Study On Middle-Late Pleistocene Palaeogeography Of Dali Nor Palaeolake In The Southeastern Mongolia Plateau,China

Based on field measurement on 8 typical sedimentary sections in Dali Nor area,and chronostratigraphic framework created by OSL and ESR,this paper discussed the formation and evolution of palaeo-Lake.And by using analysis on the environmental proxies,middle-late Pleistocene lake evolution and paleoclimate changes were recovered.The study shows that:(1)According to detailed geomorphology and sedimentology research of eight sections in field,this dissertation found more evidence for the existence of the palaeo-lake.(2)According to the lithofacies,granulometry,geochemistry analyses and chronology of section JP1,the palaeoclimatic evolution in Dali Nor since 210 ka was recovered.The evolution was divided into four stages,i.e.,?:210?149 ka,?:149?72 ka,?:72?60ka,?:60?26 ka,and experienced hot-dry,warn-wet,cold-dry and warn-wet climate orderly.(3)The lithofacies and granulometry of 8 lacustrine sections in Dali Nor area uncovered the evolutionary precess of palaeolake.The palaeolake formed high water level in MIS5,shrunk in MIS4 and recovered in MIS3.Also in the MIS3,the palaeolake developed the highest water level above 1300 m and became a huge palaeolake Jingpeng-Dali Nor.The palaeolake shrunk sharply in the LGM and recovered later.During 12.96?11.69 ka,the palaeolake appeared another high water level above 1200 m and a new stage of palaeolake Jingpeng-Fushenghao.(4)This paper reconstructed the water region of huge Jingpeng-Dali Nor palaeolake at its highest water level,which covered the Dali Nor basin and the upstream area of Xilamulun River and reached almost 3000 km~2.The water region of palaeolake Jingpeng-Fushenghao was also reconstructed at its high water level,which covered the part region of the upstream area of Xilamulun River and reached almost600 km~2.