@article{WangHerzschuhLiuetal.2014, author = {Wang, Yongbo and Herzschuh, Ulrike and Liu, Xingqi and Korup, Oliver and Diekmann, Bernhard}, title = {A high-resolution sedimentary archive from landslide-dammed Lake Mengda, north-eastern Tibetan Plateau}, series = {Journal of paleolimnolog}, volume = {51}, journal = {Journal of paleolimnolog}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-012-9666-6}, pages = {303 -- 312}, year = {2014}, abstract = {Lacustrine sediments have been widely used to investigate past climatic and environmental changes on millennial to seasonal time scales. Sedimentary archives of lakes in mountainous regions may also record non-climatic events such as earthquakes. We argue herein that a set of 64 annual laminae couplets reconciles a stratigraphically inconsistent accelerator mass spectrometry (AMS) C-14 chronology in a similar to 4-m-long sediment core from Lake Mengda, in the north-eastern Tibetan Plateau. The laminations suggest the lake was formed by a large landslide, triggered by the 1927 Gulang earthquake (M = 8.0). The lake sediment sequence can be separated into three units based on lithologic, sedimentary, and isotopic characteristics. Starting from the bottom of the sequence, these are: (1) unweathered, coarse, sandy valley-floor deposits or landslide debris that pre-date the lake, (2) landslide-induced, fine-grained soil or reworked landslide debris with a high organic content, and (3) lacustrine sediments with low organic content and laminations. These annual laminations provide a high-resolution record of anthropogenic and environmental changes during the twentieth century, recording enhanced sediment input associated with two phases of construction activities. The high mean sedimentation rates of up to 4.8 mm year(-1) underscore the potential for reconstructing such distinct sediment pulses in remote, forested, and seemingly undisturbed mountain catchments.}, language = {en} } @phdthesis{Aichner2009, author = {Aichner, Bernhard}, title = {Aquatic macrophyte-derived biomarkers as palaeolimnological proxies on the Tibetan Plateau}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42095}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {The Tibetan Plateau is the largest elevated landmass in the world and profoundly influences atmospheric circulation patterns such as the Asian monsoon system. Therefore this area has been increasingly in focus of palaeoenvironmental studies. This thesis evaluates the applicability of organic biomarkers for palaeolimnological purposes on the Tibetan Plateau with a focus on aquatic macrophyte-derived biomarkers. Submerged aquatic macrophytes have to be considered to significantly influence the sediment organic matter due to their high abundance in many Tibetan lakes. They can show highly 13C-enriched biomass because of their carbon metabolism and it is therefore crucial for the interpretation of δ13C values in sediment cores to understand to which extent aquatic macrophytes contribute to the isotopic signal of the sediments in Tibetan lakes and in which way variations can be explained in a palaeolimnological context. Additionally, the high abundance of macrophytes makes them interesting as potential recorders of lake water δD. Hydrogen isotope analysis of biomarkers is a rapidly evolving field to reconstruct past hydrological conditions and therefore of special relevance on the Tibetan Plateau due to the direct linkage between variations of monsoon intensity and changes in regional precipitation / evaporation balances. A set of surface sediment and aquatic macrophyte samples from the central and eastern Tibetan Plateau was analysed for composition as well as carbon and hydrogen isotopes of n-alkanes. It was shown how variable δ13C values of bulk organic matter and leaf lipids can be in submerged macrophytes even of a single species and how strongly these parameters are affected by them in corresponding sediments. The estimated contribution of the macrophytes by means of a binary isotopic model was calculated to be up to 60\% (mean: 40\%) to total organic carbon and up to 100\% (mean: 66\%) to mid-chain n-alkanes. Hydrogen isotopes of n-alkanes turned out to record δD of meteoric water of the summer precipitation. The apparent enrichment factor between water and n-alkanes was in range of previously reported ones (≈-130 per mille) at the most humid sites, but smaller (average: -86 per mille) at sites with a negative moisture budget. This indicates an influence of evaporation and evapotranspiration on δD of source water for aquatic and terrestrial plants. The offset between δD of mid- and long-chain n-alkanes was close to zero in most of the samples, suggesting that lake water as well as soil and leaf water are affected to a similar extent by those effects. To apply biomarkers in a palaeolimnological context, the aliphatic biomarker fraction of a sediment core from Lake Koucha (34.0° N; 97.2° E; eastern Tibetan Plateau) was analysed for concentrations, δ13C and δD values of compounds. Before ca. 8 cal ka BP, the lake was dominated by aquatic macrophyte-derived mid-chain n-alkanes, while after 6 cal ka BP high concentrations of a C20 highly branched isoprenoid compound indicate a predominance of phytoplankton. Those two principally different states of the lake were linked by a transition period with high abundances of microbial biomarkers. δ13C values were relatively constant for long-chain n-alkanes, while mid-chain n-alkanes showed variations between -23.5 to -12.6 per mille. Highest values were observed for the assumed period of maximum macrophyte growth during the late glacial and for the phytoplankton maximum during the middle and late Holocene. Therefore, the enriched values were interpreted to be caused by carbon limitation which in turn was induced by high macrophyte and primary productivity, respectively. Hydrogen isotope signatures of mid-chain n-alkanes have been shown to be able to track a previously deduced episode of reduced moisture availability between ca. 10 and 7 cal ka BP, indicated by a 20 per mille shift towards higher δD values. Indications for cooler episodes at 6.0, 3.1 and 1.8 cal ka BP were gained from drops of biomarker concentrations, especially microbial-derived hopanoids, and from coincidental shifts towards lower δ13C values. Those episodes correspond well with cool events reported from other locations on the Tibetan Plateau as well as in the Northern Hemisphere. To conclude, the study of recent sediments and plants improved the understanding of factors affecting the composition and isotopic signatures of aliphatic biomarkers in sediments. Concentrations and isotopic signatures of the biomarkers in Lake Koucha could be interpreted in a palaeolimnological context and contribute to the knowledge about the history of the lake. Aquatic macrophyte-derived mid-chain n-alkanes were especially useful, due to their high abundance in many Tibetan Lakes and their ability to record major changes of lake productivity and palaeo-hydrological conditions. Therefore, they have the potential to contribute to a fuller understanding of past climate variability in this key region for atmospheric circulation systems.}, language = {en} } @misc{DallmeyerClaussenNietal.2017, author = {Dallmeyer, Anne and Claussen, Martin and Ni, Jian and Cao, Xianyong and Wang, Yongbo and Fischer, Nils and Pfeiffer, Madlene and Jin, Liya and Khon, Vyacheslav and Wagner, Sebastian and Haberkorn, Kerstin and Herzschuh, Ulrike}, title = {Biome changes in Asia since the mid-Holocene}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {643}, issn = {1866-8372}, doi = {10.25932/publishup-41875}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418755}, pages = {107 -- 134}, year = {2017}, abstract = {The large variety of atmospheric circulation systems affecting the eastern Asian climate is reflected by the complex Asian vegetation distribution. Particularly in the transition zones of these circulation systems, vegetation is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate-vegetation relationship is lacking. To assess the Holocene vegetation change and to obtain an ensemble of potential mid-Holocene biome distributions for eastern Asia, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient Holocene climate simulations performed in coupled atmosphere-ocean(-vegetation) models. The simulated biome changes are compared with pollen-based biome records for different key regions. In all simulations, substantial biome shifts during the last 6000 years are confined to the high northern latitudes and the monsoon-westerly wind transition zone, but the temporal evolution and amplitude of change strongly depend on the climate forcing. Large parts of the southern tundra are replaced by taiga during the mid-Holocene due to a warmer growing season and the boreal treeline in northern Asia is shifted northward by approx. 4 degrees in the ensemble mean, ranging from 1.5 to 6 degrees in the individual simulations, respectively. This simulated treeline shift is in agreement with pollen-based reconstructions from northern Siberia. The desert fraction in the transition zone is reduced by 21\% during the mid-Holocene compared to pre-industrial due to enhanced precipitation. The desert-steppe margin is shifted westward by 5 degrees (1-9 degrees in the individual simulations). The forest biomes are expanded north-westward by 2 degrees, ranging from 0 to 4 degrees in the single simulations. These results corroborate pollen-based reconstructions indicating an extended forest area in north-central China during the mid-Holocene. According to the model, the forest-to-non-forest and steppe-to-desert changes in the climate transition zones are spatially not uniform and not linear since the mid-Holocene.}, language = {en} } @article{CookHoviusWittmannOelzeetal.2017, author = {Cook, Kristen L. and Hovius, Niels and Wittmann-Oelze, Hella and Heimsath, Arjun M. and Lee, Yuan-Hsi}, title = {Causes of rapid uplift and exceptional topography of Gongga Shan on the eastern margin of the Tibetan Plateau}, series = {Earth \& planetary science letters}, volume = {481}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2017.10.043}, pages = {328 -- 337}, year = {2017}, abstract = {Erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation, relief development, and crustal weakening. In many orogenic systems, it can be difficult to distinguish whether true feedbacks exist, or whether observed features are a consequence of tectonic forcing. To help elucidate these interactions, we examine Gongga Shan, a 7556 m peak on the eastern margin of the Tibetan Plateau where cosmogenic Be-10 basin-wide erosion rates reach >5 mm/yr, defining a region of localized rapid erosion associated with a restraining bend in the left-lateral Xianshuihe Fault. Erosion rates are consistent with topography, thermochronometry, and geodetic data, suggesting a stable pattern of uplift and exhumation over at least the past 2-3 My. Transpression along the Xianshuihe Fault, orographically enhanced precipitation, thermally weakened crust, and substantial local relief all developed independently in the Gongga region and existed there prior to the uplift of Gongga Shan. However, only where all of these conditions are present do the observed topographic and erosional extremes exist, and their relative timing indicates that these conditions are not a consequence of rapid uplift. We conclude that their collocation at 3-4 Ma set into motion a series of feedbacks between erosion and uplift that has resulted in the exceptionally high topography and rapid erosion rates observed today.}, language = {en} } @article{HuangJacksonDekkersetal.2019, author = {Huang, Wentao and Jackson, Michael J. and Dekkers, Mark J. and Zhang, Yang and Zhang, Bo and Guo, Zhaojie and Dupont-Nivet, Guillaume}, title = {Challenges in isolating primary remanent magnetization from Tethyan carbonate rocks on the Tibetan Plateau: Insight from remagnetized Upper Triassic limestones in the eastern Qiangtang block}, series = {Earth \& planetary science letters}, volume = {523}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2019.06.035}, pages = {15}, year = {2019}, abstract = {Carbonate rocks, widely used for paleomagnetically quantifying the drift history of the Gondwana derived continental blocks of the Tibetan Plateau and evolution of the Paleo/Meso/Neo-Tethys Oceans, are prone to pervasive remagnetization. Identifying remagnetization is difficult because it is commonly undetectable through the classic paleomagnetic field tests. Here we apply comprehensive paleomagnetic, rock magnetic, and petrographic studies to upper Triassic limestones in the eastern Qiangtang block. Our results reveal that detrital/biogenic magnetite, which may carry the primary natural remanent magnetization (NRM), is rarely preserved in these rocks. In contrast, authigenic magnetite and hematite pseudomorphs after pyrite, and monoclinic pyrrhotite record three episodes of remagnetization. The earliest remagnetization was induced by oxidation of early diagenetic pyrite to magnetite, probably related to the collision between the northeastern Tibetan Plateau and the Qiangtang block after closure of the Paleo-Tethys Ocean in the Late Triassic. The second remagnetization, residing in hematite and minor goethite, which is the further subsurface oxidation product of pyrite/magnetite, is possibly related to the development of the localized Cenozoic basins soon after India-Asia collision in the Paleocene. The youngest remagnetization is a combination of thermoviscous and chemical remanent magnetization carried by authigenic magnetite and pyrrhotite, respectively. Our analyses suggest that a high supply of organic carbon during carbonate deposition, prevailing sulfate reducing conditions during early diagenesis, and widespread orogenic fluid migration related to crustal shortening during later diagenesis, have altered the primary remanence of the shallow-water Tethyan carbonate rocks of the Tibetan Plateau. We emphasize that all paleomagnetic results from these rocks must be carefully examined for remagnetization before being used for paleogeographic reconstructions. Future paleomagnetic investigations of the carbonate rocks in orogenic belts should be accompanied by thorough rock magnetic and petrographic studies to determine the origin of the NRM. (C) 2019 Elsevier B.V. All rights reserved.}, language = {en} } @article{GaoZeilingerXuetal.2013, author = {Gao, Mingxing and Zeilinger, Gerold and Xu, Xiwei and Wang, Qingliang and Hao, Ming}, title = {DEM and GIS analysis of geomorphic indices for evaluating recent uplift of the northeastern margin of the Tibetan Plateau, China}, series = {Geomorphology : an international journal on pure and applied geomorphology}, volume = {190}, journal = {Geomorphology : an international journal on pure and applied geomorphology}, number = {20}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2013.02.008}, pages = {61 -- 72}, year = {2013}, abstract = {The northeastern margin of the Tibetan Plateau is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located in the transition zone between the Tibetan Plateau and the Loess Plateau. Active deformation that may affect the topography in this region can be quantified using geomorphic indices. Therefore, we applied geomorphic indices such as the hypsometric integral and the stream length gradient index to infer neo-tectonics in the northeastern margin of the Tibetan Plateau. Different time-scaled geodetic leveling data and river incision rates were also integrated into the investigation. The results show that the hypsometric integrals are not significantly affected by lithology but spatially correspond to the hanging walls of thrust faults. The hypsometric integrals are also positively correlated with the leveling data. Although the stream length gradient index is influenced by lithology, its most pronounced anomalies of the stream length gradient are associated with the thrust faults. Consequently, the uplift in the northeast margin of the Tibetan Plateau appeared to be concentrated along the hanging walls of the thrust faults.}, language = {en} } @article{HerzschuhNiBirksetal.2011, author = {Herzschuh, Ulrike and Ni, Jian and Birks, H. John B. and B{\"o}hner, J{\"u}rgen}, title = {Driving forces of mid-Holocene vegetation shifts on the upper Tibetan Plateau, with emphasis on changes in atmospheric CO2 concentrations}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {30}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, number = {15-16}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2011.03.007}, pages = {1907 -- 1917}, year = {2011}, abstract = {Numerous pollen records across the upper Tibetan Plateau indicate that in the early part of the mid-Holocene, Kobresia-rich high-alpine meadows invaded areas formerly dominated by alpine steppe vegetation rich in Artemisia. We examine climate, land-use, and CO2 concentration changes as potential drivers for this marked vegetation change. The climatic implications of these vegetational shifts are explored by applying a newly developed pollen-based moisture-balance transfer-function to fossil pollen spectra from Koucha Lake on the north-eastern Tibetan Plateau (34.0 degrees N; 97.2 degrees E; 4540 m a.s.l.) and Xuguo Lake on the central Tibetan Plateau (31.97 degrees N; 90.3 degrees E; 4595 m a.s.l.), both located in the meadow-steppe transition zone. Reconstructed moisture-balances were markedly reduced (by similar to 150-180 mm) during the early mid-Holocene compared to the late-Holocene. These findings contradict most other records from the Indian monsoonal realm and also most non-pollen records from the Tibetan Plateau that indicate a rather wet early- and mid-Holocene. The extent and timing of anthropogenic land-use involving grazing by large herbivores on the upper Tibetan Plateau and its possible impacts on high-alpine vegetation are still mostly unknown due to the lack of relevant archaeological evidence. Arguments against a mainly anthropogenic origin of Kobresia high-alpine meadows are the discovery of the widespread expansion of obviously 'natural' Kobresia meadows on the south-eastern Tibetan Plateau during the Lateglacial period indicating the natural origin of this vegetation type and the lack of any concurrence between modern human-driven vegetation shifts and the mid-Holocene compositional changes. Vegetation types are known to respond to atmospheric CO2 concentration changes, at least on glacial-interglacial scales. This assumption is confirmed by our sensitivity study where we model Tibetan vegetation at different CO2 concentrations of 375 (present-day), 260 (early Holocene), and 650 ppm (future scenario) using the BIOME4 global vegetation model. Previous experimental studies confirm that vegetation growing on dry and high sites is particularly sensitive to CO2 changes. Here we propose that the replacement of drought-resistant alpine steppes (that are well adapted to low CO2 concentrations) by mesic Kobresia meadows can, at least, be partly interpreted as a response to the increase of CO2 concentration since 7000 years ago due to fertilization and water-saving effects. Our hypothesis is corroborated by former CO2 fertilization experiments performed on various dry grasslands and by the strong recent expansion of high-alpine meadows documented by remote sensing studies in response to recent CO2 increases.}, language = {en} } @misc{MischkeZhangFan2015, author = {Mischke, Steffen and Zhang, Chengjun and Fan, Rong}, title = {Early to mid-Holocene lake high-stand sediments at Lake Donggi Cona, northeastern Tibetan Plateau, China -}, series = {Quaternary research : an interdisciplinary journal}, volume = {83}, journal = {Quaternary research : an interdisciplinary journal}, number = {1}, publisher = {Elsevier}, address = {San Diego}, issn = {0033-5894}, doi = {10.1016/j.yqres.2014.06.005}, pages = {256 -- 258}, year = {2015}, language = {en} } @article{WangLiuMischkeetal.2012, author = {Wang, Yongbo and Liu, Xingqi and Mischke, Steffen and Herzschuh, Ulrike}, title = {Environmental constraints on lake sediment mineral compositions from the Tibetan Plateau and implications for paleoenvironment reconstruction}, series = {Journal of paleolimnolog}, volume = {47}, journal = {Journal of paleolimnolog}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-011-9549-2}, pages = {71 -- 85}, year = {2012}, abstract = {Inorganic minerals form a major component of lacustrine sediments and have the potential to reveal detailed information on previous climatic and hydrological conditions. The ability to extract such information however, has been restricted by a limited understanding of the relationships between minerals and the environment. In an attempt to fill in this gap in our knowledge, 146 surface sediment samples have been investigated from 146 lakes on the Tibetan Plateau. The mineral compositions derived from these samples by X-Ray Diffraction (XRD) were used to examine the relationships between mineral compositions and the environmental variables determined for each site. Statistical techniques including Multivariate regression trees (MRT) and Redundancy Analysis (RDA), based on the mineral spectra and environmental variables, reveal that the electrical conductivity (EC) and Mg/Ca ratios of lake water are the most important controls on the composition of endogenic minerals. No endogenic minerals precipitate under hyper-fresh water conditions (EC lower than 0.13 mS/cm), with calcite commonly forming in water with EC values above 0.13 mS/cm. Between EC values of 0.13 and 26 mS/cm the mineral composition of lake sediments can be explained in terms of variations in the Mg/Ca ratio: calcite dominates at Mg/Ca ratios of less than 33, whereas aragonite commonly forms when the ratio is greater than 33. Where EC values are between 26 and 39 mS/cm, monohydrocalcite precipitates together with calcite and aragonite; above 39 mS/cm, gypsum and halite commonly form. Information on the local geological strata indicates that allogenic (detrital) mineral compositions are primarily influenced by the bedrock compositions within the catchment area. By applying these relationships to the late glacial and Holocene mineral record from Chaka Salt Lake, five lake stages have been identified and their associated EC conditions inferred. The lake evolved from a freshwater lake during the late glacial (before 11.4 cal. ka BP) represented by the lowest EC values (< 0.13 mS/cm), to a saline lake with EC values slightly higher than 39 mS/cm during the early and mid Holocene (ca. 11.4-5.3 cal. ka BP), and finally to a salt lake (after 5.3 cal. ka BP). These results illustrate the utility of our mineral-environmental model for the quantitative reconstruction of past environmental conditions from lake sediment records.}, language = {en} } @misc{AichnerFeakinsLeeetal.2015, author = {Aichner, Bernhard and Feakins, Sarah J. and Lee, J. E. and Herzschuh, Ulrike and Liu, X.}, title = {High-resolution leaf wax carbon and hydrogen isotopic record of the late Holocene paleoclimate in arid Central Asia}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {506}, issn = {1866-8372}, doi = {10.25932/publishup-40844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-408442}, pages = {15}, year = {2015}, abstract = {Central Asia is located at the confluence of large-scale atmospheric circulation systems. It is thus likely to be highly susceptible to changes in the dynamics of those systems; however, little is still known about the regional paleoclimate history. Here we present carbon and hydrogen isotopic compositions of n-alkanoic acids from a late Holocene sediment core from Lake Karakuli (eastern Pamir, Xinjiang Province, China). Instrumental evidence and isotopeenabled climate model experiments with the Laboratoire de Meteorologie Dynamique Zoom model version 4 (LMDZ4) demonstrate that delta D values of precipitation in the region are influenced by both temperature and precipitation amount. We find that these parameters are inversely correlated on an annual scale, i.e., the climate has varied between relatively cool and wet and more warm and dry over the last 50 years. Since the isotopic signals of these changes are in the same direction and therefore additive, isotopes in precipitation are sensitive recorders of climatic changes in the region. Additionally, we infer that plants use year-round precipitation (including snowmelt), and thus leaf wax delta D values must also respond to shifts in the proportion of moisture derived from westerly storms during late winter and early spring. Downcore results give evidence for a gradual shift to cooler and wetter climates between 3.5 and 2.5 cal kyr BP, interrupted by a warm and dry episode between 3.0 and 2.7 kyr BP. Further cool and wet episodes occur between 1.9 and 1.5 and between 0.6 and 0.1 kyr BP, the latter coeval with the Little Ice Age. Warm and dry episodes from 2.5 to 1.9 and 1.5 to 0.6 kyr BP coincide with the Roman Warm Period and Medieval Climate Anomaly, respectively. Finally, we find a drying tend in recent decades. Regional comparisons lead us to infer that the strength and position of the westerlies, and wider northern hemispheric climate dynamics, control climatic shifts in arid Central Asia, leading to complex local responses. Our new archive from Lake Karakuli provides a detailed record of the local signatures of these climate transitions in the eastern Pamir.}, language = {en} } @phdthesis{Mey2016, author = {Mey, J{\"u}rgen}, title = {Intermontane valley fills}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-103158}, school = {Universit{\"a}t Potsdam}, pages = {xii, 111}, year = {2016}, abstract = {Sedimentary valley fills are a widespread characteristic of mountain belts around the world. They transiently store material over time spans ranging from thousands to millions of years and therefore play an important role in modulating the sediment flux from the orogen to the foreland and to oceanic depocenters. In most cases, their formation can be attributed to specific fluvial conditions, which are closely related to climatic and tectonic processes. Hence, valley-fill deposits constitute valuable archives that offer fundamental insight into landscape evolution, and their study may help to assess the impact of future climate change on sediment dynamics. In this thesis I analyzed intermontane valley-fill deposits to constrain different aspects of the climatic and tectonic history of mountain belts over multiple timescales. First, I developed a method to estimate the thickness distribution of valley fills using artificial neural networks (ANNs). Based on the assumption of geometrical similarity between exposed and buried parts of the landscape, this novel and highly automated technique allows reconstructing fill thickness and bedrock topography on the scale of catchments to entire mountain belts. Second, I used the new method for estimating the spatial distribution of post-glacial sediments that are stored in the entire European Alps. A comparison with data from exploratory drillings and from geophysical surveys revealed that the model reproduces the measurements with a root mean squared error (RMSE) of 70m and a coefficient of determination (R2) of 0.81. I used the derived sediment thickness estimates in combination with a model of the Last Glacial Maximum (LGM) icecap to infer the lithospheric response to deglaciation, erosion and deposition, and deduce their relative contribution to the present-day rock-uplift rate. For a range of different lithospheric and upper mantle-material properties, the results suggest that the long-wavelength uplift signal can be explained by glacial isostatic adjustment with a small erosional contribution and a substantial but localized tectonic component exceeding 50\% in parts of the Eastern Alps and in the Swiss Rh{\^o}ne Valley. Furthermore, this study reveals the particular importance of deconvolving the potential components of rock uplift when interpreting recent movements along active orogens and how this can be used to constrain physical properties of the Earth's interior. In a third study, I used the ANN approach to estimate the sediment thickness of alluviated reaches of the Yarlung Tsangpo River, upstream of the rapidly uplifting Namche Barwa massif. This allowed my colleagues and me to reconstruct the ancient river profile of the Yarlung Tsangpo, and to show that in the past, the river had already been deeply incised into the eastern margin of the Tibetan Plateau. Dating of basal sediments from drill cores that reached the paleo-river bed to 2-2.5 Ma are consistent with mineral cooling ages from the Namche Barwa massif, which indicate initiation of rapid uplift at ~4 Ma. Hence, formation of the Tsangpo gorge and aggradation of the voluminous valley fill was most probably a consequence of rapid uplift of the Namche Barwa massif and thus tectonic activity. The fourth and last study focuses on the interaction of fluvial and glacial processes at the southeastern edge of the Karakoram. Paleo-ice-extent indicators and remnants of a more than 400-m-thick fluvio-lacustrine valley fill point to blockage of the Shyok River, a main tributary of the upper Indus, by the Siachen Glacier, which is the largest glacier in the Karakoram Range. Field observations and 10Be exposure dating attest to a period of recurring lake formation and outburst flooding during the penultimate glaciation prior to ~110 ka. The interaction of Rivers and Glaciers all along the Karakorum is considered a key factor in landscape evolution and presumably promoted headward erosion of the Indus-Shyok drainage system into the western margin of the Tibetan Plateau. The results of this thesis highlight the strong influence of glaciation and tectonics on valley-fill formation and how this has affected the evolution of different mountain belts. In the Alps valley-fill deposition influenced the magnitude and pattern of rock uplift since ice retreat approximately 17,000 years ago. Conversely, the analyzed valley fills in the Himalaya are much older and reflect environmental conditions that prevailed at ~110 ka and ~2.5 Ma, respectively. Thus, the newly developed method has proven useful for inferring the role of sedimentary valley-fill deposits in landscape evolution on timescales ranging from 1,000 to 10,000,000 years.}, language = {en} } @phdthesis{Wang2011, author = {Wang, Yongbo}, title = {Late glacial to Holocene climate and vegetation changes on the Tibetan Plateau inferred from fossil pollen records in lacustrine sediments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63155}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The past climate in central Asia, and especially on the Tibetan Plateau (TP), is of great importance for an understanding of global climate processes and for predicting the future climate. As a major influence on the climate in this region, the Asian Summer Monsoon (ASM) and its evolutionary history are of vital importance for accurate predictions. However, neither the evolutionary pattern of the summer monsoon nor the driving mechanisms behind it are yet clearly understood. For this research, I first synthesized previously published Late Glacial to Holocene climatic records from monsoonal central Asia in order to extract the general climate signals and the associated summer monsoon intensities. New climate and vegetation sequences were then established using improved quantitative methods, focusing on fossil pollen records recovered from Tibetan lakes and also incorporating new modern datasets. The pollen-vegetation and vegetation-climate relationships on the TP were also evaluated in order to achieve a better understanding of fossil pollen records. The synthesis of previously published moisture-related palaeoclimate records in monsoonal central Asia revealed generally different temporal patterns for the two monsoonal subsystems, i.e. the Indian Summer Monsoon (ISM) and East Asian Summer Monsoon (EASM). The ISM appears to have experienced maximum wet conditions during the early Holocene, while many records from the area affected by the EASM indicate relatively dry conditions at that time, particularly in north-central China where the maximum moisture levels occurred during the middle Holocene. A detailed consideration of possible driving factors affecting the summer monsoon, including summer solar insolation and sea surface temperatures, revealed that the ISM was primarily driven by variations in northern hemisphere solar insolation, and that the EASM may have been constrained by the ISM resulting in asynchronous patterns of evolution for these two subsystems. This hypothesis is further supported by modern monsoon indices estimated using the NCEP/NCAR Reanalysis data from the last 50 years, which indicate a significant negative correlation between the two summer monsoon subsystems. By analogy with the early Holocene, intensification of the ISM during coming decades could lead to increased aridification elsewhere as a result of the asynchronous nature of the monsoon subsystems, as can already be observed in the meteorological data from the last 15 years. A quantitative climate reconstruction using fossil pollen records was achieved through analysis of sediment core recovered from Lake Donggi Cona (in the north-eastern part of the TP) which has been dated back to the Last Glacial Maximum (LGM). A new data-set of modern pollen collected from large lakes in arid to semi-arid regions of central Asia is also presented herein. The concept of "pollen source area" was introduced to modern climate calibration based on pollen from large lakes, and was applied to the fossil pollen sequence from Lake Donggi Cona. Extremely dry conditions were found to have dominated the LGM, and a subsequent gradually increasing trend in moisture during the Late Glacial period was terminated by an abrupt reversion to a dry phase that lasted for about 1000 years and coincided with the first Heinrich Event of the northern Atlantic region. Subsequent periods corresponding to the warm B{\o}lling-Aller{\o}d period and the Younger Dryas cold event were followed by moist conditions during the early Holocene, with annual precipitation of up to about 400 mm. A slightly drier trend after 9 cal ka BP was then followed by a second wet phase during the middle Holocene that lasted until 4.5 cal ka BP. Relatively steady conditions with only slight fluctuations then dominated the late Holocene, resulting in the present climatic conditions. In order to investigate the relationship between vegetation and climate, temporal variations in the possible driving factors for vegetation change on the northern TP were examined using a high resolution late Holocene pollen record from Lake Kusai. Moving-window Redundancy Analyses (RDAs) were used to evaluate the correlations between pollen assemblages and individual sedimentary proxies. These analyses have revealed frequent fluctuations in the relative abundances of alpine steppe and alpine desert components, and in particular a decrease in the total vegetation cover at around 1500 cal a BP. The climate was found to have had an important influence on vegetation changes when conditions were relatively wet and stable. However, after the 1500 cal a BP threshold in vegetation cover was crossed the vegetation appears to have been affected more by extreme events such as dust storms or fluvial erosion than by the general climatic trends. In addition, pollen spectra over the last 600 years have been revealed by Procrustes analysis to be significantly different from those recovered from older samples, which is attributed to an increased human impact that resulted in unprecedented changes to the composition of the vegetation. Theoretical models that have been developed and widely applied to the European area (i.e. the Extended R-Value (ERV) model and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model) have been applied to the high alpine TP ecosystems in order to investigate the pollen-vegetation relationships, as well as for quantitative reconstructions of vegetation abundance. The modern pollen-vegetation relationships for four common pollen species on the TP have been investigated using Poaceae as the reference taxa. The ERV Submodel 2 yielded relatively high PPEs for the steppe and desert taxa (Artemisia Chenopodiaceae), and low PPEs for the Cyperaceae that are characteristic of the alpine Kobresia meadows. The plant abundances on the central and north-eastern TP were quantified by applying these PPEs to four post-Late Glacial fossil pollen sequences. The reconstructed vegetation assemblages for the four pollen sequences always yielded smaller compositional species turnovers than suggested by the pollen spectra, indicating that the strength of the previously-reported vegetation changes may therefore have been overestimated. In summary, the key findings of this thesis are that (a) the two ASM subsystems show asynchronous patterns during both the Holocene and modern time periods, (b) fossil pollen records from large lakes reflect regional signals for which the pollen source areas need to be taken into account, (c) climate is not always the main driver for vegetation change, and (d) previously reported vegetation changes on the TP may have been overestimated because they ignored inter-species variations in pollen productivity.}, language = {en} } @article{LiLiuWangetal.2017, author = {Li, Kai and Liu, Xingqi and Wang, Yongbo and Herzschuh, Ulrike and Ni, Jian and Liao, Mengna and Xiao, Xiayun}, title = {Late Holocene vegetation and climate change on the southeastern Tibetan Plateau: Implications for the Indian Summer Monsoon and links to the Indian Ocean Dipole}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {177}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.10.020}, pages = {235 -- 245}, year = {2017}, abstract = {The Indian Summer Monsoon (ISM) is one of the most important climate systems, whose variability and driving mechanisms are of broad interest for academic and societal communities. Here, we present a well-dated high-resolution pollen analysis from a 4.82-m long sediment core taken from Basomtso, in the southeastern Tibetan Plateau (TP), which depicts the regional climate changes of the past millennium. Our results show that subalpine coniferous forest was dominant around Basomtso from ca. 867 to ca. 750 cal. yr BP, indicating a warm and semi-humid climate. The timberline in the study area significantly decreased from ca. 750 to ca.100 cal. yr BP, and a cold climate, corresponding to the Little Ice Age (LIA) prevailed. Since ca. 100 cal. yr BP, the vegetation type changed to forest-meadow with rising temperatures and moisture. Ordination analysis reveals that the migration of vegetation was dominated by regional temperatures and then by moisture. Further comparisons between the Basomtso pollen record and the regional temperature reconstructions underscore the relevance of the Basomtso record from the southeastern TP for regional and global climatologies. Our pollen based moisture reconstruction demonstrates the strong multicentennial-scale link to ISM variability, providing solid evidence for the increase of monsoonal strengths over the past four centuries. Spectral analysis indicates the potential influence of solar forcing. However, a closer relationship has been observed between multicentennial ISM variations and Indian Ocean sea surface temperature anomalies (SSTs), suggesting that the variations in monsoonal precipitation over the southeastern TP are probably driven by the Indian Ocean Dipole on the multicentennial scale. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ZhangCaoYuanetal.2022, author = {Zhang, Di and Cao, Kai and Yuan, Xiaoping and Wang, Guocan and van der Beek, Peter}, title = {Late Oligocene-early Miocene origin of the First Bend of the Yangtze River explained by thrusting-induced river reorganization}, series = {Geomorphology}, volume = {411}, journal = {Geomorphology}, publisher = {Elsevier Science}, address = {Amsterdam [u.a.]}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2022.108303}, pages = {13}, year = {2022}, abstract = {The origin of the First Bend of the Yangtze River is key to understanding the birth of the modern Yangtze River. Despite considerable efforts, the timing and mechanism of formation of the First Bend remain highly debated. Inverse river-profile modeling of three tributaries (Chongjiang, Lima, and Gudu) of the Jinsha River, integrated with regional tectonic and geomorphic interpretations, allows the onset of incision at the First Bend to be constrained to 28-20 Ma. The spatio-temporal coincidence of initial river incision and activity of Yulong Thrust Belt in southeastern Tibet highlights thrusting to be fundamental in reshaping the pre-existing stream network at the First Bend. These results enable us to reinterpret a change in sedimentary environment from a braided river to a swamp-like lake in the Jianchuan Basin south of the First Bend, recording the destruction of the hypothesized southwards-flowing paleo-Jinsha and Shuiluo Rivers at ~36-35 Ma by magmatism. During the late Oligoceneearly Miocene, the paleo-Shuiluo River was diverted to the north by focused rock uplift due to thrusting along the Yulong Thrust Belt, which also led to exhumation of the Jianchuan Basin. Diversion of the paleo-Shuiluo River can be explained by capture from a downstream river in the footwall of the Yulong Thrust Belt. Subsequent rapid headward erosion, that was caused by thrusting-induced drop of local base level, is recorded by upstream younging ages for the onset of incision and led to the formation of the First Bend. The combination of new ages for the onset of incision at 28-20 Ma at the First Bend and younger ages upstream indicates northwards expansion of the Jinsha River at a rate of 62 +/- 18 mm/yr. Our results suggest that the origin of the First Bend was likely triggered by thrusting at 28-20 Ma, after which the Yangtze River formed.}, language = {en} } @article{WangZhangWuennemannetal.2015, author = {Wang, Rong and Zhang, Yongzhan and W{\"u}nnemann, Bernd and Biskaborn, Boris K. and Yin, He and Xia, Fei and Zhou, Lianfu and Diekmann, Bernhard}, title = {Linkages between Quaternary climate change and sedimentary processes in Hala Lake, northern Tibetan Plateau, China}, series = {Journal of Asian earth sciences}, volume = {107}, journal = {Journal of Asian earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {1367-9120}, doi = {10.1016/j.jseaes.2015.04.008}, pages = {140 -- 150}, year = {2015}, abstract = {Profundal lake sediment cores are often interpreted in line with diverse and detailed sedimentological processes to infer paleoenvironmental conditions. The effects of frozen lake surfaces on terrigenous sediment deposition and how climate changes on the Tibetan Plateau are reflected in these lakes, however, is seldom discussed. A lake sediment core from Hala Lake (590 km(2)), northeastern Tibetan Plateau spanning the time interval from the Last Glacial Maximum to the present was investigated using high-resolution grain-size composition of lacustrine deposits. Seismic analysis along a north-south profile across the lake was used to infer the sedimentary setting within the lake basin. Periods of freezing and melting processes on the lake surface were identified by MODIS (MOD10A1) satellite data. End-member modeling of the grain size distribution allowed the discrimination between lacustrine, eolian and fluvial sediments. The dominant clay sedimentation (slack water type) during the global Last Glacial Maximum (LGM) reflects ice interceptions in long cold periods, in contrast to abundant eolian input during abrupt cold events. Therefore, fluvial and slack water sedimentation processes can indicate changes in the local paleoclimate during periods of the lake being frozen, when eolian input was minor. Inferred warm (i.e., similar to 22.7 and 19.5 cal. ka BP) and cold (i.e., similar to 11-9 and 3-1.5 cal. ka BP) spells have significant environmental impacts, not only in the regional realm, but they are also coherent with global-scale climate events. The eolian input generally follows the trend of the mid-latitude westerly wind dynamics in winter, contributing medium-sized sand to the lake center, deposited within the ice cover during icing and melting phases. Enhanced input was dominant during the Younger Dryas, Heinrich Event 1 and at around 8.2 ka, equivalent to the well-known events of the North Atlantic realm. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{WischnewskiMackayApplebyetal.2011, author = {Wischnewski, Juliane and Mackay, Anson W. and Appleby, Peter G. and Mischke, Steffen and Herzschuh, Ulrike}, title = {Modest diatom responses to regional warming on the southeast Tibetan Plateau during the last two centuries}, series = {Journal of paleolimnolog}, volume = {46}, journal = {Journal of paleolimnolog}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-011-9533-x}, pages = {215 -- 227}, year = {2011}, abstract = {A general mean annual temperature increase accompanied with substantial glacial retreat has been noted on the Tibetan Plateau during the last two centuries but most significantly since the mid 1950s. These climate trends are particularly apparent on the southeastern Tibetan Plateau. However, the Tibetan Plateau (due to its heterogeneous mountain landscape) has very complex and spatially differing temperature and precipitations patterns. As a result, intensive palaeolimnological investigations are necessary to decipher these climatic patterns and to understand ecological responses to recent environmental change. Here we present palaeolimnological results from a (210)Pb/(137)Cs-dated sediment core spanning approximately the last 200 years from a remote high-mountain lake (LC6 Lake, working name) on the southeastern Tibetan Plateau. Sediment profiles of diatoms, organic variables (TOC, C:N) and grain size were investigated. The (210)Pb record suggests a period of rapid sedimentation, which might be linked to major tectonic events in the region ca. 1950. Furthermore, unusually high (210)Pb supply rates over the last 50 years suggest that the lake has possibly been subjected to increasing precipitation rates, sediment focussing and/or increased spring thaw. The majority of diatom taxa encountered in the core are typical of slightly acidic to circumneutral, oligotrophic, electrolyte-poor lakes. Diatom species assemblages were rich, and dominated by Cyclotella sp., Achnanthes sp., Aulacoseira sp. and fragilarioid taxa. Diatom compositional change was minimal over the 200-year period (DCCA = 0.85 SD, p = 0.59); only a slightly more diverse but unstable diatom assemblage was recorded during the past 50 years. The results indicate that large-scale environmental changes recorded in the twentieth century (i.e. increased precipitation and temperatures) are likely having an affect on the LC6 Lake, but so far these impacts are more apparent on the lake geochemistry than on the diatom flora. Local and/or regional peculiarities, such as increasing precipitation and cloud cover, or localized climatic phenomena, such as negative climate feedbacks, might have offset the effects of increasing mean surface temperatures.}, language = {en} } @article{HerzschuhBorkowskiScheweetal.2014, author = {Herzschuh, Ulrike and Borkowski, Janett and Schewe, Jacob and Mischke, Steffen and Tian, Fang}, title = {Moisture-advection feedback supports strong early-to-mid Holocene monsoon climate on the eastern Tibetan Plateau as inferred from a pollen-based reconstruction}, series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, volume = {402}, journal = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2014.02.022}, pages = {44 -- 54}, year = {2014}, abstract = {(Paleo-)climatologists are challenged to identify mechanisms that cause the observed abrupt Holocene monsoon events despite the fact that monsoonal circulation is assumed to be driven by gradual insolation changes. Here we provide proxy and model evidence to show that moisture-advection feedback can lead to a non-linear relationship between sea-surface and continental temperatures and monsoonal precipitation. A pollen record from Lake Ximencuo (Nianbaoyeze Mountains) indicates that vegetation from the eastern margin of the Tibetan Plateau was characterized by alpine deserts and glacial flora after the Last Glacial Maximum (LGM) (21-15.5 cal kyr BP), by alpine meadows during the Late Glacial (15.5-10.4 cal kyr BP) and second half of the Holocene (5.0 cal kyr BP to present) and by mixed forests during the first half of the Holocene (10.4-5.0 cal kyr BP). The application of pollen-based transfer functions yields an abrupt temperature increase at 10.4 cal kyr BP and a decrease at 5.0 cal kyr BP of about 3 degrees C. By applying endmember modeling to grain-size data from the same sediment core we infer that frequent fluvial events (probably originating from high-magnitude precipitation events) were more common in the early and mid Holocene. We assign the inferred exceptional strong monsoonal circulation to the initiation of moisture-advection feedback, a result supported by a simple model that reproduces this feedback pattern over the same time period. (C) 2014 Published by Elsevier B.V.}, language = {en} } @misc{KorzeniowskaKorup2017, author = {Korzeniowska, Karolina and Korup, Oliver}, title = {Object-based detection of lakes prone to seasonal ice cover on the Tibetan Plateau}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1037}, issn = {1866-8372}, doi = {10.25932/publishup-47503}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-475037}, pages = {25}, year = {2017}, abstract = {The Tibetan Plateau, the world's largest orogenic plateau, hosts thousands of lakes that play prominent roles as water resources, environmental archives, and sources of natural hazards such as glacier lake outburst floods. Previous studies have reported that the size of lakes on the Tibetan Plateau has changed rapidly in recent years, possibly because of atmospheric warming. Tracking these changes systematically with remote sensing data is challenging given the different spectral signatures of water, the potential for confusing lakes with glaciers, and difficulties in classifying frozen or partly frozen lakes. Object-based image analysis (OBIA) offers new opportunities for automated classification in this context, and we have explored this method for mapping lakes from LANDSAT images and Shuttle Radar Topography Mission (SRTM) elevation data. We tested our algorithm for most of the Tibetan Plateau, where lakes in tectonic depressions or blocked by glaciers and sediments have different surface colours and seasonal ice cover in images obtained in 1995 and 2015. We combined a modified normalised difference water index (MNDWI) with OBIA and local topographic slope data in order to classify lakes with an area > 10 km(2). Our method derived 323 water bodies, with a total area of 31,258 km(2), or 2.6\% of the study area (in 2015). The same number of lakes had covered only 24,892 km(2) in 1995; lake area has increased by -26\% in the past two decades. The classification had estimated producer's and user's accuracies of 0.98, with a Cohen's kappa and F-score of 0.98, and may thus be a useful approximation for quantifying regional hydrological budgets. We have shown that our method is flexible and transferable to detecting lakes in diverse physical settings on several continents with similar success rates.}, language = {en} } @article{KorzeniowskaKorup2017, author = {Korzeniowska, Karolina and Korup, Oliver}, title = {Object-Based Detection of Lakes Prone to Seasonal Ice Cover on the Tibetan Plateau}, series = {Remote sensing}, volume = {9}, journal = {Remote sensing}, publisher = {MDPI}, address = {Basel}, issn = {2072-4292}, doi = {10.3390/rs9040339}, pages = {23}, year = {2017}, language = {en} } @article{MischkeLaiZhang2014, author = {Mischke, Steffen and Lai, Zhongping and Zhang, Chengjun}, title = {Re-assessment of the paleoclimate implications of the Shell Bar in the Qaidam Basin, China}, series = {Journal of paleolimnolog}, volume = {51}, journal = {Journal of paleolimnolog}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-012-9674-6}, pages = {179 -- 195}, year = {2014}, abstract = {The Shell Bar in the Qaidam Basin, China, is a prominent geological feature composed of millions of densely packed Corbicula shells. Since the mid 1980s, it has been regarded as evidence for existence of a large lake during Marine Isotope Stage (MIS) 3 in the presently hyper-arid Qaidam Basin. Early studies suggested the bivalve shells accumulated at the shore of a large lake, whereas more recent work led to the conclusion that the Shell Bar was formed within a deeper water body. Based on our re-assessment of sediments and fossils from the Shell Bar, investigation of exposed fluvio-lacustrine sections upstream of the Shell Bar and study of nearby modern streams, we infer that the Shell Bar represents a stream deposit. Corbicula is a typical stream-dweller around the world. Preservation of Corbicula shells of different sizes, as well as occurrence of many articulated shells, provide evidence against post-mortem transport and accumulation along a lake shore. Additionally, the SE-NW alignment of the Shell Bar is similar to modern intermittent stream beds in its vicinity and corresponds to the present-day slope towards the basin centre further NW, and furthermore, the predominantly sandy sediments also indicate that the Shell Bar was formed in a stream. Abundant ostracod shells in the Shell Bar sediments originated from stream-dwelling species that are abundant in modern streams in the vicinity of the Shell Bar, or in part from fluvio-lacustrine sediments exposed upstream of the Shell Bar, as a result of erosion and re-deposition. Deflation of alluvial fine-grained sediments in the Shell Bar region and protection of the stream deposits by the large and thick-walled Corbicula shells reversed the former channel relief and yielded the modern exposure, which is a prominent morphological feature. Occurrence of Corbicula shells in the Qaidam Basin indicates climate was apparently warmer than present during the formation of the Shell Bar because Corbicula does not live at similar or higher altitudes in the region today. Because the Shell Bar is no longer considered a deposit formed within a lake, its presence does not indicate paleoclimate conditions wetter than today.}, language = {en} }