WARM-HUMID CLIMATE IN NORTHWEST CHINA DURING THE PERIOD OF 40～30ka B. P.:GEOLOGICAL RECORDS AND ORIGIN
Yang Bao① Shi Yafeng ①② (① Institute of Cold and Arid Regions Environmental and Engineering Research, Chinese Academy of Sciences, Lanzhou 730000; ② Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008)
A large number of geological records from Northwest China, including ice core, lake sediment, pollen and loess-paleosol, were examined in this paper. During the period of 40～30ka B.P., the Aiding Lake had an area of 2 500～3 000km2. The Chaiwobu Lake was much larger than its present size and might be connected with the Aiding Lake. The Manas Lake, a dry saline lake today, experienced a humid episode in 37～32 14C ka B.P., with a lake area of 8 000 km2. The Balikun Lake was a deepwater one. The Lop Nur Lake was far wider than its present size, and its slight saltiness is supported by many hydrophyte pollen grains, expecially Typha . Calcareous crusts in the terrace of the Keriya River on the southern margin of Tarim Basin indicate that precipitation at that time should be 3～8 times higher than the present one. The Qarhan Lake was 2.6 times greater than the present size, with an annual precipitation of 150 to 350 mm. Between 41 and 33 ka B.P. the highest lake level of the Juyan Ze Lake was at 22 to 30 m above the present lake level. A lake of about 33 000km2 occurred in the Gashun/Aogun Nur area. A 50 cm-thick calcareous crust in Badain Jaran Desert indicates that precipitation should be 2～7 times than the present one. Between 40 and 23ka B.P. a lake occurred at Baijian Hu of Tengger Shamo. There was a relatively warm-humid climate in the Duantouliang region of northwestern Tengger Desert, where temperature was 2°～3℃ than the present one and precipitation was 250～350 mm more than the present one, developing a broad-leaf forest. The causes responsible for such changes were probably due to the increase in ocean surface temperature and evaporation resulted from high radiation caused by precessional at middle and low latitudes and therefore westerly circulation and summer monsoon carried large amount of moisture to Northwest China.
【Fund】： 中国科学院寒区旱区环境与工程研究所知识创新工程项目 (批准号 :CACX2 0 0 2 10 2 );; 中国科学院知识创新工程重大项目 (批准号 :KZCX1- 10 - 0 6和KZCX2 - 30 1)资助
【CateGory Index】： P532
【CateGory Index】： P532