西藏纳木错地区116 ka以来的湖相沉积及其环境演化与气候变迁

The Lacustrine Sediments of the Nam Co Basin in Tibet from 116 ka and Related Environmental Evolution and Climate Changes

水准测量表明，西藏纳木错沿岸发育了拔湖48m以下的6级湖岸阶地和拔湖48m以上、最高至139．2m的高位湖相沉积。根据实测训面、地层序列和岩性特征，并结合同位素测年等资料，可将该套湖相沉积地层划分为1个群、2个组。通过易溶盐、pH值、地球化学、粘土矿物、介形类和孢粉分析等的研究发现，湖相沉积中记录了116ka B．P．以来的环境演化与气候变迁的信息。自116ka B．P．以来，以全新世气候最宜期时，最温暖湿润；在90．1ka B．P．和86．5ka B．P．的相对温暖期时，气温相当或略高于现今，属温和轻失或偏干，湿度稍大；在36～35ka B．P．时段，气温和湿度较现今略高或较高。这表明自晚更新世以来，该区环境在逐渐变暖的总趋势上，经历了多次明显的冷暖与干湿波动。

The results of the measurement by the water-level instrument show that there are the lacustrine deposits from 48 to 139.2 meters and the six grade lake terraces whose heights are less than 48 meters above the lake-level along the coasts of the Nam Co Lake. According to the measurement of geological sections, strata sequence and lithology, isotopic dating of the lacustrine and lakeshore deposits, the strata of the lacustrine deposits has been divided into one group and two formations. The studies of the salt sediments, pH value, geochemistry, clay minerals, ostracoda and sporopollen analysis show that the lakeshore deposits recorded the information of the environmental evolution and climate changes from 116 ka B.P. The dada shows that from 116 ka B.P. the best warm and humid climate occurred in Holocene, but from 90. 1 to 86. 5 ka B.P. the climate is relative warmer, temperature was equal or slightly higher than that of the present, belongs to warm and humid or slightly dry climate; from 36.0 to 35.0 ka B.P. air temperature and humidity is slightly high or higher than that of the present. The study results show that the environment have experienced many times of cold-warm changes and dryhumid changes within the total changing trend from cold to warm gradually since the Late Pleistocene.