Palaeoenvironmental Reconstruction of Zoige Basin of Eastern Tibetan Plateau During the Past 140 ka

Abstract

The Tibetan Plateau plays a major role on modern atmospheric circulation of Northern Hemi- sphere, especially with respect to the Tropical Easterly Jet and monsoon circulation. Understanding the past climate in the plateau, especially during the late Pleistocene when the Tibetan Plateau uplifting accelerated, will be very important. A 310m core(RM) (33°57′N, 102°21′E) collected from the central part of Zoige Basin, east Tibetan Plateau was analyzed. The upper 31m provide a continuous palaeoclimate information in the past 140ka, which is reconstructed on the basis of stable isotope analyses (δ~(18) O and δ~(13) C of authigenic carbonate), content of carbonate, organic matter and pollen, etc. The results reveal significant changes of palaeoenvironmental condition, induced by climate changes and/or local hydrological factors. Five stages are identified. Stage 5 (140 - 82kaBP) equivalent to Last Interglaciation was warm and wet. The primary productivity was high due to the optimum associaton of heat and moisture. 5 substages (5a - 5e) can be divided, moreover, 5c can be further divided into 5 subordinate substages (5e_1 - 5e_5 ). In the record, 5e is the warmest substage among them, while 5a is the optimum, and 5c is a weakly warm period. A series of cooling events have been recorded since stage 4 (82 - 10kaBP). i. e. 66, 51. 5, 33, 28, 21 kaBP, equivalent to H6, HS, H4, H3, H2 event reported in deep-sea sediment. Comparison study has been done for the RM core record with the other records adjacent and in the world. The result also shows that the stage 3 was a conspicious period, when the climate was very optimum. The basin was cut off by the Yellow River ca 30kaBP, correspondingly the lacustrine deposits were replaced by fluvial and swamp deposits.