Ostracod-based reconstruction of Late Quaternary lake level changes within the Tangra Yumco lake system (southern Tibetan Plateau): OSTRACOD-BASED LAKE LEVEL RECONSTRUCTION OF THE TANGRA YUMCO SYSTEM

Tangra Yumco, a large saline lake located in the central-southern part of the Tibetan Plateau, lies in a hydrologically closed basin and is part of a cascade lake system including Tangqung Co, Tangra Yumco and Xuru Co. The extension and position of this lake system makes it valuable for reconstructing palaeoclimatic variations through the lake history and to compare both with the adjacent lake systems. We reconstructed Late Quaternary lake level changes based on data from two lacustrine sediment cores. A micropalaeontological analysis focusing on Ostracoda was carried out combined with dating (C-14, Pb-210, Cs-137), sedimentology and stable isotope data from bulk sediment. Ostracod analysis involves the quantitative documentation of associations. An ostracod-based transfer function for specific conductivity was applied to assess and refine lake level changes and to compare the results with other lake level reconstructions from the Tibetan Plateau for evaluating inter-regional climatic patterns. Seven ostracod species were detected, with Leucocytherella sinensis dominating the associations followed by Leucocythere? dorsotuberosa, Limnocythere inopinata and Tonnacypris gyirongensis. Fabaeformiscandona gyirongensis, Candona candida and Candona xizangensis were found in only a few samples and at low percentages. The synthesis of ostracod-based environmental reconstruction and chronology for samples from Tangra Yumco reveals the evolution of the lake system during the past 17ka. A low lake level around 17calkaBP is followed by a recovering until the reaching of a high stand around 8-9calkaBP. Subsequently, between 7.7 and 2.5calkaBP, it remained relatively stable with a subsequent short-living lowstand-highstand cycle at around 2ka. Thereafter, the ostracod-based conductivity transfer function shows an increase of conductivity corresponding to a lake level rising phase at around 0.4ka. The recorded changes are indicators of past climatic conditions and refine the palaeoclimatic models in this area. Copyright (C) 2018 John Wiley & Sons, Ltd.