THE ENVIRONMENTAL CHANGE RECORDED IN JIANGXIGOU LOESS SECTIONS IN QINGHAI LAKE REGION

The Qinghai Lake area is a hot spot in global change studies,due to its sensitivity to global warming.During the last deglaciation,aeolian deposits were widely distributed in the region,with drastic environmental and climatic changes.In this paper,we studied two loess sections(JXG1and JXG2) near the Jiangxigou town to the south of Qinghai Lake,upon which we reconstructed the regional environmental changes since the last deglaciation.The results show that :(1) During 13～11.5kaBP,the paleolclimate was cold and dry there.Aeolian deposition prevailed and sandy loess formed.In general,the region was changing from a cold and dry to a cool and humid environment;(2) During 11.5～5kaBP,pedogenesis was relatively strong.Maximum moisture levels occurred during the period of 9～5kaBP,and in general,the paleoclimate was warm and wet;(3) After 5kaBP,climate often alternated,dust storm occurred frequently,vegetation coverage decreased,and the climate entered a relatively unstable stage.The environmental changes of the Jiangxigou Loess section are comparable with those revealed by the boreholes in the Qinghai Lake and the Heimahe loess section.The redness of the Jiangxigou loess section is a sensitive index to environmental change.The loess deposition since the last deglaciation in Qinghai Lake area was mainly controlled by the ice volume of the northern hemisphere,which was driven by the summer solar irradiation at the high latitude.The Westerlies played the role as a cold-air conveyer between the North Atlantic and the northeastern Tibetan Plateau.