Depositional-tectonic transitions and hydrocarbon source rocks in the Jurassic southern Qiangtang basin

Abstract：The analysis of the depositional-tectonic transition based on the study of the sequence stratigraphy and lithofacies-paleogeography is an important idea to study the temporal-spatial evolution of the depositional systems. From such an analysis, the authors find out that in the Jurassic southern Qiangtang went through the evolution from the passive continental margin through the failed foreland to an uplift which was finally eroded. The environment of formation of source rocks in southern Qiangtang has been preliminarily determined. During four marine transgressions there occurred two depositional cycles from terrigenous clastic rocks to carbonate rocks. During the four depositional-tectonic transitions, three sequences of black shale were developed, which belong to passive continental-margin source rocks (one sequence) and foreland source rocks (two sequences) respectively. They provide a material basis for petroleum evaluation of the Jurassic southern Qiangtang basin.