| Qaidam Basin which is situated at the northeastern Tibetan Plateau, is in the central part of the arid central Asia, and the arid central Asia is the biggest non-zonal arid area in temperate zone on earth. Basin is the conjunction area among the Westerly jet, Southeastern Asia Monsoon and Southwestern Asia Monsoon that influence the climate of China. It has not only a fragile eco-environmental system with a changeable climate, but also is sensitive to the regional and the human.The later phase of Marine Oxygen Isotope Stage 3 (MIS3a) is a very especially time. The arid on west of China is one of the most sensitive area that strongly response to human induced global warming. So, the study on the climate change history in the arid-cold of the northeastern Tibetan Plateau is of great theoretical and applied importance.For these reasons, this thesis based on the analyses on TOC, CaCO3,δ18O,δ13C,δ13Corg of the Shell Bar sediments in the Qaidam Basin, and compared with grain size and chronology establishment. The climate-environmental change history is discussed between 39.7 and 17.5 ka BP.The environmental change of the studied section can be divided into five stages. From 39.7 to 35.5 ka BP is the period of high paleolake level development. From 35.5 to 33.3 ka BP and 33.3 to 27.1 ka BP, TOC and CaCO3 contents,δ18O value are high, whileδ13Corg value and median size content are low, reflects that the temperature and the lake level are high. About 27.1～22.2 ka BP and 22.2～17.5 ka BP, both temperature and the lake level are lower than previous stages (but the climate was still warmer and humid than that of today). The lake level decreased between 32.3 and 32.1 ka BP, 30.3 and 29.7 ka BP, 28.3 and 27.1 ka BP. Generally speaking, the climate was warm and humid in Qaidam Basin and the high lake level sustained between 39.7 and 17.5 ka BP. The lake retreated abruptly at 17.5 ka BP, with a very strong increase of evaporation which resulted in the salt formation and retreat of the high lake level.As a whole, it presented that climate was warm and humid. Expecially below of section, the temperature and humidity are higher than that of today, resulted in high lake levels in the section.Based on the regional correlations between elevated high Qaidam Basin and lower Tengger desert, it show a similar evolution patter because in both areas the palaolake level started to increase and lake areas started to advance. The climate reconstructed in both areas show that it was warm and humid between 35 and 21ka BP, with a substantial increase of the temperature and precipitation, especially precipitation, and resulted in high lake levels in both areas. The study results from the separated geological evidences prove that palaolake in such different areas not only posses a similar evolution pattern but also started synchronously, imply the climate change resulted from the regional changes which links to global changes, providing new data for understanding the mechanisms of the climate change.
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