Abstract:

On the basis of the studies on outcrop sedimentary section,well logs and organic geochemistry of Jurassic System,2 types of Jurassic tectonic sequences showing the dynamic processes of foreland basin are recognized in Qaidam Basin.One is the tectonic sequence converted from elastic to plastic subsidence corresponding to the thrusting and loading of orogenic belt,another one is plastic resubsiding tectonic sequence corresponding to the plastic subsidence of basin basement.Jurassic System of Qaidam Basin can be subdivided into 8 tectonic sequences,the succession from Pliensbachian to Bajoeian includes 4 tectonic subsequences of the first type;the succession of Bathonian lower Callovian includes 2 plastic resubsiding tectonic sequences;the succession of upper Callovian Upper Jurassic includes 2 tectonic sequences of the first type again.The total Jurassic fill succession of Qaidam indicates that the basin underwent 3 evolution stages such as multicycle converted elastic plastic subsidence stage,plastic resubsiding stage and converted elastic plastic subsidence stage again.This evolutional process of the basin is closely related to the thrusting and loading of orogenic belt toward foreland zone.