A late Pleistocene-Holocene lacustrine record from Lake Manas, Zunggar (northern Xinjiang, western China)

Information on the Late Quaternary palaeoclimate in the Zunggar desert (northern Xinjiang) is deduced from the study of three 5-m long cores taken from Lake Manas. Analyses, including the mineralogical composition of bulk sediments, stable isotope contents of carbonates, organic matter, pollen and diatoms, were performed to help reconstruct the environmental evolution of the area. The chronology is provided by 9 AMS C-14 dates done on carbonates or organic matter. The record suggests a Late Pleistocene humid episode radiocarbon-dated at 37,000-32,000 yr B.P. This episode is followed by a period of extreme aridity, attributed to the Last Glacial Maximum. The Early-Mid Holocene record indicates conditions generally wetter than today, as previously established for western China. However, our results show that the Holocene period is rather complex. After a minor wet/warm pulse estimated to be around 12,000 yr B.P., the most important environmental change is recorded at approximate to 10,000 yr B.P. It led to the establishment of a steppic vegetation cover in the catchment, and of a permanent lake which lasted approximate to 4000 years. Fluvial sedimentation took place between about 6000 and 4500 yr B.P., and it coincided with a decrease in moisture availability for vegetation growth. A second lacustrine episode is recorded from about 4500 to 2500 yr B.P., although the pollen record and a sudden influx in detrital organic matter su est a short-term dry event around 3800-3500 yr B.P. The last 2500 years show climate unstability and the step-wise establishment of hypersaline conditions in Lake Manas. The major post glacial environmental changes appear to be roughly in phase with those observed in Tibet.