【作者】 李元芳； 张青松； 李炳元；

【Author】 Li Yuanfan Zhang Qingsong and Li BingyuanInstitute of Geography ,Chinese Academy of Sciences,Beijing 100101

【机构】 中国科学院地理研究所；

【摘要】 <正> 本区位于青藏高原西部,界于昆仑山系以南,喀喇昆仑山和唐古拉山脉以北,区内多为东西向的中小起伏的高山和宽坦的湖盆,山地海拔一般为5500—6000m,湖盆海拔常在4200—5000m之间.除西北边缘和东部边缘地区,大部分湖泊为内流的封闭湖泊.由于本区地势高亢,气候寒冷干燥,年平均气温在0℃左右,年降水量除东部局部地区为300mm,其他均在200mm以下(中国科学院青藏综合科学考察队,1984).湖泊主要靠融水和河水补给,又因蒸发量大,除极少数湖泊为淡水湖外,主要是半咸水湖、咸水湖和盐湖(表1),湖泊的矿化度变化与距离补给水源的远近有关,如班公错东部湖区有班公错流域中最大的河流麻嘎藏布河注入,其矿化度低,最高仅为0.74g/L,而中部和西部湖区入湖径流少,则湖水矿化度可达2.76—19.16g/L.更多还原

【Abstract】 Three cores of samples from Gounong Co, Sumxi Co, and Banggong Co and lacustrine sedimentary samples from one exposure near the Hongshan lake were collected.In order to obtain information about the environmental changes in the western Tibet since late Pleistocene, detail analyses of ostracods have been carried out.On the basis of the distribution of ostracod fossils and their palaeoecological characters , it can be considered that a cold climate occurred between 20 and 10.2 ka BP, especially in the period 20-15ka BP.Gounong Co had been already a lake at about 20ka BP.Hydrologic conditions might slightly improve which infers a little warm up by the time of about 15-11.Ska BP.However, the range of climatic variation was quite small in last glaciation.No ostracod has been found or only a few species (example halophilous species Eucypris inflata) exist in the strata of 11.5-10.2ka BP which infers the lakes probably retreated in this time.This may correspond to the cooling event of Younger Dryas.The temperature rose rapidly about 10-9.6ka BP.Fine hydrologic conditions appeared during the period about 7.8-5.5ka BP which coincided with the rise of lake level and a warm-humid climate.Climatic deterioration occurred since 6-5.5ka BP, the Banggong Co lake water body became slight saline after 5.5 ka BP.更多还原