末次间冰期—末次冰期柴达木盆地东部气候演化形式

Study on the climatic changes between the last interglacial age and the last glacial age recorded by ostracoda in eastern Qaidam Basin

柴达木盆地第四系富含介形类化石,介形类生物组合可以反映古气候变化。以盆地东部达参1井中的两种主要介形类(Ilyocyprisinermis和Cyprideistorasa)的丰度特征为气候指标,对末次间冰期和末次冰期的盆地气候演变形式进行了恢复。认为柴达木盆地东部末次间冰期和末次冰期的气候演化既有着和全球同步的特点,也有着本区域独自的特征。介形类丰度曲线表明:末次间冰期(MIS5),以Cyprideistorasa为主,整体上为暖型气候,依据介形类特征,又可分为5e,5c,5a三个暖期和5d,5b两个冷期,暖期到冷期都以介形类丰度的大幅突降为特征;末次冰期(MIS4 2)以Ilyocyprisinermis为主,整体为冷型气候。其中,早冰阶(MIS4)两种介形类丰度都较低,而间冰阶(MIS3)介形类丰度明显增高,并可划分为3c,3a两个暖期和3b一个冷期。在间冰阶结束之后,介形类大量消失,Ilyocyprisinermis完全灭绝,石盐大范围析出,盆地进入了末次冰期盛冰阶(MIS2)。

The Quaternary deposits of the Qaidam Basin are abundant in Ostracoda whose combination can be used to study the evolution of the climate because of their sensitivity to the climatic changes. There are two main Ostracoda-Ilyocypris inermis and Cyprideis torasa-which occupied above 90 percent of total Ostracoda abundance in upper well Dacan1 located in the southeast basin. The abundance curve of these two Ostracoda shows that during the last interglacial age the Qaidam Basin has undergone three warmer periods, 5e, 5c and 5a, and two colder periods, 5d and 5b, indicated by higher and lower abundances respectively. During the last glacial age the Qaidam Basin has undergone three steps-the early glacial step, the interglacial step and the late glacial step. The interglacial step can be divided into two warmer periods, 3c and 3a. and one colder period, 3b. These stages can be correlated with other climatic records, and demonstrates that the climatic change of the Qaidam Basin has the same characteristics as that of globe.