柴达木盆地达布逊湖地区3万年来气候演化的微古生物记录

柴达木盆地第四系富含各种生物化石，尤以介形类最为丰富。以盆地东部达布逊湖东南岸的达参1井浅部的介形类特征为基础，划分出了3万a来的9个古气候演化阶段，其中I1－I5对应于冰后期，Ⅱ1－Ⅱ4对应于末次冰期的晚冰期。这9个阶段中，26．3－20．0、12．2－10．1、8．0－4．5、3．8－2．5kaBP4个阶段生物丰度和分异度都较高，反映了当时气候温暖湿润，适于生物生长。20．3和2．8kaBP是晚更新世以来的两次气候极适宜时段，生物丰度和分异度都达到了最高，而30kaBP左右的生物突然大量灭绝和盐层开始析出是全球性的气候变冷以及青藏高原的第5次隆升的结果。

CLIMATIC EVOLUTION RECORDED BY OSTRACODA IN DABUSUN LAKE IN QAIDAM BASIN DURING THE PAST 30KA YEARS

Qaidam basin is located in Northwest China. With its unique geographic position, Quaternary lacustrine sediments of about 3 000 m thick and abundant Ostracoda fossils of more than 40 species, Qaidam basin is of importance in studying the Quaternary climate variation in China. Based on the age data of the Shui 6 core whose sediment environment was the same as that of Dacan 1 well, the sequence of climate evolution during the past 30 ka in Dabusun Lake (in Qaidam basin) have been reconstructed. The results indicate that the climate evolution in the past 30 ka can be divided into nine stages. Among these nine stages, there were four warm stages recorded by high Ostracoda abundance and diversity, that is, 26 3~20 0 kaBP, 12 2~10 1 kaBP, 8 0~4 5 kaBP and 3 8~2 5 kaBP respectively. 20 3 kaBP and 2 8 kaBP periods had most optimum climate, which are showed by the highest abundance and diversity of Ostracoda. But in about 30 kaBP, majority of Ostracoda suddenly became distinct and the halite layer began to come into being. These two events probably resulted from two reasons: the global climate change and the fifth uplift of the Qinghai Tibet Plateau.