Abstract: The desert loess transitional zone located between the northern part of loess plateau and the southern fringe of Mu Us Desert is very sensitive to the climatic changes. There has received great attention. In this paper, Haizetan profile of Jinbian County (37°42'N,108°48'E) situated in the southern edge of Mu Us Desert, has developed a thick lake swamp sediments, which has completely documented the history of East Asia monsoon and desert evolution since the late glacial epoch. The major climatic variations have been recorded and analyzed based on the sedimental facies, stratigraphic data, geo chemistry, pollen records from lake swamp deposit sequences. Some results are concluded: (1) The climate before 12 ka BP was colder and drier than that in Holocene; Sediments with a thick eolian sand layer indicated intensified winter monsoon and strong wind sand activities. (2) During the period from 12 to 10 ka BP, climatic indicator analysis reflected higher content of Fe 2O 3, Al 2O 3,Co,Ni and lower content of Na 2O,K 2O,Sr,Ba, and high pollen concentration, which suggested that climatic conditions had started to ameliorate and became relatively warm and wet. (3) During the period of 10~8.5 ka B P, the general climate was warmer and wetter, which was resulted from enhanced summer monsoon activity due to the increased summertime solar radiation in Northe rn Hemisphere. During the period the summer monsoon dominated and precipitation, pollen volume increased. Around about 9 ka BP, the pollen volume reached its peak, rainfall was abundant. However, the lowest pollen content between 10 and 9.5 a BP indicated that the climate changed to dry cold dramatically and deposited eolian sand layer. This stage matched the Younger Dryas sub period of North Atlantic Period in Europe. (4) The period between 8.5 and 3.0 ka BP correlated with Megathermal Phase of Holocene. The climate became warmer and wetter resulted from intensified summer monsoon activity. Many researches indicate that during 8.5~3.0 ka BP it was warm and wet in other regions, such as in eastern and northern China. (5) Since 3.0 ka BP, the climate in this area gradually became dry or approx imated to present climatic condition.

Key words: The late glacial epoch, Mu Us Desert, Climatic change, Younger Dryas event