The Palaeoclimate record around 5000 a BP in the Westerlies Bosten Lake,Xinjiang,China

Bosten Lake（86°40’;7°26’E,41°56’;2°14’N）,one of the largest freshwater lakes in the interior of China,is located in the southeastern corner of the Yanqi Basin at the southern piedmont of the Tianshan Mountains,northwestern China.Bosten Lake,about 1000 km;in area,is the terminal lake of the Kaidu River,the only permanent inflowing river,and is the headwater（i.e.,the source） of the Kongqi River.The present average lake level is about 1048 m a.s.L and the average depth is about 8 m with a maximum depth of 17 m.The mean annual precipitation is only 68 mm with a mean annual evaporation of;000 mm within the low-elevation part of the drainage basin.The water balance of Bosten Lake is primarily controlled by the lake evaporation and inflowing runoff of the Kaidu River that is contributed by snow- and glacier-melt water in high elevations and the precipitation within the entire drainage basin.A 953 cm core BSTC2000 of Bosten Lake in the soudiern Xinjiang of northwestern China reconstructed the palaeocliamtic change in detail interval about 6400 cal a BP to 5000 cal a BP based on a chronology supported by9 AMS C dates publishes in The Holocene.For the Sr/Ca（as a salinity proxy）,8 O and 8 C of bulk sediment carbonate（as a temperature proxy）,it is shown that this period was cold but high effective humidity climate intercrossed five warm/low effective humidity stages.The periods of about 6400;975 a BP,5725;400 a BP,5325;250 a BP,5200;150 a BP,5080;025 a BP and 5000;950 a BP were the cold and high effective humidity.There are fitted well with the moving of glaciers in Xinjiang and Tibet plateau,and have a well remote relationship with Neolithic Culture contabescence around 5000 a BP in the southern part of China also.It’s more important to prove and inosculate the pattern of Holocene climatic variations summarized by Denton and Karlen（1973） as the moving of glaciers and pollen records in the south and north semi-sphere.From this Bosten Lake core BSTC2000,we can believe convincingly that there existed a long period of cold climate and influenced deeply the ecosystem in this area.And from the core paleocliamte reconstructed,it is expressed that westerlies style formed since about 6400 a BP in the westerlies Xinjiang at persent.