LAKE EVOLUTION IN THE TENGGER DESERT, NORTHWESTERN CHINA, DURING THE LAST 40,000 YEARS

Climatic changes inferred from lacustrine deposits and lake-level fluctuations in northwestern and central China are mainly based on paleoclimatic records from the Tibetan Plateau, while there is still a lack of data relating to the semiarid/arid desert regions of Inner Mongolia, In the Tengger Desert, different paleo-lake levels at Baijian Hu are documented by six paleoshorelines and stratified lake carbonates, The highest lake level occurred ca, 39,000 C-14 yr B,P. and prevailed over about 16,000 km(2), From sediment structure, geochemical composition, and ostracods we infer humid/cool conditions until 23,000 C-14 yr B,P, In the northern Badanjilin Desert at Gaxan Nur/Sogu Nur, high lake levels can be deduced from mollusc-bearing paleobeaches and lake carbonates, which have been dated to 34,000 C-14 yr B,P, and indicate a lake that covered some 32,000 km(2), After ca, 20,000 yr B,P, the climate became dry with increased eolian activity and decreasing lake levels. Reestablishment of wet conditions occurred ca, 13,000 yr B,P, The Holocene is represented by stratified lake deposits that alternate with fluvial and eolian deposits, indicating a longterm oscillating trend toward arid conditions, The existence of widespread freshwater lakes during the late Pleistocene indicates a semihumid climate without an accompanying fall in temperature to arctic conditions. (C) 1995 University of Washington.