羌塘盆地东部中生代沉积特征与构造演化

Mesozoic sedimentary characteristics and tectonic evolution in the eastern part of the Qiangtang basin

羌塘盆地东部基底由前石炭纪吉塘岩群组成,沉积盖层为晚古生代一白垩纪地层。其中,中生代海相地层在盆地内分布广泛,沉积体系多样,构造古地理转换频繁。中生代盆地包括南羌塘坳陷、唐古拉山隆起带、北羌塘坳陷等3个构造单元,内部又可以划分出不同时期多个次级凹陷和凸起。盆地的发展和演化既受南、北两侧板块结合带控制,又受盆地内部被分划性断裂带围限的各断块差异性活动约束,依次经历了晚三叠世前陆盆地阶段,“北羌塘”早-中侏罗世伸展裂陷盆地发育阶段,多玛侏罗纪-早白垩世早期被动大陆边缘陆表海盆地发展阶段、晚期前陆盆地阶段,晚白垩世南羌塘山间压陷盆地演化阶段。实质上,该盆地是不同时期原型盆地有序叠加而构成的大型叠复式盆地。

The basement of the eastem Qiangtang basin is composed of the pre-Carboniferous Jitang Group-complex and the sedimentary cover of the basin consists of Late Paleozoic-Cretaceous strata. In the basin cover, Mesozoic marine strata are widespread, there area a variety of sedimentary sequences and Mesozoic tectono-paleogeographic transition occurred frequendy. The Mesozoic basin can be divided into three tectonic units： the north and south Qiangtang depressions and Tanggula uplift, and in each tectonic unit several secondary depressions and uplifts of different stages may be distinguished. The development and evolution of the eastem Qiangtang basin, which are controlled by the plate junction zones at the north and south sides and constrained by differential activities of various blocks bounded by the divisional fault zones inside the basin, progressed through the Late Triassic foreland basin stage, Early-Mid Jurassoc ＂northem Qiangtang＂extensional foreland basin stage, Jurassic-Early Cretaceous Doima passive continental-margin basin development stage and later foreland basin development stage and Late Cretaceous southern Qiangtang intermontane compressional-depressed basin evolution stage. In essence, the eastern Qiangtang basin is a huge superposed basin formed by order stacking of prototype basins in different periods of time.