Elemental Geochemistry Of Carbonate Cement From Core TS95 And Environmental Evolution Of Lake Tianshuihai Since 135ka B.P.

Sediment deposited since 135 ka BP in paleo-lake of Tianshuihai in West Kunlun Mountains, Western Qinghai-Tibet Plateau, contains much of carbonate. Samples of the latest 135 ka from Core TS95, which was recovered at modern Tianshuihai lake in 1995, are leached using IN HC1 and leachant are analyzed using ICP-AES. It is found that concentration of elements in leachant such as Mn, Na, K, Ba, Zn and ratios of Sr/Ca, Mg/Ca vary coherently with other climatic and environmental proxies from Core TS95, deep-sea sediment and loess-paleosol series, suggesting that sedimentation of these elements and ratios in cement of Core TS95 are controlled by global climatic and environmental variations. Paleo-salinity and lacustrine evolution of paleo-lake of Tianshuihai for the latest 135 ka is reconstructed based mainly on ratios of Sr/Ca, Mg/Ca, and elements of Na and K. In general, Paleo-salinity of Lake Tianshuihai rose up during glacial period and fell down during inter-glacial period, while paleo-temperature of water of Lake Tianshuihai was relatively higher during inter-glacial period and relatively lower during glacial period, suggesting that hydrology of paleo-lake of Tianshuihai for the latest 135 ka was probably controlled mainly by melting water during summer. During inter-glacial period, relatively higher temperature resulted in more melting water and paleo-lake of Tianshuihai extended, while on the contrary, relatively lower temperature resulted in less melting water and paleo-lake of Tianshuihai shrank during glacial period. In addition, there was a noticeable overall increasing trend for the salinity evolution of paleo-lake of Tianshuihai since 135 ka BP, indicating persistent and increasing aridity in West Kunlun Mountains during Late Pleistocene. This trend resulted probably from uplift of Qinghai-Tibet Plateau since Late Pleistocene. At about 58 ka BP, the transition from marine oxygen isotope stage 4 to 3, a hydrological event was suggested for paleo-lake of Tianshuihai, which showed remarkable changes for many proxies before and after this transition. It is not clear whether this hydrological event relates only to global climatic and environmental transition, or to tectonic uplift of Qinghai-Tibet Plateau at about 50-60 ka BP, or to some other factors. Paleo-lake of Tianshuihai disintegrated at about 20 ka BP, which was a consequence of extensive shrink of paleo-lake of Tianshuihai during Last Glacial Maximum.