GRAIN-SIZE CHARACTERISTICS AND THEIR ENVIRONMENTAL SIGNIFICANCE OF GAHAI LAKE SEDIMENTS IN QAIDAM BASIN

This article analyzes characteristics of grain-sizes and changes of climate and environment since about 11 000 aBP ago using high-resolution grain-size data and information of lithology and pollen assemblage from core DG02 in Gaihai Lake. The research result shows that sediment in Gahai Lake has well recorded the processes of the lake water from wetting-up to drying-up. The climatic changes can be divided into four stages as follows:late deglaciation (11 324~10 290 aBP),when the lake level was low,the area was shrinking, the driving force was strong and the sediment particles were coarse with arid climate;early Holocene(10 290~8 850 aBP),when the lake water level was high,the sediment particles were fine with wet climate in the transition phase;mid Holocene(8 850~4 400 aBP),when the lake water level was much lower and expanding, the driving force was the weakest and the sediment particles were the finest with wet climate;late Holocene(4 400~200 aBP),when the lake water level was low and shrinking, the driving force was strong and the sediment particles were coarse with arid climate. The climatic changes and important dry and wet events in Gahai Lake area were coincident with other research results at home and abroad.