than those seen in the paleolimno-logical record. Sagebrush steppe was more widespread than at present through the late Pleistocene and early Holocene, giving way somewhat to expanded shadscale vegetation between 8500 and 6800 yr B.P. Shadscale steppe contracted by 4000 yr B.P., but had greater than modern coverage until 1000 to 500 yr ago. Pinyon-juniper woodland was established in the southern Ruby Mountains by 4700 yr B.P. ?? 1992.

  11. Landscape evolution of the Ulan Buh Desert in northern China during the late Quaternary

    NASA Astrophysics Data System (ADS)

    Chen, Fahu; Li, Guoqiang; Zhao, Hui; Jin, Ming; Chen, Xuemei; Fan, Yuxin; Liu, Xiaokang; Wu, Duo; Madsen, David

    2014-05-01

    The evolution of arid environments in northern China was a major environmental change during the Quaternary. Here we present the dating and environmental proxy results from a 35 m long core (A-WL10ZK-1) collected from the Ulan Buh Desert (UBD), along with supplemental data from four other cores. The UBD is one of the main desert dune fields in China and our results indicate the UBD has undergone complex evolution during the late Quaternary. Most of the present UBD was covered by a Jilantai-Hetao Mega-paleolake lasting until ~ 90 ka ago. A sandy desert environment prevailed throughout the UBD during the last glacial period and early Holocene. A wetland environment characterized by the formation of numerous interdunal ponds in the northern UBD occurred at ~ 8-7 ka, although a dune field persisted in the southern UBD. The modern UBD landscape formed after these wetlands dried up. During the last 2000 years, eolian sand from the Badain Jaran Desert has invaded the northern UBD, while farming and overgrazing resulted in the formation of the eastern UBD. We suggest that the formation of UBD landforms is related to the disintegration of the megalake Jilantai-Hetao and to summer monsoon changes during the last glaciation and Holocene.

  12. Radiocarbon dates and late-Quaternary stratigraphy from Mamontova Gora, unglaciated central Yakutia, Siberia, U.S.S.R.

    USGS Publications Warehouse

    Pewe, T.L.; Journaux, A.; Stuckenrath, R.

    1977-01-01

    A fine exposure of perennially frozen ice-rich silt and associated flora and vertebrate fauna of late-Quaternary age exists at Mamontova Gora along the Aldan River in central Yakutia, Siberia, U.S.S.R. The silt deposit caps a 50-m-high terrace and consists of three units. An upper layer 1-2 m thick overlies a 10-15-m-thick brownish to black silt layer. The lower silt layer is greenish to gray and about 15 m thick. All the silt is well sorted with 60% of the particles falling between 0.005 and 0.5 mm in diameter and is generally chemically and mineralogically homogeneous. The middle unit contains may extinct vertebrate mammal remains and ice wedges. The lower unit contains little vegetation and no ice wedges. The silt is widespread and exists as a loamy blanket on terraces at various elevations on both sides of the lower Aldan River. The origin of the silt blanket of late-Quaternary age in central Yakutia has long been controversial. Various hypotheses have been suggested, including lacustrine and alluvial, as well as frost-action origins. It is sometimes referred to as loess-like loam. Pe??we?? believes the silt at Mamontova Gora is loess, some of which has been retransported very short distances by water. The silt probably was blown from wide, braided, unvegetated flood plains of rivers draining nearby glaciers. The silt deposits are late Quaternary in age and probably associated with the Maximum glaciation (Samarov) and Sartan and Syryan glaciations of Wisconsinan age. On the basis of biostratigraphy, 10 radiocarbon dates, and their relation to the nearby glacial record, it is felt that the upper unit at Mamontova Gora is Holocene and the middle unit is Wisconsinan. The youngest date available from the middle unit at this particular location is 26,000 years. Dates greater than 56,000 years were obtained in the lower part of the middle unit. The lower unit is definitely beyond the range of radiocarbon dating and probably is older than the last interglacial. The

  13. Munroa argentina, a Grass of the South American Transition Zone, Survived the Andean Uplift, Aridification and Glaciations of the Quaternary

    PubMed Central

    Amarilla, Leonardo D.; Anton, Ana M.; Chiapella, Jorge O.; Manifesto, María M.; Angulo, Diego F.; Sosa, Victoria

    2015-01-01

    The South American Transition Zone (SATZ) is a biogeographic area in which not only orogeny (Andes uplift) and climate events (aridification) since the mid-Miocene, but also Quaternary glaciation cycles had an important impact on the evolutionary history of the local flora. To study this effect, we selected Munroa argentina, an annual grass distributed in the biogeographic provinces of Puna, Prepuna and Monte. We collected 152 individuals from 20 localities throughout the species’ range, ran genetic and demographic analyses, and applied ecological niche modeling. Phylogenetic and population genetic analyses based on cpDNA and AFLP data identified three phylogroups that correspond to the previously identified subregions within the SATZ. Molecular dating suggests that M. argentina has inhabited the SATZ since approximately 3.4 (4.2–1.2) Ma and paleomodels predict suitable climate in these areas during the Interglacial period and the Last Glacial Maximum. We conclude that the current distribution of M. argentina resulted from the fragmentation of its once continuous range and that climate oscillations promoted ecological differences that favored isolation by creating habitat discontinuity. PMID:26110533

  14. Late Neogene to Quaternary environmental changes in the Antarctic Peninsula region: evidence from drift sediments

    NASA Astrophysics Data System (ADS)

    Hillenbrand, Claus-Dieter; Ehrmann, Werner

    2005-02-01

    Clay-mineral composition and biogenic opal content in upper Miocene to Quaternary drift sediments recovered at two Ocean Drilling Program (ODP) sites from the continental rise in the Bellingshausen Sea had been analyzed in order to reconstruct the climatic and glacial history of the Antarctic Peninsula. The clay mineral composition at both sites is dominated by smectite, illite, and chlorite, and alternates between a smectite-enriched and a chlorite-enriched assemblage throughout the last 9.3 my. The spatial distribution of clay minerals in Holocene sediments west of the Antarctic Peninsula facilitates the identification of particular source areas, and thus the reconstruction of transport pathways. The similarity to clay mineral variations reported from upper Quaternary sequences suggests that the short-term clay-mineralogical fluctuations in the ODP cores reflect glacial-interglacial cyclicity. Thus, repeated ice advances and retreats in response to a varying size of the Antarctic Peninsula ice cap are likely to have occurred throughout the late Neogene and Quaternary. The clay minerals in the drift sediments exhibit only slight long-term variations, which are caused by local changes in glacial erosion and in supply of source rocks, rather than by major climatic changes. The opal records at the ODP sites are dominated by long-term variations since the late Miocene. We infer that the opal content in the drift sediments, although it is influenced by dissolution in the water column and the sediment column and by the burial with lithogenic detritus, provides a signal of paleoproductivity. Because the annual sea-ice coverage is regarded as the main factor controlling biological productivity, the opal signal helps to reconstruct paleoceanographic changes in the Bellingshausen Sea. Slightly enhanced opal deposition during the late Miocene indicates slightly warmer climatic conditions in the Antarctic Peninsula area than at present. During the early Pliocene, enhanced

  15. Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation

    USGS Publications Warehouse

    Carrara, P.E.; Ager, T.A.; Baichtal, J.F.

    2007-01-01

    The interpretation of the extent of late Wisconsin glaciation in southeastern Alaska has varied between geologists and biologists. Maps and reports of the region prepared by geologists commonly indicated that late Wisconsin ice extended as a large uniform front west to the edge of the continental shelf. However, the distribution of plants and animals in the region has led many biologists to suggest that there may have been ice-free areas that served as refugia during the late Wisconsin. Based on analyses of aerial photographs, topographic maps, and bathymetric charts, in conjunction with a review of previous literature and reconnaissance fieldwork throughout the region, this study presents data supporting a limited ice extent in the Alexander Archipelago during the late Wisconsin and identifies possible ice-free areas that may have served as refugia. These areas include (1) the Fairweather Ground, (2) the Herbert Graves Island area, (3) the western coast of southern Baranof Island and adjacent continental shelf, (4) Coronation Island and the adjacent continental shelf, (5) the Warren Island area, (6) the continental shelf from west of Heceta Island to Forrester Island in the south, (7) parts of the west coast of southern Dall Island, and (8) lowland areas in southern Prince of Wales Island. The identification of these possible refugia has bearing on the recolonization of the Alexander Archipelago, as they could have served as centers of biotic dispersal upon regional deglaciation and as stepping stones for early humans with a maritime tradition entering the western hemisphere from Asia. ?? 2007 NRC Canada.

  16. Late-quaternary vegetational dynamics and community stability reconsidered

    NASA Astrophysics Data System (ADS)

    Delcourt, Paul A.; Delcourt, Hazel R.

    1983-03-01

    Defining the spatial and temporal limits of vegetational processes such as migration and invasion of established communities is a prerequisite to evaluating the degree of stability in plant communities through the late Quaternary. The interpretation of changes in boundaries of major vegetation types over the past 20,000 yr offers a complementary view to that provided by migration maps for particular plant taxa. North of approximately 43°N in eastern North America, continual vegetational disequilibrium has resulted from climatic change, soil development, and species migrations during postglacial times. Between 33° and 39°N, stable full-glacial vegetation was replaced by a relatively unstable vegetation during late-glacial climatic amelioration; stable interglacial vegetation developed there after about 9000 yr B.P. Late-Quaternary vegetation has been in dynamic equilibrium, with a relatively constant flora, south of 33°N on upland interfluves along the northern Gulf Coastal Plain, peninsular Florida, and west-central Mexico.

  17. Loess sedimentation in Tibet: provenance, processes, and link with Quaternary glaciations

    USGS Publications Warehouse

    Sun, Jielun; Li, S.-H.; Muhs, D.R.; Li, B.

    2007-01-01

    Well-preserved loess deposits are found on the foothills of mountains along the middle reaches of the Yarlung Zangbo River in southern Tibet. Optically stimulated luminescence (OSL) dating is used to determine loess ages by applying the single-aliquot regeneration technique. Geochemical, mineralogical, and granulometric measurements were carried out to allow a comparison between loess from Tibet and the Chinese Loess Plateau. Our results demonstrate that (i) the loess deposits have a basal age of 13-11 ka, suggesting they accumulated after the last deglaciation, (ii) loess in southern Tibet has a "glacial" origin, resulting from eolian sorting of glaciofluvial outwash deposits from braided river channels or alluvial fans by local near-surface winds, and (iii) the present loess in the interior of Tibet has accumulated since the last deglaciation when increased monsoonal circulation provided an increased vegetation cover that was sufficient for trapping eolian silt. The lack of full-glacial loess is either due to minimal vegetation cover or possibly due to the erosion of loess as glaciofluvial outwash during the beginning of each interglacial. Such processes would have been repeated during each glacial-interglacial cycle of the Quaternary. ?? 2007 Elsevier Ltd. All rights reserved.

  18. Precise timing and rate of massive late Quaternary soil denudation

    NASA Astrophysics Data System (ADS)

    Cooke, M. Jennifer; Stern, Libby A.; Banner, Jay L.; Mack, Lawrence E.; Stafford, Thomas W., Jr.; Toomey, Rickard S., III

    2003-10-01

    Strontium isotopes are a unique tool to study soil-erosion dynamics. Changes in Sr isotope ratios (87Sr/86Sr) provide a record of late Quaternary landscape denudation of the Edwards Plateau of central Texas, United States. The use of Sr isotopes as a tracer for soil erosion is based on the observation that, in central Texas, the 87Sr/86Sr ratio of soil correlates with soil thickness. Plants and animals express the 87Sr/86Sr ratio of exchangeable Sr in the soil. Therefore, we use changes in Sr isotope ratios through a well-dated stratigraphic sequence of fossil plants and animals in Hall's Cave, Kerr County, Texas, as a proxy for temporal changes in soil thickness. By using this record we are able to characterize late Quaternary climate-driven soil-erosion dynamics on the Edwards Plateau. We find that continuous erosion removed at least 180 cm of soil at a constant minimum rate of 11 cm/k.y.; this continuous phase of erosion ended ca. 5 ka. The Sr isotope record of soil erosion is consistent with late Quaternary environmental change in central Texas that has been independently modeled by using local and regional climate records. However, the rate of this climate-driven soil-erosion event was an order of magnitude slower than recent soil erosion caused by human land use. These results link erosion to century- to millennial-scale climate change and are cautionary evidence that even greater landscape degradation may result from coincident climatic variability and anthropogenic influences.

  19. A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

    USGS Publications Warehouse

    Ridge, J.C.; Evenson, E.B.; Sevon, W.D.

    1992-01-01

    In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (??? 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, gre??zes lite??es, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (??? 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ??? 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and

  20. Late-Quaternary exhumation rates constrained by OSL thermochronometry at the Franz Josef Glacier, New Zealand

    NASA Astrophysics Data System (ADS)

    Duverger, Arnaud; King, Georgina; Valla, Pierre; Cox, Simon; Herman, Frederic

    2016-04-01

    The Southern Alps of New Zealand are often cited as the primary example of a mountain range that has reached exhumation and topographic steady state, especially on the West Coast where exhumation rates reach up to about 10 mm/yr. However, cyclic climatic changes, throughout the Quaternary period have meant that the Alps cycled between being completely glaciated and ice free. The impact that such glacial cycles may have had on the spatial variability of erosion rates remains poorly constrained. Here we use Optically Stimulated Luminescence (OSL) as a very low temperature thermochronometer to constrain rock cooling histories at 10-100 kyr timescales on samples collected near the Franz Josef glacier. OSL-thermochronometry is based on the amount of electrons accumulated in the lattice defects of natural minerals such as quartz or feldspar, due to the competing effects of charge trapping due to the natural radioactivity within the rock and charge detrapping due to thermal loss during rock exhumation towards the surface. We collected 9 samples along the Waiho valley (crossing the Alpine Fault) and the Franz Josef glacier to quantify late-Quaternary exhumation rates and their potential spatial variations. Bedrock samples have been crushed to extract the light-safe rock interiors which have then been processed to isolate potassium-rich feldspars (K-feldspars). We used the Infra-Red Stimulated Luminescence at 50°C (IRSL50) protocol, including the measurement of the natural IRSL50 trapped charge population and the laboratory characterization of sample-specific thermal and athermal kinetic parameters. Once measured, the luminescence signal can be inverted into cooling histories. We also explored the potential of the recently developed multi-OSL-thermochronometer (King et al., accepted) to better constrain the cooling path. Our first OSL measurements show that samples are not in saturation and thus contain useful thermochronometric information over the last ~100 kyr. Inverse

  1. Late Quaternary terrestrial vertebrate coprolites from New Zealand

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2014-08-01

    Over the past decade, concerted efforts to find and study Late Quaternary terrestrial vertebrate coprolites in New Zealand have revealed new insights into the diets and ecologies of New Zealand's prehistoric birds. Here, we provide a broader review of the coprolites found in natural (non-archaeological) Late Quaternary deposits from New Zealand. We summarise the morphological diversity of the coprolites, and discuss the taphonomy of the sites in which they are found. Since the 1870s more than 2000 coprolites have been discovered from 30 localities, all restricted to the South Island. The distribution of coprolite localities appears to reflect the presence of geological and climatic factors that enhance the potential for coprolite preservation; coprolites require dry conditions for preservation, and have been found on the ground surface within drafting cave entrances and at shallow (<300 mm) depths beneath rock overhangs with a northerly aspect. We classify the coprolites into eleven morphotypes, each of which may represent a range of different bird and/or reptile species. A review of genetically identified specimens shows that coprolites of different bird species overlap in size and morphology, reinforcing the need for identifications to be based on ancient DNA analysis.

  2. Evidence for two pulses of glaciation during the late Proterozoic in northern Utah and southeastern Idaho.

    USGS Publications Warehouse

    Crittenden, M.D., Jr.; Christie-Blick, N.; Link, P.K.

    1983-01-01

    Over much of this area, the glacial deposits and associated rocks thicken westward and form the basal part of a miogeoclinal wedge that accumulated near the late Proterozoic and early Paleozoic continental margin. In the east, such deposits are thin and rest on Archean basement or rocks of Proterozoic Y age; in the west, they are part of thicker sequences in which deposition apparently continued without significant interruption from late Proterozoic into Cambrian time. Recent mapping shows that glacial episodes represented either by diamictite or by dropstones enclosed in fine-grained laminated beds are separated by as much as 1000m of non-glacial deposits, including black slate, alternating graywacke and siltstone, quartzite, and conglomerate. Using reasonable sedimentation rates for such deposits and by comparison with modern analogues, we infer that two episodes of glaciation, each probably consisting of multiple advances and retreats, were separated by a non-glacial interval of a few hundred thousand to a few million years' duration.-from Author

  3. Detailed view into the dynamics of the Late Miocene glaciation episode that accompanied terrestrial evolution

    NASA Astrophysics Data System (ADS)

    Tzanova, A.; Herbert, T.; Lawrence, K. T.; Peterson, L.; Kelly, C. S.

    2015-12-01

    We focus on the period of ~ 9 - 5 Ma when an episode of notably cool temperatures corresponds to evidence of high latitude Northern Hemisphere glaciation and mid-latitude terrestrial evolution. Alkenone-based sea surface temperatures (SST) from six globally distributed sites: ODP Sites 907 and 982 in the North Atlantic, ODP Site 1088 in the South Atlantic and ODP Sites 883, 884 and 887 in the North Pacific, and the Monte dei Corvi marine section in the Mediterranean unequivocally establish a dramatic, Late Miocene cold episode that persisted over approximately 2.5 Myr. In this work we establish the timing and synchronization of temperature decrease as well as rebound at orbital timescales. All sites were notably warmer than their modern annual average at ~9 Ma and exhibit sustained cooling beginning at ~8 Ma. SSTs rebound close to ~5.9 Ma at most locations suggesting that the cooling trend that began in the Late Miocene slowed down or even reversed in some locations in the Pliocene. The newly reconstructed SSTs highlight the role of cooling and an increase in equator to pole temperature gradients in terrestrial evolution at this pivotal time.

  4. Reconstructing the pre-Quaternary landscape in Agnew-Lawlers area, Western Australia with emphasis on the Permo-Carboniferous glaciation and post-glacial weathering

    NASA Astrophysics Data System (ADS)

    Salama, Walid; Anand, Ravi R.

    2016-04-01

    redox reactions. The formation of smectite and ferruginous cements in this unit is attributed to weathering of ferromagnesian and opaque heavy minerals under oxic and slightly alkaline conditions. Mineralogical and geochemical changes dominated in the upper unit is related mainly to Post-Permian chemical weathering, where almost all rock-forming minerals are altered to kaolinite and alkali and alkaline earth elements are leached forming bleached white saprolitic diamictites. A change in clay minerals from kaolinite in the weathered Permo-Carboniferous succession to smectite in the overlying Cenozoic succession demarcates the unconformity and probably reflects a change to an arid climatic condition. Chemically, the Cenozoic succession shows a sharp increase in Ti/Al and La/Ce ratios and a decrease in Ce anomaly that remain constant in the Permo-Carboniferous section. These mineralogical and chemical variations through the Phanerozoic stratigraphic section can be used to follow the landscape and climatic evolution since the late Palaeozoic glaciation.

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

    NASA Astrophysics Data System (ADS)

    Barrows, Timothy T.; Hope, Geoffrey S.; Prentice, Michael L.; Fifield, L. Keith; Tims, Stephen G.

    2011-09-01

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

  6. Global warming: Perspectives from the Late Quaternary paleomammal record

    SciTech Connect

    Graham, R.W. )

    1993-03-01

    Global warming at the end of the Pleistocene caused significant environmental changes that directly and indirectly effected biotic communities. The biotic response to this global warming event can provide insights into the processes that might be anticipated for future climatic changes. The megafauna extinction may have been the most dramatic alteration of mammalian communities at the end of the Pleistocene. Late Quaternary warming also altered regional diversity patterns for some small mammal guilds without extinction. Reductions in body size for both small and large mammal species were also consequences of these environmental fluctuations. Geographic shifts in the distributions of individual mammal species resulted in changes in species composition of mammalian communities. The individualistic response of biota to environmental fluctuations define some boundary conditions for modeling communities. Understanding these boundary conditions is mandatory in planning for the preservation of biodiversity in the future. Finally, it is essential to determine how global warming will alter seasonal patterns because it is apparent from the paleobiological record that not all Quaternary warming events have been the same.

  7. Late Quaternary folding of coral reef terraces, Barbados

    NASA Astrophysics Data System (ADS)

    Taylor, Frederick W.; Mann, Paul

    1991-02-01

    Uplifted late Ouaternary coral reefs on the island of Barbados record folding of the emergent crest of the Lesser Antilles accretionary prism (Barbados Ridge complex) since ca. 1 Ma. Three northeast striking folds are defined by systematic changes in altitudes in the crest of First High Cliff, a mostly constructional reef terrace about 125 ka, and Second High Cliff, a partially erosional reef terrace about 500 ka. The folds have wavelengths of 6 to 8 km and fold axes extend about 10 km. The largest anticline rises to the northeast, where it has been breached by erosion exposing highly deformed Eocene to lower Miocene rocks of the Scotland District. Uplift rates based on heights of the last interglacial First High Cliff range from 0.07 to 0.44 mm/yr. Quaternary folding on Barbados indicates that the crest of the accretionary prism continues to be an active fold belt undergoing northwestsoutheast shortening.

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

    PubMed Central

    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.

    2005-01-01

    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

  9. Late Quaternary sea-level changes of the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Lokier, Stephen W.; Bateman, Mark D.; Larkin, Nigel R.; Rye, Philip; Stewart, John R.

    2015-07-01

    Late Quaternary reflooding of the Persian Gulf climaxed with the mid-Holocene highstand previously variously dated between 6 and 3.4 ka. Examination of the stratigraphic and paleoenvironmental context of a mid-Holocene whale beaching allows us to accurately constrain the timing of the transgressive, highstand and regressive phases of the mid- to late Holocene sea-level highstand in the Persian Gulf. Mid-Holocene transgression of the Gulf surpassed today's sea level by 7100-6890 cal yr BP, attaining a highstand of > 1 m above current sea level shortly after 5290-4570 cal yr BP before falling back to current levels by 1440-1170 cal yr BP. The cetacean beached into an intertidal hardground pond during the transgressive phase (5300-4960 cal yr BP) with continued transgression interring the skeleton in shallow-subtidal sediments. Subsequent relative sea-level fall produced a forced regression with consequent progradation of the coastal system. These new ages refine previously reported timings for the mid- to late Holocene sea-level highstand published for other regions. By so doing, they allow us to constrain the timing of this correlatable global eustatic event more accurately.

  10. Formation of Late Quaternary paleoshorelines in Crete, Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Mouslopoulou, Vasiliki; Begg, John; Nicol, Andrew; Oncken, Onno; Prior, Christine

    2015-12-01

    Paleoshorelines of Late Quaternary age in western Crete do not exclusively increase in age with rising altitude as is generally observed worldwide. At numerous sites, for example, Late-Holocene paleoshorelines decrease in age with increasing altitude while in other cases paleoshorelines at similar altitude vary in age by tens of thousands of years. We propose that the observed paleoshoreline altitude-age relationships can be accounted for by eustatic sea-level changes and tectonic rock uplift without requiring substantial errors on radiocarbon ages or tectonic subsidence, as has been previously proposed. To test this model we use a dataset consisting of altitude and age data for 71 individual paleoshorelines sampled from 21 sites distributed along the entire Cretan coastline. These data include radiocarbon ages of marine biota (40 new dates) within beachrock resting on paleoshorelines ranging up to 48 kyr BP in age and ≤20 m above present sea-level. We find that paleoshoreline formation reflects Late Holocene tectonic rock uplift in western Crete, preceded by eustatic sea-level rise and by >10 kyr BP rock uplift along the entire island. Our observations contravene existing models as they suggest that some paleoshorelines, and their associated lithified beachrock, survived passage through the wave-zone multiple times and formed throughout the sea-level cycle (i.e., preservation is not restricted to highstand deposits). These results may have application globally in regions where erosion-resistant carbonate beachrock mantles paleoshorelines.

  11. Late Quaternary geomorphology and soils in Crater Flat, Yucca mountain area, southern Nevada

    SciTech Connect

    Peterson, F.F.; Bell, J.W.; Ramelli, A.R.; Dorn, R.I.; Ku, T.L.

    1995-04-01

    Crater Flat is an alluvium-filled structural basin on the west side of Yucca Mountain, Nevada, which is under consideration for a high-level nuclear waste repository. North-trending, late Quaternary faults offset alluvium in Crater Flat both along the canyons of the western flanks of Yucca Mountain and out on the piedmont slope. We believe the initial lack of young offsets at Yucca Mountain was in part due to unrecognized late Quaternary stratigraphy. We hypothesize that alluviation in the Yucca Mountain region was more active during the late Quaternary than previously thought. Several techniques were tried to test this hypothesis. Results are compared with previous soils and surface-exposure dating studies, and correlated to stratigraphy of other late Quaternary units in the southern Nevada, Death Valley, and Mojave Desert areas, and provide new stratigraphic data relevant to understanding climatic-alluvial processes in the Basin and Range Province during the late Quaternary. 76 refs., 7 figs., 6 tabs.

  12. Late Quaternary river drainage and fish evolution, Southland, New Zealand

    NASA Astrophysics Data System (ADS)

    Craw, D.; Burridge, C.; Anderson, L.; Waters, J. M.

    2007-02-01

    Late Quaternary to Holocene landscape evolution in southern New Zealand was dominated by glacial outwash processes. Evolution of the drainage network on a regional scale was punctuated by numerous river capture events associated with outwash transport and deposition. River capture events can be inferred from geological and topographic observations throughout the region. Independent evidence for river capture and drainage reorientation can be obtained from genetic studies of a freshwater-limited fish ( Galaxias 'southern', informal name). Regionally extensive interlinking of principal rivers (Mataura, Oreti, Aparima) via coalescence of alluvial plains onshore, and offshore at sea level lowstands, has resulted in a widespread genetic homogenisation of fish populations (< 0.9% mtDNA divergence). Genetically similar populations of G. 'southern' are present in an adjacent catchment (Von) that was captured episodically by the neighbouring major river system (Clutha). The low degree of genetic divergence between Oreti and Von catchments (< 0.15% mtDNA divergence) demonstrates that genetic interaction between fish populations was severed recently, probably during the early Holocene. This is in accord with radiocarbon dating (11-13 ka) of the youngest gravel level within the intervening divide. In contrast, morphologically similar fish in another adjacent major river (Waiau) have a minimum mtDNA divergence of 2.4% from the fish in the Mataura, Oreti, and Aparima Rivers. This genetic separation occurred at ca. 145-240 ka, based on the late Quaternary outwash terrace dating, in agreement with "molecular clock" estimates. Geological and genetic data in combination provide powerful tools for the elucidation of local and regional geomorphic evolution where river capture is an important process. The potential is strong for genetic data alone to provide information on the relative and absolute timing of river capture events, but must be interpreted in the context of severance of

  13. Study on the Late Quaternary Activity of Niyang River Fault

    NASA Astrophysics Data System (ADS)

    Fangtou, T.

    2015-12-01

    Niyang River fault with north-west trending is located on the west side of the Eastern Himalayan Syntaxis. It dislocated the eastern segment of Brahmaputra fault zone. We study the late Quaternary activity of the Niyang River fault by the high-resolution image data in combination with detailed field investigation, GPS observation, trenching and radiocarbon dating of charcoal samples. The GPS observation data shows that the movement characteristics of Niyang River fault is dextral strike-slip with extrusion at present, its strike-slip rate is 3~4mm/a and its extrusion rate is 2~3mm/a. The trench at Bayi town revealed that the first terraces of Niyang River was dislocated 50cm by the fault and it is dated to be 1220±40cal.a BP.. We found that third Lake terraces of the Linzhi ancient lakes was dislocated about 1.5m at Mirui town and it is dated to be 18060±60cal.a BP.. By the fault influence, there are different elevations at the same level terraces of Niyang river and the Linzhi ancient lakes both sides of Niyang river near Bayi town. The altitude of the second terraces of Niyang River is about 20 meters at eastern side higher than western side and it is dated to be between 8860±40cal.a BP. and 9870±50cal.a BP., the altitude of the third lake terraces of the Linzhi ancient lakes is about 60 meters at eastern side higher than western side. So, the average vertical slip rate of Niyang River fault was about 2mm/a since Holocene and its average vertical slip rate was about 3mm/a since late period of the late Pleistocene. This is consistent with GPS observation data. All these data suggest that Niyang River fault is active since Holocene. So further detailed research will be necessary to determine the range of the latest activity of this fault, movement characteristics and velocity and recurrence intervals of major earthquakes. These data will be a great significance for earthquake zonation and assessment of seismic risk in this region. Keywords:Niyang River fault

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

    USGS Publications Warehouse

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

    2008-01-01

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

  15. Late Quaternary land-sea correlations, northern Labrador, Canada

    SciTech Connect

    Clark, P.; Josenhans, H.

    1985-01-01

    Late Quaternary glacial and postglacial units in the Torngat Mountains, northern Labrador, are correlated with units identified on the adjacent continental shelf. The late Wisconsinan Laurentide Ice Sheet drained through major valleys of the Torngat Mountains as outlet glaciers, depositing the Saglek Moraines. These are of regional extent and have been mapped from Saglek Fiord north to Noodleook Fiord. A C-14 date of 18,210 +/- 1900 BP on total organic matter (TOM) from lake sediment dammed by a segment of the Saglek Moraines is interpreted as a maximum date for deposition of the Saglek Moraine system because of possible contamination. Glacial sediments comprising the Saglek Moraines are correlated with upper till mapped in troughs and saddles on the continental shelf. Outlet glaciers depositing a late Wisconsinan unit flowed through Labrador fiords and onto the shelf at low basal shear stresses, particularly on the shelf where, although grounded, they were hydrostatically buoyed up and moved principally by sliding. A glaciomarine unit conformably overlies late Wisconsinan till on the shelf and on the land. This unit is a gravelly clayey silt, contains abundant foraminifera, and has up to 60% limestone in the pebble fraction. C-14 dates suggest deposition of this unit began ca. 10,000 BP on the shelf and 9000 BP on the land, an ended by 8000 BP. Limestone pebbles in this unit suggest a source in part from sediment-laden icebergs and pack-ice from the north. Marine deposition from ca. 8000-0 BP is characterize by basinal sedimentation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  17. Late Quaternary slip on the Santa Cruz Island fault, California

    USGS Publications Warehouse

    Pinter, N.; Lueddecke, S.B.; Keller, E.A.; Simmons, K.R.

    1998-01-01

    The style, timing, and pattern of slip on the Santa Cruz Island fault were investigated by trenching the fault and by analysis of offset late Quaternary landforms. A trench excavated across the fault at Christi Beach, on the western coast of the island, exposed deformation of latest Pleistocene to Holocene sediments and pre-Quaternary rocks, recording repeated large-magnitude rupture events. The most recent earthquake at this site occurred ca. 5 ka. Coastal terraces preserved on western Santa Cruz Island have been dated using the uranium-series technique and by extrapolation using terrace elevations and the eustatic record. Offset of terraces and other landforms indicates that the Santa Cruz Island fault is predominantly left lateral, having a horizontal slip rate of not more than 1.1 mm/yr and probably about 0.8 mm/yr. The fault also has a smaller reverse component, slipping at a rate of between 0.1 and 0.2 mm/yr. Combined with measurements of slip per event, this information suggests a long-term average recurrence interval of at least 2.7 k.y. and probably 4-5 k.y., and average earthquake magnitudes of Mw 7.2-7.5. Sense of slip, recurrence interval, and earthquake magnitudes calculated here for the Santa Cruz Island fault are very similar to recent results for other faults along the southern margin of the western Transverse Range, including the Malibu Coast fault, the Santa Monica fault, the Hollywood fault, and the Raymond fault, supporting the contention that these faults constitute a continuous and linked fault system, which is characterized by large but relatively infrequent earthquakes.

  18. Glaciation and deglaciation of the Libyan Desert: The Late Ordovician record

    NASA Astrophysics Data System (ADS)

    Le Heron, D. P.; Armstrong, H. A.; Wilson, C.; Howard, J. P.; Gindre, L.

    2010-01-01

    Detailed outcrop studies at the flanks of Al Kufrah Basin, Libya, reveal the nature of glacially-related sedimentation and post-depositional deformation styles produced in association with the Late Ordovician glaciation, during which ice sheets expanded northward over North Africa to deposit the Mamuniyat Formation. At the SE basin flank (Jabal Azbah), the Mamuniyat Formation is sand-dominated, and incises interfingering braidplain and shallow marine deposits of the Hawaz Formation. The glacially-related sediments include intercalations of mud-chip bearing tabular sandstones and intraformational conglomerates, which are interpreted as turbidite and debrite facies respectively. These record aggradation of an extensive sediment wedge in front of a stable former ice margin. An increase in mudstone content northward is accompanied by the occurrence of more evolved turbidites. A widespread surface, bearing streamlined NW-SE striking ridges and grooves, punctuates this succession. The structures on the surface are interpreted to have formed during a regional north-westward ice advance. Above, siltstones bearing Arthrophycus burrows, and Orthocone-bearing sandstones beneath tidal bars testify to glaciomarine conditions for deposition of the underflow deposits beneath. By contrast, the northern basin margin (Jabal az-Zalmah) is appreciably different in recording shallower water/paralic sedimentation styles and major glaciotectonic deformation features, although facies analysis also reveals northward deepening. Here, a siltstone wedging from 8 to 50 m toward the north was deposited (lower delta plain), succeeded by climbing ripple cross-laminated sandstones up to 60 m in thickness (distal through proximal delta mouth bar deposits) with occasional diamictite interbeds. These rocks are deformed by thrusts and > 50 m amplitude fault-propagation folds, the deformation locally sealed by a diamictite then overlain by conglomeratic lag during ultimate deglaciation. Integrating

  19. Timing of late Pleistocene glaciation in Mongolia: Surface exposure dating reveals a differentiated pattern of glacial forcing

    NASA Astrophysics Data System (ADS)

    Pötsch, Steffen; Rother, Henrik; Lorenz, Sebastian; Walther, Michael; Lehmkuhl, Frank

    2015-04-01

    of atmospheric circulation and its significance for controlling regional precipitation results in a more differentiated pattern of late Pleistocene glaciation in Mongolia than previously recognized. Compared to other glacial records from High Asia, the observed patterns of past glaciations in Mongolia show similar results (i.e. ice maxima during interstadial wet phases) compared to monsoon influenced regions in southern Central Asia and NE-Tibet, while major expansion during insolation minima (MIS-4 and MIS-2) are more in tune with glacier responses known from western Central Asia and Siberia.

  20. Marine and Terrestrial Evidence for Glaciation during the Pliocene - a Global Synthesis

    NASA Astrophysics Data System (ADS)

    De Schepper, S.; Gibbard, P. L.; Salzmann, U.; Ehlers, J.

    2014-12-01

    The Pliocene climate is globally warm and characterized by high atmospheric carbon dioxide concentrations. Nevertheless, considerable evidence for substantial glaciation events has been identified in both the Northern and Southern Hemisphere prior to the Quaternary. Evidence on land is fragmentary, but marine records of glaciation present a more complete history of Pliocene glaciation. A global compilation of glacial evidence (De Schepper et al. 2014) demonstrates that there are four large glaciation events in the Southern and/or Northern Hemisphere prior to the latest Pliocene intensification of Northern Hemisphere glaciation. Two global glacial events are identified in the early Pliocene, one around the early/late Pliocene transition, and one during the late Pliocene Marine Isotope Stage M2. ReferenceDe Schepper, S., Gibbard, P.L., Salzmann, U., Ehlers, J., 2014. A global synthesis of the marine and terrestrial evidence for glaciation during the Pliocene Epoch. Earth-Science Reviews 135, 83-102.

  1. A 10Be Chronology of Late Pleistocene and Holocene Glaciation in the Rwenzori Mountains, Uganda

    NASA Astrophysics Data System (ADS)

    Baber, M.; Kelly, M. A.; Russell, J. M.; Loomis, S. E.

    2012-12-01

    Although the retreat of glaciers in East Africa has been monitored over the last century, longer-term records of African glacier fluctuations are scarce. The Rwenzori Mountains, located on the border of Uganda and the Democratic Republic of Congo, host the largest glacial system in Africa and provide an opportunity for extensive investigation of past glaciations. We mapped and applied surface exposure (10Be) dating to glacial moraines deposited since the end of the last ice age in the Rwenzori Mountains to test the feasibility of 10Be dating at this site and to develop a chronology of glacial fluctuations. Our study is the first to use 10Be dating of glacial features in Africa and is possible because the Rwenzori host quartz-rich lithologies. By comparing the timing of Rwenzori glacial advances with other paleoclimate records from East Africa, we also will examine the climatic conditions which influenced tropical glacier fluctuations. Osmaston (1989) mapped moraines in the Rwenzori Mountains, documenting three stages of Pleistocene and Holocene glaciations, the Mahoma, Omurubaho and Lac Gris stages. The Mahoma stage moraines are estimated to be older than 17,980 ± 780 yr BP (D. M. Livingstone, 1962) by basal 14C dating of sediments from Lake Mahoma, situated in large lateral moraine at 2990 m asl. The age of the Omurubaho stage moraine is estimated from a basal 14C age (7,730 ± 150 yr BP) Lower Kitandara Lake (3990 m asl) and dammed by an Omurubaho stage moraine. The Lac Gris moraines are estimated at ~150-700 yr BP (de Heinzelin, 1953; Bergström, 1955) based on rates of lichen growth and plant colonization on moraines about 200 m below current glacial positions on Mt. Stanley. Though considerable uncertainty remains for the ages of these glacier deposits, these three stages most likely represent ages from the LGM to the LIA. We present two new 10Be ages of boulders from two moraines in the Nyamagusani Valley, ~4000 m asl. Sample KOP-2 (4033 m asl) is from the

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

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    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

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

    SciTech Connect

    Palmer, J.R.; Hoffman, D. . Dept. of Natural Resources)

    1993-03-01

    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.

  4. Late Quaternary Pollen Record from Cheyenne Bottoms, Kansas

    NASA Astrophysics Data System (ADS)

    Fredlund, Glen G.

    1995-01-01

    A sediment and pollen record from Cheyenne Bottoms, a large (166 km 2) enclosed basin in central Kansas, provides evidence for local and regional vegetation and climate change during the late Quaternary (ca. 30,000 yr.). Although radiocarbon dating of the carbonate-rich lacustrine sediments remains problematic, a basic chronological framework for the section is established. Two major litho- and biostratigraphic units, a Farmdalian zone (ca. 30,000 to 24,000 yr B.P.) and a Holocene zone (ca. 11,000 yr B.P. to present), are separated by a major unconformity spanning the Woodfordian (ca. 24,000 to 11,000 yr B.P.). Pollen and sedimentary data indicate a period of basin-wide drying preceding this unconformity. The sustained absence of sediment accumulation within this playa-like basin suggests that early Woodfordian conditions were increasingly arid with strengthened surface winds. Before this, persistent shallow water marshland dominated the local basin-bottom vegetation. Regional upland vegetation was an open grassland-sage steppe throughout the Farmdalian with limited populations of spruce, juniper, aspen, birch, and boxelder in riparian settings and escarpments. Throughout the Holocene, water levels within the basin fluctuated. Changes in wetland vegetation resulting from water level fluctuation have increased during the last 3,000 yr indicating that periodic episodes of wetland loss and rebound are not unique to postsettlement conditions but are an ongoing phenomenon at Cheyenne Bottoms.

  5. Patterns of late Quaternary shelf-margin sedimentation, southwest Louisiana

    SciTech Connect

    Suter, J.R.; Berryhill, H.L.

    1986-09-01

    Late Quaternary extension of the continental shelf in the northern Gulf of Mexico has been largely accomplished by deposition at the shelf margin during sea level lowstands. The distribution and geometry of facies suggest that delta progradation during sea level fall and lowstand is a principal process for shelf accretion. Along the shelf margin of southwest Louisiana, sets of deltaic deposits corresponding to the last two lowstands of sea level have been mapped from high-resolution seismic profiles. Individual deltas extend farther than 5000 m/sup 2/ and are more than 160 m thick. Diapirism has had a controlling effect on sedimentation patterns of the shelf-margin deltas throughout their depositional histories. Shelf-margin deltas have also been the loci for the transfer of large volumes of sediment from the shelf to the upper slope by mass transport, with buried submarine troughs formed by retrogressive shelf-edge failure in association with major streams acting as conduits for sediment movement. In southwest Louisiana, mass transport deposits follow depressions formed by salt diapirism rather than creating broad aprons on the slope.

  6. Comment on "Quaternary glaciations: from observations to theories" by D. Paillard [Quat. Sci. Rev. 107 (2015), 11-24

    NASA Astrophysics Data System (ADS)

    Bol'shakov, Vyacheslav A.; Kuzmin, Yaroslav V.

    2015-07-01

    In the invited review by Paillard (2015), comprehensive information about both theoretical and empirical studies of Pleistocene glaciations and their causes are presented. D. Paillard's review concludes that Milankovitch's (1930, 1941) theory cannot explain the 100,000 yr periodicity of glaciations within the last one million years, and that an additional factor must be responsible for global climate fluctuations. According to Paillard (2015), changes in the carbon dioxide (CO2) content of the atmosphere are responsible. This statement radically alters the conventional viewpoint about the leading role of orbital variations on global Pleistocene climate (e.g., Hays et al., 1976).

  7. Holarctic phylogeography of the root vole (Microtus oeconomus): implications for late Quaternary biogeography of high latitudes.

    PubMed

    Brunhoff, C; Galbreath, K E; Fedorov, V B; Cook, J A; Jaarola, M

    2003-04-01

    A species-wide phylogeographical study of the root vole (Microtus oeconomus) was performed using the whole 1140 base pair mitochondrial (mt) cytochrome b gene. We examined 83 specimens from 52 localities resulting in 65 unique haplotypes. Our results demonstrate that the root vole is divided into four main mtDNA phylogenetic lineages that seem to have largely allopatric distributions. Net divergence estimates (2.0-3.5%) between phylogroups, as well as relatively high nucleotide diversity estimates within phylogroups, indicate that the distinct phylogeographical structure was initiated by historical events that predated the latest glaciation. European root voles are divided into a Northern and a Central mtDNA phylogroup. The mtDNA data in concert with fossil records imply that root voles remained north of the classical refugial areas in southern Europe during the last glacial period. The currently fragmented populations in central Europe belong to a single mtDNA phylogroup. The Central Asian and the North European lineages are separated by the Ural Mountains, a phylogeographical split also found in collared lemmings (Dicrostonyx) and the common vole (M. arvalis). The Beringian lineage occurs from eastern Russia through Alaska to northwestern Canada. This distribution is congruent with the traditional boundaries of the Beringian refugium and with phylogeographical work on other organisms. In conclusion, similarities between the phylogeographical patterns in the root vole and other rodents, such as Arctic and subarctic lemmings, as well as more temperate vole species, indicate that late Quaternary geological and climatic events played a strong role in structuring northern biotic communities. PMID:12753215

  8. Middle and Late Weichselian (Devensian) glaciation history of south-western Norway, North Sea and eastern UK

    NASA Astrophysics Data System (ADS)

    Sejrup, H. P.; Nygård, A.; Hall, A. M.; Haflidason, H.

    2009-02-01

    Data from eastern England, Scotland, the northern North Sea and western Norway have been compiled in order to outline our current knowledge of the Middle and Late Weichselian glacial history of this region. Radiometric dates and their geological context from key sites in the region are presented and discussed. Based on the available information the following conclusions can be made: (i) Prior to 39 cal ka and most likely after ca 50 cal ka Scotland and southern Norway were extensively glaciated. Most likely the central North Sea was not glaciated at this time and grounded ice did not reach the shelf edge. (ii) During the time interval between 29 and 39 ka periods with ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) alternated with periods of restricted glaciation in Scotland and western Norway. (iii) Between 29 and 25 ka maximum Weichselian glaciation of the region occurred, with the Fennoscandian and British ice sheets coalescing in the central North Sea. (iv) Decoupling of the ice sheets had occurred at 25 ka, with development of a marine embayment in the northern North Sea (v) Between 22 and 19 ka glacial ice expanded westwards from Scandinavia onto the North Sea Plateau in the Tampen readvance. (vi) The last major expansion of glacial ice in the offshore areas was between 17.5 and 15.5 ka. At this time ice expanded in the north-western part of the region onto the Måløy Plateau from Norway and across Caithness and Orkney and to east of Shetland from the Moray Firth. The Norwegian Channel Ice Stream (NCIS), which drained major parts of the south-western Fennoscandian Ice Sheet, was active at several occasions between 29 and 18 ka.

  9. Scorched mussels (BIVALVIA: MYTILIDAE: BRACHIDONTINAE) from the temperate coasts of South America: phylogenetic relationships, trans-Pacific connections and the footprints of Quaternary glaciations.

    PubMed

    Trovant, Berenice; Orensanz, J M Lobo; Ruzzante, Daniel E; Stotz, Wolfgang; Basso, Néstor G

    2015-01-01

    This study addresses aspects of the phylogeny and phylogeography of scorched mussels (BIVALVIA: MYTILIDAE: BRACHIDONTINAE) from southern South America (Argentina and Chile), as well as their ecophylogenetic implications. Relationships were inferred from sequences of two nuclear (28S and 18S) and one mitochondrial (COI) genes, using Bayesian and maximum likelihood analyses. Our results indicate that the monophyletic BRACHIDONTINAE include three well supported clades: [i] Brachidontes Swainson (=Hormomya Mörch), [ii] Ischadium Jukes-Browne+Geukensia van de Poel, and [iii] Austromytilus Laseron+Mytilisepta Habe (usually considered a member of the SEPTIFERINAE)+Perumytilus Olsson. Species of clade [iii] are distributed along the temperate coasts of the Pacific Ocean. Available evidence supports divergence between Austromytilus (Australia) and Perumytilus (South American) following the breakup of Australian, Antarctic and South American shelves. Four brachidontins occur in southern South America: Brachidontes rodriguezii (d'Orbigny), B. granulatus (Hanley), and two genetically distinct clades of Perumytilus. The latter are confined to the Chile-Peru (North Clade) and Magellanic (South Clade) Biogeographic Provinces, respectively warm- and cold-temperate. The South Clade is the only brachidontin restricted to cold-temperate waters. Biogeographic considerations and the fossil record prompted the hypothesis that the South Clade originated from the North Clade by incipient peripatric differentiation, followed by isolation during the Quaternary glaciations, genetic differentiation in the non-glaciated coasts of eastern Patagonia, back-expansion over southern Chile following post-LGM de-glaciation, and development of a secondary contact zone between the two clades in south-central Chile. Evidence of upper Pleistocene expansion of the South Clade parallels similar results on other organisms that have colonized coastal ecosystems from eastern Patagonia since the LGM

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  12. Fluvial sensitivity to Late Quaternary climate changes in NW Romania

    NASA Astrophysics Data System (ADS)

    Perşoiu, Ioana; Rădoane, Maria; Robu, Delia; Tanţău, Ioan

    2013-04-01

    Fluvial archives became increasingly important for the reconstruction of past environments, as they record a sum of climate, vegetation, hydrologic and anthropic changes. This is especially important for the Late Quaternary, when climate and human activities had recorded large spatial and temporal variations. Here we present a tale of fluvial behavior during the last ca. 24.000 years in NW Romania, based on 1) absolute ages and fluvial architecture of sediments exposed in 8 openings located along the Someşu Mic River, and 2) depth-age models, grain size, LOI and gastropods assemblage analysis on 2 cores located upstream from Ştiucilor Lake, a natural lake along a small tributary of the Someşu Mic River, formed by salt disolution on top of a narrow diapiric anticline. During the Late Glacial (LG), Ştiucilor Lake was more extended then is today, with a high input of coarse materials (sands) from the slopes; and dramatically reducing its size in the Early Holocene, a transition marked by the abrupt occurrence of Holocene gyttja on top of LG sands, 1 km upstream from the present lake. Further upstream, at ca. 4 km from the present day edge of the lake, clays and sandy clays were deposited during the Bolling - Allerod (BA), followed by fine - medium sands of Younger Dryas (YD) age. On top of these sands, clays, sandy clays and gyttja occur, suggesting a returning to a less energetic sedimentary environment in the Holocene. In both cores, the sediments become lacustrine, with clays and fine sands, attesting the expansion of the lake's surface, followed by large fluctuations during the Holocene. The river fed by this stream - Someşu Mic, was a coarse gravel, shallow braided river before the Last Glacial Maximum and until the YD. The channel metamorphosis into a narrow, incised, meandering one, occurred ca. 1500 years after the beginning of the Holocene. However, sedimentological evidences suggest that this transition from braided to meandering channel was not a

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

    NASA Astrophysics Data System (ADS)

    Stuart, Anthony

    2010-05-01

    Anthony J. Stuart1 & Adrian M. Lister2 1 Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. Email: tony.s@megafauna.org.uk 2 Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. Email: a.lister@nhm.ac.uk. 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

  14. Late Quaternary accretion and decline of syngenetic ice-rich permafrost

    NASA Astrophysics Data System (ADS)

    Wetterich, Sebastian; Strauss, Jens; Fuchs, Margret C.; Schirrmeister, Lutz

    2016-04-01

    The region of perennially frozen ground constitutes one quarter of the northern hemisphere landmass. Negative annual mean air temperatures and ground freezing periods exceeding ground thaw periods are the prerequisites for downward freezing of loose deposits and bedrock in non-glaciated regions. Hence, permafrost distribution and thickness on Earth are closely related to late Quaternary climate variations and ecosystem modifications. Generally, glacial stages are expected to promote permafrost accretion and ground ice formation in accumulating sediments, whereas interglacial stages lead to intense permafrost thaw and ground-ice melt. Deep freezing synchronous with ongoing sedimentation is termed as syngenetic while epigenetic freezing occurs in pre-existing deposits. Typical landforms of syngenetic permafrost are ice-wedge polygons of past tundra environments. Ice-rich silty and/or peaty deposits intersected by large ice wedges (up to several decameters in height and meters in with) build-up unique Ice Complex (IC) strata, which are aligned to mid- and late Pleistocene stadial and interstadial stages. The most prominent example for such formations is the Yedoma IC of MIS 3 interstadial age. Increasing air and ground temperatures during warm stages disturbed the thermal equilibrium at the upper permafrost boundary and subsequently led to permafrost thaw, ground-ice melt and surface subsidence. Typical permafrost degradation processes are thermokarst and thermo-erosion that result in large lake-filled basins (up to kilometers in diameter) and valley structures, respectively. The modern periglacial surface in Alaskan and East Siberian lowlands preserves Yedoma IC remnants in uplands and hills next to widely-distributed thermokarst basins since lateglacial and Holocene warming affected up to 70% of the original IC distribution on an area of more than 1,000,000 km2. The overarching climate-driven pattern of cold-stage IC permafrost accretion and warm-stage IC permafrost

  15. Late Quaternary dynamics of a South African floodplain wetland and the implications for assessing recent human impacts

    NASA Astrophysics Data System (ADS)

    Tooth, S.; Rodnight, H.; McCarthy, T. S.; Duller, G. A. T.; Grundling, A. T.

    2009-05-01

    Knowledge of the long-term geomorphological dynamics of wetlands is limited, so currently there is an inadequate scientific basis for assessing anthropogenically induced changes and for developing conservation, remediation, and/or sustainable management guidelines for these fragile ecosystems. Along the upper Klip River, eastern South Africa, geomorphological and sedimentological investigations, geochronology, and remote sensing have been used to establish the late Quaternary dynamics of some internationally important floodplain wetlands, thus providing a reference condition against which to assess the extent of recent human impacts. Optically stimulated luminescence dating reveals that the wetlands have developed over at least the last 30 ky as a result of slow meander migration (< 0.2 m y - 1 ), irregular cutoff events, and infrequent avulsions (approximately one every 3-6 ky) that have occurred autogenically as a natural part of meander-belt development. Following European settlement in the Klip valley (late nineteenth century), however, modifications to local flora and fauna, as well as the initiation of local wetland drainage schemes, have had major impacts. In particular, proliferation of exotic willows and associated debris jams, and the artificial excavation of a 1.2-km-long channel section across the wetlands have initiated an ongoing avulsion that is characterised by failure (gradual abandonment) of the main channel and rapid incision of a headcutting channel. Compared to the pre-settlement condition, little change in lateral migration activity has occurred, but this avulsion provides a clear example of anthropogenically accelerated change, occurring only ~ 1 ky after the last natural avulsion and in a part of the wetlands where avulsions have not occurred previously. Subsequent human interventions have included installing weirs in an attempt to control the resulting erosion and promote reflooding, but ongoing maintenance has been required. In areas that

  16. Three dimensional view of paleooceanic events in the NE Atlantic during the late Pliocene onset of N. hemisphere glaciation

    SciTech Connect

    Loubere, P.

    1985-01-01

    Presently, the NE Atlantic has a distinctly three layered water column composed of sub-polar surface waters; warm, saline Mediterranean Intermediate Water; and North Atlantic Deep Water (NADW). The flow of Mediterranean water into the Norwegian Sea contributes to the formation of NADW. A detailed view of the paleooceanic evolution of the NE Atlantic water column during the onset of Northern Hemisphere glaciation is provided by a comparison of the planktonic Foraminiferal, benthic Foraminiferal, isotopic and sedimentologic records of DSDP Sites 548 (1253 m. water, sample spacing of less than 10,000 years), 116 (1151 m. water) and 552A (2311 m. water). At the surface, an initial cooling event occurred between 3.3 and 2.9 Myr, bracketing the global benthic positive oxygen isotope shift. Following the cooling event, surface conditions became much more variable with a dominant cyclicity of 42,000 years. Hence, the cooling event may represent a time of important permanent change in the high latitude climatic system. At mid-depth, the first Late Pliocene indication of Mediterranean Water was found at 2.8 Myr. There maybe a causative link between the latter event and the appearance of Mediterranean Water along with its possible intrusion into the Norwegian Sea. Progressive surface cooling began at 2.6 Myr and led to glaciations by 2.4 Myr. Glacial periodicity was dominated by a 42,000 year cycle, with little sign of the 100,000 year period. During the glaciations there was an inverse response in the benthic fauna between intermediate and abyssal depths; indicating a deep circulation behavior different from the Pleistocene.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Response to “Comment on 'The transition on North America from the warm humid Pliocene to the glaciated Quaternary traced by eolian dust deposition at a benchmark North Atlantic Ocean drill site', by David Lang et al.”

    NASA Astrophysics Data System (ADS)

    Lang, David C.; Bailey, Ian; Wilson, Paul A.; Foster, Gavin L.; Bolton, Clara T.; Friedrich, Oliver; Gutjahr, Marcus

    2014-11-01

    In volume 93 of Quaternary Science Reviews we published a new record of terrigenous inputs to Integrated Ocean Drilling Program (IODP) Site U1313 that tracks the history of aeolian dust deposition in the North Atlantic Ocean and aridity on North America during the late Pliocene-earliest Pleistocene intensification of northern hemisphere glaciation (iNHG, 3.3 to 2.4 Ma). Naafs et al. (2014) are generally supportive but question one of our conclusions, specifically our argument that "glacial grinding and transport of fine grained sediments to mid latitude outwash plains is not the fundamental mechanism controlling the magnitude of the flux of higher plant leaf waxes from North America to Site U1313 during iNHG." They suggest that our argument is predominantly based on our observation that the relationship between sediment lightness (L*)-based terrigenous inputs and dust-derived biomarkers, which is observed to be linear elsewhere (Martínez-Garcia et al., 2011), is non-linear at Site U1313.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  20. Paleoclimatic Comparisons Between Three Late Quaternary Amazonian Lacustrine Records

    NASA Astrophysics Data System (ADS)

    Cordeiro, R. C.; Martins, G. S.; Fontes, D.; Turcq, B.; Sifeddine, A.; Seoane, J. S.; Conceição, M. G.; Barbosa, M.; Rodrigues, R. A.; Moreira, L.

    2012-12-01

    In recent years many records made in the cores of ice has shown significant changes in temperature associated with changes in atmospheric composition. The most notable changes occur between the glacials and interglacials cycles. Climatic changes in tropical areas during the global climatic changes is highly debatable. Even today, there are many controversies about the extent of the occurrence of dry weather in the Amazon during glacial periods. In the region of São Gabriel da Cachoeira, polynic diagram of Lagoa da Pata showed that vegetation remained with elements of forest trees, with replacement of elements of cold weather during the last glacial. In Carajás were observed substitution forest to savannah, during the last glacial. We present here a comparison of organic and inorganic geochemical sediment record of tree distinct Amazonian sectors: Morro dos Seis Lagos (AM) is located at 0°17‧9.68″ N and 66°40‧36.18″ W (Lagoa da Pata, LPT V core position) located in the forested upper Rio Negro basin in humid climate area (~3000 mm/yr), Carajás Region at 5°50‧ to 6°35‧ S and 49°30‧ to 52°00‧ situated 800 m high in lateritic crust in south eastern Amazonia (1800mm/yr) and São Benedito Region (PA) at 9°7'0.87"S and 56°16'0.00"W (Lago do Saci, Sac01/05 core position) in south Amazonia with a mean precipitation as Carajás around 1800 mm/yr. A comparison of these records reveals important changes in the environmental history of the Amazonian hydrological regime during the late Quaternary. The results of geochemical analyses reveal three hydrological and climatic regimes from 50,000 cal yr BP until the present. The first phase, between 50,000 until ~25,000 cal yr BP, was characterized by relatively high lake level as suggested by high organic carbon values in Lagoa da Pata and Carajás principally in the beginning of the period. In Saci Lake in the beginning of the record (35,500 cal yr BP) high values of TOC were observed relatively to last

  1. Map of glacial limits and possible refugia in the southern Alexander Archipelago, Alaska, during the late Wisconsin glaciation

    USGS Publications Warehouse

    Carrara, Paul E.; Ager, Thomas A.; Baichtal, James F.; VanSistine, D. Paco

    2003-01-01

    During the late Wisconsin glaciation (circa 26,000-13,000 carbon-14 yr BP) the Cordilleran glacier complex formed vast ice fields and large glaciers along the crest of the Coast Mountains. As these glaciers flowed west to the Pacific Ocean, they were joined by local glaciers originating on the higher reaches of the Alexander Archipelago (Mann and Hamiltion, 1995). This extensive volume of ice was channeled into deep troughs (present-day fiords) that formed major outlet glaciers, such as the glaciers that occupied Chatham Strait and Dixon Entrance. In several places along the coast, deep glacially scoured submarine troughs indicate that glaciers reached to the edge of the continental shelf. For instance, the glacier that extended into the Dixon Entrance trough is known to have extended to the edge of the continental shelf. Its retreat began sometime after 16,000-15,000 carbon-14 yr BP (Barrie and Conway, 1999).

  2. The ``Problem of the quaternary'' and the taxonomic rank of the late cenozoic in the international stratigraphic scale

    NASA Astrophysics Data System (ADS)

    Zubakov, V. A.

    2011-02-01

    An international scientific conflict has arisen around the International Stratigraphic Scale, the main document that regulates the rules of reading of geological records and, hence, concerns all Earth sciences. The matter of debate is the geological time scale of 2004, developed by the International Commission on Stratigraphy, where the Quaternary system was abandoned. This ICS decision triggered a protest among Quaternary geologists, members of INQUA, and became the subject of much controversy. This article provides a comprehensive analysis of the Quaternary problem and proposes a reasonable scientific solution that may be appropriate for both parties. The subject of Late Cenozoic geology is discussed: glaciations, human evolution, and recent deposits. In contrast to Charles Lyell's definition of the Plio-Pleistocene according to the percentage of modern mollusk species, it is defined here as a blanket formation, which is correlative to the topography and consists of mapped stratogens hosting fossils of modern biogeocenoses. Features of the description of the Plio-Pleistocene in terms of gravitational orbital tuning are considered. Four paleogeographic phases of modern environment evolution are recognized and ranked as stages: (1) The Messinian evolutionary explosion involved the appearance of many biogeocenoses and the bipedal walking of our extinct ancestors armed with sticks. It was a consequence of the Early Greenland (7.6 Ma BP) and Patagonian (6.7 Ma BP) hyperglaciations. (2) The Zanclean age is marked by climatic and hydrological but not evolutionary boundaries. (3) The appearance of the Villafranchian animal assemblage and Australopithecus, who used stones as weapon: 4.0-3.6 Ma BP. Orogeny and isolation of the Arctic Ocean changed the global climate dramatically. (4) The sexual revolution became the third evolutionary jump: the appearance of the first woman, "Eve", and the genus Homo with her: 1.9 Ma BP. According to the current view, the Plio

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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

  4. Passive margin uplift around the North Atlantic region and its role in Northern Hemisphere late Cenozoic glaciation

    NASA Astrophysics Data System (ADS)

    Eyles, Nicholas

    1996-02-01

    Tectonic-climatic models of late Cenozoic global cooling emphasize the importance of middle latitude uplifts (e.g., Tibetan Plateau and the American west) but ignore widespread tectonic events on the margins of the North Atlantic Ocean. Pleistocene glaciations, after 2.5 Ma, are characterized by circum North Atlantic continental ice sheets that formed by the coalescence of perennial snow fields on extensive plateau surfaces in eastern Canada, northwest Britain, and Scandinavia. Plateaus record Cenozoic uplift of peneplains in response to semisynchronous magmatic underplating and thermal buoyancy of rifted continental margins. High-standing plateaus are very sensitive to small reductions in summer temperature. As late Cenozoic climate cooling proceeded, driven by uplift in regions external to the North Atlantic region, elevated plateaus became sites for extensive snow fields and ultimately ice sheets. Circum-Atlantic uplift took place in the key latitudinal belt that is most sensitive to orbitally forced changes in solar irradiation; this, together with albedo effects from large snow fields, could have amplified the relatively weak Milankovitch signal.

  5. Fluvio-deltaic progradation in forced regressive deglacial succession: lessons from the Lake Saint-Jean (Québec, Canada, late Quaternary)

    NASA Astrophysics Data System (ADS)

    Nutz, Alexis; Ghienne, Jean-François; Schuster, Mathieu; Roquin, Claude; Dietrich, Pierre; Bouchette, Frédéric; Cousineau, Pierre A.

    2015-04-01

    Deltas simultaneously respond to modifications in water discharge, sediment supply and base-level change. As a consequence, they provide accurate archive for deciphering environmental change through times. In this contribution, a Late Quaternary deglacial sequence is documented from Lake Saint-Jean basin (Québec, Canada) where sediments have recorded the Laurentide ice sheet (LIS) retreat accompanied by the invasion of marine waters (Laflamme Gulf) from ca. 12.9 cal. ky BP. Subsequently, fluvio-deltaic and then coastal prograding wedges emplaced following the base level fall induced by the glacio-isostatic rebound. The related succession, representing a transition from glacial to post-glacial periods within a previously glaciated area, was investigated through recent geological mapping, preserved landforms, facies analysis, and new optical stimulated luminescence (OSL) and radiocarbon (14C) dates. Three basin-scale geological sections are presented focusing on the architectures and facies of fluvio-deltaic progradations emplaced from 12.9 cal. ka BP to present-day in Lake Saint-Jean. Overlying the bedrock, isolated ice-contact fan deposits are capped by glacimarine muds. Above, fluvio-deltaic and coastal prograding systems were deposited following four major evolutions through time: (i) deltaic systems progressively increased in width, (ii) coastal influence on sedimentation increased, (iii) hydrographic drainage systems became more organised, and (iv) delta graded from steep (Gilbert delta) to low-angle foresets (mouth-bar delta). These evolutions in fluvio-deltaic systems are attributed to the modifications in water discharge, sediment supply and rate of base level fall driven by the deglaciation. The presented succession is considered as representative of the sedimentological signature of fluvial progradations in forced regressive deglacial sequences. Derived from the Lake Saint-Jean basin, this study provides new elements for the recognition and interpretation

  6. Late Quaternary environments and biogeography in the Great Basin

    NASA Astrophysics Data System (ADS)

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

    1982-01-01

    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. Plate tectonics hiati as the cause of global glaciations: 2. The late Proterozoic 'Snowball Earth'

    NASA Astrophysics Data System (ADS)

    Osmaston, M. F.

    2003-04-01

    A fundamental reappraisal of the mechanisms that drive plate tectonics has yielded the remarkable conclusion that, for at least the past 130 Ma, the principal agent has not been ridge-push or slab-pull but a CW-directed torque (probably of electromagnetic origin at the CMB) reaching the deep (>600 km, e.g.[1]) tectospheric keel of the Antarctica craton. Major changes in spreading direction marked both ends of the 122--85 Ma Cretaceous Superchron and started by forming the Ontong Java Plateau. Action of MORs as gearlike linkages has driven Africa and India CCW since Gondwana breakup and continues to drive the Pacific plate CCW. In the Arctic there is now no cratonic keel to pick up any corresponding polar torque, so northern hemisphere plate tectonics is far less active. The thesis of this contribution is that in the Neoproterozoic the lack of cratons at high latitudes would have deprived plate tectonics of this motivation, causing MORs to die (see below) and a major fall in sea-level, leading to global glaciation as outlined in Part 1 for the Huronian events. Like that seen during that first hiatus, dyke-swarm volcanism could have arisen from thermal shrinkage of the global lithosphere, providing CO2 and ash-covering that interrrupted glacial episodes. In oceanic settings this volcanism would have lowered pH and supplied Fe2+ for shallow bio-oxygenic action to deposit as BIF. My multifacet studies of the subduction process convince me that the rapid development of "flat-slab" interface profiles involves the physical removal of hanging-wall material in front of the downbend by basal subduction tectonic erosion (STE). Historically this, and its inferred ubiquity in the Archaean as the precursor to PSM (Part 1), suggests that the required subducting-plate buoyancy is thermal. Accordingly, a redesign [2] of the MOR process has incorporated the heat-containing LVZ as an integral part of the plate and luckily provides a lot more ridge-push to ensure the subduction of

  8. Measuring Late Quaternary Ursid Diminution in the Midwest

    NASA Astrophysics Data System (ADS)

    Wolverton, Steve; Lyman, R. Lee

    1998-05-01

    Paleobiologists generally agree that within the past 10,000 yr North American black bears ( Ursus americanus) have decreased in body and tooth size. Some researchers infer that diminution was gradual and continuous; thus, one might infer that a specimen is old if it is larger than an average-size modern bear. Ursid remains recovered in the 1950s from Lawson Cave, Missouri, that are larger than some modern bears have been reported to date to the late Pleistocene, but association with modern taxa, taphonomic considerations, and a radiocarbon date of 200 yr B.P. indicate that they are modern. Modern specimens from Lawson Cave and other parts of the American Midwest are relatively large compared to modern North American black bears from other areas, suggesting that many supposed late Pleistocene bears from the area might be modern also.

  9. Late Quaternary depositional history of the Albemarle Embayment, NC

    SciTech Connect

    Riggs, S.R.; Klingman, C.R.; Wyrick, R.A. . Dept. of Geology)

    1993-03-01

    The depositional history of Albemarle Embayment documents deep fluvial incisement by the Roanoke River system during glacial episodes and subsequent infilling by fluvial-estuarine-barrier island sediment sequences during interglacial transgressions. Unraveling the Holocene time slice will help reconstruct complex Quaternary records of multiple incisement and backfilling. A network of drill holes, vibracores, and seismic data suggest a four-phase infill history over the last 12,000 years. (1) Lower Roanoke River: (a) Bedload-charged, braided fluvial systems deposited basal sequences of sand and gravel prior to [approximately]5,000 BP. (b) Aggradational, swamp-forest floodplains developed [approximately]5,000 BP and bound the modern incised channels characterized by minimal bedload sedimentation. (2) Albemarle sound: (a) In the central basin, the basal channel sand sequence is overlain by an open estuarine, highly interlaminated sand and mud sequence that accumulated between [approximately]12,000 BP and [approximately]2,000 BP. (b) Depositional patterns within this unit suggest multiple oscillations of Holocene sea level that caused channel reincisement and subsequent backfilling. (c) Present estuarine marsh sedimentation began in protected coastal areas [approximately]5,000 BP. (3) Outer banks: (a) Barrier islands first influenced sedimentation in the area after [approximately]5,000 BP producing a semi-enclosed Albemarle Sound. (b) Deposition within the central basin shifted to uniform organic-rich muds that grade eastward into overwash and inlet sands. (4) Modern man: (a) colonial development within the drainage basins in the early 1700's AD produced a wedge of orange mud in inner Albemarle Sound. (b) Dam construction in the 1950's terminated orange mud deposition and the central basin reverted to organic-rich mud sedimentation.

  10. Stratigraphical evidence of late Amazonian periglaciation and glaciation in the Astapus Colles region of Mars

    NASA Astrophysics Data System (ADS)

    Soare, Richard J.; Osinski, Gordon R.

    2009-07-01

    Recent modeling of the meteorological conditions during and following times of high obliquity suggests that an icy mantle could have been emplaced in western Utopia Planitia by atmospheric deposition during the late Amazonian period [Costard, F.M., Forget, F., Madeleine, J.B., Soare, R.J., Kargel, J.S., 2008. Lunar Planet. Sci. 39. Abstract 1274; Madeleine, B., Forget, F., Head, J.W., Levrard, B., Montmessin, F., 2007. Lunar Planet. Sci. 38. Abstract 1778]. Astapus Colles (ABa) is a late Amazonian geological unit - located in this hypothesized area of accumulation - that comprises an icy mantle tens of meters thick [Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888]. For the most part, this unit drapes the early Amazonian Vastitas Borealis interior unit (ABvi); to a lesser degree it overlies the early Amazonian Vastitas Borealis marginal unit (ABvm) and the early to late Hesperian UP plains unit HBu2 [Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888]. Landscapes possibly modified by late-Amazonian periglacial processes [Costard, F.M., Kargel, J.S., 1995. Icarus 114, 93-112; McBride, S.A., Allen, C.C., Bell, M.S., 2005. Lunar Planet. Sci. 36. Abstract 1090; Morgenstern, A., Hauber, E., Reiss, D., van Gasselt, S., Grosse, G., Schirrmeister, L., 2007. J. Geophys. Res. 112, doi:10.1029/2006JE002869. E06010; Seibert, N.M., Kargel, J.S., 2001. Geophys. Res. Lett. 28, 899-902; Soare, R.J., Kargel, J.S., Osinski, G.R., Costard, F., 2007. Icarus 191, 95-112; Soare, R.J., Osinski, G.R., Roehm, C.L., 2008. Earth Planet. Sci. Lett. 272, 382-393] and glacial processes [Milliken, R.E., Mustard, J.F., Goldsby, D.L., 2003. J. Geophys. Res. 108 (E6), doi:10.1029/2002JE002005. 5057; Mustard, J.F., Cooper, C.D., Rifkin, M.K., 2001. Nature 412, 411-414; Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888] have been reported within the region. Researchers have assumed that the

  11. Late quaternary plant zonation and climate in southeastern Utah

    SciTech Connect

    Betancourt, J.L.

    1984-01-31

    Plant macrofossils from packrat middens in two southeastern Utah caves outline development of modern plant zonation from the late Wisconsin. Allen Canyon Cave (2195 m) and Fishmouth Cave (1585 m) are located along a continuous gradient of outcropping Navajo Sandstone that extends from the Abajo Mountains south to the San Juan River. By holding the site constant, changes in the floral composition for a plot of less than one hectare can be observed, even if sporadically, over tens of millennia. At Allen Canyon Cave, Engelmann spruce-alpine fir forest was replaced by the present vegetation consisting of pinyon-juniper woodland on exposed ridgetops and cliffside stands of Douglas fir, ponderosa pine, and aspen. Xerophytic woodland plants such as pinyon, plains prickly pear, and narrowleaf yucca arrived sometime in the middle Holocene between 7200 and 3400 B.P. At Fishmouth Cave, Utah juniper in Holocene middens replaced blue spruce, limber pine, Douglas fir, and dwarf and Rocky Mountain junipers in late Wisconsin samples. Quantitative climatic estimates are derived for the late Wisconsin by applying vertical gradients for temperature and precipitation to the amount of vegetation depression. The Fishmouth Cave sequence indicates a minimum lowering of 850 m for blue spruce, limber pine, and dwarf juniper. A depression of at least 700 m for Engelmann spruce and alpine fir is suggested for the Allen Canyon locality. Use of conservatively low gradients for stations below 2080 m yields a 3-4 C cooling from present mean annual temperature and 35 to 60% more rainfall than today. Steeper gradients associated with more mountainous terrain suggest a 5 C lowering in temperature and up to 120% increase over modern precipitation. 81 references, 6 figures, 10 tables.

  12. Evidence against Late Quaternary activity along the Northern Karakoram Fault

    NASA Astrophysics Data System (ADS)

    Robinson, A. C.; Owen, L. A.; Hedrick, K.; Blisniuk, K.; Sharp, W. D.; Chen, J.; Schoenbohm, L. M.; Imrecke, D. B.; Yuan, Z.; Li, W.

    2012-12-01

    Although the entire 1000 km long Karakoram fault has long been interpreted to be active, recent work based primarily on interpretation of satellite imagery suggests that the northern end of the fault, where it enters the Pamir mountains, is inactive. We present field observations and geochronologic data from the southern end of the Tashkurgan valley, in the Pamir, on the Karakoram fault where it splits into two identifiable strands; an eastern strand which is the main trace of the Karakoram fault, and a western strand called the Achiehkopai fault. These results support the interpretation that the northern Karakoram fault is currently inactive, and has been for at least 200 ka: 1) Near the village of Dabudaer in the southern Tashkurgan valley the main trace of the Karakoram fault is orthogonally cut by a narrow incised valley with no observed lateral offset across the fault. Within this valley, a strath terrace ~50 m above the active drainage which overlies the main trace of the Karakoram fault which is capped by a carbonate cemented conglomerate. U-series analyses of carbonate cement from a correlative deposit located several km away yields a minimum depositional age of 76±12 ka. This age is coeval with the local Tashkurgan glacial stage we dated using Be-10 surface exposure dating (66±10 ka; Owen et al., 2012, Quaternary Science Reviews) suggesting both the conglomerate and strath terrace formed during this glacial stage. 2) ~25 km south of Dabudar, the main trace of the Karakoram projects beneath Tashkurgan glacial stage moraine and fluvial-glacial deposits which similarly show no evidence of disturbance by strike-slip deformation. Both of the above results demonstrate the main trace of the Karakoram fault has been inactive since at least ~70 ka. 3) Both the Karakoram and Achiehkopai faults are overlain by older Dabudaer glacial stage moraine deposits which are interpreted to be at least as old as the penultimate glacial, but may be >200 ka based on our Be-10

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

    PubMed Central

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

    2009-01-01

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

  14. Late quaternary evolution of the Orinoco Delta, Venezuela

    USGS Publications Warehouse

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

    2002-01-01

    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

  15. Biotic response to late Quaternary rapid climate switches in Santa Barbara Basin: Ecological and evolutionary implications

    SciTech Connect

    Cannariato, K.G.; Kennett, J.P.; Behl, R.J.

    1999-01-01

    Benthic foraminiferal assemblages from Santa Barbara Basin exhibit major faunal and ecological switches associated with late Quaternary millennial- to decadal-scale global climate oscillations. Repeated turnovers of entire faunas occurred rapidly (<40--400 yr) without extinction or speciation in conjunction with Dansgaard-Oeschger shifts in thermohaline circulation, ventilation, and climate, confirming evolutionary model predictions of Roy et al. Consistent faunal successions of dysoxic taxa during successive interstadials reflect the extreme sensitivity and adaptation of the benthic ecosystem to the rapid environmental changes that marked the late Quaternary and possibly other transitional intervals in the history of the Earth`s ocean-atmosphere-cryosphere system. These data support the hypothesis that broad segments of the biosphere are well adapted to rapid climate change.

  16. Late quaternary geologic framework, north-central Gulf of Mexico

    USGS Publications Warehouse

    Kindinger, Jack G.; Penland, Shea; Williams, S. Jeffress; Brooks, Gregg R.; Suter, John R.; McBride, Randolph A.

    1991-01-01

    The geologic framework of the north-central Gulf of Mexico shelf is composed of multiple, stacked, delta systems. Shelf and nearshore sedimentary facies were deposited by deltaic progradation, followed by shoreface erosion and submergence. A variety of sedimentary facies has been identified, including prodelta, delta fringe, distributary, lagoonal, barrier island, and shelf sand sheet. This study is based on the interpretation and the synthesis of > 6,700 km of high-resolution seismic profiles, 75 grab samples, and 77 vibracores. The nearshore morphology, shallow stratigraphy, and sediment distribution of the eastern Louisiana shelf are the products of transgressive sedimentary processes reworking the abandoned St. Bernard delta complex. Relatively recent Mississippi delta lobe consists primarily of fine sand, silt, and clay. In the southern portion of the St. Bernard delta complex, asymmetrical sand ridges (>5 m relief) have formed as the result of marine reworking of distributary mouth-bar sands. Silty sediments from the modern Mississippi Birdsfoot delta onlap the St. Bernard delta complex along the southern edge. The distal margin of the St. Bernard complex is distinct and has a sharp contact on the north near the Mississippi Sound barrier island coastline and a late Wisconsinan delta to the south. The Chandeleur Islands and the barrier islands of Mississippi Sound have been formed by a combination of Holocene and Pleistocene fluvial processes, shoreface erosion, and ravinement of the exposed shelf. Sediments underlying the relatively thin Holocene sediment cover are relict fluvial sands, deposited during the late Wisconsinan lowstand. Subsequent relative sea-level rise allowed marine processes to rework and redistribute sediments that formed the nearshore fine-grained facies and the shelf sand sheet.

  17. Stable isotopes in collagen and Late Quaternary carnivore palaeoecology

    NASA Astrophysics Data System (ADS)

    Bocherens, Hervé

    2010-05-01

    Several taxa of large carnivores co-occurred during the late Pleistocene in the steppe-tundra ecosystem, such as wolf Canis lupus, cave lion Panthera leo spelaea, cave hyaena Crocuta crocuta spelaea, brown bear Ursus arctos and cave bear Ursus spelaeus and Ursus ingressus. This abundance of taxa belonging to the same guild raises questions about niche partitioning, especially in terms of dietary specialization and prey selection. Observations of the dietary ecology of the extant relatives of these late Pleistocene carnivores does not provide unambiguous answers as these populations live under very different environmental conditions where other potential prey species are present, but it appears that most of these modern large carnivores are relatively flexible in their prey selection. Palaeontological investigations dealing with faunal associations and activity marks on fossil bones also have their limitations, such as taphonomic biases (palimpsests rather than biological associations) and do not allow the quantification of consumption of various preys. In contrast, carbon and nitrogen isotopic signatures of bone collagen depend directly on those of the average diet. Since different potential prey species occurring in the steppe-tundra exhibit consistent isotopic differences for these chemical elements, it is possible to relate the carbon and nitrogen isotopic signatures measured in fossil carnivores with the preferential consumption of some prey species. Some amount of quantification can be provided using modified versions of mixing models developed for modern ecosystems. In addition, this isotopic approach is individual-based and it is therefore possible to investigate intra- and inter-population differences in prey selection, as well as possible chronological trends and differences linked to genetic differences by combining isotopic and ancient DNA studies on the same material. The isotopic approach has already shown that among the tested large carnivores, cave

  18. Soil-landscape development and late Quaternary environmental change in coastal Estremadura, Portugal

    NASA Astrophysics Data System (ADS)

    Daniels, Michael; Haws, Jonathan; Benedetti, Michael; Bicho, Nuno

    2015-04-01

    This poster integrates soil-landscape analysis with archaeological survey and paleoenvironmental reconstruction. Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms, and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the distribution and condition of Paleolithic archaeological sites and help understand the record of human settlement in the region. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine (Pinus pinaster) forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. A conceptual model of soil-landscape evolution through the late Quaternary and Holocene results from the integration of soil profile data, proxy paleoenvironmental data, and the partial record of human settled as revealed in the archaeological record.

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

    NASA Astrophysics Data System (ADS)

    Benvenuti, Marco; Bonini, Marco; Moroni, Adriana

    2016-09-01

    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.

  20. Late Quaternary vegetation and climate of southern Tierra del Fuego

    NASA Astrophysics Data System (ADS)

    Heusser, Calvin J.

    1989-05-01

    Vegetation and climate over approximately the past 13,000 yr are reconstructed from fossil pollen in a 9.4-m mire section at Caleta Róbalo on Beagle Channel, Isla Navarino (54°56'S, 67°38'W), southern Tierra del Fuego. Fifty surface samples reflecting modern pollen dispersal serve to interpret the record. Chronologically controlled by nine radiocarbon dates, fossil pollen assemblages are: Empetrum-Gramineae- Gunnera-Tubuliflorae (zone 3b, 13,000-11,850 yr B.P.), Gramineae- Empetrum-assorted minor taxa (zone 3a, 11,850-10,000 yr B.P.), Nothofagus-Gramineae-Tubuliflorae-Polypodiaceae (zone 2, 10,000-5000 yr B.P.), Nothofagus-Empetrum (zone 1b, 5000-3000 yr B.P.), and Empetrum-Nothofagus (zone 1a, 3000-0 yr B.P.). Assemblages show tundra under a cold, dry climate (zone 3), followed by open woodland (zone 2), as conditions became warmer and less dry, and later, with greater humidity and lower temperatures, by closed forest and the spread of mires (zone 1). Comparisons drawn with records from Antarctica, New Zealand, Tasmania, and the subantarctic islands demonstrate broadly uniform conditions in the circumpolar Southern Hemisphere. The influences of continental and maritime antarctic air masses were apparently considerable in Tierra del Fuego during cold late-glacial time, whereas Holocene climate was largely regulated by interplay between maritime polar and maritime tropical air.

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

    USGS Publications Warehouse

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

    2001-01-01

    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.

  2. Late Quaternary paleosols and climate change in southern New Mexico

    SciTech Connect

    Monger, H.C. . Agronomy Dept.); Cole, D.R. ); Gish, J.W. )

    1992-01-01

    A climate change toward more arid conditions in the southwest US has been postulated for a period around 7 ka. In southern NM, deposition of the youngest generation of alluvial fans surrounding arid mountains began around 7 ka based on radiocarbon dates of charcoal. The deposition of these fans has been interpreted as evidence for aridity because plant cover would have declined, thus making the landscape more susceptible to erosion and sedimentation. Isotopes of pedogenic calcite and pollen content in well-preserved paleosols associated with alluvial fans provide additional evidence for testing the aridity hypothesis. Buried paleosols, ranging from 23,070 [+-] 190 to 9,070 [+-] 70 yr BP, contain pedogenic calcite that is isotopically heavier in carbon than calcite in soils younger than 7 ka. The buried paleosols have a mean delta C-13 values of [minus]2.2 [+-] 0.8 [per thousand] (PDP). In contrast, soils younger than 7 ka have a man delta C-13 value of [minus]7.8 [+-] 1.3 [per thousand]. The higher delta C-13 values in buried paleosols may reflect the presence of abundant C[sub 4] grasses, similar to the present vegetation in the southern High Plains, which would have curtailed erosion. Pollen analysis reveals that buried paleosols contain more grass pollen than soils younger than 7 ka, which contain high proportions of desertscrub pollen taxa. delta O-18 values of pedogenic calcite are similar for the buried paleosols ([minus]5.2 [+-] 0.3 [per thousand] PDB) and soils younger than 7 ka ([minus]5.1 [+-] 0.6 [per thousand]). These values indicate a relatively constant mean annual temperature of approximately 14C, which prevailed throughout late Pleistocene and Holocene time.

  3. Reconstructing late Quaternary deep-water masses in the eastern Arctic Ocean using benthonic Ostracoda

    USGS Publications Warehouse

    Jones, R. Ll; Whatley, R.C.; Cronin, T. M.; Dowsett, H.J.

    1999-01-01

    The distribution of Ostracoda in three long cores from the deep eastern Arctic Ocean was studied to determine the palaeoceanographical history of the Eurasian Basin during the late Quaternary. The samples for this study were obtained from the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau during the Arctic 91 expedition. Ostracoda previously studied in coretops at the same sites as the present study have shown that individual species have a strong association with different water masses and bathymetry. Throughout the late Quaternary, cores exhibit ostracod-rich layers separated by barren intervals. On the basis of biostratigraphical, isotopic and palaeomagnetic data the fossiliferous levels are interpreted as representing interglacial stages. The twenty most significant species were selected for subsequent quantitative investigation using Cluster and Factor analyses, in order to determine similarity and variance between the assemblages. An additional statistical method employing Modern Analogues and the Squared Chord Distance dissimilarity coefficient was utilized to compare the present late Quaternary fossil samples with a modern Arctic database. The results reveal a major faunal division within the Arctic Ocean Deep Water (AODW). Highly abundant and diverse assemblages within the cores were found to group and have good analogues with the Recent bathyal depth (1000-2500 m) upper AODW assemblages. Conversely, assemblages with low abundance and diversity correlate well with abyssal depth (> 3000 m) lower AODW assemblages. The palaeoceanographical history is complicated by the influence of adjacent water masses such as Canada Basin Deep Water (CBDW), Greenland Sea Deep Water (GSDW) and most importantly, Arctic Intermediate Water (AIW), which all had an influence on the ostracod assemblages during the late Quaternary. An enhanced flow of warm saline AIW into the Eurasian Basin results in species-rich upper AODW assemblages having good analogues down to 2750 m

  4. Late Quaternary deformation rates in the Pamir-Tian Shan collision zone, NW China

    NASA Astrophysics Data System (ADS)

    Thompson, J. A.; Li, T.; Burbank, D. W.; Chen, J.; Bookhagen, B.; Bufe, A.; Yang, H.

    2014-12-01

    Deformation of the Pamir and Tian Shan orogens initiated during the Neogene as a result of the Indo-Eurasian colision. The arid landscape in the western Tarim Basin, NW China, preserves suites of fluvial terraces crossing many of the Late Neogene active structures, creating fault and fold scarps. We present new deformation rates on five faults and folds, which in combination with previous studies, highlight the spatial and temporal patterns of deformation during the Late Quaternary. Suites of terraces spanning ~130 ka to ~8 ka document the basinward propagation of deformation, with the fastest rates currently located on actively deforming structures at the interface of the Pamir-Tian Shan orogens. During the last ~6 ka, the Pamir deformation front has stepped north, creating the Mingyaole South Thrust, which produced the 1985 M7.4 Wuqia Earthquake. Trenching on several sections of this fault reveal an earthquake reoccurence interval of ~1.0 ky. The Late Quaternary deformation rates on faults and folds along the Pamir-Tian Shan collision zone indicate that the locus of deformation was not concentrated on a single structure, but rather was concurrently distributed across a zone of structures. Despite numerous structures accommodating the shortening and the locus of deformation shifting throughout the Late Quaternary, the total shortening across the Pamir-Tian Shan collision zone since ~0.35 Ma has remained steady and is approximately equal to the current geodetic rate of 6-9 mm/a, as well as broadly similar to preliminary InSAR-derived deformation rates across the region.

  5. Seismic expression of Late Quaternary Banda submarine canyon and fan offshore northern Baja California

    SciTech Connect

    Legg, M.R.

    1987-05-01

    High-resolution seismic reflection profiles obtained throughout the inner California continental borderland offshore northwestern Baja California, Mexico, show the presence of numerous modern submarine canyons and associated fans. One set of these, the Banda submarine canyon/fan, is of relatively recent origin, as demonstrated by onlap of the basal fan sediments against an acoustically transparent, presumably hemipelagic deposit. Late Quaternary sedimentation rates inferred from isotopically dated piston core samples place the age of the postulated hemipelagic unit at approximately 650,000 years ago. The Banda submarine canyon heads within the Bahia Todos Santo and passes through a narrow gorge between Punta Banda and Islas Todos Santos. It is proposed that this submarine canyon and fan system formed entirely during late Quaternary time, following the breach of the Punta Banda ridge during a late Pleistocene high sea level stand. The presence of an ancient, buried channel exiting to the north out of Bahia Todos Santos probably marks the head of an earlier submarine canyon which acted as the conduit of clastic sediments from Valle Maneadero to the deep borderland basins. The now active Banda submarine canyon pirated the supply of terrigenous clastics from this older canyon. The active Agua Blanca fault zone cuts across the head of Banda submarine canyon, suggesting that tectonic movements may have played a role in the development of the Banda submarine canyon and fan system.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  7. Seismic stratigraphy and depositional history of late Quaternary deposits in the Yellow Sea.

    NASA Astrophysics Data System (ADS)

    Lee, Gwang-Soo; Yoo, Dong Geun; Bae, Sungho; Choul Kim, Dae; Yi, Hi-Il

    2016-04-01

    To identify the seismic stratigraphy and depositional history of late Quaternary deposits in the Yellow Sea, approximately 52,600 line-km of Chirp seismic profiles and 5,060 line-km of Sparker seismic profiles were analyzed. The Yellow Sea are correspond to three sedimentary environments: (1) a various scale sand ridges/waves and mud belt (the western inner-shelf of the Korean Peninsula), (2) recent- and paleo-channels, erosional and broad surface (the center of the Yellow Sea), and (3) prodelta mud patch (the eastern offshore of China). Based on the seismic stratigraphic analysis of seismic profiles, the late Quaternary deposits in the Yellow Sea are divided into five distinctive seismic units (units CY1~5), consisting of two depositional sequences that can be defined as erosional and disconformable strata. Each unit show different seismic facies and geometry, and is clearly separated by each bounding surface. The major depositional processes and sediment dispersal systems during the late Quaternary in the Yellow Sea are: (1) regressive estuarine/deltaic deposits (unit CY1), (2) transgressive incised channel fill (unit CY2), (3) transgressive sand sheet (unit CY3), (4) transgressive sand ridges (unit CY4), and (5) prodelta/recent mud (unit CY5). The depositional sequences follow the general concepts of sequence stratigraphy very well. Lower sequence (DI) correspond to the falling stage systems tract regarded as regressive estuarine or deltaic deposits (unit CY1), whereas upper sequence (DII) consists of a set of the transgressive (units CY2, CY3, and CY4) and highstand systems tract (unit CY5) formed since the last-glacial period.

  8. Thermoluminescence and new 14C age estimates for late quaternary loesses in southwestern Nebraska

    USGS Publications Warehouse

    Maat, P.B.; Johnson, W.C.

    1996-01-01

    Loess of late Quaternary age mantles most of Nebraska south of the Platte River Valley. At least five late Quaternary loesses are recognized: from oldest to youngest, one or more undifferentiated pre-lllinoian loesses, the Loveland Loess, the Gilman Canyon Loess, which exhibits a well developed soil and rests unconformably on the Sangamon soil, the Peoria Loess capped by the Brady soil, and the Bignell Loess, which is distributed discontinuously. Previous research shows that the Loveland Loess is Illinoian. the Gilman Canyon Loess and Peoria Loess are Wisconsin, and the Bignell Loess is Holocene. We present here the first thermoluminescence (TL) age estimates and new C ages for these late Quaternary loesses at two key sections in southwestern Nebraska, the Eustis ash pit and the Bignell Hill road cut. TL age estimates from all samples collected from Eustis ash pit and Bignell Hill were internally consistent. TL and C age estimates from these two sections generally agree and support previous age determinations. The TL age estimate on Loveland Loess indicates deposition at 163 ka. TL and radiocarbon age estimates indicate that Oilman Canyon Loess, believed to be deposited during the Farmdale interstade, first began to accumulate at about 40 ka: the lower part of the Gilman Canyon Loess is 36 ka at Eustis and the middle of the unit is 30 ka at Bignell Hill. The lower and upper parts of the Peoria Loess give age estimates of 24 ka and 17 ka, respectively. TL age estimates for deposition of the Bignell Loess are 9 ka near the base, in agreement with radiocarbon age estimates, and 6 ka immediately below the modern soil, substantiating its Holocene age. Comparisons of TL age estimates with ??18O and insolation curves which show loess deposition during interglacial and interstadial as well as glacial periods, indicate that loess deposition on the Great Plains can occur under a variety of climatic conditions.

  9. Late quaternary insects of Rancho La Brea and McKittrick, California

    NASA Astrophysics Data System (ADS)

    Miller, Scott E.

    1983-07-01

    Asphalt-impregnated sediments at Rancho La Brea (Los Angeles County) and McKittrick (Kern County) in California provide a rich Quaternary insect record. Ages of various sites at Rancho La Brea range from more than 40,000 14C yr B.P. to modern. McKittrick insects studied by W. D. Pierce are not contemporaneous with the late Pleistocene vertebrate fauna, but are only about 7000 14C yr old. The major paleoecological groupings are: (1) ground dwellers, (2) aquatics. (3) scavengers, and (4) miscellaneous. Contrary to conclusions of earlier authors, most specimens represent modern species. Only two apparent terminal Pleistocene extinctions are recognized. both dung beetles (Scarabaeidae).

  10. Paleoclimatic forcing of magnetic susceptibility variations in Alaskan loess during the late Quaternary

    SciTech Connect

    Beget, J.E.; Stone, D.B.; Hawkins, D.B. )

    1990-01-01

    Visual matches and statistical tests suggest correlations between marine isotope curves, retrodictive solar insolation at lat 65{degree}N, and magnetic susceptibility profiles through late Quaternary age Alaskan loess sections. The susceptibility changes largely appear to reflect variability in magnetite content due to climatically controlled changes in wind intensity and competence. Magnetic susceptibility profiles through massive loess can provide stratigraphic context for intercalated paleosols and tephras. A prominent paleosol correlated with marine isotope stage 5 occurs several metres above the Old Crow ash in loess sections, indicating that this important tephra is older than suggested by thermoluminescence dates, and may have been deposited ca. 215 {plus minus}25 ka.

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  13. A late Quaternary lake record from the Qilian Mountains (NW China): evolution of the primary production and the water depth reconstructed from macrofossil, pollen, biomarker, and isotope data

    NASA Astrophysics Data System (ADS)

    Herzschuh, Ulrike; Zhang, Chengjun; Mischke, Steffen; Herzschuh, Rainer; Mohammadi, Farhid; Mingram, Birgit; Kürschner, Harald; Riedel, Frank

    2005-04-01

    The history (45-0 ka BP) of the aquatic vegetation composition of the shallow alpine Lake Luanhaizi from the NE Tibetan Plateau is inferred from aquatic plant macrofossil frequencies and aquatic pollen and algae concentrations in the sediments. C/N (range: 0.3-100), δ 13C (range: -28 to -15‰), and n-alkane measurements yielded further information on the quantitative composition of sedimentary organic matter. The inferred primary production of the former lake ecosystem has been examined in respect of the alternative stable state theory of shallow lakes [Scheffer, M., 1989. Alternative stable states in eutrophic, shallow freshwater systems: a minimal model. Hydrobiological Bulletin 23, 73-83]. Switches between clear and turbid water conditions are explained by a colder climate and forest decline in the catchment area of Lake Luanhaizi. The macrofossil-based reconstruction of past water depth and salinity ranges, as well as other organic matter (OM) proxies allowed climatic inferences of the summer monsoon intensity during the late Quaternary. Around 45 ka BP, conditions similar to or even moister than present-day climate occurred. The Lake Luanhaizi record is further evidence against an extensive glaciation of the Tibetan Plateau and its bordering mountain ranges during the Last Glacial Maximum. Highest lake levels and consequently a strong summer monsoon are recorded for the early Holocene period, while gradually decreasing lake levels are reconstructed for the middle and late Holocene.

  14. Slope Deposits and (Paleo)Soils as Geoarchives to Reconstruct Late Quaternary Environments of Southern Africa

    NASA Astrophysics Data System (ADS)

    Huerkamp, K.; Voelkel, J.; Heine, K.; Bens, O.

    2009-04-01

    Although it is clear that large, rapid temperature changes have occurred during the last glacial-interglacial cycle and the Holocene in southern Africa, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. Using slope deposits and soils as palaeoclimatic geoarchives we will overcome these constraints. The role of many geoarchives in the reconstruction of the Quaternary climate in southern Africa remains controversial, since the paleoclimate data are based on evidence from marine cores, lake sediments, speleothems and spring sinter, fluvial sediments, aeolian sands and dust, colluvium, and coastal sediments. To elucidate climate controls on Quaternary landscape evolution and to use these data for palaeoclimatic reconstructions, thus far slope deposits and soils have been investigated. Climatic controls on these cycles are incompletely known. The availability of results from earlier fieldwork, micromorphology, Optical Stimulated Luminescence (OSL), 14C dating and stable carbon isotope analysis will permit a thorough assessment of slope deposits and soils in terms of their palaeoenvironmental potential. The knowledge of suitable areas and sites in different climatic zones of southern Africa where slope deposits and soils have already been found document the late Quaternary climatic history and even climatic anomalies (e.g. Younger Dryas period at Eksteenfontein, 8.2 ka event at Tsumkwe, 4 ka event in the Auob valley, Little Ice Age in the Namib Desert). The findings will show the late Quaternary history of precipitation fluctuations, of the shifting of the ITCZ (and the ABF - Agulhas-Benguela Front), of wind intensities and directions, and of extreme precipitation events. The project will employ state-of-the-art geoscience methodology to interpret the record of precipitation changes of the late Quaternary, including the shifting of the summer and winter rain belts, the

  15. Glaciations in response to climate variations preconditioned by evolving topography.

    PubMed

    Pedersen, Vivi Kathrine; Egholm, David Lundbek

    2013-01-10

    Landscapes modified by glacial erosion show a distinct distribution of surface area with elevation (hypsometry). In particular, the height of these regions is influenced by climatic gradients controlling the altitude where glacial and periglacial processes are the most active, and as a result, surface area is focused just below the snowline altitude. Yet the effect of this distinct glacial hypsometric signature on glacial extent and therefore on continued glacial erosion has not previously been examined. Here we show how this topographic configuration influences the climatic sensitivity of Alpine glaciers, and how the development of a glacial hypsometric distribution influences the intensity of glaciations on timescales of more than a few glacial cycles. We find that the relationship between variations in climate and the resulting variation in areal extent of glaciation changes drastically with the degree of glacial modification in the landscape. First, in landscapes with novel glaciations, a nearly linear relationship between climate and glacial area exists. Second, in previously glaciated landscapes with extensive area at a similar elevation, highly nonlinear and rapid glacial expansions occur with minimal climate forcing, once the snowline reaches the hypsometric maximum. Our results also show that erosion associated with glaciations before the mid-Pleistocene transition at around 950,000 years ago probably preconditioned the landscape--producing glacial landforms and hypsometric maxima--such that ongoing cooling led to a significant change in glacial extent and erosion, resulting in more extensive glaciations and valley deepening in the late Pleistocene epoch. We thus provide a mechanism that explains previous observations from exposure dating and low-temperature thermochronology in the European Alps, and suggest that there is a strong topographic control on the most recent Quaternary period glaciations. PMID:23302860

  16. Arctic-alpine blockfields in the northern Swedish Scandes: late Quaternary - not Neogene

    NASA Astrophysics Data System (ADS)

    Goodfellow, B. W.; Stroeven, A. P.; Fabel, D.; Fredin, O.; Derron, M.-H.; Bintanja, R.; Caffee, M. W.

    2014-07-01

    Autochthonous blockfield mantles may indicate alpine surfaces that have not been glacially eroded. These surfaces may therefore serve as markers against which to determine Quaternary erosion volumes in adjacent glacially eroded sectors. To explore these potential utilities, chemical weathering features, erosion rates, and regolith residence durations of mountain blockfields are investigated in the northern Swedish Scandes. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay / silt ratios, secondary mineral assemblages, and imaging of chemical etching of primary mineral grains in fine matrix are each used for this purpose. Secondly, erosion rates and regolith residence durations of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surfaces. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite consistent variability according to slope position. In addition, average erosion rates of ~16.2 and ~6.7 mm ka-1, calculated for the two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few metres in thickness, within a late Quaternary time frame. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. The persistence of autochthonous blockfields over multiple glacial-interglacial cycles confirms

  17. Late Tertiary and Quaternary geology of the Tecopa basin, southeastern California

    SciTech Connect

    Hillhouse, J.W.

    1987-12-31

    Stratigraphic units in the Tecopa basin, located in southeastern California, provide a framework for interpreting Quaternary climatic change and tectonism along the present Amargosa River. During the late Pliocene and early Pleistocene, a climate that was appreciably wetter than today`s sustained a moderately deep lake in the Tecopa basin. Deposits associated with Lake Tecopa consists of lacustrine mudstone, conglomerate, volcanic ash, and shoreline accumulations of tufa. Age control within the lake deposits is provided by air-fall tephra that are correlated with two ash falls from the Yellowstone caldera and one from the Long Valley caldera. Lake Tecopa occupied a closed basin during the latter part, if not all, of its 2.5-million-year history. Sometime after 0.5 m.y. ago, the lake developed an outlet across Tertiary fanglomerates of the China Ranch Beds leading to the development of a deep canyon at the south end of the basin and establishing a hydrologic link between the northern Amargosa basins and Death Valley. After a period of rapid erosion, the remaining lake beds were covered by alluvial fans that coalesced to form a pediment in the central part of the basin. Holocene deposits consist of unconsolidated sand and gravel in the Amargosa River bed and its deeply incised tributaries, a small playa near Tecopa, alluvial fans without pavements, and small sand dunes. The pavement-capped fan remnants and the Holocene deposits are not faulted or tilted significantly, although basins to the west, such as Death Valley, were tectonically active during the Quaternary. Subsidence of the western basins strongly influenced late Quaternary rates of deposition and erosion in the Tecopa basin.

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

    USGS Publications Warehouse

    Swezey, C.

    2001-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Daniels, J. Michael

    2008-10-01

    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.

  1. Geochemical evidence for the origin of late Quaternary loess in central Alaska

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.R.

    2006-01-01

    Loess is extensive in central Alaska, but there are uncertainties about its source and the direction of paleo-winds that deposited it. Both northerly and southerly winds have been inferred. The most likely sources of loess are the Tanana River (south), the Nenana River (southeast), and the Yukon River (north). Late Quaternary loess in central Alaska has immobile trace-element compositions (Cr/Sc, Th/Ta, Th/ Sc, Th/U, Eu/Eu*, GdN/YbN) that indicate derivation mostly from the Tanana River. However, other ratios (As/Sb, Zr/Hf, LaN/YbN) and quantitative modeling indicate that the Yukon River was also a source. During the last glacial period, there may have been a longer residence time of the Siberian and Canadian high-pressure cells, along with a strengthened Aleutian low-pressure cell. This would have generated regional-scale northeasterly winds and explains derivation of loess from the Yukon River. However, superim-posed upon this synoptic-scale circulation, there may have been strong, southerly katabatic winds from expanded glaciers on the northern flank of the Alaska Range. These winds could have provided eolian silt from the Tanana River. Yukon River and Tanana River sediments are highly calcareous, whereas Fairbanks-area loess is not. This suggests that carbonate leaching in loess kept ahead of sedimentation and that late Quaternary loess in central Alaska was deposited relatively slowly. ?? 2006 NRC Canada.

  2. Late Pleistocene glaciations of the arid subtropical Andes and new results from the Chajnantor Plateau, northern Chile

    NASA Astrophysics Data System (ADS)

    Ward, Dylan J.; Cesta, Jason M.; Galewsky, Joseph; Sagredo, Esteban

    2015-11-01

    The spatiotemporal pattern of glaciation along the Andes Mountains is an important proxy record reflecting the varying influence of global and regional circulation features on South American climate. However, the timing and extent of glaciation in key parts of the orogen, particularly the deglaciated arid Andes, are poorly constrained. We present new cosmogenic 10Be and 36Cl exposure ages for glacial features on and near the Chajnantor Plateau (23 °S). The new dates, although scattered due to cosmogenic inheritance, imply that the most recent extensive glacial occupation ended before or during the global Last Glacial Maximum (LGM). We discuss this new record in the context of published glacial chronologies from glacial features in Peru, Bolivia, and northern Chile rescaled using the latest cosmogenic 10Be production rate calibration for the tropical Andes. The results imply regionally synchronous moraine stabilization ca. 25-40 ka, 15-17 ka, and 12-14 ka, with the youngest of these moraines absent in records south of ˜20 °S, including in our new Chajnantor area chronology. This spatial pattern implicates easterly moisture in generating sufficient snowfall to glaciate the driest parts of the Andes, while allowing a role for westerly moisture, possibly modulated by the migration of the Southern Westerly Wind belt, in the regions near and south of the Atacama Desert.

  3. The Late Quaternary tephrostratigraphy of annually laminated sediments from Meerfelder Maar, Germany

    NASA Astrophysics Data System (ADS)

    Lane, Christine S.; Brauer, Achim; Martín-Puertas, Celia; Blockley, Simon P. E.; Smith, Victoria C.; Tomlinson, Emma L.

    2015-08-01

    The record of Late Quaternary environmental change within the sediments of Meerfelder Maar in the Eifel region of Germany is renowned for its high precision chronology, which is annually laminated throughout the Last Glacial to Interglacial transition (LGIT) and most of the Holocene. Two visible tephra layers are prominent within the floating varve chronology of Meerfelder Maar. An Early Holocene tephra layer, the Ulmener Maar Tephra (∼11,000 varve years BP), provides a tie-line of the Meerfelder Maar record to the varved Holocene record of nearby Lake Holzmaar. The Laacher See Tephra provides another prominent time marker for the late Allerød, ∼200 varve years before the transition into the Younger Dryas at 12,680 varve years BP. Further investigation has now shown that there are also 15 cryptotephra layers within the Meerfelder Maar LGIT-Holocene stratigraphy and these layers hold the potential to make direct comparisons between the Meerfelder Maar record and other palaeoenvironmental archives from across Europe and the North Atlantic. Most notable is the presence of the Vedde Ash, the most widespread Icelandic eruption known from the Late Quaternary, which occurred midway through the Younger Dryas. The Vedde Ash has also been found in the Greenland ice cores and can be used as an isochron around which the GICC05 and Meerfelder Maar annual chronologies can be compared. Near the base of the annual laminations in Meerfelder Maar a cryptotephra is found that correlates to the Neapolitan Yellow Tuff, erupted from Campi Flegrei in southern Italy, 1200 km away. This is the furthest north that the Neapolitan Yellow Tuff has been found, highlighting its importance in the construction of a European-wide tephrostratigraphic framework. The co-location of cryptotephra layers from Italian, Icelandic and Eifel volcanic sources, within such a precise chronological record, makes Meerfelder Maar one of the most important tephrostratotype records for continental Europe

  4. Late Quaternary distribution dynamics and phylogeography of the red deer ( Cervus elaphus) in Europe

    NASA Astrophysics Data System (ADS)

    Sommer, R. S.; Zachos, F. E.; Street, M.; Jöris, O.; Skog, A.; Benecke, N.

    2008-04-01

    Here we present spatial-temporal patterns for European late Quaternary red deer (Cervus elaphus), based on radiocarbon-supported evidence derived mainly from archaeological sites. This is followed by an overview of the recent phylogeography of this species using haplogroup studies of recent molecular data. The implications of the synthesis of palaeontological and genetic data are discussed and we propose that present day European red deer haplogroup distributions are best explained against the history of late Quaternary population contractions into and expansions from glacial refugia. Around 800 records of Cervus elaphus were assigned to the period covering the later part of the Last Glacial and the Early to Middle Holocene. Red deer becomes increasingly visible in faunal assemblages dated to late OIS-3 (<40.0 ka 14C BP). The species persisted throughout the LGM on the Iberian Peninsula, in adjacent regions of South-Western France (Gascony, Dordogne, Languedoc), on the Italian Peninsula, in the Balkans and Greece, and east of the Carpathians in Moldavia. We suggest that genetic exchange between the populations of the Balkans and the East of the Carpathians remained uninterrupted during the LGM. The expansion of red deer from its southern refugia into Central and Northern Europe begins rapidly at 12,500 14C BP. The expansion of red deer coincides with the sudden rise in temperature at the onset of Greenland Interstadial 1e and the dispersion of open birch woodland into the northern half of Europe. Radiocarbon supported records show a more or less universal distribution of Cervus elaphus across Europe following the Pleistocene/Holocene climatic change at 10.0 ka 14C BP for the first time. Molecular data and fossil record combined provide a clearer temporal and spatial pattern for the Lateglacial recolonisation process of the northern part of Europe.

  5. Late quaternary dynamics in the Madeira River basin, southern Amazonia (Brazil), as revealed by paleomorphological analysis.

    PubMed

    Hayakawa, Ericson H; Rossetti, Dilce F

    2015-03-01

    Ancient drainage systems are being increasingly documented in the Amazon basin and their characterization is crucial for reconstructing fluvial evolution in this area. Fluvial morphologies, including elongate belts, are well preserved along the Madeira River. Digital Elevation Model from the Shuttle Radar Topography Mission favored the detection of these features even where they are covered by dense rainforest. These paleomorphologies are attributed to the shifting position of past tributaries of the Madeira River through avulsions. These radial paleodrainage networks produced fan-shaped morphologies that resemble distributary megafans. Distinguishing avulsive tributary systems from distributary megafans in the sedimentary record is challenging. Madeira´s paleodrainage reveals the superposition of tributary channels formed by multiple avulsions within a given time period, rather than downstream bifurcation of coexisting channels. Channel avulsion in this Amazonian area during the late Quaternary is related to tectonics due to features as: (i) straight lineaments coincident with fault directions; (ii) northeastward tilting of the terrain with Quaternary strata; and (iii) several drainage anomalies, including frequent orthogonal drainage inflections. These characteristics altogether lead to propose that the radial paleodrainage present at the Madeira River margin results from successive avulsions of tributary channels over time due to tectonics. PMID:25806978

  6. Tropical forest changes during the late quaternary in African and South American lowlands

    NASA Astrophysics Data System (ADS)

    Servant, Michel; Maley, Jean; Turcq, Bruno; Absy, Maria-Lucia; Brenac, Patrice; Fournier, Marc; Ledru, Marie-Pierre

    1993-05-01

    Arboreal pollen and montane elements of Late Quaternary pollen assemblages from three lacustrine cores (West Cameroon, southeastern Amazonia and central Brazil) are correlated, by the radiocarbon chronology, with other palaeoenvironmental records in Africa and South America. We observe in both continents a well-developed dense forest at 30,000 and 9000 yr B.P. The succession of vegetation types during the Late Quaternary appeared strongly related to the regional conditions: (1) the dense forest was more or less degraded depending on the regions during the last full glacial period (20,000-15,000 yr B.P.); (2) a slow increase of tree elements is evidenced in some areas during the Late Glacial (15,000-10,000 yr B.P.), whereas short-term fluctuations occurred in central Brazil during the same time; (3) a strong regression of the forest during the middle Holocene (6000-5000 yr B.P.), in the southern tropical zone of South America, was in opposition to a full forest development in Africa. In both continents two main features characterize the tropical forest evolution: (1) Montane elements developed in the lowlands during the last glacial period and in some southern or northern regions during the early Holocene; and (2) the climate seasonality was enhanced in several regions since 8500-7500 yr B.P. For a tentative explanation, we relate the cold or cool climate, inferred by palaeoecological evidences in the glacial period and glacial-interglacial transition, to polar air-masses reaching more frequently the tropical zone. This interpretation explains the apparent contradiction between the markedly low temperature of the continental lowlands opposed: (1) at 18,000 yr B.P., to the 1-2°C lower Sea Surface Temperature of tropical oceans and (2) to the global warming during the late glacial. During the middle and Late Holocene, climate evolution was mainly influenced by the latitudinal shift of the ITCZ positions in July and January and, in South America, by short-term changes

  7. Glacistore: Understanding Late Cenozoic Glaciation and Basin Processes for the Development of Secure Large Scale Offshore CO2 Storage (North Sea).

    NASA Astrophysics Data System (ADS)

    Stewart, H. A.; Barrio, M.; Akhurst, M.; Aagaard, P.; Alcalde, J.; Bauer, A.; Bradwell, T.; Cavanagh, A.; Faleide, J. I.; Furre, A. K.; Haszeldine, S.; Hjelstuen, B. O.; Holloway, S.; Johansen, H.; Johnson, G.; Kuerschner, W.; Mondol, N. H.; Querendez, E.; Ringrose, P. S.; Sejrup, H. P.; Stewart, M.; Stoddart, D.; Wilkinson, M.; Zalmstra, H.

    2014-12-01

    The sedimentary strata of the North Sea Basin (NSB) record the glacial and interglacial history of environmental change in the Northern Hemisphere, and are a proposed location for the engineered storage of carbon dioxide (CO2) captured from power plant and industrial sources to reduce greenhouse gas emissions. These aspects interact in the geomechanical and fluid flow domain, as ice sheet dynamics change the properties of potential seal and reservoir rocks that are the prospective geological storage strata for much of Europe's captured CO2. The intensification of the global glacial-interglacial cycle at the onset of the Pleistocene (2.5-2.7 Ma) was a critical tipping-point in Earth's recent climate history. The increased severity of glaciations at the Plio-Pleistocene boundary triggered the first development of large-scale continental ice sheets in the Northern Hemisphere. The central part of the NSB preserves a unique history of the depositional record spanning at least the last 3 Ma, which also forms the overburden and seal to the underlying CO2 reservoirs. There is good evidence that these ice sheets created strong feedback loops that subsequently affected the evolution of the Quaternary climate system through complex ocean-atmosphere-cryosphere linkages. Understanding NSB dynamics, including the role of fluids in controlling compaction, cementation, and diagenetic processes in shale-dominated basins, is essential for CO2 storage site characterisation to increase understanding and confidence in secure storage. An increased understanding of the overlying sequence will inform quantitative predictions of the performance of prospective CO2 storage sites in glaciated areas in Europe and worldwide; to include improved resolution of glacial cycles (depositional and chronological framework), characterise pore fluids, flow properties of glacial landforms within the sequence (e.g. tunnel valleys) and the geomechanical effects (quantify compaction, rock stiffness, strength

  8. Mapped plant macrofossil and pollen records of late Quaternary vegetation change in eastern North America

    SciTech Connect

    Jackson, S.T.; Overpeck, J.T.; Webb, T. III ||

    1995-06-01

    We compiled a plant macrofossil database for 12 eastern North American tree and shrub taxa (Picea sp., P. glauca, P. mariana, Larix laricina, Abies balsamea, Tsuga canadensis, Pinus strobus, P. banksiana, P. resinosa, Betula papyrifera, B. alleghaniensis, B. Series Humiles) at 264 late Quaternary sites. Presence/absence maps for these taxa at 18,000, 15,000, 12,000, 9000, 6000, 3000, and 0 {sup 14}C yr B.P. show changes in geographic ranges of these species in response to climatic change. Comparison of the macrofossil maps with isopoll maps for corresponding taxa corroborates inferences from the pollen data, and reveals species-level patterns not apparent in the pollen maps.

  9. Late Quaternary environments and prehistoric occupation in the lower White Nile valley, central Sudan

    NASA Astrophysics Data System (ADS)

    Williams, Martin A. J.; Usai, Donatella; Salvatori, Sandro; Williams, Frances M.; Zerboni, Andrea; Maritan, Lara; Linseele, Veerle

    2015-12-01

    Despite the major contributions provided over fifty years ago by A.J. Arkell and J.D. Tothill to our understanding of late Quaternary environments and prehistoric occupation near the confluence of the Blue and White Nile in central Sudan, three key questions have remained unresolved since then. (a) Was the decline in Nile flood levels from early Holocene times onwards caused by a reduction in Nile discharge, or by channel incision, or both? (b) Was the regional climate wetter during times of high Nile floods and drier during times of low Nile floods? (c) Given the high degree of disturbance of Mesolithic and later prehistoric sites, is it possible to identify primary-context, stratified and undisturbed occupation? Drawing upon dated evidence from three sites to the east of and three to the west of the lower White Nile, we provide a qualified answer to the first question and documented affirmative answers to the second and third questions.

  10. A protocol for subsampling Late Quaternary coprolites for multi-proxy analysis

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2016-04-01

    The study of Late Quaternary coprolites can provide unique insights into various aspects of the biology and ecology of extinct species and prehistoric humans. Coprolite studies are becoming increasingly multi-disciplinary, allowing a greater amount of information to be obtained from individual specimens. Subsampling is a critical part of multi-proxy coprolite analysis, yet no standardised subsampling protocols exist, and details of subsampling methods have rarely been reported in published studies. Here, we outline a procedure for the subsampling of coprolites for multi-proxy analysis. The method is designed to minimise the risk of sample contamination for sensitive analyses (e.g. ancient DNA, palynology), thereby maximising the robustness of interpretations made from the results. We also stress the need for voucher samples to be retained to ensure the repeatability of results and allow for further analytical methods to be applied to specimens in the future.

  11. Late Quaternary in a South Atlantic estuarine system: Stratigraphic and paleontologic indicators of coastal evolution

    NASA Astrophysics Data System (ADS)

    Aliotta, Salvador; Ginsberg, Silvia S.; Spagnuolo, Jorge O.; Farinati, Ester; Giagante, Darío; Vecchi, Laura G.

    2013-08-01

    The decisive influence of Late Quaternary sea level changes on the geological evolution of the coastal plain and adjacent continental shelf around the world has long been recognized. Coastal environments evolve actively during transgressive-regressive cycles whose development depends on sea level and sediment supply variations. The interaction of these variables was key to the current morphological and sedimentological configuration of coastal regions. Particularly, the estuarine system of Bahía Blanca (Argentina) presents various types of deposits and marine fossil accumulations, such as paleochannels in the subbottom, sand-shell ridges and extensive layers with fossils in life position. These features are important geological indicators, because its analysis allows us to define different paleoenvironmental conditions that prevailed during the coastal evolutionary process.

  12. Response to comment on "No late Quaternary strike-slip motion along the northern Karakoram fault"

    NASA Astrophysics Data System (ADS)

    Robinson, Alexander C.; Owen, Lewis A.; Chen, Jie; Schoenbohm, Lindsay M.; Hedrick, Kathryn A.; Blisniuk, Kimberly; Sharp, Warren D.; Imrecke, Daniel B.; Li, Wenqiao; Yuan, Zhaode; Caffee, Marc W.; Mertz-Kraus, Regina

    2016-06-01

    In their comment on "No late Quaternary strike-slip motion along the northern Karakoram fault", while Chevalier et al. (2016) do not dispute any of the results or interpretations regarding our observations along the main strand of the northern Karakoram fault, they make several arguments as to why they interpret the Kongur Shan Extensional System (KES) to be kinematically linked to the Karakoram fault. These arguments center around how an "active" fault is defined, how slip on segments of the KES may be compatible with dextral shear related to continuation of the Karakoram fault, and suggestions as to how the two fault systems might still be connected. While we appreciate that there are still uncertainties in the regional geology, we address these comments and show that their arguments are inconsistent with all available data, known geologic relationships, and basic kinematics.

  13. Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

    NASA Astrophysics Data System (ADS)

    Chipman, M. L.; Hudspith, V.; Higuera, P. E.; Duffy, P. A.; Kelly, R.; Oswald, W. W.; Hu, F. S.

    2015-07-01

    Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range is 0-0.05 pieces cm-2 yr-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  15. Delineation of Late Quaternary depositional sequences by high-resolution seismic stratigraphy, Louisiana continental shelf

    SciTech Connect

    Suter, J.R.; Berryhill, H.L. Jr.; Penland, S.

    1987-05-01

    Interpretations of over 20,000 line km of single-channel, high-resolution seismic reflection profiles, coupled with nearshore vibracores and logs of industrial platform borings, provide the data base for determining the history and stratigraphy of late Quaternary sea level fluctuations on the Louisiana continental shelf. Regional unconformities, formed by subaerial exposure of the shelf during glacio-eustatic sea level withdrawals and modified by shoreface erosion during ensuing transgression, serve as markers to identify the boundaries of depositional sequences. Unconformities are recognizable on seismic profiles by high-amplitude reflectors as well as discordant relationships between reflectors. Within the upper Quaternary section, six depositional sequences have been recognized. Five of these are related to glacio-eustatic sea level fluctuations, involving sea level fall close to, or beyond, the margin of the continental shelf. Three of these fluctuations culminated in the deposition of shelf margin delta sequences. Extensive fluvial channeling characterizes the regressive phase of these sequences. Transgressive phases are marked by infilling of fluvial channels, flood-plain aggradation, truncation, or deposition of sand sheets, depending upon sediment supply and rate of sea level rise. Sequences 4 and 5 are correlated with the late Wisconsinan glacial stage and Holocene transgression. The upper portion of sequence 5 consists of an early Holocene Mississippi delta complex. Abandonment and transgression of this delta are responsible for the formation of sequence 6. Although these deposits cover a smaller area, this demonstrates that deltaic processes can produce sequences similar to those driven by glacially controlled sea level changes.

  16. Assessing Timescales and Controls of Floodplain Evolution in Monsoonal Australia during the Late Quaternary

    NASA Astrophysics Data System (ADS)

    May, J. H.; Preusser, F.

    2014-12-01

    Subtropical and tropical river systems are considered unique and sensitive archives for the detection of past changes in global circulation patterns due to their strategic position between significant atmospheric phenomena. In semi-arid to arid Central Australia, many of the hydrological variations have generally been attributed to variations in monsoon strength and position. While an increasing number of studies has recently addressed the reconstruction of monsoonal variations from high-resolution proxy records in tropical Australasia, very little data is available on the landscape-scale impacts such as weathering, erosion, flooding and sediment transport. Therefore, unraveling the impacts of past changes in monsoonal intensity on fluvial systems in Australia's tropical north - the 'Top End' - will substantially contribute to our understanding of cause and effect of climate change. Our study presents first results from the Adelaide River, one of the major river systems draining the 'Top End'. Here, extensive but currently inactive floodplains have accreted along the middle reaches of the catchment upstream of bedrock constrictions. Virtually no data is so far available from these floodplains although their stratigraphic and sedimentary record should contain valuable information on the late Quaternary evolution of the fluvial system in northern Australia. We have cored a transect of nine sediment profiles across the floodplains and levees associated with the Adelaide River. Based on these profiles, we (i) document their geomorphologic setting based on the analysis of high-resolution (LIDAR) elevation models and remote sensing data, (ii) establish a first stratigraphy for these floodplains based on field description, grain sizes and detailed total element data, (iii) present a chronological framework for the sediments based on luminescence dating, and (iv) discuss the significance of these results in terms of the larger-scale evolution of paleoenvironments and sea

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

    NASA Astrophysics Data System (ADS)

    McLean, Bryan S.; Emslie, Steven D.

    2012-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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

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

    USGS Publications Warehouse

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

    2013-01-01

    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

  20. Late Quaternary Paleohydrology of the Madre de Dios River, southwestern Amazon Basin, Peru

    NASA Astrophysics Data System (ADS)

    Rigsby, Catherine A.; Hemric, Erin M.; Baker, Paul A.

    2009-12-01

    Late Quaternary climatic and hydrologic variability triggered changes in fluvial deposition and erosion along the course of the Madre de Dios River, Peru, the largest tributary basin of the Madeira basin, itself the largest tributary basin of the Amazon. Three laterally extensive, Quaternary-age, terrace tracts are present within the Madre de Dios basin. Analysis of sedimentary facies, present in the modern cut banks and terraced sequences, along with radiocarbon dates on fossil wood and leaf material preserved in the terraced strata, allow reconstruction of the Late Quaternary depositional history of the sedimentary sequences, including determination of the approximate timing of aggradation and downcutting episodes and its relationship to the timing of past climate change in this portion of the Amazon basin and beyond. The Quaternary sediments underlying the terraces most often recorded deposition in a coarse-grained meandering fluvial system. The T3 terrace, the highest terrace, is underlain by the Miocene (?) Ipururi Formation, which is unconformably overlain by the late Miocene-Pleistocene (?) (> 48,000 cal yrs BP) Madre de Dios Formation, a multistory coarse-sandy to gravelly channel and point bar complex. The latter was downcut before 29,850 ± 100 cal yrs BP. This downcut landscape was infilled by meandering fluvial strata characterized by gravelly channel deposits in a sequence dominated by floodplain and lateral accretion deposits. These strata were in turn downcut to form the T2 terrace before 11,970 ± 100 cal yrs BP. A third episode of aggradation resulted in the deposition of a sand-dominated meandering channel complex that infilled the T2 valley and was subsequently downcut after 3780 ± 50 cal yrs BP. This most recent terrace is infilled by the modern fluvial sediment, which has been actively aggrading since at least 870 ± 50 cal yrs BP. Importantly, the Madre de Dios fluvial system actively aggraded between 30,000 and 25,000 cal yrs BP, (and likely

  1. Late Quaternary marginal marine deposits and palaeoenvironments from northeastern Buenos Aires Province, Argentina: A review

    NASA Astrophysics Data System (ADS)

    Aguirre, M. L.; Whatley, R. C.

    The late Quaternary marginal marine deposits along eastern Argentina (Southwestern Atlantic) are reviewed according to our present knowledge. In the northeastern coastal area of Buenos Aires Province they have been assigned to a series of transgressions and regressions ranging from the late Pliocene to the late Quaternary. The most widely accepted model is Frenguelli's (1957) classical chronostratigraphical scheme of: 'Belgranense', late Pleistocene marine sediments at 3-6 m above m.s.l. and ca. 26,000->35,000 14C years BP, the 'Querandinense', Pleistocene-Holocene estuarine sediments below or at present m.s.l., and the most extensive 'Platense', mid-Holocene marine deposits at 4.5-2 m above m.s.l. dated at ca. 8000-1340 14C years BP. The restricted 'Belgranense' deposits, recorded in Samborombon Bay, in Magdalena at ca. 32,000 BP, near Mar Chiquita at ca. 24,900 and 30,500 BP and southwards in Bahía Blanca at ca. 26,000-35,500 BP, may belong to an interstadial (González et al., 1986). The molluscan composition suggests a marine invasion of the area but not a typical interglacial cycle characterized by euhaline and warm water elements. However, the oxygen isotope record argues against an interstadial during the interval 34-27 ka and the chronological control for these deposits is very poor, suggesting that they most probably have been elevated neotectonically. The Pleistocene-Holocene 'Querandinense' deposits, extensively distributed along the Bonaerensian coastal plain and continental shelf (ca. 11,000 14C years BP), with very low faunal diversity, abundance of freshwater ostracods and absence of the warm water molluscs characteristic of the Holocene ridges, indicate low salinity and cool water conditions. Further dating and isotope analysis of these deposits are required for a better understanding of the chronology of climatic events by the end of the Pleistocene in this area and to establish whether or not they could correspond to the Younger Dryas event of

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

    NASA Astrophysics Data System (ADS)

    Oldknow, Chris; Hooke, Janet; Lang, Andreas

    2016-04-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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

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

    NASA Astrophysics Data System (ADS)

    Jiang, Qinhua; Piperno, Dolores R.

    1999-09-01

    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.

  5. The calculation of climatic indices for Late Quaternary faunal assemblages from South African sites

    NASA Astrophysics Data System (ADS)

    Thackeray, Francis

    2013-04-01

    The relative abundance of rodents and insectivores from several Late Quaternary sites in South Africa have been studied using multivariate analysis (notably factor analysis). The highest loadings on the first factor (F1) are obtained for taxa that are today found in warm subtropical environments, contrasting with taxa which have low F1 loadings and which are today distributed in more southerly latitudes and at high altitudes. The latter taxa with low loadings on F1 are able to tolerate cold conditions (and are relatively common in Terminal Pleistocene assemblages associated with Oxygen Isotope Stage 2). A summary statistic based on F1 (SSF1) is calculated and interpreted as a temperature index. The dated temperature indices for Boomplaas cave correlate well (r=0.95) with dated deuterium isotope ratios for a Vostok core in Antarctica. Similarly, a moisture index (SSF3) is calculated from factor analysis of the relative abundances of the same faunal assemblages. The results are assessed in terms of a non-linear pattern of variability in temperature and moisture indices calculated from pollen as well as mammalian microfauna. The changes in climate are likely to have influenced the distribution and abundance of human populations in the Late Pleistocene in southern Africa.

  6. Dynamics of Mediterranean late Quaternary fluvial activity: An example from the River Ebro (north Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Soria-Jáuregui, Ángel; González-Amuchástegui, María José; Mauz, Barbara; Lang, Andreas

    2016-09-01

    Late Pleistocene and Holocene fluvial evolution of the upper River Ebro (Miranda basin, north Spain) is analysed using geomorphological, sedimentological, and optical dating techniques. Maximum regional crustal uplift of 0.98 m/ka approximately helped preserve a suite of terraces in the Miranda basin: 5 river terraces (T1-5) were identified and their formation attributed to MIS 6 (T1), MIS 5d (T2), MIS 4 (T3), MIS 2 (T4), MIS 1 (T5). Alluvium deposited in terraces T1, T2, T3, and T4 is well-sorted, clast-supported gravels; whereas the T5 deposit is exclusively composed of silt. Gravels were deposited during cold and dry periods when reduced vegetation cover on hillslopes increased sediment supply to the trunk river. Silt was deposited in overbank settings under warmer and wetter climate conditions when vegetation cover stabilised hillslopes and restricted sediment supply. It also resulted in lower peak discharge and reduced flow velocities over vegetated floodplains. The chronological sequence of terraces indicates that incision occurred during climatic transitions. We conclude that the upper River Ebro responded to fluctuations in sediment supply and discharge controlled by late Quaternary climate cycles.

  7. Late-Quaternary Dynamics of Temperate Forests: Applications of Paleoecology to Issues of Global Environmental Change

    NASA Astrophysics Data System (ADS)

    Delcourt, Paul A.; Delcourt, Hazel R.

    Paleoecological evidence recently summarized from 162 fossil-pollen sites in eastern North America provides new insights concerning the nature and rate of response of temperate forest ecosystems to late Pleistocene and Holocene environmental changes. Across this subcontinental region (25°N to 60°N; 50°W to 100°W), temperate forests have changed in composition, location and area occupied in adjustment to major episodes of climatic cooling and warming during glacial-interglacial cycles of the Quaternary. Forest taxa have migrated differentially, reflecting their individualistic life-history characteristics, dispersal and competitive abilities, and tolerance thresholds to environmental changes, as well as the geographic distribution of corridors and barriers to plant migration. Gradient analysis and ecological ordination of paleovegetational data illustrate that: (1) both positions and breadth of major vegetational ecotones have shifted latitudinally over the past 20 ka; (2) good modern analogues exist for certain full-glacial warm-temperate and boreal forests; (3) during the transition from Pleistocene to Holocene conditions, mixed conifer-northern hardwoods forests, spreading across newly deglaciated terrain, lacked good analogues within the modern vegetation; and (4) most cool-temperate deciduous forest communities north of 35°N developed in the Holocene. Forest clearance and cultivation by Native Americans along principal riverways resulted in a transformation from natural to cultural landscapes during the mid- and late Holocene intervals. Fragmentation of temperate forests accelerated with the onset of EuroAmerican settlement and technologic developments after the Industrial Revolution.

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

    NASA Astrophysics Data System (ADS)

    Faith, J. Tyler

    2011-01-01

    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.

  9. Late Pleistocene glaciation in the Central Andes: Temperature versus humidity control — A case study from the eastern Bolivian Andes (17°S) and regional synthesis

    NASA Astrophysics Data System (ADS)

    Kull, C.; Imhof, S.; Grosjean, M.; Zech, R.; Veit, H.

    2008-01-01

    A glacier-climate model was used to calculate climatic conditions in a test site on the east Andean slope around Cochabamba (17°S, Bolivia) for the time of the maximum Late Pleistocene glaciation. Results suggest a massive temperature reduction of about - 6.4 °C (+ 1.4/- 1.3 °C), combined with annual precipitation rates of about 1100 mm (+ 570 mm/- 280 mm). This implies no major change in annual precipitation compared with today. Summer precipitation was the source for the humidity in the past, as is the case today. This climate scenario argues for a maximum advance of the paleo-glaciers in the eastern cordillera during the global Last Glacial Maximum (LGM, 20 ka BP), which is confirmed by exposure age dates. In a synthesized view over the central Andes, the results point to an increased summer precipitation-driven Late Glacial (15-10 ka BP) maximum advance in the western part of the Altiplano (18°S-23°S), a temperature-driven maximum advance during full glacial times (LGM) in the eastern cordillera, and a pre- and post-LGM (32 ka BP/14 ka BP) maximum advance around 30°S related to increased precipitation and reduced temperature on the western slope of the Andes. The results indicate the importance of understanding the seasonality and details of the mass balance-climate interaction in order to disentangle drivers for the observed regionally asynchronous past glaciations in the central Andes.

  10. Shoreline and Lacustrine Records of Late Quaternary Climate Change in the Chihuahuan Desert, Mexico

    NASA Astrophysics Data System (ADS)

    Castiglia, P. J.; Fawcett, P. J.

    2001-12-01

    Spatial and temporal patterns of Quaternary moisture and temperature variability in northern Mexico are difficult to reconstruct given the paucity of continuous, long-term Quaternary climate records from the region. Preliminary shoreline age dates and a pair of lacustrine sediment cores from Laguna Fresnal in northern Chihuahua, Mexico, record climate-driven variations in both lake level and sedimentologic input. Reeves (1969) first described Laguna Fresnal as part of Pluvial Lake Palomas, a Pleistocene lake composed of 3 interconnected sub-basins: Laguna Guzman, Santa Maria, and Fresnal. Six AMS 14C age dates from previously unrecognized lake fauna on a beach ridge complex indicate a number of Holocene lakes as well. These preserved shorelines increase in age with distance and elevation from the playa surface and include early Holocene (8456\\pm97 14C yrs BP; 1225 m asl), middle Holocene (6180\\pm53, 6401\\pm58, and 6721\\pm68 14C yrs BP; 1200 m asl), and Little Ice Age (435\\pm39 14C yrs BP; 1175 m asl) lake stands. These ages correlate with beach ridge chronologies throughout the western US and northern Mexico. However, during the middle Holocene Laguna Fresnal exhibits a pronounced high stand while other records show a prolonged dry episode. Two 17 m-long cores from the basin center provide a continuous record of sedimentation during the late Quaternary. Several abrupt changes in lake level are indicated by mud cracks preserved as sharp, light gray lineations (487-548 cm and 975-1130 cm), sharply overlain by finely laminated silt and clay. Drying episodes are preserved in the basal section of the cores as several 0.5-2 cm-thick gypsum horizons, overlain by 3-5 cm-thick, carbon-poor (0.02-0.05% TOC), light gray silt. Five distinct zones of coupled, alternating relatively high and low average magnetic susceptibility (MS) and bulk density further reveals changes in lacustrine sedimentation. Peaks in MS generally correlate with peaks in bulk density, with the

  11. Late Quaternary stratigraphy and geochronology of the western Killpecker Dunes, Wyoming, USA

    USGS Publications Warehouse

    Mayer, J.H.; Mahan, S.A.

    2004-01-01

    New stratigraphic and geochronologic data from the Killpecker Dunes in southwestern Wyoming facilitate a more precise understanding of the dune field's history. Prior investigations suggested that evidence for late Pleistocene eolian activity in the dune field was lacking. However, luminescence ages from eolian sand of ???15,000 yr, as well as Folsom (12,950-11,950 cal yr B.P.) and Agate Basin (12,600-10,700 cal yr) artifacts overlying eolian sand, indicate the dune field existed at least during the latest Pleistocene, with initial eolian sedimentation probably occurring under a dry periglacial climate. The period between ???13,000 and 8900 cal yr B.P. was characterized by relatively slow eolian sedimentation concomitant with soil formation. Erosion occurred between ???8182 and 6600 cal yr B.P. on the upwind region of the dune field, followed by relative stability and soil formation between ???5900 and 2700 cal yr B.P. The first of at least two latest Holocene episodes of eolian sedimentation occurred between ???2000 and 1500 yr, followed by a brief (???500 yr) episode of soil formation; a second episode of sedimentation, occurring by at least ???700 yr, may coincide with a hypothesized Medieval warm period. Recent stabilization of the western Killpecker Dunes likely occurred during the Little Ice Age (???350-100 yr B.P.). The eolian chronology of the western Killpecker Dunes correlates reasonably well with those of other major dune fields in the Wyoming Basin, suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late Quaternary. Similar to dune fields on the central Great Plains, dune fields in the Wyoming Basin have been active under a periglacial climate during the late Pleistocene, as well as under near-modern conditions during the latest Holocene. ?? 2003 University of Washington. All rights reserved.

  12. Late Quaternary river incision rate from L'Aquila-Scoppito Basin (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Nocentini, Marco; Tallini, Marco; Asti, Riccardo; Cosentino, Domenico

    2014-05-01

    L'Aquila-Scoppito Basin (ASB) is part of the wider L'Aquila Basin, one of the most tectonically active intermontane basins of central Apennines (Italy). ASB is a semi-enclosed intermontane sedimentary basin of morphotectonic origin, W-E trending and approximately 20 km2 wide, with mean elevations ranging between 850 and 650 m a.s.l. and it is crossed by two main water courses: the Aterno River and the Raio Creek. Structurally, the ASB may be considered as an half-graben, bordered northerly by the south-dipping Scoppito-Preturo normal Fault and easterly by the southwest dipping Pettino Fault. In the L'Aquila-Scoppito Basin a series of erosional and depositional post Middle Pleistocene events generated three order of fluvial terraces, generally not completely preserved. The first order of fluvial terrace, the Vetoio Synthem (T1), is a fill terrace carved into both the L'Aquila Breccia Synthem (Middle Pleistocene) and the Madonna della Strada Synthem (Lower Pleistocene), whose top is preserved near the L'Aquila airport and the S. Salvatore hospital, approximately at 20-25 m above the present thalweg of the Aterno River. The second order of terrace, the Pile Synthem (T2), is a strath terrace embedded into T1 and carved into both the Lower Pleistocene deposits and the pre-Quaternary bedrock. The top of T2 is located at 10-13 m above the present thalweg of the Raio Creek. Charcoaled plant remains founded within the sandy layers of T2 give a 14C 2σ age of 41854-40464 BP (MIS 3). This age is in agreement with traces of lithic industry of Mousterian age (late Middle Paleolithic) inside the gravels. The youngest order of terrace, Ponte Peschio Synthem (T3), lies 5-7 m above both the Raio and the Aterno thalwegs. T3 is embedded into T1 and carved in the L'Aquila Breccia Synthem, near the S. Salvatore hospital, while at Ponte Peschio it is embedded into T2 and is carved directly into the pre-Quaternary bedrock. Then, also T3 may be interpreted as a strath terrace. River

  13. Los Angeles Seismotectonics: Evidence from Shotgun Seismicity Patterns and the Gridlock of Late Quaternary Faults and Folds

    NASA Astrophysics Data System (ADS)

    Hauksson, E.; Michael, A.

    2001-12-01

    The high tectonic strain rates in the Los Angeles region are caused by the San Andreas fault to the north that strikes more westerly than the relative plate motion velocity, and secondary effects such as basin formation, and possibly the upper mantle drip beneath the Transverse Ranges. The last 25 years of background seismicity in this region is spatially scattered and cannot easily be associated with the complex network of existing late Quaternary faults or folds. To explain the regionally distributed seismicity and faulting patterns we propose the following model of seismotectonic deformation for the Los Angeles region. First, the regional tectonic strain loading is spread almost uniformly from east to west across the region, causing only minor variations in the loading rate of late Quaternary faults. Second, these late Quaternary faults that have cumulative offsets of at least few kilometers are aseismic during the interseismic period and only accommodate large earthquakes. Third, most of the late Quaternary faults have similar slip rate and are of similar importance for accommodating crustal deformation, and thus have similar repeat times for large earthquakes. Fourth, the background seismicity mostly accommodates secondary deformation associated with geometrical complexities of existing geological structures. In a few cases the background seismicity however, forms halos around the faults suggesting narrow central locked fault zones and an adjacent seismic zone of ongoing buildup of tectonic strain. To refine these patterns of seismicity we have relocated the last 25 years of Los Angeles seismicity using double-difference earthquake location methods to refine hypocenters based on three-dimensional velocity models to obtain high-resolution hypocenters. These DD hypocenters provide improved resolution of seismicity patterns and facilitate improved association between seismicity and late Quaternary faults and active geological structures. The background seismicity

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

    NASA Astrophysics Data System (ADS)

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

    2005-10-01

    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.

  15. Salt lake Laguna de Fuente de Piedra (S-Spain) as Late Quaternary palaeoenvironmental archive

    NASA Astrophysics Data System (ADS)

    Höbig, Nicole; Melles, Martin; Reicherter, Klaus

    2014-05-01

    This study deals with Late Quaternary palaeoenvironmental variability in Iberia reconstructed from terrestrial archives. In southern Iberia, endorheic basins of the Betic Cordilleras are relatively common and contain salt or fresh-water lakes due to subsurface dissolution of Triassic evaporites. Such precipitation or ground-water fed lakes (called Lagunas in Spanish) are vulnerable to changes in hydrology, climate or anthropogenic modifications. The largest Spanish salt lake, Laguna de Fuente de Piedra (Antequera region, S-Spain), has been investigated and serves as a palaeoenvironmental archive for the Late Pleistocene to Holocene time interval. Several sediment cores taken during drilling campaigns in 2012 and 2013 have revealed sedimentary sequences (up to 14 m length) along the shoreline. A multi-proxy study, including sedimentology, geochemistry and physical properties (magnetic susceptibility) has been performed on the cores. The sedimentary history is highly variable: several decimetre thick silty variegated clay deposits, laminated evaporites, and even few-centimetre thick massive gypsum crystals (i.e., selenites). XRF analysis was focussed on valuable palaeoclimatic proxies (e.g., S, Zr, Ti, and element ratios) to identify the composition and provenance of the sediments and to delineate palaeoenvironmental conditions. First age control has been realized by AMS-radiocarbon dating. The records start with approximately 2-3 m Holocene deposits and reach back to the middle of MIS 3 (GS-3). The sequences contain changes in sedimentation rates as well as colour changes, which can be summarized as brownish-beige deposits at the top and more greenish-grey deposits below as well as highly variegated lamination and selenites below ca. 6 m depth. The Younger Dryas, Bølling/Allerød, and the so-called Mystery Interval/Last Glacial Maximum have presumably been identified in the sediment cores and aligned to other climate records. In general, the cores of the Laguna de

  16. A fractal analysis of quaternary, Cenozoic-Mesozoic, and Late Pennsylvanian sea level changes

    NASA Technical Reports Server (NTRS)

    Hsui, Albert T.; Rust, Kelly A.; Klein, George D.

    1993-01-01

    Sea level changes are related to both climatic variations and tectonic movements. The fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1.26 established for annual precipitation records. A similar fractal dimension (1.22) based on delta(O-18/O-16) in deep-sea sediments has been suggested to characterize climatic change during the past 2 m.y. Our analysis indicates that sea level changes over the past 150,000 to 250,000 years also exhibit comparable fractal dimensions. Sea level changes for periods longer than about 30 m.y. are found to produce fractal dimensions closer to unity and Missourian (Late Pennsylvanian) sea level changes yield a fractal dimension of 1.41. The fact that these sea level curves all possess fractal dimensions less than 1.5 indicates that sea level changes exhibit nonperiodic, long-run persistence. The different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment recored by prevailing processes during deposition. For example, during the Quaternary, glacio-eustatic sea level changes correlate well with the present climatic signature. During the Missourian, however, mechanisms such as plate reorganization may have dominated, resulting in a significantly different fractal dimension.

  17. Sequence stratigraphy and composition of late quaternary shelf-margin deltas, Northern Gulf of Mexico

    SciTech Connect

    Morton, R.A.; Suter, J.R.

    1996-04-01

    High-resolution seismic profiles and foundation borings from the northwestern Gulf of Mexico record the physical attributes and depositional histories of several late Quaternary sequences that were deposited by wave-modified, river-dominated shelf-margin deltas during successive periods of lowered sea level. Each progressively younger deltaic sequence is thinner and exhibits a systematic decrease in the abundance and concentration of sand, which is attributed to a shift in the axes of trunk streams and greater structural influence through time. Our study shows that (1) contemporaneous structural deformation controlled the thickness of each sequence, the oblique directions of delta progradation, the axes of major fluvial channels, and the geometries of delta lobes at the shelf margin; (2) sedimentation was rapid in response to rapid eustatic fluctuations and structural influence; (3) boundaries of these high-frequency sequences are the correlative conformities of updip fluvial incision and coincide with downlap surfaces at the shelf margin; (4) the downlap surfaces are not true surfaces, but zones of parallel reflections that become progressively higher and younger in the direction of progradation; (5) the downlap zones are composed of marine muds that do not contain the high concentrations of shell debris expected in condensed sections; (6) possible paleosols capping the two oldest sequences are regressive surfaces of subaerial exposure that were preserved during transgressions; and (7) no incised valleys or submarine canyons breach the paleoshelf margin, even though incised drainages were present updip and sea level curves indicate several periods of rapid fall.

  18. Enhanced insights into late Quaternary African hydroclimate dynamics using a water-isotope enabled climate model

    NASA Astrophysics Data System (ADS)

    Singarayer, Joy; Holloway, Max

    2016-04-01

    The climate of intertropical Africa is strongly governed by the dynamics of the tropical rainbelt, which is often associated with the Intertropical Convergence Zone (ITCZ). On millennial time-scales the primary drivers of variation in the rainbelt include orbital configuration changes to insolation seasonality and high-latitude forcing (e.g. Heinrich events). The spatial pattern of precipitation variability in tropical and subtropical Africa over the late Quaternary is complex and has long been debated. Stable water isotopes from inland lakes and off-shore ocean core records have provided longitudinal records, variously interpreted as changes to precipitation intensity or changes to moisture source location due to atmospheric circulation changes (or a combination of several factors). In this preliminary study we have used a global climate model, HadCM3, in which water isotopes are interactively coupled to produce snapshots at 1000-year intervals covering the last deglaciation (21kyr to pre-industrial). In conjunction with a comparison to available palaeodata, this enables us to better elucidate the connections between precipitation and other climate factors with changes to the water isotope signature, as well as how this varies regionally and through time.

  19. Identification of a late Quaternary alluvial-aeolian sedimentary sequence in the Sichuan Basin, China

    NASA Astrophysics Data System (ADS)

    Feng, Jin-Liang; Ju, Jian-Ting; Chen, Feng; Hu, Zhao-Guo; Zhao, Xiang; Gao, Shao-Peng

    2016-03-01

    The late Quaternary sedimentary sequence in the northwestern part of the Sichuan Basin consists of five lithological units and with increasing depth include the: Chengdu Clay; Brown Clay; Red Clay; Sandy Silt; and basal Muddy Gravel. The genesis, provenance and age of the sediments, as well as the possible presence of hiatuses within this sequence are debated. Measurements of grain-size, magnetic susceptibility, quartz content, quartz δ18O values, element composition, and Sr-Nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence. The new data confirm that the sediments in study site are alluvial-aeolian in origin, with basal alluvial deposits overlain by aeolian deposits. Like the uppermost Chengdu Clay, the underlying Brown Clay and Red Clay are aeolian in origin. In contrast, the Silty Sand, like the basal Muddy Gravel, is an alluvial deposit and not an aeolian deposit as previously thought. Moreover, the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses. Sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the Sichuan Basin and those on the eastern Tibetan Plateau are different. Furthermore, the loess deposits on the eastern Tibetan Plateau are derived from heterogeneous local sources.

  20. Imprint of Late Quaternary Climate Change on the Mid-Atlantic Landscape

    NASA Astrophysics Data System (ADS)

    Pavich, M.; Markewich, H.; Newell, W. L.; Litwin, R.; Smoot, J.; Brook, G.

    2009-12-01

    Recent geomorphic, lithostratigraphic, palynologic and chronostratigraphic investigations of the mid-Atlantic region show that much of the modern landscape flanking the Chesapeake Bay and the Potomac River is developed on late Quaternary sediments. These deposits, dated by OSL and 14C, include transgressive marine and estuarine sediments deposited between 120ka and 32ka, and parabolic dunes formed between 32ka and 15ka. The stacked estuarine units were deposited in a subsiding basin as eustatic sea level fell from +7m to -60m. The estuarine units contain pollen that provides evidence for millennial scale climate fluctuations. The dunes formed during the period of rapid expansion of the Laurentide Ice Sheet as sea level fell to -120m. Permafrost features such as frost wedges and periglacial “pots” formed during cold intervals associated with marine oxygen isotope stages 4 and 2. This periglacial climate, along with glacioisostatic adjustments to growth and decay of the Laurentide Ice Sheet, affected landscape processes at least as far south as the Potomac River valley. While many of these features were recognized in earlier mapping and stratigraphic investigations, OSL dating has greatly extended the range of available dates and significantly improved our understanding of the impacts of highly variable periglacial climate on this region.

  1. Two late quaternary pollen records from the upper Kolyma region, Soviet Northeast: A preliminary report

    SciTech Connect

    Anderson, P.M.; Brubaker, L.; Andreev, A.A.; Chernenky, B.I.; Federova, I.N.

    1992-03-01

    Pollen records from Sosednee and Elikchan Lakes provide the first continuous late Quaternary vegetation history for the upper Kolyma drainage of the Soviet Northeast. Full-glacial spectra at these sites are similar to those from Eastern Beringia, with high percentages of grass, sedge, and wormwood pollen indicative of herb tundra. In the Elikchan area at approximately 12,500 B.P., herb tundra was replaced by a stone pine-larch forest, perhaps similar to forests in the modern region. In contrast, the herb tundra near Sosednee Lake was succeeded by a birch-alder shrub tundra followed by a larch woodland. Stone pine increased in the region after larch and prior to 8600 B.P. A Holocene decline in stone pine, which is evident at Elikchan Lake, is less marked or absent at Sosednee Lake. The differences in these pollen records is somewhat surprising given the proximity of the two sites. Such differences indicate that numerous well-dated sites will be needed to describe the vegetation and climate histories of Western Beringia.

  2. Eolian additions to late Quaternary alpine soils, Indian Peaks Wilderness Area, Colorado Front Range

    USGS Publications Warehouse

    Muhs, D.R.; Benedict, J.B.

    2006-01-01

    Surface horizons of many alpine soils on Quaternary deposits in high-mountain settings are enriched in silt. The origin of these particles has been debated, particularly in the Rocky Mountain region of North America. The most common explanations are frost shattering of coarser particles and eolian additions from distant sources. We studied soil A horizons on alpine moraines of late-glacial (Satanta Peak) age in the Colorado Front Range. Surface horizons of soils on these moraines are enriched in silt and have a particle size distribution that resembles loess and dust deposits found elsewhere. The compositions of sand and silt fractions of the soils were compared to possible local source rocks, using immobile trace elements Ti, Nb, Zr, Ce, and Y. The sand fractions of soils have a wide range of trace element ratios, similar to the range of values in the local biotite gneiss bedrock. In contrast, silt fractions have narrower ranges of trace element ratios that do not overlap the range of these ratios in biotite gneiss. The particle size and geochemical results support an interpretation that silts in these soils are derived from airborne dust. Eolian silts were most likely derived from distant sources, such as the semiarid North Park and Middle Park basins to the west. We hypothesize that much of the eolian influx to soils of the Front Range occurred during an early to mid-Holocene warm period, when sediment availability in semiarid source basins was at a maximum.

  3. Characteristics and formation of rain forest soils derived from late Quaternary basaltic rocks in Leyte, Philippines

    NASA Astrophysics Data System (ADS)

    Navarrete, Ian A.; Tsutsuki, Kiyoshi; Asio, Victor B.; Kondo, Renzo

    2009-09-01

    This study was conducted to evaluate the physical, chemical, and mineralogical characteristics of rain forest soils derived from late Quaternary basaltic rocks in Leyte, Philippines. Four sites along a catena were selected at an elevation of 75-112 m above sea level with an average annual rainfall of 3,000 mm and an average temperature of 28°C. Results indicate that the soils are deep, clayey, and reddish in color, which is indicative of the advanced stage of soil development. They also posses excellent physical condition (friable and highly porous) although they are plastic and sticky when wet as is usual for clayey soils. In terms of chemical characteristics, the soils are acidic with low CEC values and generally low in organic matter and nutrient contents. The clay mineralogy of the soils is dominated by halloysite and kaolinite with minor amounts of goethite and hematite, and they also have generally high dithionite-extractable Fe contents confirming the advanced stage of their development. The soils in the more stable slope positions (PL-1, PL-2, and PL-4) have generally similar characteristics and appeared more developed than the one in the less stable position (PL-3). The most important pedogenic processes that formed the soils appear to be weathering, loss of bases and acidification, desilification, ferrugination, clay formation and translocation, and structure formation. The nature of the parent rock and climatic conditions prevailing in the area as well as slope position appear to have dominant effects on the development of the soils.

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

    PubMed

    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

    2016-01-01

    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. PMID:26821754

  5. An improved age framework for late Quaternary silicic eruptions in northern Central America

    NASA Astrophysics Data System (ADS)

    Rose, William I.; Conway, F. Michael; Pullinger, Carlos R.; Deino, Alan; McIntosh, William C.

    Five new stepwise-heating 40Ar/39Ar ages and one new high-sensitivity 14C date of ash-fall and ash-flow deposits from late Quaternary silicic volcanoes in northern Central America document the eruption rates and frequencies of five major rhyodacite and rhyolite calderas (Atitlán, Amatitlán, Ayarza, Coatepeque, and Ilopango) located north of the basalt, andesite, and dacite stratovolcanoes of the Central American volcanic front. These deposits form extensive time-stratigraphic horizons that intercalate regionally, and knowledge of dates and stratigraphy provides a valuable framework for age determinations of more localized volcanic and nonvolcanic events. The new data, especially when integrated with previous stratigraphic and dating work, show that all five calderas erupted several times in the past 200ka and, despite a lack of historic activity, should be considered as active centers that could produce highly explosive eruptions again. Because of their locations near the highly vulnerable economic hearts of Guatemala and El Salvador, the risks of eruptions from these calderas should be carefully considered along with risks of major earthquakes and volcanic front volcanoes, which are much more frequent but inflict less severe and extensive damage. This investigation also includes some examples of dating efforts that failed to produce reasonable results.

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

    NASA Astrophysics Data System (ADS)

    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.

    2014-12-01

    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.

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

    USGS Publications Warehouse

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

    2009-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Behling, Hermann; Negrelle, Raquel R. B.

    2001-11-01

    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.

  9. Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

    SciTech Connect

    Paces, J.B.; Taylor, E.M.; Bush, C.

    1993-12-31

    Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 {+-} 1, 30 {+-} 3, 45 {+-} 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in a good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

  10. Vertical tectonics in northern Escanaba Trough as recorded by thick late Quaternary turbidites

    USGS Publications Warehouse

    Normark, W.R.; Serra, F.

    2001-01-01

    Escanaba Trough, the southernmost segment of the Gorda Ridge, is filled by as much as 500 m of late Quaternary turbidite and hemipelagic sediment. Coring at Deep Sea Drilling Project Site 35 and Ocean Drilling Program (ODP) Sites 1037 and 1038 together with 4.5-kHz deep-tow and 3.5-kHz surface-ship seismic reflection profiles enable a distinct pattern of reflections to be mapped throughout Escanaba Trough in the upper part of this sediment fill. The uppermost 80 m of turbidite sediment, which includes at least 11 turbidity current events, were deposited in 3200 m. The turbidity currents were trapped upon entering Escanaba Trough, resulting in all of the sediment in suspension in the flows being deposited. The thickness of the turbidite layers reflects both the flow thickness and the vertical grain concentration within the flow that deposited the layer. Variations in the turbidite thickness with respect to water depth can be used to estimate the degree of relative vertical movement within the floor of Escanaba Trough. In the area of hydrothermal activity near ODP Site 1038, uplift of as much as 140 m has occurred over the past 8 kyr. Copyright 2001 by the American Geophysical Union.

  11. Species-specific responses of Late Quaternary megafauna to climate and humans.

    PubMed

    Lorenzen, Eline D; Nogués-Bravo, David; Orlando, Ludovic; Weinstock, Jaco; Binladen, Jonas; Marske, Katharine A; Ugan, Andrew; Borregaard, Michael K; Gilbert, M Thomas P; Nielsen, Rasmus; Ho, Simon Y W; Goebel, Ted; Graf, Kelly E; Byers, David; Stenderup, Jesper T; Rasmussen, Morten; Campos, Paula F; Leonard, Jennifer A; Koepfli, Klaus-Peter; Froese, Duane; Zazula, Grant; Stafford, Thomas W; Aaris-Sørensen, Kim; Batra, Persaram; Haywood, Alan M; Singarayer, Joy S; Valdes, Paul J; Boeskorov, Gennady; Burns, James A; Davydov, Sergey P; Haile, James; Jenkins, Dennis L; Kosintsev, Pavel; Kuznetsova, Tatyana; Lai, Xulong; Martin, Larry D; McDonald, H Gregory; Mol, Dick; Meldgaard, Morten; Munch, Kasper; Stephan, Elisabeth; Sablin, Mikhail; Sommer, Robert S; Sipko, Taras; Scott, Eric; Suchard, Marc A; Tikhonov, Alexei; Willerslev, Rane; Wayne, Robert K; Cooper, Alan; Hofreiter, Michael; Sher, Andrei; Shapiro, Beth; Rahbek, Carsten; Willerslev, Eske

    2011-11-17

    Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped 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 encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic 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. PMID:22048313

  12. A high-resolution geochemical record of Late Quaternary paleohydrological conditions from Chihuahuan Desert, Mexico

    NASA Astrophysics Data System (ADS)

    Quiroz-Jiménez, J.; Roy, P.

    2013-05-01

    Paleolake Babicora is located at 29°N in the northern Mexico and sediments deposited in the basin provide useful information about the late Quaternary paleohydrological conditions of Chihuahuan Desert. The proxy-records of productivity, pluvial discharge into the basin, lake water salinity and aeolian activity in surroundings of the basin over the last 80 cal ka BP were reconstructed by analyzing the concentrations of total organic carbon, carbonates, C/N, Ti, Sr and Zr/Al in a 976 cm long sediment core. During 80-58 cal ka BP, the pluvial discharge was higher and the water column was characterized by lower salinity (wet conditions). Terrestrial vegetation had higher influence on the organic carbon deposited between 71 and 53 cal ka BP. We record paleohydrological instability with millennial-scale fluctuations in the last 40 cal ka BP. Arid conditions possibly reached its maximum at ca. 40 cal ka BP, characterized with a hiatus in sedimentation related to aeolian activity. Comparison between the paleohydrological record from Babicora and variability of winter precipitation from southwest USA suggest that the runoff into Babicora was controlled by summer season precipitation. The periods of more pluvial discharge were contemporary to the north Atlantic interstadials and vice versa.

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

    NASA Astrophysics Data System (ADS)

    Kothyari, Girish Ch.; Luirei, Khayingshing

    2016-09-01

    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).

  14. A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change

    USGS Publications Warehouse

    Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

    1994-01-01

    Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals. Glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals. The variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods. We also infer an increased contribution of eolian sediment during the colder, windier, and more arid glacial conditions when extensive loess deposits were formed throughout Europe and Asia. Eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals. Variations in magnetic concentration and mineralogy of Lake Baikal sediment correlate to the SPECMAP marine oxygen-isotope record. The high degree of correlation between Baikal magnetic concentration/mineralogy and the SPECMAP oxygen-isotope record indicates that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 ka. This correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method. Future work must include providing better age control and additional climate proxy data, thereby strengthening the correlation of continental and marine climate records. ?? 1994.

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

    USGS Publications Warehouse

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

    1997-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  17. Late Quaternary paleosols, stratigraphy and landscape evolution in the Northern Pampa, Argentina

    NASA Astrophysics Data System (ADS)

    Kemp, Rob A.; Zárate, Marcelo; Toms, Phillip; King, Matthew; Sanabria, Jorge; Arguello, Graciella

    2006-07-01

    The field properties, micromorphology, grain-size, geochemistry, and optically stimulated luminescence (OSL) ages of two late Quaternary sections have been used to reconstruct the sequence of pedosedimentary processes and to provide insights into landscape evolution in part of the Northern Pampa of Argentina. Paleosols developed in paludal sediments adjacent to the Paraná river at Baradero and in loess at Lozada can both be correlated and linked to other sites, thus enabling for the first time the tentative recognition and tracing of a diachronous soil stratigraphic unit that probably spans the equivalent of at least part of marine oxygen isotope stage (OIS) 5. The paleosol at Lozada was truncated and buried beneath fluvial sediments during the time span of OIS 4 and 3. Eolian gradually replaced paludal inputs at Baradero over this period, and there were also two clearly defined breaks in sedimentation and development of paleosols. The period corresponding to OIS 2 was marked by significant loess accumulation at both sites with accretion continuing into the mid-Holocene only at Lozada. The more developed nature of the surface soil at Baradero probably reflects a combination of a moister climate and a longer soil-forming interval.

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

    PubMed Central

    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.

    2016-01-01

    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. PMID:26821754

  19. Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance

    USGS Publications Warehouse

    Muhs, D.R.; Aleinikoff, J.N.; Stafford, Thomas W., Jr.; Kihl, R.; Been, J.; Mahan, S.A.; Cowherd, S.

    1999-01-01

    Loess in eastern Colorado covers an estimated 14000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20-14 ka) and correlates reasonably well with the culmination and retreat of Pinedale glaciers in the Colorado Front Range during the last glacial maximum. The second period of loess deposition occurred between ca. 11 000 and 9000 14C yr B.P. This interval may be Holocene or may correlate with a hypothesized Younger Dryas glacial advance in the Colorado Front Range. Sedimentologic, mineralogic, and geochemical data indicate that as many as three sources could have supplied loess in eastern Colorado. These sources include glaciogenic silt (derived from the Colorado Front Range) and two bedrock sources, volcaniclastic silt from the White River Group, and clays from the Pierre Shale. The sediment sources imply a generally westerly paleowind during the last glacial maximum. New carbon isotope data, combined with published faunal data, indicate that the loess was probably deposited on a cool steppe, implying a last glacial maximum July temperature depression, relative to the present, of at least 5-6??C. Overall, loess deposition in eastern Colorado occurred mostly toward the end of the last glacial maximum, under cooler and drier conditions, with generally westerly winds from more than one source.

  20. Late Quaternary vegetation history of North Stradbroke Island, Queensland, eastern Australia

    NASA Astrophysics Data System (ADS)

    Moss, Patrick T.; Tibby, John; Petherick, Lynda; McGowan, Hamish; Barr, Cameron

    2013-08-01

    Currently there is a paucity of records of late Quaternary palaeoenvironmental variability available from the subtropics of Australia. The three continuous palaeoecological records presented here, from North Stradbroke Island, subtropical Queensland, assist in bridging this large spatial gap in the current state of knowledge. The dominance of arboreal taxa in the pollen records throughout the past >40,000 years is in contrast with the majority of records from temperate Australia, and indicates a positive moisture balance for North Stradbroke Island. The charcoal records show considerable inter-site variability indicating the importance of local-scale events on individual records, and highlighting the caution that needs to be applied when interpreting a single site as a regional record. The variability in the burning regimes is interpreted as being influenced by both climatic and human factors. Despite this inter-site variability, broad environmental trends are identifiable, with changes in the three records comparable with the OZ-INTIMATE climate synthesis for the last 35,000 years.

  1. Late tertiary and quaternary fluvial deposits in the Mesilla and Hueco bolsons, El Paso area, Texas

    NASA Astrophysics Data System (ADS)

    Stuart, Charles J.; Willingham, Daniel L.

    1984-03-01

    The late Tertiary to Quaternary Fort Hancock and Camp Rice Formations fill several extensional basins of the southern Rio Grande Rift. Interior drainage and central playa lakes characterize most of these rift basins. However, sedimentation in two basins located in the central part of the southern rift, the Mesilla and Hueco bolsons, was also greatly influenced by a northern segment of the ancestral Rio Grande river system. During the late Pliocene, a large-scale stream system entered the north end of the Mesilla bolson and deposited a south-sloping fluvial plain that overwhelmed playa lake and bolson-margin areas. The fluvial plain subsequently advanced across the eastern or southeastern margins of the Mesilla bolson then inundated a playa lake in the adjacent Hueco bolson. The Fort Hancock Formation was deposited during fluvial inundation of the bolsons. Four lithofacies of the Fort Hancock Formation are recognized: claystone, mudstone and sandstone, channelized sandstone, and conglomerate. The conglomerate and claystone facies were deposited in bolson-margin and playa depositional environments, respectively. The channelized sandstone facies formed the proximal fluvial plain of the ancestral Rio Grande system. The mudstone and sandstone facies formed in both playa-margin and distal fluvial-plain environments. By the middle Pleistocene, a major drainage basin south of the Hueco bolson, which formed the southern segment of the ancestral Rio Grande system, extended northward into the Hueco and Mesilla bolsons. At this time, the Rio Grande system was entirely integrated from southern Colorado to the Gulf of Mexico. Pebbly, coarse sand transported through this channel system formed the middle Pleistocene Camp Rice Formation.

  2. Late Quaternary Alluvial Fans and Beach Ridge Systems in Jakes Valley, Central Great Basin, USA

    NASA Astrophysics Data System (ADS)

    Garcia, A. F.; Stokes, M.; Benitez, L.

    2002-12-01

    Alluvial fan and lake beach ridge landforms provide archives of the geomorphic response to Late Quaternary climate change within the Great Basin region. This study presents the first detailed results of landform mapping and soil characterization from Jakes Valley, a high altitude (1920m) and internally drained basin, located within a previously unstudied part of White Pine County, East-Central Nevada. Mountain front alluvial fans sourced from the White Pine and Egan Ranges (west-east basin margins) are characterized by four morphostratigraphic units: Qf0 (oldest) through to Qf3 (youngest). Analysis of the soil properties of these stratigraphic units reveals two landform-soil assemblages: 1) Qf0-1, characterized by well-developed calcic soils (stages III+ to IV) and 2) Qf2-3, characterized by less well-developed calcic soils (stages I to II). Beach ridge systems formed during pluvial lake highstands are extensively developed into the mid and distal parts of alluvial fans. Integrated field and aerial photograph mapping has revealed a sequence of between 4-6 ridges with linear and / or highly curved / arcuate morphologies. Beach ridge soil properties are characterized by less well-developed calcic soils (stages I+ to II) that are similar to soils formed in Qf2 alluvial fan units. The interaction between the alluvial fan and beach ridge landforms can be utilized to explore the geomorphic response in relation to climatic amelioration during the Late Pleistocene-Holocene transition. Of particular interest is the common occurrence of the curved / arcuate beach ridges which may correspond to a period of fan progradation coincident with base-level lowering.

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

    NASA Astrophysics Data System (ADS)

    Hirsch, F.; Raab, T. A.

    2011-12-01

    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.

  4. Patterns and processes of Late Quaternary environmental change in a montane region of southwestern Europe

    NASA Astrophysics Data System (ADS)

    Carrión, José S.

    2002-10-01

    This paper examines the Late Quaternary (c. 20,300-<505 cal yr BP) environmental history of Siles, a lake situated at 1320 m in the Segura mountains of southern Spain, with the goal of establishing the mechanisms exerting control on vegetation change. Palaeoecological indicators include pollen, microcharcoal, spores of terrestrial plants, fungi, and non-siliceous algae, and other microfossils. The Siles sequence is shown to be sensitive to climatic change, although the control exerted by climate on vegetation is ultimately shaped by disturbances and species interactions, determining the occurrence of century-scale lags and threshold responses. Biotically induced changes of vegetation are also shown at the intrazonal level of variation. The new sequence is placed in the context of two previous records to postulate a picture of Holocene environmental change for the Segura region. The existence of mid-elevation glacial refugia for a number of temperate and Mediterranean trees is shown. A mid-Holocene phase (c. 7500-5200 cal yr BP) emerges regionally as the time of maximum forest development and highest lake levels. The early Holocene occurs as a generally dry, pyrophytic period of pine forests, with grassland scrub in high altitudes, and the late Holocene as a period of protracted vegetation sensitivity, with return to development of pine forests, spread of xerophytic communities, and increased fire activity, under the context of dry spells, localized anthropogenic disturbance, and shallowing and desiccation of lakes. Several events described here correlate with established times of abrupt transitions in the climates of northern Europe, the Mediterranean basin, north Africa, and the Sahel.

  5. Morphology and Late Quaternary sedimentation in the Gulf of Oman Basin

    NASA Astrophysics Data System (ADS)

    Uchupi, Elazar; Swift, S. A.; Ross, D. A.

    The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000-20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin.

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

    NASA Astrophysics Data System (ADS)

    Pope, Richard; Hughes, Philip

    2014-05-01

    local last glacial maximum and are coeval with the later part of the Tymphian stage in the Pindus range. Refs: Hughes, P.D., Woodward, J.C., Gibbard, P.L., Macklin, M.G., Gilmour, M.A. & Smith G.R. (2006) The glacial history of the Pindus Mountains, Greece. Journal of Geology 114, 413-434. Hughes, P.D., Woodward, J.C., van Calsteren, P.C. and Thomas, L.E. (2011) The Glacial History of The Dinaric Alps, Montenegro. Quaternary Science Reviews 30, 3393-3412. Woodward, J.C., Hamlin, R.H.B., Macklin, M.G., Hughes, P.D. & Lewin, J. (2008) Pleistocene catchment dynamics in the Mediterranean: glaciation, fluvial geomorphology and the slackwater sediment record. Geomorphology 101, 44-67.

  7. Profiling of late Trias-early Quaternary surface in the Eskisehir basin using microtremors

    NASA Astrophysics Data System (ADS)

    Tün, Muammer; Pekkan, Emrah; Özel, Oğuz

    2015-04-01

    Earthquakes in our country and in the world cause damage and collapse of engineering structures due to several reasons. Settlement areas are under the effect of strong and long-duration seismic vibrations due to resonance and focusing effects. In this study, we propose the first approximation for thickness of Quaternary sediment and late Trias topography for the Eskisehir basin in microtremor methods. The 3-D basin structures and site resonance frequencies in the Eskişehir Basin were investigated by geophysical measurements based on the 318 single station and 9 array sites microtremor methods situated on soft soil sediments and rock units within the study area. The microtremor data collection, processing, and interpretation of the H/V curves were carried out following the recommendations and guidelines of the SESAME consortium (Site EffectS assesment using AMbient Excitation) The signals recorded were analysed for horizontal to the vertical (H/V) spectral ratio using GEOPSY software. The H/V ratios were calculated for the frequency range 0.2 to 20 Hz, using 60 s as a time window length and removing time windows contaminated by transients. Almost of the HVSR curves on the alluvium deposits have a low-frequency peak at 0.6-0.8 Hz and a second peak at 4-10 Hz. We used the Spatial Autocorrelation (SPAC) method in Eskisehir Basin using broadband seismometers distributed in triangular arrays. We derive a power-law relationship that correlates the fundamental site resonance frequencies with the sedimentary cover thickness obtained from the seismic reflection data, borehole data and shear wave velocity data in the study area. We use this relationship to estimate bedrock depth and thickness of alluvial deposits in the Eskisehir basin. Our estimation of maximum basin depths is 650 m for the Muttalip. The thickness of quaternary sediment is 25 m for Eskisehir alluvium. The estimated thickness is used to plot digital elevation model and cross profiles correlating with

  8. Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective

    NASA Astrophysics Data System (ADS)

    Shibahara, Akihiko; Ohkushi, Ken'ichi; Kennett, James P.; Ikehara, Ken

    2007-09-01

    A strong oxygen minimum zone (OMZ) currently exists at upper intermediate water depths on the northern Japanese margin, NW Pacific. The OMZ results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters. We investigated late Quaternary history (last 34 kyr) of ocean floor oxygenation and the OMZ using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off Shimokita Peninsula and Tokachi, northern Japan, at water depths between 975 and 1363 m. These cores are well located within the present-day OMZ, a region of high surface water productivity, and in close proximity to the source region of North Pacific Intermediate Water. Late Quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments. Foraminiferal assemblages are interpreted to represent three main groups representing oxic, suboxic, and dysoxic conditions. Assemblage changes in all three cores and hence in bottom water oxygenation coincided with late Quaternary climatic episodes, similar to that known for the southern California margin. These episodes, in turn, are correlated with orbital and millennial climate episodes in the Greenland ice core including the last glacial episode, Bølling-Ållerød (B/A), Younger Dryas, Preboreal (earliest Holocene), early Holocene, and late Holocene. The lowest oxygen conditions, marked by dysoxic taxa and laminated sediments in one core, occurred during the B/A and the Preboreal intervals. Suboxic taxa dominated mainly during the last glacial, the Younger Dryas, and most of the Holocene. Dysoxic conditions during the B/A and Preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern Pacific. Remarkable similarities are evident in the late Quaternary sequence of benthic

  9. Geochemical and Sedimentological Records of Late Quaternary Climate Change, Lake Tanganyika, Tropical East Africa

    NASA Astrophysics Data System (ADS)

    Felton, A. A.; Russell, J. M.; Cohen, A. S.; Baker, M. E.; McGlue, M. M.; Lezzar, K. E.

    2005-12-01

    We have analyzed piston core records from Lake Tanganyika (western Tanzania, East African Rift Valley) to investigate possible signals of tropical paleoclimate change during the Late Quaternary. Long paleoclimate records from East Africa are of importance for understanding climatic processes such as the role of solar variability in regulating tropical climates at Milankovitch time scales, and the relationship between abrupt climate changes, migration of Intertropical Convergence Zone, and regional climate variability (Nicholson, 2000). However, records of pre-Holocene climate variability from tropical African lakes (>25ka) are still quite rare. Long records from Lake Tanganyika are of particular interest given the lake's antiquity and its demonstrated potential for producing high resolution (frequently annually laminated) sedimentary records (Cohen et al., 1993). We analyzed physical properties, grain size, total organic carbon, major, minor and trace element variability, and biogenic silica data for a 7.75 m core from the Kalya slope and horst region of central Lake Tanganyika at 640m water depth. Nine 14C dates provide an age model for the core, which spans ~62 cal kyr. Elemental concentrations preserved in Lake Tanganyika sediments record variability in deposition and runoff into the lake basin. Under conditions of rapid erosion, exposure and rapid weathering of bedrock has been shown to generate high concentrations of original silicate minerals enriched in soluble cations such as sodium and potassium, elements that are also biologically conservative. Prior to 40ka cal yr. core sediments are characterized by high magnetic susceptibility, intermediate levels of organic carbon, low to intermediate levels of biogenic silica, and fine grain size, indicative of relatively high precipitation. There is a profound decrease in magnetic susceptibility, a decrease in organic carbon and an increase in grain size at 40ka cal yr, which persists until ~16ka cal yr. Seismic

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  11. Evolution and floodplain history of the Middle Sacramento River from the late Quaternary to modern times

    NASA Astrophysics Data System (ADS)

    Will, M.; Aalto, R. E.; Fuchs, M.

    2011-12-01

    California has an extensive and storied research history in fluvial geomorphology dating back to G.K.Gilbert's studies of sediment transport in the Feather and Sacramento Rivers a century ago. Given the importance of Californian river systems in the field of geomorphology it is therefore surprising that there are still major gaps in understanding the late Quaternary evolution of the Sacramento River and the continuing responses of the modern system. Studies of river response to environmental change have been popular in Europe, but the Western US lacks so many similar investigations of the late Quaternary evolution of major rivers. We help to address this shortcoming by presenting detailed geochronology and other results from a research campaign along the largest natural reach of the largest river in California. The unique ownership history of the Rancho Llano Seco has preserved a near-pristine floodplain structure with an extensive network of natural floodplain channels. This therefore provides an excellent research environment to investigate natural occurring infilling processes and to study the fluvial history of the Sacramento River and modern floodplain development. Our research documents both the long-term evolution of the Sacramento River system and provides extensive, quantitative insight into modern day sedimentation rates in regards to topographic location. At Llano Seco there are 3 types of channels interpreted as Holocene meander belt, and anastomosing or braiding floodplain channel systems, and other floodplain units - these have been previously mapped from air photos and geologic surveys. However, the temporal control on these geologic units has been poor, with no absolute dating. To provide dates we sampled and analyzed 22 deep pits (3-5m) and more than 70 shallow cores (~1m), establishing a thorough chronology with OSL and 14-C (for long-term system dynamics) and high resolution 210-Pb and 137-Cs dating (to document modern evolution of an extensive

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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

  13. Late Quaternary glacial relief evolution revealed by luminescence thermochronometry (Granite Range, Alaska)

    NASA Astrophysics Data System (ADS)

    Valla, P.; Guralnik, B.; Lowick, S.; Champagnac, J.; Herman, F.; Jain, M.; Murray, A.

    2012-12-01

    Long-term exhumation and topographic evolution of mountain belts arise from complex coupling between tectonics, climate and surface processes. Glacial and periglacial processes are especially potent agents to reshape the alpine landscapes by valley carving and/or limiting topography. The recent development of luminescence thermochronometry (e.g., Herman et al., 2010) and its very low closure temperature (0-60°C) opens a new spatial and temporal "window" for the study of latest stages of rock exhumation and thus to address potential topographic relief changes during the late Quaternary. We apply this new method in the Wrangell-St Elias National Park (Alaska), an alpine landscape that exhibits typical glacial features (U-shaped valleys, cirques, moraines). This setting provides an exceptional opportunity to infer potential differences in relief evolution under a gradient of glacial forcing. The Granite Range presents a consistent and progressive eastward increase in the mean elevation, glacier activity, and topographic relief, while low-temperature thermochonometry data display rather homogeneous, yet largely scattered (apatite (U-Th)/He ages of ~15±7 Ma) throughout the massif (e.g., Spotila and Berger, 2010 and references therein). We sampled four elevation profiles over an 80-km East-West transect across the Granite Range (bounded by Tana River to the West and Chitina River to the North). Feldspar separates from 15 bedrock surface samples were dated using an IR-50 SAR protocol (e.g., Murray et al., 2000), and exhibit good internal reproducibility. Apparent ages vary from ~250 ka in the western part of the range, towards younger ages of ~30 ka in the east, thus supporting the notion of high rates of erosion correlated with intense glacial/periglacial activity. We then use a kinetic model to convert apparent ages in mean cooling histories, and couple it with Pecube model (Braun et al., 2012) to extract tectono-geomorphic scenarios. Our results reveal spatially

  14. 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

    NASA Astrophysics Data System (ADS)

    Diedrich, Cajus G.

    2010-05-01

    , Harz Mountain Karst) such as humans (archaeology cf. Günther 1988) but there are also lacking radiocarbon dating series or new excavations. Humans must have been in antagonism to the large predators about their prey and also their Late Palaeolithic sanctuaries - the large caves especially in southern Europe, in which they left thousands of animal figurations mainly during the Gravettian to Late Magdalenian periods (e.g. Breuil 1952, Begouen and Clottes 1987, Chauvet et al. 1995). Therefore the extinction reason of the largest predators of the Late Quaternary seems to be a complex combination of climate change with resulting maximum glacier extension which finally caused a southern directed megafaunal migration and reduction of the available caves and habitat areas in general. Finally in those southern European regions a higher competition about larger caves as cave bear hibernation places, hyena den sites and human settlement/sanctuary sites must have happened. Therefore an active hunt onto lions and hyenas can not be excluded nor be proven well yet, even if there are finds of necklesses in Europe from Late Palaeolithic ages made of mainly carnivore teeth including rare lion and hyena teeth, which might have been only collected. The resettlement of the northern European region by humans and a reduced "reindeer fauna" and its main and largest predators such as wolves and wolverines after the maximum glacier extension in the middle Late Weichselian started not before the Late Magdalenian (Magdalénian V: e.g. Perick Caves, Martins Cave - Sauerland Karst; Rübeland Caves - Harz Mountain Karst, Teufelsbrücke stone arch - Thuringian Karst). Humans occupied at that post-maximum glaciation time many caves in the Sauerland Karst region and even at open air sites in the Münsterland Bay or central Germany (cf. Bosinski 1987, Günther 1988). Within this Late Magdalénian V-VI times in the record of ten thousands of bones from more then 100 sites no hyena or lion remains are

  15. Late Quaternary paleodune deposits in Abu Dhabi Emirate, UAF: Paleoclimatic implications

    SciTech Connect

    Brouwers, E.M.; Bown, T.M. ); Hadley, D.G. )

    1993-04-01

    Remnants of late Quaternary paleodunes are exposed near the coast of the Arabian Gulf and in large inland playas and interdunal areas in central and western Abu Dhabi Emirate over a distance of >45 km normal to the coast. Paleodunes occur south of Madinat Zayed (lat. 23[degree]35 N), which marks the northern limit of a modern dune field that grades into the mega-dune sand sea of the ar Rub al Khali, Saudi Arabia. Coastal paleodunes are composed of weakly cemented millolid foraminifers, ooids, and rounded biogenic grains, whereas inland and southward the paleodunes show a progressive increase in the proportion of eolian quartz sand. The paleodunes exhibit large-scale trough foresets in remnant exposures 0.5 to 10 m thick, indicating paleowind directions from 65[degree] to 184[degree] (dominantly southeast transport). Scattered paleoplaya remnants provide paleodune scale. Paleoplaya deposits form buttes 30--50 m high. If coeval with the Paleodunes, large-scale paleodune fields are implied (100+ m high), comparable to star dunes and sand mountains at the northwestern edge of the ar Rub al Khali. Based on U-Th isotopic analyses, the carbonate paleodune sands are >160ka and probably >250ka. The carbonate source was a shallow, nearly dry Arabian Gulf at a time when large areas were exposed during a low sea-level stand. Paleowind direction indicates that Pleistocene prevailing winds were northwesterly, the direction of the dominant (winter shamal) wind today. The geographic extend and implied magnitude of the paleodunes suggest large-scale eolian transport of carbonate sand during the Pleistocene disiccation, and admixed quartz sand identifies a youthful stage of contemporaneous evolution of the ar Rub al Khali. Wave-eroded paleodunes probably floor much of the present-day Gulf and extend beneath the modern dunes and sand mountains.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

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

    USGS Publications Warehouse

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

    2009-01-01

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

  18. Erosion and deposition on the eastern margin of the Bermuda Rise in the late Quaternary

    NASA Astrophysics Data System (ADS)

    McCave, I. N.; Hollister, C. D.; Laine, E. P.; Lonsdale, P. F.; Richardson, M. J.

    1982-05-01

    A near-bottom survey has been made on the Eastward Scarp (32°50'N, 57°30'W) of the Bermuda Rise, which rises 1150 m above the 5500-m deep Sohm Abyssal Plain in the western North Atlantic. The survey reveals evidence of erosion and deposition at present and in the late Quaternary by the deeper levels of the westward flowing Gulf Stream Return Flow. Four distinct regions of increasing bed gradient show increasing sediment smoothing and scour in the transition from plateau to abyssal plain. Bedforms observed are current crescents, crag and tail, triangular ripples, elongate mounds, transverse mud ripples, lineations, and furrows ranging from 10 to 1 m or less in depth, decreasing generally with bed gradient. Measured near-bottom current speeds are up to 20 cm s -1. Temperature structure on the lower, steep, slopes suggests that detachment of bottom mixed layers may occur there. Extensive net erosion appears to be confined to the lower steep slopes of the scarp. Reflection profiles (4 kHz) show that there has been erosion in areas thinly draped with recent sediments and in areas that show development of small scarps. The distribution of subsurface acoustic characteristics of the region corresponds broadly to the areas characterized by bed gradient and distinct sedimentation conditions. Subsurface hyperbolae, possibly caused by buried furrows, show furrow persistence through several tens of metres of deposition. Erosion occurs up to the top of the scarp during episodes of presumed stronger currents, which may correspond with intensified circulation during glacials.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Sedimentary architecture of the cross-shelf Bering Trough is studied using 5 high resolution seismic profiles integrated with the drilling data acquired during Integrated Ocean Drilling Program (IODP) Expedition 341. The objectives of this work are to constrain the number of advance-retreat cycles that have occurred through the Late Quaternary, examine the impact of the Bering Glacier on the continental shelf and slope, and reconstruct Bering Glacier dynamics. By tying these sequences with δ18O stratigraphy, we can test the Bering Glacier's relation to global ice sheet evolution and better understand the degree to which the glacial advance-retreat cycles were in phase with global events. Our results show that: (1) Identification of erosional surfaces and glacigenic landforms that record positions of stillstand events and diagnose the style of retreat allow us to distinguish nine phases of glacial advances and subsequent retreats. (2) Mapping shows that glacier pathways and flow directions through time are influenced by the occurrence of thick grounding-zone deposits and shifting foci of erosion. (3) Continuous buildup of glacigenic sediment fills tectonically created accommodation space and allows the glacier to advance seaward for the last three advances. Discovery of systematic, prominent deposition of glacial diamict and ice-rafted debris (IRD) during phases of glacial retreat is supported by the drilling data and suggests reconsideration of IRD impact on slope sedimentation. (4) The trough mouth fan started its development during marine isotope stage (MIS) 6, progressively advancing to the position of present shelf edge during the subsequent MIS 4 and MIS 2 and is recognized by evidence of extensive deposition of glacigenic debris flows on the slope. (5) Sedimentation rates in the depocenter are exceptionally high and are estimated to be 1-2 m/k.y. through the middle Pleistocene on the shelf and 4-5 m/k.y. average through MIS 6 on the slope.

  20. Waxing and Waning of Forests: Late Quaternary Biogeography of Lake Malawi, Southeast Africa

    NASA Astrophysics Data System (ADS)

    Ivory, S.; Lézine, A. M.; Vincens, A.; Cohen, A. S.

    2014-12-01

    African ecosystems are at great risk due to climate and land-use change. Despite the status of several of these regions as biodiversity hotspots, long-standing ideas about African ecology and biogeography have been unable to be tested until now due to lack of sufficiently long records. Here, we present the first long, continuous terrestrial record of vegetation from Lake Malawi, East Africa which goes back to the early Late Quaternary, permitting us to investigate changes in physiognomy and forest composition over many transitions. In this record, we observe eight phases of forest expansion and collapse. Although diversity is much greater during forest phases, composition varies little from phase to phase. Very high abundances of afromontane taxa suggest frequent widespread colonization of the lowlands by modern high elevation trees. Although there are clear successional stages within each forest such that turnover is great within a single phase, among forest samples between phases, there is little dissimilarity. Each forest phase is interrupted by rapid decline of arboreal taxa and expansion of semi-arid grasslands or woodlands whose composition varies greatly from phase to phase. The variable composition of the more open phases, all occurring during arid periods, is likely dynamically linked to thresholds in regional hydrology associated with lake level and moisture recycling within the watershed. This vegetation is unlike any found at Malawi today, with assemblages suggesting strong Somali-Masai affinities. Furthermore, nearly all semi-arid assemblages contain small abundances of forest taxa typically growing in areas with wetter edaphic conditions, suggesting that moist lowland gallery forests were present but restricted to waterways during exceptionally arid times. The waxing and waning of forests throughout this interval has important implications for early human biogeography across Africa as well as disturbance regimes that are crucial for the maintenance of

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

    USGS Publications Warehouse

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

    1999-01-01

    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.

  2. Late quaternary temperature record from buried soils of the North American Great Plains

    USGS Publications Warehouse

    Nordt, L.; Von Fischer, J.; Tieszen, L.

    2007-01-01

    We present the first comprehensive late Quaternary record of North American Great Plains temperature by assessing the behavior of the stable isotopic composition (??13C) of buried soils. After examining the relationship between the ??13C of topsoil organic matter and July temperature from 61 native prairies within a latitudinal range of 46??-38??N, we applied the resulting regression equation to 64 published ??13C values from buried soils of the same region to construct a temperature curve for the past 12 k.y. Estimated temperatures from 12 to 10 ka (1 k.y. = 1000 14C yr B.P.) fluctuated with a periodicity of ???1 k.y. with two cool excursions between -4.5 and -3.5 ??C and two warmer excursions between -1 and 0 ??C, relative to modern. Early Holocene temperatures from ca. 10-7.5 ka were -1.0 to -2.0 ??C before rising to +1.0 ??C in the middle Holocene between 6.0 and 4.5 ka. After a cool interlude from 4.2 to 2.6 ka, when temperatures dropped to slightly below modern, another warm interval ensued from 2.6 to 1 ka as temperatures increased to ???+0.5 ??C. A final decline in temperature to below modern occurred beginning ca. 0.5 ka. Cooler than present temperatures in the Great Plains indicate telecommunications with cool-water episodes in the Gulf of Mexico and North Atlantic potentially governed by a combination of glacial meltwater pulses and low solar irradiance. ?? 2007 Geological Society of America.

  3. Evidence for Early Pleistocene Glaciation obtained from borecores collected in East-Central Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Barendregt, R. W.; Andriashek, L. D.; Jackson, L. E.

    2014-12-01

    Borecores collected from the east-central region of Alberta, Canada have recently been sub-sampled and studied for paleomagnetic remanence characteristics. A preliminary magnetostratigraphy has been established for sediments previously assumed to represent multiple continental (Laurentide) glaciations, but for which no geochronology was available for the pre-late Wisconsin units. Comprised primarily of tills and lesser thicknesses of interbedded glacio-lacustrine and outwash sediments, the record is extensive, reaching to thicknesses of 300 metres within buried valleys. Most of the sampled units are not accessible from outcrop, and their sedimentology and stratigraphy is derived from core data only. The lowermost tills are reversely magnetized in the majority of borecores sampled to date. These tills are underlain by Empress Formation sediments and/or Colorado Group shales, and overlain by normally magnetized sediments. Both tills contain substantial weathering horizons at their surface, suggesting that interglacial or nonglacial conditions persisted for some time after each period of till deposition. Whether these tills represent a single Early Pleistocene glaciation, or perhaps two, will require additional borecore measurements. This new record of Early Pleistocene glaciation(s) in east-central Alberta places the westernmost extent of earliest Laurentide ice some 300 km farther westward from its previously established limit in the Saskatoon to Regina region of the western Canadian prairies, but still well short of the all-time limit and elevation reached during the Late Wisconsin (Late Pleistocene) in the foothills of the Alberta and Montana Rocky Mountains. Key Words: East-Central Alberta glacial history, Early Pleistocene (Laurentide) glaciation, till magnetostratigraphy, Quaternary history of Western Canadian Prairies, continental glaciations of North America.

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

    NASA Astrophysics Data System (ADS)

    Çiner, Attila; Sarıkaya, Mehmet Akif; Yıldırım, Cengiz

    2015-05-01

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

  5. Late Quaternary Arc-parallel Extension of the Kongur Extensional System (KES), Chinese Pamir

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Schoenbohm, Lindsay M.; Yuan, Zhaode; Li, Wenqiao; Li, Tao; Owen, Lewis A.; Sobel, Edward R.; Hedrick, Kate

    2015-04-01

    Active deformation in the Chinese Pamir plateau is dominated by east-west extension along the active Kongur extensional system (KES). The KES lies along the northeastern margin of the Pamir at the western end of the Himalayan-Tibetan orogenic belt, and is part of a regional fault system which accommodates east-west extension in the hanging wall of the active Main Pamir Thrust (MPT). Previous work has shown that the MPT has been active since at least the Late Oligocene and accommodates northward motion of the Pamir salient over the Tarim and Tajik basins. It has been proposed that North-directed thrusting along the Main Pamir thrust has been interpreted to be related to east-west extension in the northern Pamir by either extensional collapse of over-thickened crust, or radial thrusting, or oroclinal bending along the Main Pamir Thrust. Alternatively, the east-west extension is related to northward propagation of the right-slip Karakoram fault. A newer model relates the extension to gravitational collapse of the Pamir into the Tadjik depression. Clearly the precise driver remains poorly understood. To better understand the nature of extension in the Pamir and to test the existing models, late Quaternary slip rate along the KES need to be defined using geomorphic mapping, geodetic surveying, Be-10 surface exposure and depth profile dating to quantify rates of fault slip using multiple landforms as strain markers such as offset outwash terraces, lateral moraines, and landslides at five sites, to identify spatial patterns in deformation rates. The preliminary results show that the overall extension direction is subhorizontal, is oriented E-W, and occurs at a high rate of about 7 mm/yr along the Muji and Qimugan faults to the north and deceased to about 1 mm/yr at Kuzigan to the south near Tashkurgan town, which matches the pattern of GPS data. A regional compilation from this study and existing data shows that recent extension along the KES is arc-parallel extension

  6. The null hypothesis: steady rates of erosion, weathering and sediment accumulation during Late Cenozoic mountain uplift and glaciation

    NASA Astrophysics Data System (ADS)

    Willenbring, J. K.; Jerolmack, D. J.

    2015-12-01

    At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from this equilibrium condition arise from the transient response of landscape denudation to climatic and tectonic perturbations, and may be long lived. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. To support this contention, we synthesize existing data for weathering fluxes, global sedimentation rates, sediment yields and tectonic motions. The records show a remarkable constancy in the pace of Earth-surface evolution over the last 10 million years. These findings provide strong support for the null hypothesis; that global rates of landscape change have remained constant over the last ten million years, despite global climate change and massive mountain building events. Two important implications are: (1) global climate change may not change global denudation rates, because the nature and sign of landscape responses are varied; and (2) tectonic and climatic perturbations are accommodated in the long term by changes in landscape form. This work undermines the hypothesis that increased weathering due to late Cenozoic mountain building or climate change was the primary agent for a decrease in global temperatures.

  7. Geochronology of Quaternary glaciations in the Puruo Kangri, the largest ice field in the middle and low altitudes of the Earth

    NASA Astrophysics Data System (ADS)

    Yi, Chaolu

    2016-04-01

    Using 10Be surface exposure dating, optically stimulated luminescence dating (OSL),we show that the glacial advances occurred during marine isotope stages 12, 10, 8, 6, 4, 3, 2, as well as in the Younger Dryas, early and late Holocene, and the Little Ice Age.

  8. Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA

    SciTech Connect

    Berry, M.E. . Dept. of Geology)

    1992-01-01

    Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain, McGee (S--near Bishop), and Bishop Creek drainages. The profile data indicate that movement of the range-front faults (HCF and WCFZ), which is characterized by normal slip, has offset Tioga-age deposits 6.5-26 m. Offset of Tahoe-age moraines cannot be measured directly because the landforms are buried at the mountain-front by moraines from later glaciations. However, the amount of offset is estimated at 52--130 m, based on crest-height differences between Tahoe and Tioga moraines. The rates of slip are highest on the northern end of the HCF, at McGee (N) Creek; the higher slip rates in this latter area may be related to its close proximity to the Long Valley caldera, where tectonic processes are complex and considered closely related to ongoing magmatic activity. The preservation of bevels on the fault scarps in both HCF and WCFZ, combined with the amounts of surface offset on the late-Pleistocene moraines, and AMS C-14 dates for charcoal found in fault-scarp colluvium, indicate that large ground-rupturing events have occurred on these faults during the Holocene. In contrast to the mountain-front faults, faults in the CWFZ, on a broad warp that separates the WCFZ from range-front faults to the south of Bishop, do not cross Tioga moraines, implying that surface rupture has not occurred in the CWFZ for at least 15,000-25,000 years. The degraded morphology of the fault scarps on adjacent Tahoe and pre-Tahoe moraines, which have been offset between 10.5 and 30 m, attests to the lack of late-Pleistocene and Holocene fault activity in this latter area.

  9. The transition on North America from the warm humid Pliocene to the glaciated Quaternary traced by eolian dust deposition at a benchmark North Atlantic Ocean drill site

    NASA Astrophysics Data System (ADS)

    Lang, David C.; Bailey, Ian; Wilson, Paul A.; Beer, Christopher J.; Bolton, Clara T.; Friedrich, Oliver; Newsam, Cherry; Spencer, Megan R.; Gutjahr, Marcus; Foster, Gavin L.; Cooper, Matthew J.; Milton, J. Andrew

    2014-06-01

    We present Plio-Pleistocene records of sediment color, %CaCO3, foraminifer fragmentation, benthic carbon isotopes (δ13C) and radiogenic isotopes (Sr, Nd, Pb) of the terrigenous component from IODP Site U1313, a reoccupation of benchmark subtropical North Atlantic Ocean DSDP Site 607. We show that (inter)glacial cycles in sediment color and %CaCO3 pre-date major northern hemisphere glaciation and are unambiguously and consistently correlated to benthic oxygen isotopes back to 3.3 million years ago (Ma) and intermittently so probably back to the Miocene/Pliocene boundary. We show these lithological cycles to be driven by enhanced glacial fluxes of terrigenous material (eolian dust), not carbonate dissolution (the classic interpretation). Our radiogenic isotope data indicate a North American source for this dust (˜3.3-2.4 Ma) in keeping with the interpreted source of terrestrial plant wax-derived biomarkers deposited at Site U1313. Yet our data indicate a mid latitude provenance regardless of (inter)glacial state, a finding that is inconsistent with the biomarker-inferred importance of glaciogenic mechanisms of dust production and transport. Moreover, we find that the relation between the biomarker and lithogenic components of dust accumulation is distinctly non-linear. Both records show a jump in glacial rates of accumulation from Marine Isotope Stage, MIS, G6 (2.72 Ma) onwards but the amplitude of this signal is about 3-8 times greater for biomarkers than for dust and particularly extreme during MIS 100 (2.52 Ma). We conclude that North America shifted abruptly to a distinctly more arid glacial regime from MIS G6, but major shifts in glacial North American vegetation biomes and regional wind fields (exacerbated by the growth of a large Laurentide Ice Sheet during MIS 100) likely explain amplification of this signal in the biomarker records. Our findings are consistent with wetter-than-modern reconstructions of North American continental climate under the warm high

  10. Climatic, geomorphic, and archaeological implications of a late Quaternary alluvial chronology for the lower Salt River, Arizona, USA

    NASA Astrophysics Data System (ADS)

    Huckleberry, Gary; Onken, Jill; Graves, William M.; Wegener, Robert

    2013-03-01

    Recent archaeological excavations along the lower Salt River, Arizona resulted in the unexpected discovery of buried late Pleistocene soils and cultural features dating 5800-7100 cal YBP (Early Archaic), the latter representing the earliest evidence of human activity in the lower Salt River floodplain thus far identified. Because the lower Salt River floodplain has been heavily impacted by recent agriculture and urbanization and contains few stratigraphic exposures, our understanding of the river's geological history is limited. Here we present a late Quaternary alluvial chronology for a segment of the lower Salt River based on 19 accelerator mass spectrometry 14C and four optically stimulated luminescence ages obtained during two previous geoarchaeological investigations. Deposits are organized into allostratigraphic units and reveal a buried late Pleistocene terrace inset into middle-to-late Pleistocene terrace deposits. Holocene terrace fill deposits unconformably cap the late Pleistocene terrace tread in the site area, and the lower portion of this fill contains the Early Archaic archaeological features. Channel entrenchment and widening ~ 900 cal YBP eroded much of the older terrace deposits, leaving only a remnant of fill containing the buried latest Pleistocene and middle-to-late Holocene deposits preserved in the site area. Subsequent overbank deposition and channel filling associated with a braided channel system resulted in the burial of the site by a thin layer of flood sediments. Our study confirms that the lower Salt River is a complex mosaic of late Quaternary alluvium formed through vertical and lateral accretion, with isolated patches of buried soils preserved through channel avulsion. Although channel avulsion is linked to changes in sediment load and discharge and may have climatic linkages, intrinsic geomorphic and local base level controls limit direct correlations of lower Salt River stratigraphy to other large rivers in the North American

  11. Geochemical proxies for weathering and provenance of Late Quaternary alluvial core-sediments from NW India

    NASA Astrophysics Data System (ADS)

    Singh, Ajit; Amir, Mohd; Paul, Debajyoti; Sinha, Rajiv

    2014-05-01

    The Indo-Gangetic alluvial plains are formed by sediment deposition in the foreland basin as a result of upliftment and subsequent erosion of the Himalaya. Earlier study (Sinha et al., 2013) has shown the subsurface existence of buried channel bodies beneath the Ghaggar plains in NW Indo-Gangetic plains. The mapped sand bodies follow trace of a paleochannel that begins at the mountain front near the exit of river Sutlej and extends to the northern margin of the Thar desert, suggesting existence of a large Himalayan-sourced river (Singh et al., 2011) in the past. The buried sand bodies hold potential records of erosion history over the Himalaya that could be used to assess climate-controlled erosion over the Himalaya. Geochemical variations in the sediments from two (~45m long) cores drilled below the trace of the paleochannel (upstream) near Sirhind, Punjab and two cores (GS-10 & 11) from downstream near Kalibangan, Rajasthan, are used in this study to understand the erosional pattern over the Himalaya during Late Quaternary. Down-core variations in chemical index of alteration (CIA=51-79) along with K2O/Na2O and Al2O3/(CaO+Na2O) ratios are consistent with the trends of SW summer monsoonal fluctuations during the Glacial-Interglacial periods indicating climate controlled weathering at the source; higher values during Interglacial and lower during Glacial periods with maximum value during the Holocene. Sr-Nd isotopic compositions of drill-cores sediments, 87Sr/86Sr (0.7314-0.7946), ɛNd (-23.2 to -14) are within the range of silicate rocks from the Higher and Lesser Himalaya. Significant down-core variations in 87Sr/86Sr and ɛNd are observed that reflect the mixing of varying proportions of the Higher and Lesser Himalayan sediments, the two dominant sources to the core sites. Sediments deposited during MIS-2 and MIS-4, cold and dry Glacial periods, show high 87Sr/86Sr and low ɛNd suggesting an enhanced contribution from the Lesser Himalayan rocks that are

  12. Late Quaternary stream incision rates due to tectonic uplift in North Peloponnese, Greece

    NASA Astrophysics Data System (ADS)

    Karymbalis, E.; Ferentinou, M.; Gaki-Papanastassiou, K.; Papanastassiou, D.; Maroukian, H.

    2012-04-01

    of erosion so bedrock incision rates can be directly calculated. For each cross-section the high (Hv) and the width (Wv) of the valley were measured while the ratio of valley width and valley high (Vf) was also estimated. Valley side slope angles were also determined and their distribution along the study streams was discussed. The mean incision rate of each stream for the last 350kyrs was estimated and both spatial and temporal variations of incision rates along the reaches of the studied streams were reconstructed. Valley morphometric parameters were also studied utilizing Artificial Neural Networks. The geomorphic evolution of the studied streams has been affected by the lithology of the bedrock, the tectonic uplift of the area, sea level fluctuations during the Late Quaternary and the head-ward erosion and incision of the channels. The high of the valleys for each marine terrace is gradually greater from east to west. This indicates that incision rates are comparable with the component of regional uplift and with the slip rate of the Xylokastro fault over the last 350 kyrs.

  13. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    Remains of fishes, birds and mammals are rarely reported from Quaternary deposits in Greenland. The oldest remains come from Late Pliocene and Early Pleistocene deposits and comprise Atlantic cod, hare, rabbit and ringed seal. Interglacial and interstadial deposits have yielded remains of cod, little auk, collared lemming, ringed seal, reindeer and bowhead whale. Early and Mid-Holocene finds include capelin, polar cod, red fish, sculpin, three-spined stickleback, Lapland longspur, Arctic hare, collared lemming, wolf, walrus, ringed seal, reindeer and bowhead whale. It is considered unlikely that vertebrates could survive in Greenland during the peak of the last glaciation, but many species had probably already immigrated in the Early Holocene.

  14. Late-Quaternary Speleothem Records from the Balkan Peninsula - Potential, Objectives and First Results

    NASA Astrophysics Data System (ADS)

    John, I.; McCoy, W. D.; Markovic, S.; Endlicher, W.

    2010-12-01

    Mid-latitude speleothems often contain detailed, high-resolution records of local and regional interglacial climate changes. Many speleothem records of Holocene (MIS 1) and Eemian (MIS 5e) climate evolution have been investigated, but there is very little work being done in the Balkan region, despite the fact that the area is very rich in limestone caves with speleothems. Situated at the interface between temperate-continental and Mediterranean climates, present-day climate on the Balkan Peninsula is determined by two major upper-level jet streams, the polarfront jet (PFJ) and the subtropical jet (STJ). On a seasonal scale, both features exert varying influence and determine frontogenesis processes, cyclonic activity and precipitation. On decadal to millennial time-scales, changes and fluctuations in the position and permanency of these atmospheric circulation features influence the isotope signature in rainfall and ultimately in cave drip waters and related speleothems. We are investigating speleothems from Serbia, Montenegro and Bosnia-Herzegovina to study Late Quaternary climatic changes and to learn how both synoptic-scale systems were linked during the Holocene and previous interglacial periods. By example of a stalagmite collected in Vernjikica Cave, Serbia (Carpatho-Balkans), the project's potential to address important aspects of paleoclimatic research in the Mediterranean realm is discussed. The first studied, fine-laminated calcite stalagmite is about 50 cm tall and extends conically from the base to the top, presenting at least two visible growth discontinuities. Four preliminary uranium-series ages (234U/230Th) constrain the general period of growth to MIS 5d to MIS 5b. Preliminary results suggest that the stable oxygen isotope profile obtained from the axial zone largely reflects the unaltered isotopic composition of the cave drip water. The observed shifts in the isotope records display long-term changing climate conditions from temperate warm and

  15. Sedimentology and paleohydrology of Late Quaternary lake deposits in the northern Namib Sand Sea, Namibia

    NASA Astrophysics Data System (ADS)

    Teller, James T.; Rutter, Nat; Lancaster, N.

    The Namib Sand Sea is the largest active desert dunefield in southern Africa, and is comprised mainly of large north-south linear dunes. In the interdune areas of the northern Sand Sea eleven small areas of calcareous lacustrine sediment have been studied. These beds are typically less than a metre thick and are dominantly comprised of calcareous sandstones to mudstones and sandy limestones. The carbonates are mainly magnesian calcites (1-14% MgCO 3) with some protodolomite and aragonite. Calcified reed casts and fresh to brackish water gastropods, diatoms, and ostracods are present in some beds. δ18O values indicate a hot and dry climate. A number of enriched δ13C values may reflect high salinity, low organic populations, or carbonate recrystallization. These carbonate-rich lacustrine deposits are indicative of increased periods of moisture availability in this normally hyperarid region during the Late Quaternary. The origin of the water responsible for depositing these sediments may be: (1) ponding at the end point of the Tsondab River, which at one time extended farther west into the Sand Sea; (2) flooding into interdune corridors when water levels rose in rivers such as the Kuiseb; (3) groundwater seepage into depressions either through dunes that border rivers or from the underlying Tsondab Sandstone; and (4) increased rainfall. We do not believe that there is evidence to support a major increase in precipitation over the region. However, even a small increase in precipitation in the headwaters of valleys that drain toward the Sand Sea might: (1) generate enough additional runoff to extend the terminal point of rivers such as the Tsondab farther into the dunes; (2) cause lateral flooding from major valleys into interdune corridors; and (3) recharge aquifers. The sedimentary records at Narabeb, Ancient Tracks, and West Pan, which lie along the old course of the Tsondab River, favor a ponded river origin for them, whereas groundwater seepage is favored at

  16. Is late Quaternary climate change governed by self-sustained oscillations in atmospheric CO2?

    NASA Astrophysics Data System (ADS)

    Wallmann, Klaus

    2014-05-01

    A simple earth system model is developed to simulate global carbon and phosphorus cycling over the late Quaternary. It is focused on the geological cycling of C and P via continental weathering, volcanic and metamorphic degassing, hydrothermal processes and burial at the seabed. A simple ocean model is embedded in this geological model where the global ocean is represented by surface water, thermocline and deep water boxes. Concentrations of dissolved phosphorus, dissolved inorganic carbon, and total alkalinity are calculated for each box. The partial pressure of CO2 in the atmosphere (pCO2A) is determined by exchange processes with the surface ocean and the continents. It serves as key prognostic model variable and is assumed to govern surface temperatures and global sea-level. The model is formulated as autonomous system, in which the governing equations have no explicit time-dependence. For certain parameter values, the model does not converge towards a steady-state but develops stable self-sustained oscillations. These free oscillations feature pCO2A minima and maxima consistent with the ice-core record when vertical mixing in the ocean is allowed to vary in response to pCO2A-controlled temperature change. A stable 100-kyr cycle with a rapid transition from glacial to interglacial conditions is obtained when additional non-linear equations are applied to calculate deep ocean mixing, iron fertilization and the depth of organic matter degradation as function of pCO2A-controlled surface temperature. The δ13C value of carbon in the ocean/atmosphere system calculated in these model runs is consistent with the benthic δ13C record. However, the simulated 13C depletion in the glacial ocean is not driven by the decline in terrestrial carbon stocks but by sea-level change controlling the rates of organic carbon burial and weathering at continental margins. The pCO2A- and δ13C oscillations develop without any form of external Milankovitch forcing. They are induced and

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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

  18. Modern Climate Analogues of Late-Quaternary Paleoclimates for the Western United States.

    NASA Astrophysics Data System (ADS)

    Mock, Cary Jeffrey

    This study examined spatial variations of modern and late-Quaternary climates for the western United States. Synoptic climatological analyses of the modern record identified the predominate climatic controls that normally produce the principal modes of spatial climatic variability. They also provided a modern standard to assess past climates. Maps of the month-to-month changes in 500 mb heights, sea-level pressure, temperature, and precipitation illustrated how different climatic controls govern the annual cycle of climatic response. The patterns of precipitation ratios, precipitation bar graphs, and the seasonal precipitation maximum provided additional insight into how different climatic controls influence spatial climatic variations. Synoptic-scale patterns from general circulation model (GCM) simulations or from analyses of climatic indices were used as the basis for finding modern climate analogues for 18 ka and 9 ka. Composite anomaly maps of atmospheric circulation, precipitation, and temperature were compared with effective moisture maps compiled from proxy data to infer how the patterns, which were evident from the proxy data, were generated. The analyses of the modern synoptic climatology indicate that smaller-scale climatic controls must be considered along with larger-scale ones in order to explain patterns of spatial climate heterogeneity. Climatic extremes indicate that changes in the spatial patterns of precipitation seasonality are the exception rather than the rule, reflecting the strong influence of smaller-scale controls. Modern climate analogues for both 18 ka and 9 ka clearly depict the dry Northwest/wet Southwest contrast that is suggested by GCM simulations and paleoclimatic evidence. 18 ka analogues also show the importance of smaller-scale climatic controls in explaining spatial climatic variation in the Northwest and northern Great Plains. 9 ka analogues provide climatological explanations for patterns of spatial heterogeneity over several

  19. Origin, age, and paleoclimatic setting of the Late Quaternary deposits in Wadi Feiran, Sinai Peninsula: Geomorphologic, geochronologic, and isotopic constraints

    NASA Astrophysics Data System (ADS)

    Farag, A. Z. A.; Sultan, M.; Forman, S. L.; Krishnamurthy, R. V.

    2015-12-01

    There is considerable debate on the origin, age, and paleoclimatic setting of Late Quaternary deposits within the basement complex of the Sinai Peninsula. Our research in Wadi Feiran focused on documenting the sedimentology, stratigraphy, geochemistry and chronology of Late Quaternary deposits in the Feiran (lat. 28.706 N; long. 33.665; elevation: 715 to 772 m a.m.s.l) and Tarfa (lat. 28.692 N; long. 33.933 E; elevation: 1160 to 1244 m a.m.s.l) oases. Sequence stratigraphy, analysis of remote sensed images, and groundwater levels in these two areas indicate that the investigated deposits are structurally-controlled as they are found in areas with anomalously elevated groundwater levels and upstream from shear zone/wadi intersections. Sediments are largely arenaceous upstream and transition downstream to marly successions. We infer that these sediments were not deposited in lake settings because of the absence of shorelines and associated littoral, sublittoral and deeper water facies, and the presence of rhizoliths, secondary calcite veins and gastropods, all of which suggest deposition in a spring or wetland environment. A short hydrologic residence time and/or deposition in an open water system is supported by the lack of correlation (R = 0.08) between δ18O and δ13C values in carbonate deposits. Our findings are consistent with deposition of sediments by alluvial, fluvial and paludal processes under variable hydrologic conditions and higher water table conditions. Quartz extracts from these sediments yielded optically stimulated luminescence ages between ca. 27 and 11 ka and place these wetter conditions during the last glacial period and extend the "greening" of North Africa further eastward. Our findings are consistent with models which identify the wet periods in the Late Quaternary in the Sinai Peninsula and in North Africa as being glacial periods.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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

  1. Late Quaternary glacial relief evolution and fracture-density control on erosion revealed by low-temperature thermochronometry and remote sensing (Granite Range, Alaska)

    NASA Astrophysics Data System (ADS)

    Valla, Pierre; Champagnac, Jean-Daniel; Herman, Frédéric; Lowick, Sally; Guralnik, Benny; Shuster, David; Fellin, Giuditta

    2013-04-01

    Long-term erosion and topographic evolution of mountain belts arise from complex coupling between tectonics, climate and surface processes. The Granite Range (Wrangell-St Elias National Park, Alaska) presents an ideal setting to study such interactions. Its alpine landscape, preserving typical glacial features (U-shaped valleys, cirques), appears highly smoothed in the west, and progressively more rugged towards the east. In the field, this is evidenced by minor and only localized faulting of massive bedrock (granite and paragneiss) in the west, while the eastern part shows highly fractured bedrock (penetrative faults, fault gouges). Remote-sensing analysis confirms that fracture density is much higher towards east, and also reveals high post-glacial incision only in areas associated with high fracture density. To quantify our morphometric observations, we sampled four elevation profiles (~15 samples in total) over an 80-km East-West transect for low-temperature thermochrometry. Apatite (U-Th-Sm)/He dating provides ages between ~10 and 30 Ma, in agreement with published data, and shows apparent low long-term exhumation rates (~0.05-0.1 km/Ma). Preliminary 4He/3He thermochronometry data reveal a more complex exhumation history, with a significant increase since ~6-5 Ma which can be related to either onset of glaciations in Alaska or a major change in tectonic activity occurring at that period. Further data collected within the Granite Range will help to decipher the origin of this late-Miocene acceleration in exhumation. We also performed luminescence thermochronometry measured on feldspar separates from bedrock samples. Our results show a strong East-West gradient in samples saturation ratio. Apparent ages vary from ~250 ka in the western part of the range, towards younger ages of ~30 ka in the east. This pattern reveals spatially variable erosion rates during the late Quaternary associated with a major fracture-density control on erosion, and further supports the

  2. Synchronous Late Quaternary slip rate variability on two strands of the San Jacinto fault, California

    NASA Astrophysics Data System (ADS)

    Le, K. N.; Oskin, M.

    2007-12-01

    We present new results that show slip rates varied synchronously by a factor of two over the past 35 kyr along two parallel strands of the San Jacinto fault. Our results combine high-resolution LiDAR digital topography, field mapping and 10Be exposure-age dating from two of the most active strands of the southern San Jacinto fault: the Clark fault (CLF) and Coyote Creek fault (CCF). These faults form numerous NW-striking scarps that offset three generations of Quaternary alluvial fan surfaces, Q2b, Q3a, and Q3b. We dated alluvial fans along both the CCF and CLF using 10Be sampling methods adapted for available material and degradation of the surface. For younger surfaces with well-preserved bar and swale morphology, we used a new sampling method where 12 to 20 chips from quartz-bearing boulders lodged within a bar were amalgamated into a single sample. For older surfaces we either sampled individual meter-sized boulders or collected samples from a 2 m-deep depth profile. Surface ages are consistent between CCF and CLF sites: 40 ± 12 ka and 31 ± 6 ka for Q2b, 7.1 ± 1.6 ka and 4.6 ± 1.6 ka for Q3a, respectively. Samples from Q3b near the CLF yielded ages of 1.0 ± 0.2 ka and 2.1 ± 0.3 ka. CCF samples have not yet been corrected 10Be inheritance, thus we use the CLF ages to calculate preliminary slip rates. Late Pleistocene to present rates are CLF: 2.2 ± 0.5 mm/yr, CCF: 3.4 ± 0.9 mm/yr, and 5.6 ± 1.4 mm/yr combined. Mid-Holocene to present rates are CLF: 4.1 ± 1.5 mm/yr, CCF: 6.7 ± 2.8 mm/yr, and 10.9 ± 4.3 mm/yr combined. Latest Holocene CLF slip rate exceeds 3 mm/yr. The combined Late Pleistocene to present slip rate for the southern San Jacinto fault is less than one third the rate deduced from the onset of faulting ca. 1 Ma. Mid-Holocene to present slip rates for both the CLF and CCF are about double their ca. 35 kyr rates, but are less than the 16 - 20 mm/yr geodetic loading rates and the >16 mm/yr slip rate since 1 ka at Hog Lake. We conclude that (1

  3. Late Quaternary marine records from High Arctic Canada: problems, solutions, and multiproxy perspectives

    NASA Astrophysics Data System (ADS)

    Pienkowski, Anna; Furze, Mark; England, John; MacLean, Brian; von Prause, Markus; Blasco, Steve

    2013-04-01

    The Canadian Arctic Archipelago (= CAA) constitutes a significant geographic region within the Arctic Ocean Basin, influencing its oceanography, biology, ecology, and climate. Yet comparatively little is known about the long-term (post-Late Wisconsinan) environmental history of the marine channels of this region (the "Northwest Passage" = NWP). New marine data emerging from the central CAA extending back to regional deglaciation highlight the potential of multiproxy approaches in high-latitude settings. Five long (piston and trigger-weight) cores in an east-west transect through the NWP, investigated for sedimentological characteristics, microfossils (dinocysts, non-pollen palynomorphs, benthic and planktonic foraminifera, ostracods), and stable isotope ratios, show a dynamic late Quaternary environmental history. Our data suggest grounded glacial ice, rapid deglaciation, and a characteristic progression from ice-proximal to ice-distal conditions. Despite chronological complexities (scarcity of dateable materials, Portlandia Effect), age model extrapolations place deglaciation at ~11.0-10.3 cal ka BP (location dependent). Noticeable biological activity is marked by the appearance of planktonic foraminifera (Neogloboquadrina pachyderma) at ~10.0 cal ka BP. This signals the penetration of (Atlantic-derived) Arctic Intermediate Water (AIW) into the central NWP following deglaciation, likely facilitated by higher sea-levels permitting increased flow across inter-channel sills. Subsequent (~9.0-7.0 cal ka BP) ameliorated conditions (open-water season greater than present) marked by substantial diversification and abundance across all microfossil groups may correspond to a previously postulated "Holocene Thermal Optimum". After ~7.0 cal ka BP increased sea-ice and modern microfossil assemblages imply conditions similar to modern, likely due to the exclusion of AIW due to glacioisostatic shallowing combined with climate cooling. Remaining micropalaeontological challenges

  4. Late Quaternary environmental changes in Marguerite Bay, Antarctic Peninsula, inferred from lake sediments and raised beaches

    NASA Astrophysics Data System (ADS)

    Hodgson, Dominic A.; Roberts, Stephen J.; Smith, James A.; Verleyen, Elie; Sterken, Mieke; Labarque, Minke; Sabbe, Koen; Vyverman, Wim; Allen, Claire S.; Leng, Melanie J.; Bryant, Charlotte

    2013-05-01

    The Antarctic Peninsula is one of the fastest-warming regions on Earth, but its palaeoenvironmental history south of 63° latitude is relatively poorly documented, relying principally on the marine geological record and short ice cores. In this paper, we present evidence of late-Quaternary environmental change from the Marguerite Bay region combining data from lake sediment records on Horseshoe Island and Pourquoi-Pas Island, and raised beaches at Horseshoe Island, Pourquoi-Pas Island and Calmette Bay. Lake sediments were radiocarbon dated and analysed using a combination of sedimentological, geochemical and microfossil methods. Raised beaches were surveyed and analysed for changes in clast composition, size and roundness. Results suggest a non-erosive glacial regime could have existed on Horseshoe Island from 35,780 (38,650-33,380) or 32,910 (34,630-31,370) cal yr BP onwards. There is radiocarbon and macrofossil evidence for possible local deglaciation events at 28,830 (29,370-28,320) cal yr BP, immediately post-dating Antarctic Isotopic Maximum 4, and 21,110 (21,510-20,730 interpolated) cal yr BP coinciding with, or immediately post-dating, Antarctic Isotopic Maximum 2. The Holocene deglaciation of Horseshoe Island commenced from 10,610 (11,000-10,300) cal yr BP at the same time as the early Holocene temperature maximum recorded in Antarctic ice cores. This was followed by the onset of marine sedimentation in The Narrows, Pourquoi-Pas Island, before 8850 (8480-9260) cal yr BP. Relative sea level high stands of 40.79 m above present at Pourquoi-Pas Island and 40.55 m above present at Calmette Bay occurred sometime after 9000 cal yr BP and suggest that a thicker ice sheet, including grounded ice streams, was present in this region of the Antarctic Peninsula than that recorded at sites further north. Isolation of the Narrows Lake basin on Pourquoi-Pas Island shows relative sea level in this region had fallen rapidly to 19.41 m by 7270 (7385-7155) cal yr BP

  5. Late Cenozoic deep weathering patterns on the Fennoscandian shield in northern Finland: A window on ice sheet bed conditions at the onset of Northern Hemisphere glaciation

    NASA Astrophysics Data System (ADS)

    Hall, Adrian M.; Sarala, Pertti; Ebert, Karin

    2015-10-01

    The nature of the regolith that existed on the shields of the Northern Hemisphere at the onset of ice sheet glaciation is poorly constrained. In this paper, we provide the first detailed account of an exceptionally preserved, deeply weathered late Neogene landscape in the ice sheet divide zone in northern Finland. We mine data sets of drilling and pitting records gathered by the Geological Survey of Finland to reconstruct regional preglacial deep weathering patterns within a GIS framework. Using a large geochemical data set, we give standardised descriptions of saprolite geochemistry using a variant of the Weathering Index of Parker (WIP) as a proxy to assess the intensity of weathering. We also focus on mineral prospects and mines with dense pit and borehole data coverage in order to identify links between geology, topography, and weathering. Geology is closely linked to topography on the preglacial shield landscape of northern Finland and both factors influence weathering patterns. Upstanding, resistant granulite, granite, gabbro, metabasalt, and quartzite rocks were associated with fresh rock outcrops, including tors, or with thin (< 5 m) grusses. Plains developed across less resistant biotite gneisses, greenstones, and belts of alternating rock types were mainly weathered to thick (10-20 m) grusses with WIPfines values above 3000 and 4000. Beneath valley floors developed along mineralised shear and fracture zones, weathering penetrated locally to depths of > 50 m and included intensely weathered kaolinitic clays with WIPfines values below 1000. Late Neogene weathering profiles were varied in character. Tripartite clay-gruss-saprock profiles occur only in limited areas. Bipartite gruss-saprock profiles were widespread, with saprock thicknesses of > 10 m. Weathering profiles included two discontinuities in texture, materials and resistance to erosion, between saprolite and saprock and between saprock and rock. Limited core recovery when drilling below the soil

  6. Late quaternary depositional systems and sea level change-Santa Monica and San Pedro Basins, California continental borderland

    SciTech Connect

    Nardin, T.R.

    1983-07-01

    A suite of seismic reflection data that provides different degrees of resolution and penetration was used to map the depositional systems that have developed in Santa Monica and San Pedro basins during the late Quaternary. Submarine fan growth, particularly at the mouths of Hueneme and Redondo Canyons, has been the dominant mode of basin filling. Mass movement processes, ranging from creep to large-scale catastrophic slumping, have been important locally. In general, large-scale fan growth fits Normark's model in which the suprafan is the primary locus of coarse sediment deposition. Smaller scale morphologic and depositional patterns on the Hueneme and Redondo fans (e.g., distributary channels and coarse sediment concentrations basinward of the inner suprafan) suggest that a significant amount of coarse sediment presently bypasses the suprafans, however. Long-distance coarse sediment transport was particularly pronounced during late Wisconsinan lowstand of sea level and resulted in progradation of lower mid-fan and lower fan deposits.

  7. Glaciation in the Late Noachian Icy Highlands: Ice accumulation, distribution, flow rates, basal melting, and top-down melting rates and patterns

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2015-02-01

    Geological evidence for extensive non-polar ice deposits of Amazonian age indicates that the current cold and dry climate of Mars has persisted for several billion years. The geological record and climate history of the Noachian, the earliest period of Mars history, is less certain, but abundant evidence for fluvial channels (valley networks) and lacustrine environments (open-basin lakes) has been interpreted to represent warm and wet conditions, including rainfall and runoff. Alternatively, recent atmospheric modeling results predict a "cold and icy" Late Noachian Mars in which moderate atmospheric pressure accompanied by a full water cycle produce an atmosphere where temperature declines with elevation following an adiabatic lapse rate, in contrast to the current situation on Mars, where temperature is almost completely determined by latitude. These results are formulated in the Late Noachian Icy Highlands (LNIH) model, in which these cold and icy conditions lead to the preferential deposition of snow and ice at high elevations, such as the southern uplands. What is the fate of this snow and ice and the nature of glaciation in such an environment? What are the prospects of melting of these deposits contributing to the observed fluvial and lacustrine deposits? To address these questions, we report on a glacial flow-modeling analysis using a Mars-adapted ice sheet model with LNIH climate conditions. The total surface/near-surface water inventory is poorly known for the Late Noachian, so we explore the LNIH model in a "supply-limited" scenario for a range of available water abundances and a range of Late Noachian geothermal fluxes. Our results predict that the Late Noachian icy highlands (above an equilibrium line altitude of approximately +1 km) were characterized by extensive ice sheets of the order of hundreds of meters thick. Due to extremely cold conditions, the ice-flow velocities in general were very low, less than a few mm/yr, and the regional ice

  8. Changes in Sediment Provenance to the Southeast Newfoundland Ridge from the late Eocene to the Early Oligocene; Northern Hemisphere Glaciation or Deep Water Circulation?

    NASA Astrophysics Data System (ADS)

    Scher, H. D.; Romans, B.; Moffett, Z. J.; Buckley, W. P.; Gibson, K.

    2013-12-01

    continents. There is not a long term trend nor prominent inflections in the fossil fish tooth ɛNd record that are associated with terrigenous ɛNd values so it does not appear likely that changes in sediment provenance were accompanied by a reorganization of deep water masses. Thus the preliminary results are cautiously interpreted as reflecting a sedimentological response to an overall increase in weathering/erosion of ancient continental crust, possibly on Greenland, over the investigated interval. In this context these results may reflect the emplacement of northern hemisphere ice sheets in the latest Eocene, preceded by prominent short-lived glacial events in the Eocene. The first short-lived event falls within polarity chron C17n.1n, which corresponds with the timing of a known Eocene glaciation on Antarctica and suggests that the greenhouse climate in the late Eocene supported a bipolar glacial event. We are currently generating a record of relative paleo-bottom current intensity from U1411 using the sortable silt proxy to further evaluate the role of bottom currents in terrigenous sediment provenance on the SENR.

  9. Idiosyncratic responses of evergreen broad-leaved forest constituents in China to the late Quaternary climate changes.

    PubMed

    Fan, Dengmei; Hu, Wan; Li, Bo; Morris, Ashley B; Zheng, Min; Soltis, Douglas E; Soltis, Pamela S; Zhang, Zhiyong

    2016-01-01

    Subtropical evergreen broad-leaved forest (EBLF) is one of the most important vegetation types in China. Inferences from palaeo-biome reconstruction (PBR) and phylogeography regarding range shift history of EBLF during the late Quaternary are controversial and should be reconciled. We compared phylogeographic patterns of three EBLF constituents in China, Castanopsis tibetana, Machilus thunbergii and Schima superba. Contrary to a chorus of previous phylogeographic studies and the results of species distribution modelling (SDM) of this study (in situ survival during the LGM), the three species displayed three different phylogeographic patterns that conform to either an in situ survival model or an expansion-contraction model. These results are partially congruent with the inference of PBR that EBLF was absent to the north of 24° N at the LGM. This study suggests that the constituents of EBLF could have responded idiosyncratically to climate changes during the Late Quaternary. The community assemblages of EBLF could have been changing over time, resulting in no palaeo-analogs to modern-day EBLF, which may be the main reason responsible for the failure of PBR to detect the occurrence of EBLF north of 24° N at the LGM. PMID:27534981

  10. Chronology and stratigraphy of Late Quaternary sediments in the Konya Basin, Turkey: Results from the KOPAL Project

    NASA Astrophysics Data System (ADS)

    Roberts, N.; Black, S.; Boyer, P.; Eastwood, W. J.; Griffiths, H. I.; Lamb, H. F.; Leng, M. J.; Parish, R.; Reed, J. M.; Twigg, D.; Yiǧitbaşioǧlu, H.

    1999-04-01

    The Late Quaternary environmental history of the Konya plain, in south central Turkey, is used to examine sediment facies changes in a shallow non-outlet basin which has experienced major climatically driven changes in lake extent. Two principal types of sedimentary archive are used to reconstruct a palaeoenvironmental record, namely alluvial sequences on the Çarşamba alluvial fan and sediments from residual lakes. The latter have been used to investigate broader climatic and vegetational histories via palaeolimnological techniques including pollen, diatom and stable isotope analysis. These changes are dated here by radiometric techniques including radiocarbon (AMS and conventional), OSL, and U-Th. Chronological agreement is generally good between the different dating techniques, although typically there is greatly reduced precision beyond ca. 25 ka. Lake sediment cores investigated have basal ages beyond the range of 14C dating, but contain hiatuses as a result of subsequent alternation between phases of lacustrine sedimentation and aeolian deflation. In contrast to most deepwater non-outlet lake systems, the Konya basin may have been occupied by a single extensive lake for as little as 10% of Late Quaternary time, mainly around the time of the LGM. This lake highstand was followed by an important arid interval. In the absence of unbroken chronostratigraphic sequences, palaeohydrological investigation of shallow non-outlet lakes may require analysis of basin-wide changes in sedimentation rather than reliance on single core records. Stratigraphic continuity in such sedimentary environments cannot be assumed, and requires independent chronological control through radiometric dating.