TY - JOUR A1 - Herzschuh, Ulrike A1 - Birks, H. John B. A1 - Mischke, Steffen A1 - Zhang, Chengjun A1 - Böhner, Jürgen T1 - A modern pollen-climate calibration set based on lake sediments from the Tibetan Plateau and its application to a Late Quaternary pollen record from the Qilian Mountains N2 - Aim: Fossil pollen spectra from lake sediments on the Tibetan Plateau have been used for qualitative climate reconstruction, but no modern pollen-climate calibration set based on lake sediments is available to infer past climate quantitatively. This study aims to develop such a dataset and apply it to fossil data. Location: The Tibetan Plateau, between 30 and 40 degrees N and 87 and 103 degrees E. Methods: We collected surface sediments from 112 lakes and analysed them palynologically. The lakes span a wide range of mean annual precipitation (P-ann; 31-1022 mm), mean annual temperature (T-ann; -6.5 to 1 degrees C), and mean July temperature (T-July; 2.6-19.7 degrees C). Redundancy analysis showed that the modern pollen spectra are characteristic of their respective vegetation types and local climate. Transfer functions for P-ann, T-ann and T-July were developed with weighted averaging partial least squares. Model performance was assessed by leave-one-out cross-validation. Results: The root mean square errors of prediction (RMSEP) were 104 mm (P-ann), 1.18 degrees C (T-ann) and 1.17 degrees C (T-July). The RMSEPs, when expressed as percentages of the gradient sampled, were 10.6% (P-ann), 15.7% (T-ann) and 11.9% (T-July). These low values indicate the good performance of our models. An application of the models to fossil pollen spectra covering the last c. 50 kyr yielded realistic results for Luanhaizi Lake in the Qilian Mountains on the north-eastern Tibetan Plateau (modern P-ann 480 mm; T-ann-1 degrees C). T-ann and P-ann values similar to present ones were reconstructed for late Marine Isotope Stage 3, with minimum values for the Last Glacial Maximum (c. 300 mm and 2 degrees C below present), and maximum values for the early Holocene (c. 70 mm and 0.5 degrees C greater than present). Main conclusions: The modern pollen-climate calibration set will potentially be useful for quantitative climate reconstructions from lake-sediment pollen spectra from the Tibetan Plateau, an area of considerable climatic and biogeographical importance. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=0305-0270 U6 - https://doi.org/10.1111/j.1365-2699.2009.02245.x SN - 0305-0270 ER - TY - JOUR A1 - Tian, Fang A1 - Herzschuh, Ulrike A1 - Telford, Richard J. A1 - Mischke, Steffen A1 - Van der Meeren, Thijs A1 - Krengel, Michael T1 - A modern pollen-climate calibration set from central-western Mongolia and its application to a late glacial-Holocene record JF - Journal of biogeography N2 - AimFossil pollen spectra from lake sediments in central and western Mongolia have been used to interpret past climatic variations, but hitherto no suitable modern pollen-climate calibration set has been available to infer past climate changes quantitatively. We established such a modern pollen dataset and used it to develop a transfer function model that we applied to a fossil pollen record in order to investigate: (1) whether there was a significant moisture response to the Younger Dryas event in north-western Mongolia; and (2) whether the early Holocene was characterized by dry or wet climatic conditions. LocationCentral and western Mongolia. MethodsWe analysed pollen data from surface sediments from 90 lakes. A transfer function for mean annual precipitation (P-ann) was developed with weighted averaging partial least squares regression (WA-PLS) and applied to a fossil pollen record from Lake Bayan Nuur (49.98 degrees N, 93.95 degrees E, 932m a.s.l.). Statistical approaches were used to investigate the modern pollen-climate relationships and assess model performance and reconstruction output. ResultsRedundancy analysis shows that the modern pollen spectra are characteristic of their respective vegetation types and local climate. Spatial autocorrelation and significance tests of environmental variables show that the WA-PLS model for P-ann is the most valid function for our dataset, and possesses the lowest root mean squared error of prediction. Main conclusionsPrecipitation is the most important predictor of pollen and vegetation distributions in our study area. Our quantitative climate reconstruction indicates a dry Younger Dryas, a relatively dry early Holocene, a wet mid-Holocene and a dry late Holocene. KW - Central-western Mongolia KW - Lake Bayan Nuur KW - modern pollen KW - ordination KW - palaeoclimate reconstruction KW - palaeoecology KW - transfer functions KW - WA-PLS KW - Younger Dryas Y1 - 2014 U6 - https://doi.org/10.1111/jbi.12338 SN - 0305-0270 SN - 1365-2699 VL - 41 IS - 10 SP - 1909 EP - 1922 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Mischke, Steffen A1 - Almogi-Labin, Ahuva A1 - Al-Saqarat, Bety A1 - Rosenfeld, Arik A1 - Elyashiv, Hadar A1 - Boomer, Ian A1 - Stein, Mordechai A1 - Lev, Lilach A1 - Ito, Emi T1 - An expanded ostracod-based conductivity transfer function for climate reconstruction in the Levant JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - We present the first modern calibration dataset linking ostracod assemblage composition to water chemistry, and other site-specific variables, in the hydrologically and geopolitically sensitive southern Levant region. A total of 42 ostracod taxa were recorded from the 178 sampled sites in Israel and Jordan. Ilyocypris spp., Heterocypris salina and Cypridopsis vidua are the most abundant taxa. Species strictly confined to freshwater conditions are Prionocypris zenkeri, Gomphocythere ortali and Prionocypris olivaceus. In contrast, H. sauna, Bradleytriebella lineata and Cyprideis torosa show high frequencies in brackish waters (waters with higher conductivity). Humphcypris subterranea, G. ortali, P. olivaceus and Cypridopsis elongata apparently prefer flowing waters. Specific conductivity optima and tolerance ranges were calculated for the recorded ostracod species and may be used for the palaeoenvironmental assessment of fossil ostracod assemblages. In addition, a transfer-function for quantitative specific conductivity estimation based on 141 samples was established with weighted averaging partial least squares regression (WA-PLS). The resulting coefficient of determination r(2) between observed and predicted conductivity values (0.72) and the root-mean-square error of prediction (RMSEP) in % gradient length (13.1) indicate that conductivity may be reliably estimated from ostracod assemblage data. The transfer function was first applied to last glacial ostracod assemblage data from an archaeological trench in the Sea of Galilee (northern Israel). Relatively large conductivity fluctuations between ca 1 and 7 mS cm(-1) were inferred for the period 24-20 cal ka BP. In addition, four episodes of freshwater influx near the site of the trench were identified from the presence of shells of freshwater and stream-dwelling species intermingled with very abundant shells of Cyprideis torosa. The results of our study allow a better use of Quaternary ostracods from the Levant as palaeoenvironmental indicators of water-body types and past conductivity levels and will contribute to a better understanding of Quaternary environmental and climate change in the Levant. (C) 2014 Elsevier Ltd. All rights reserved. KW - Ostracoda KW - Transfer function KW - Conductivity KW - Salinity KW - Near East KW - Sea of Galilee KW - Ohalo Site Y1 - 2014 U6 - https://doi.org/10.1016/j.quascirev.2014.04.004 SN - 0277-3791 VL - 93 SP - 91 EP - 105 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Heinecke, Liv A1 - Epp, Laura Saskia A1 - Reschke, Maria A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Mischke, Steffen A1 - Plessen, Birgit A1 - Herzschuh, Ulrike T1 - Aquatic macrophyte dynamics in Lake Karakul (Eastern Pamir) over the last 29 cal ka revealed by sedimentary ancient DNA and geochemical analyses of macrofossil remains JF - Journal of paleolimnolog KW - Potamogeton/Stuckenia KW - Arid central Asia KW - Paleo-productivity KW - Submerged vegetation composition KW - Metabarcoding KW - Chara/Characeae Y1 - 2017 U6 - https://doi.org/10.1007/s10933-017-9986-7 SN - 0921-2728 SN - 1573-0417 VL - 58 SP - 403 EP - 417 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Zhang Chengjun, A1 - Fan Rong, A1 - Li Jun, A1 - Mischke, Steffen A1 - Dembele, Blaise A1 - Hu Xiaolan, T1 - Carbon and oxygen isotopic compositions - how lacustrine environmental factors respond in northwestern and northeastern China JF - Acta geologica Sinica : english edition N2 - Surface lake sediments, 28 from Hoh Xil, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine C-13 and O-18 values. Considering the impact factors, conductivity, alkalinity, pH, TOC, C/N and carbonate-content in the sediments, Cl, P, S, and metal element ratios of Mg/Ca, Sr/Ca, Fe/Mn of bulk sediments as environmental variables enable evaluation of their influences on C-13 and O-18 using principal component analysis (PCA) method. The closure and residence time of lakes can influence the correlation between C-13 and O-18. Lake water will change from fresh to brackish with increasing reduction and eutrophication effects. Mg/Ca in the bulk sediment indicates the characteristic of residence time, Sr/Ca and Fe/Mn infer the salinity of lakes. Carbonate formation processes and types can influence the C-13-O-18 correlation. O-18 will be heavier from Mg-calcite and aragonite formed in a high-salinity water body than calcite formed in freshwater conditions. When carbonate content is less than 30%, there is no relationship with either C-13 or O-18, and also none between C-13 and O-18. More than 30%, carbonate content, however, co-varies highly to C-13 and O-18, and there is also a high correlation between C-13 and O-18. Vegetation conditions and primary productivity of lakes can influence the characteristics of C-13 and O-18, and their co-variance. Total organic matter content (TOC) in the sediments is higher with more terrestrial and submerged plants infilling. In northeastern and northwestern China, when organic matter in the lake sediments comes from endogenous floating organisms and algae, the C-13 value is high. C-13 is in the range of -4%o to 0 parts per thousand when organic matter comes mainly from floating organisms (C/N<6); in the range of -4 parts per thousand to 8 parts per thousand when organic matter comes from diatoms (C/N=6 to 8); and -8 parts per thousand to -4 parts per thousand when organic matter comes from aquatic and terrestrial plants (C/N>8). KW - Limnology KW - isotopic analysis KW - carbonates KW - organic matter KW - PCA KW - Tibet KW - Xinjiang KW - Northeastern China Y1 - 2013 U6 - https://doi.org/10.1111/1755-6724.12133 SN - 1000-9515 SN - 1755-6724 VL - 87 IS - 5 SP - 1344 EP - 1354 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Saini, Jeetendra A1 - Guenther, Franziska A1 - Aichner, Bernhard A1 - Mischke, Steffen A1 - Herzschuh, Ulrike A1 - Zhang, Chengjun A1 - Maeusbacher, Roland A1 - Gleixner, Gerd T1 - Climate variability in the past similar to 19,000 yr in NE Tibetan Plateau inferred from biomarker and stable isotope records of Lake Donggi Cona JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - We investigated 4.84-m-long sediment record spanning over the Late Glacial and Holocene from Lake Donggi Cona to be able to reconstruct circulation pattern on the Tibetan Plateau (TP). Presently, Lake Donggi Cona is located at the boundaries of Westerlies and Asian monsoon circulations in the northeastern TP. However, the exact timing and stimulating mechanisms for climatic changes and monsoon shifts in this region are still debated. We used a 19-ka-long stable isotope record of sedimentary n-alkanes to address this discrepancy by providing insights into paleohydrological conditions. The SD of nC(23) is influenced by lake water evaporation; the BD. values of sedimentary nC(29) are mainly controlled by moisture source and temperature changes. Long-chain n-alkanes dominate over the core whereas three mean clusters (i.e. microbial, aquatic and terrestrial) can be inferred. Multi-proxies suggest five major episodes in the history of Lake Donggi Cona. The Lake Donggi Cona record indicates that the Late Glacial(18.4-14.8 cal ka BP) was dominated by low productivity of mainly microbial and aquatic organisms. Relatively low delta D values suggest low temperatures and moist conditions eventually caused by stronger Westerlies, winter monsoon and melt-water influence. Likely, the shift (similar to 17.9 cal ka BP) from microbial to enhanced aquatic input suggests either a change from deep to shallow water lake or a break in local stratification. Between 14.8 and 13.0 cal ka BP, variable climatic conditions prevailed. Although the Westerlies weekend, the increase in temperature enhanced the permafrost and snow melting (displayed by a high sedimentary accumulation rate). Higher delta D values indicate increasingly arid conditions with higher temperatures which eventually lead to high evaporative conditions and lowest lake levels. Low vegetation cover and high erosion rates led to high sediment accumulation resulting in stratification followed by anoxia in the terminal lake. From 13.0 to 9.2 cal ka BP, lowered values of 813 along with high contents of terrestrial organic matter marked the early-Holocene warming indicating a further strengthening of summer precipitation and higher lake levels. A cooling trend was observed in the mid-Holocene between 9.2 and 3.0 cal ka BP accompanied by higher moisture availability (displayed by lowered SD values) caused by reduced evaporative conditions due to a drop in temperature and recovering Westerlies. After 3.0 cal ka BP, a decrease in lake productivity and cold and semi-arid conditions prevailed suggesting lower lake levels and reduced moisture from recycled air masses and Westerlies. We propose that the summer monsoon was the predominant moisture source during the Belling-Allered warm complex and early -Holocene followed by Westerlies in mid-to-late Holocene period. Stable carbon isotope values-32%o indicate the absence of C-4 -type vegetation in the region contradicting with their presence in the Lake Qinghai record. The 81) record from lake Donggi Cona highlights the importance of the interplay between Westerlies and summer monsoon circulation at this location, which is highly dynamic in northeastern plateau compared to the North Atlantic circulation and insolation changes. Consequently lake Donggi Cona might be an important anchor point for environmental reconstructions on the Tibetan Plateau. (C) 2017 The Authors. Published by Elsevier Ltd. KW - n-alkanes KW - Hydrogen isotopes (delta D) KW - Carbon isotopes (delta C-13) KW - Carbon preference index (CPI) KW - Westerlies KW - Continental air masses KW - Precipitation KW - Late Glacial and Holocene Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2016.12.023 SN - 0277-3791 VL - 157 SP - 129 EP - 140 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Heinecke, Liv A1 - Mischke, Steffen A1 - Adler, Karsten A1 - Barth, Anja A1 - Biskaborn, Boris A1 - Plessen, Birgit A1 - Nitze, Ingmar A1 - Kuhn, Gerhard A1 - Rajabov, Ilhomjon A1 - Herzschuh, Ulrike T1 - Climatic and limnological changes at Lake Karakul (Tajikistan) during the last similar to 29 cal ka JF - Journal of paleolimnolog N2 - We present results of analyses on a sediment core from Lake Karakul, located in the eastern Pamir Mountains, Tajikistan. The core spans the last similar to 29 cal ka. We investigated and assessed processes internal and external to the lake to infer changes in past moisture availability. Among the variables used to infer lake-external processes, high values of grain-size end-member (EM) 3 (wide grain-size distribution that reflects fluvial input) and high Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes), are indicative of moister conditions. High values in EM1, EM2 (peaks of small grain sizes that reflect long-distance dust transport or fine, glacially derived clastic input) and TiO2 (terrigenous input) are thought to reflect greater influence of dry air masses, most likely of Westerly origin. High input of dust from distant sources, beginning before the Last Glacial Maximum (LGM) and continuing to the late glacial, reflects the influence of dry Westerlies, whereas peaks in fluvial input suggest increased moisture availability. The early to early-middle Holocene is characterised by coarse mean grain sizes, indicating constant, high fluvial input and moister conditions in the region. A steady increase in terrigenous dust and a decrease in fluvial input from 6.6 cal ka BP onwards points to the Westerlies as the predominant atmospheric circulation through to present, and marks a return to drier and even arid conditions in the area. Proxies for productivity (TOC, TOC/TN, TOCBr), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC, delta(18) OCarb) indicate changes within the lake. Low productivity characterised the lake from the late Pleistocene until 6.6 cal ka BP, and increased rapidly afterwards. Lake level remained low until the LGM, but water depth increased to a maximum during the late glacial and remained high into the early Holocene. Subsequently, the water level decreased to its present stage. Today the lake system is mainly climatically controlled, but the depositional regime is also driven by internal limnogeological processes. KW - Arid Central Asia KW - Pamir Mountains KW - Lake sediments KW - XRF data KW - Grain-size end-member modelling KW - Geochemistry Y1 - 2017 U6 - https://doi.org/10.1007/s10933-017-9980-0 SN - 0921-2728 SN - 1573-0417 VL - 58 SP - 317 EP - 334 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Mischke, Steffen A1 - Zhang, Chengjun A1 - Fan, Rong T1 - Early to mid-Holocene lake high-stand sediments at Lake Donggi Cona, northeastern Tibetan Plateau, China - T2 - Quaternary research : an interdisciplinary journal KW - Microfossils KW - Ostracoda KW - Lake level KW - Wetlands KW - Depositional setting KW - Tibetan Plateau KW - Holocene Y1 - 2015 U6 - https://doi.org/10.1016/j.yqres.2014.06.005 SN - 0033-5894 SN - 1096-0287 VL - 83 IS - 1 SP - 256 EP - 258 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Aichner, Bernhard A1 - Herzschuh, Ulrike A1 - Wilkes, Heinz A1 - Schulz, Hans-Martin A1 - Wang, Yongbo A1 - Plessen, Birgit A1 - Mischke, Steffen A1 - Diekmann, Bernhard A1 - Zhang, Chengjun T1 - Ecological development of Lake Donggi Cona, north-eastern Tibetan Plateau, since the late glacial on basis of organic geochemical proxies and non-pollen palynomorphs JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Organic geochemical proxy data from surface sediment samples and a sediment core from Lake Donggi Cona were used to infer environmental changes on the northeastern Tibetan Plateau spanning the last 18.4 kyr. Long-chain n-alkanes dominate the aliphatic hydrocarbon fraction of the sediment extract from most surface sediment samples and the sediment core. Unsaturated mid-chain n-alkanes (nC(23:1) and nC(25:1)) have high abundances in some samples, especially in core samples from the late glacial and early Holocene. TOC contents, organic biomarker and non-pollen-palynomorph concentrations and results from organic petrologic analysis on selected samples suggest three major episodes in the history of Lake Donggi Cona. Before ca. 12.6 cal ka BP samples contain low amounts of organic matter due to cold and arid conditions during the late glacial. After 12.6 cal ka BP, relatively high contents of TOC and concentrations of Botryococcus fossils, as well as enhanced concentrations of mid-chain n-alkanes and n-alkenes suggest a higher primary and macrophyte productivity than at present This is supported by high contents of palynomorphs derived from higher plants and algae and was possibly triggered by a decrease of salinity and amelioration of climate during the early Holocene. Since 6.8 cal ka BP Lake Donggi Cona has been an oligotrophic freshwater lake. Proxy data suggest that variations in insolation drive ecological changes in the lake, with increased aquatic productivity during the early Holocene summer insolation maximum. Short-term drops of TOC contents or biomarker concentrations (at 9.9 cal ka BP, after 8.0 and between 3.5 and 1.7 cal ka BP) can possibly be related to relatively cool and dry episodes reported from other sites on the north-eastern Tibetan Plateau, which are hypothesized to occur in phase with Northern Hemisphere cooling events. KW - Biomarker KW - Holocene KW - n-alkanes KW - Total organic carbon KW - Organic matter KW - Macerals KW - Aquatic macrophytes Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2011.10.015 SN - 0031-0182 VL - 313 IS - 2 SP - 140 EP - 149 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wang, Yongbo A1 - Liu, Xingqi A1 - Mischke, Steffen A1 - Herzschuh, Ulrike T1 - Environmental constraints on lake sediment mineral compositions from the Tibetan Plateau and implications for paleoenvironment reconstruction JF - Journal of paleolimnolog N2 - 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. KW - Mineral composition KW - XRD KW - Multivariate regression trees KW - Electrical conductivity KW - Paleolimnology KW - Tibetan Plateau Y1 - 2012 U6 - https://doi.org/10.1007/s10933-011-9549-2 SN - 0921-2728 VL - 47 IS - 1 SP - 71 EP - 85 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Tian, Fang A1 - Herzschuh, Ulrike A1 - Dallmeyer, Anne A1 - Xu, Qinghai A1 - Mischke, Steffen A1 - Biskaborn, Boris T1 - Environmental variability in the monsoon-westerlies transition zone during the last 1200 years - lake sediment analyses from central Mongolia and supra-regional synthesis JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - A high resolution multi proxy (pollen, grain size, total organic carbon) record from a small mountain lake (Lake Khuisiin; 46.6 degrees N, 101.8 degrees E; 2270 m a.s.l.) in the south eastern Khangai Mountains of central Mongolia has been used to explore changes in vegetation and climate over the last 1200 years. The pollen data indicates that the vegetation changed from dry steppe dominated by Poaceae and Artemisia (ca AD 760-950), to Larix forest steppe (ca AD 950-1170), Larix Betula forest steppe (ca AD 1170-1380), meadow dominated by Cyperaceae and Poaceae (ca AD 1380-1830), and Larix Betula forest steppe (after similar to AD 1830). The cold-wet period between AD 1380 and 1830 may relate to the Little Ice Age. Environmental changes were generally subtle and climate change seems to have been the major driver of variations in vegetation until at least the early part of the 20th century, suggesting that either the level of human activity was generally low, or the relationship between human activity and vegetation did not alter substantially between AD 760 and 1830. A review of centennial scale moisture records from China and Mongolia revealed that most areas experienced major changes at ca AD 1500 and AD 1900. However, the moisture availability since AD 1500 varied between sites, with no clear regional pattern or relationship to present day conditions. Both the reconstructions and the moisture levels simulation on a millennium scale performed in the MPI Earth System Model indicate that the monsoon-westerlies transition area shows a greater climate variability than those areas influenced by the westerlies, or by the summer monsoon only. KW - Pollen KW - Grain size KW - TOC KW - Asian monsoon KW - Westerlies KW - Late Holocene KW - Vegetation change KW - Mongolia Y1 - 2013 U6 - https://doi.org/10.1016/j.quascirev.2013.05.005 SN - 0277-3791 VL - 73 IS - 2 SP - 31 EP - 47 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Proborukmi, Maria Sekar A1 - Urban, Brigitte A1 - Mischke, Steffen A1 - Mienis, Henk K. A1 - Melamed, Yoel A1 - Dupont-Nivet, Guillaume A1 - Jourdan, Fred A1 - Goren-Inbar, Naama T1 - Evidence for climatic changes around the Matuyama-Brunhes Boundary (MBB) inferred from a multi-proxy palaeoenvironmental study of the GBY#2 core, Jordan River Valley, Israel JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - The Acheulian site of Gesher Benot Ya‘aqov (GBY) in the Upper Jordan Valley revealed important data on environment and material culture, as well as evidence for hominin behavioural and cognitive patterns documented at the margins of the Hula Palaeo-lake. A 50 m long core (GBY#2) drilled at the archaeological site has provided a long Pleistocene geological, environmental and climatological record, which expands the existing knowledge of hominin-habitat relationships. Bracketed by two basalt flows dated by 40Ar/39Ar and based on the identification of the Matuyama-Brunhes Boundary (MBB) and correlation with the GBY excavation site, the sedimentary sequence provides the climatic history around the MBB. Multi-proxy data including pollen and non-pollen palynomorphs, macro-botanical remains, molluscs and ostracods provide evidence for lake and lake-margin environments during Marine Isotope Stages (MIS) 20 and 19. Semi-moist conditions were followed by a pronounced dry phase during MIS 20, and warm and moist conditions with Quercus-Pistacia woodlands prevailed during MIS 19. In contrast to the reconstructed climate change from relatively dry to moister conditions, the depositional environment developed from an open-water lake during MIS 20 to a lake margin environment in MIS 19. Generally shallower conditions at the core site in MIS 19 resulted from the progradation of the lake shore due to the filling of the basin. Micro-charcoal analysis suggests a likelihood of human-induced fire in some parts of the core, which can be correlated with artefact-containing layers of the GBY excavation site. The Hula Palaeo-lake region provided an ideal niche for hominins and other vertebrates during global glacial-interglacial climate fluctuations at the end of the Early Pleistocene. KW - Hula Basin KW - Levant KW - Hominins KW - Pollen record KW - Plant macro-remains Y1 - 2017 U6 - https://doi.org/10.1016/j.palaeo.2017.10.007 SN - 0031-0182 SN - 1872-616X VL - 489 SP - 166 EP - 185 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kalbe, Johannes A1 - Sharon, Gonen A1 - Porat, Naomi A1 - Zhang, Chengjun A1 - Mischke, Steffen T1 - Geological setting and age of the Middle Paleolithic site of Nahal Mahanayeem Outlet (Upper Jordan Valley, Israel) JF - Quaternary international : the journal of the International Union for Quaternary Research N2 - In this paper we present the sedimentary features and the luminescence chronology for Nahal Mahanayeem Outlet (NMO), an archaeological open air site at the southern margin of the Hula Basin (Northern Jordan Rift Valley, Israel). The site is characterized by a lithic assemblage ascribed primarily to the Middle Paleolithic Mousterian tradition, and by an excellent preservation of floral and faunal remains. Six geological units forming the stratigraphic sequence of the site were distinguished: (Unit 6) archaeologically sterile, light-colored limnic carbonates; (Unit 5) conglomerates of rounded basalt boulders and cobbles forming a hill-like topography; (Unit 4 and Unit 3) a sequence of similar dark silty sediments, attached to and overlaying the conglomerates, containing the archaeological horizons of the site; (Unit 2) a number of channels cutting into the top of Unit 3, filled with coarse sand and rounded basalt and limestone gravels of fluvial origin; and (Unit 1) a thin sand layer laid down by the present-day Jordan River covering another unconformity as a result of heavy machinery drainage operations in 1999. The OSL age for Unit 6 yielded a minimum age older than 460 ka. Sedimentary features and the embedded fossils suggest that Unit 1 can be linked to the Early Pleistocene Gadot Chalk. Unit 5 represents a local geological feature and could be an indicator for a period of increased erosion with formation of coarse grained sediments. The archaeological horizons form the lower parts of Unit 4 and yielded OSL-ages between 55 and 65 ka, indicating an affiliation to the sediments called "Ashmura Formation" with an Upper Pleistocene age for the site. The channel fills of Unit 2 can be dated by the recovered artifacts. These range in age from the Upper Paleolithic (Aurignacian) to historic times. Unit 1 is recent. The study of the complex NMO stratigraphy, combined with coherent OSL chronology, has enabled us to reconstruct parts of the geological history of the Hula Basin during the Late Pleistocene. It is this history that forms the background for the human migration and utilization of natural resources in the Upper Jordan Rift Valley. (C) 2013 Elsevier Ltd and INQUA. All rights reserved. Y1 - 2014 U6 - https://doi.org/10.1016/j.quaint.2013.05.052 SN - 1040-6182 SN - 1873-4553 VL - 331 SP - 139 EP - 148 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zhang, Chengjun A1 - Zhang, Wanyi A1 - Feng, Zhaodong A1 - Mischke, Steffen A1 - Gao, Xiang A1 - Gao, Dou A1 - Sun, Feifei T1 - Holocene hydrological and climatic change on the northern Mongolian Plateau based on multi-proxy records from Lake Gun Nuur JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - A multi-proxy study including analyses of delta C-13(org) for the lake sediment core GN-02 and grain size, TOC. CaCO3 content, delta C-13(carb) and delta O-18(carb) of bulk carbonate, and the mineralogy of the parallel core GN-04 from Gun Nuur was performed to reconstruct the Holocene hydrology and climate on the northern Mongolian Plateau. The chronology was established using 40 C-14 dates of bulk organic matter in addition to nine previously published radiocarbon dates for core GN-02, and further five C-14 dates for the new core GN-04. A lake reservoir effect of 1060 C-14 years was determined as the intercept of the high-resolution GN-02 age-depth model at the modern sediment surface. The size of the reservoir effect is supported by the age of the core-top sample (1200 +/- 40 C-14 years) and the determined difference between a wood-derived radiocarbon age from the GN-02 core base and the age-model inferred age for bulk organic matter at the same stratigraphic level (1000 C-14 years). Low lake level and prevailing aeolian sediment deposition at Gun Nuur under dry conditions were recorded during the earliest Holocene (> 10,800-10,300 cal a BP). Gun Nuur expanded under significantly wetter conditions between 10,300 and 7000 cal a BP. Unstable climate conditions existed in the mid Holocene (7000-2500 cal a BP) and three periods of low lake-levels and significantly drier conditions were recorded between 7000-5700, 4100-3600 and 3000-2500 cal a BP. Intermediate lake levels were inferred for the intervening periods. Around 2500 cal a BP, the climate change and wetter conditions were established again. As a consequence, the lake level of Gun Nuur rose again due to higher effective moisture and the relatively wet present conditions were achieved ca. 1600 cal a BP. Our results suggest that the initial Holocene climate change on the northern Mongolian Plateau was not accompanied by a rapid increase in precipitation as on the Tibetan Plateau. The establishment of wetter conditions in northern Mongolia lagged behind the early Holocene moisture increase on the Tibetan Plateau by ca. 1000 years. Subsiding dry air in the north of the Tibetan Plateau resulted from the strengthened summer monsoon on the Tibetan Plateau during the period of maximum summer insolation and probably inhibited a significant precipitation increase in Mongolia. The significant moisture increase in the Gun Nuur region at ca. 10.3 cal ka BP is probably not related to the northward shift of the present summer monsoon boundary or the moisture delivery from the northern Atlantic through the westerlies. Instead, water from melting snow, ice and frozen ground and the generation of precipitation from the local recycling of moisture are discussed as possible moisture source for the early onset of wetter conditions on the Mongolian Plateau. KW - Multi-proxy record KW - Sediment geochemistry KW - Mineralogy KW - Paleohydrology KW - Holocene KW - Mongolia Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.01.032 SN - 0031-0182 VL - 323 IS - 6 SP - 75 EP - 86 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Opitz, Stephan A1 - Ramisch, Arne A1 - Mischke, Steffen A1 - Diekmann, Bernhard T1 - Holocene lake stages and thermokarst dynamics in a discontinuous permafrost affected region, north-eastern Tibetan Plateau JF - Journal of Asian earth sciences N2 - Sediments of a thermokarst system on the north-eastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment related to climatic changes since the early Holocene. The thermokarst pond with a length of 360 m is situated in a 14.5 x 6 km tectonically unaffected intermontane basin, which is underlain by discontinuous permafrost. A lake sediment core and bankside lacustrine onshore deposits were analysed. Additionally, fossil lake sediments were investigated, which document a former lake-level high stand. The sediments are mainly composed of marls with variable amounts of silt carbonate micrite, and organic matter. On the basis of sedimentological (grain size data), geochemical (XRF), mineralogical (XRD) and micropaleontological data (ostracods and chironomide assemblages) a reconstruction of a paleolake environment was achieved. Lacustrine sediments with endogenic carbonate precipitation suggest a lacustrine environment since at least 19.0 cal ka BP. However, because of relocation and reworking processes in the lake, the sediments did not provide distinct information about the ultimate formation of the lake. The high amount of endogenic carbonate suggests prolonged still-water conditions at about 9.3 cal ka BP. Ostracod shells and chironomid head capsules in fossil lake sediments indicate at least one former lake-level high stand, which were developed between the early and middle Holocene. From the late Holocene the area was possibly characterized by a lake-level decline, documented by a hiatus between lacustrine sediments and a reworked loess or loess-like horizon. After the lake-level decline and the following warming period, the area was affected by thermally-induced subsidence and a re-flooding of the basin because of thawing permafrost. KW - Palaeoenvironmental reconstruction KW - Palaeolimnology KW - Lake level KW - XRD Y1 - 2013 U6 - https://doi.org/10.1016/j.jseaes.2013.08.006 SN - 1367-9120 SN - 1878-5786 VL - 76 IS - 17 SP - 85 EP - 94 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Aichner, Bernhard A1 - Makhmudov, Zafar A1 - Rajabov, Iljomjon A1 - Zhang, Qiong A1 - Pausata, Francesco Salvatore R. A1 - Werner, Martin A1 - Heinecke, Liv A1 - Kuessner, Marie L. A1 - Feakins, Sarah J. A1 - Sachse, Dirk A1 - Mischke, Steffen T1 - Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period JF - Geophysical research letters N2 - The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant. KW - climate KW - biomarker KW - geochemistry KW - modelling KW - paleoclimate KW - hydrology Y1 - 2019 U6 - https://doi.org/10.1029/2019GL085202 SN - 0094-8276 SN - 1944-8007 VL - 46 IS - 23 SP - 13972 EP - 13983 PB - American Geophysical Union CY - Washington ER - TY - INPR A1 - Mischke, Steffen A1 - Chen, Fahu T1 - Introduction to "Late Pleistocene and Holocene climate change in continental Asia" T2 - Journal of paleolimnolog Y1 - 2014 U6 - https://doi.org/10.1007/s10933-013-9750-6 SN - 0921-2728 SN - 1573-0417 VL - 51 IS - 2 SP - 157 EP - 159 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Mischke, Steffen A1 - Meyer, Hanno A1 - Plessen, Birgit A1 - Zhang, Chengjun T1 - Lake nutrient variability inferred from elemental (C, N, S) and isotopic (delta C-13, delta N-15) analyses of aquatic plant macrofossils N2 - This paper aims to highlight the potential of using elemental and stable isotope analyses of aquatic macrophytes in palaeolimnological studies. Potamogeton pectinatus material was collected from modem plants (n=68) and from late glacial and Holocene-aged sediments from Koucha Lake (northeastern Tibetan Plateau; 34.0 degrees N; 97.2 degrees E; 4540 m a.s.l.). It was analyzed for delta C-13(Potamogeton) (modern: -23 to 0 parts per thousand, fossil: -19 to -4 parts per thousand) and delta N-15(Potamogeton) (modern: -11.0 to +13.8 parts per thousand, fossil: -9.5 to +6.7 parts per thousand) in addition to elemental carbon and nitrogen (modem C/N-Potamogeton: 7 to 29; fossil: 13 to 68) and sulfur (fossil: 188-899 mu mol/g dry weight). Fossil data were interpreted in terms of palaeo-nutrient availability and palaeo-productivity based on the modem relationships between various proxies and certain environmental data. Productivity of Potamogeton pectinatus mats at Koucha Lake as indicated by palaeo-epsilon(Potamogeton-TIC) (i.e. the enrichment of delta C-13(Potamogeton) relative to the delta(CTIC)-C-13) was reduced during periods of high conductivity, especially between 10.3 and 7.4 cal kyr BP. Potamogeton pectinatus material from these periods was also characterized by high S-Potamogeton indicating high sulfide concentrations and anoxic conditions within the sediments. However, C/N- Potamogeton ratios and delta N-15(Potamogeton) from the lower core section were found to have been altered by decompositional processes. A pronounced shift in the aquatic productivity of Lake Koucha occurred at similar to 7.4 cal kyr BP when the hydrological conditions shifted towards an open lake system and water depth increased. At this time a strong increase in productivity led to a strong decrease in the water HCO3- concentration as inferred from the application of a epsilon-(Potamogeton-TIC)-InHCO3- transfer function. A comparison of reconstructed productivity changes from Koucha Lake with further environmental proxies suggests that primary productivity changes are probably a function of internal lake dynamics and were only indirectly triggered by climate change. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/02773791 U6 - https://doi.org/10.1016/j.quascirev.2010.05.011 SN - 0277-3791 ER - TY - JOUR A1 - Opitz, Stephan A1 - Wünnemann, Bernd A1 - Aichner, Bernhard A1 - Dietze, Elisabeth A1 - Hartmann, Kai A1 - Herzschuh, Ulrike A1 - IJmker, Janneke A1 - Lehmkuhl, Frank A1 - Li, Shijie A1 - Mischke, Steffen A1 - Plotzki, Anna A1 - Stauch, Georg A1 - Diekmann, Bernhard T1 - Late Glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19 kyr. The lake today fills a 30x8 km big and 95 m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatio-temporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system. The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39 m below the present level and started to rise after 19 ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13 cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3 cal ka BP, grain-size fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2 m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early to mid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3 cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base. KW - China KW - Monsoon KW - Paleolimnology KW - Multi-site study KW - Aragonite KW - XRF KW - XRD KW - Sedimentology Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.04.013 SN - 0031-0182 VL - 337 IS - 23 SP - 159 EP - 176 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wischnewski, Juliane A1 - Mackay, Anson W. A1 - Appleby, Peter G. A1 - Mischke, Steffen A1 - Herzschuh, Ulrike T1 - Modest diatom responses to regional warming on the southeast Tibetan Plateau during the last two centuries JF - Journal of paleolimnolog N2 - 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. KW - Diatoms KW - Tibetan Plateau KW - Mountain lake KW - Climate change KW - Lake sediments KW - Palaeolimnology Y1 - 2011 U6 - https://doi.org/10.1007/s10933-011-9533-x SN - 0921-2728 VL - 46 IS - 2 SP - 215 EP - 227 PB - Springer CY - Dordrecht ER -