柴达木盆地北缘侏罗纪古生态特征及其古地理意义

Palaeoecological characteristics and its palaeogeographic significance of the Jurassic in northern margin of Qaidam Basin

根据多门类化石古生态和岩相、沉积构造等资料,分析了柴达木盆地北缘侏罗纪的古气候和沉积环境。介形类、轮藻、叶肢介、双壳类和植物等化石在地层中的产出特征反映了当时以湖沼及滨浅湖为主的沉积环境,广泛分布的植物及孢粉化石组合面貌的变化揭示出盆地北缘早、中侏罗世为热带-亚热带温湿气候,早侏罗世晚期和中侏罗世晚期古气候两度明显干热化。陆生植物与湖沼相动物化石的交替出现,反映了盆地北缘侏罗纪湖泊、沼泽与低山相间分布的古地理面貌。早侏罗世湖泊多期发育但规模较小,中侏罗世中晚期湖泊规模最大。

The paleoclimate and sedimentary environments of the Jurassic in northern margin of Qaidam Basin are analyzed according to the paleoecology on multiphylum fossils, lithofacies and sedimentary structures. The characteristics of fossils such as ostracoda, charophytes, conchostraca, bivalves and plants indicate that the sedimentary environments at that time were mainly marshes and shallow shore-lakes. The fossil assemblages of plant and sporopollens indicate that it was a warm and humid climate of the tropic and subtropical zone and became drier and warmer twice in the Early and Middle Jurassic in northern margin of Qaidam Basin. The alternative occurrence of terraneous plant and animal fossils represents a palaeogeographic feature with the mosaic-distribution of lakes, marshes and low hills. The Early Jurassic lakes were developed for many times, but with a smaller scale. Lake area expanded to the largest in the middle-late Middle Jurassic.