Characteristics of Tectonic Sedimentary Evolution in Northern Depression of Beibuwan Basin

Based on the 2D and 3D seismic data interpretation,study on stratigraphy distribution and fault systems has been conducted for Beibuwan basin,and the distribution framework of depression fault systems and structural styles of this study area have been built.On the basis of stratigraphy and logging data,the faulting evolution history has been analyzed.It is revealed that three episodes of rifting phases had occurred in Paleogene in northern depression.The first was initial extensional rifting phase in Palaeocene,resulting in the development of narrow half-graben;the second was intense extensional rifting phase in the early to middle Eocene,a unified lake basin formed,and two depocenters occurred;the third was transforming stage from rifting to sagging in Oligocene,the Weixinan low uplift and No.3 fault activitied intensely,and the depocenters shifted to Haizhong sag.This study has provided basis for further work of petroleum exploration.