Structural Characteristics And Evolution Of BD North Uplift In Bohai Bay Basin

BD North Uplift is controlled by east-west boundary faults F₁and F₂,which divide Bozhong Depression and Bodong Depression into two hydrocarbon-rich depressions.The uplift area and its adjacent areas have good oil and gas exploration prospects.Based on seismic data and previous research results,this paper analyzes the geometric characteristics of BD North Uplift,divides the Tectonic evolution stages of BD North Uplift by using Balanced section technology,and discusses the genetic mechanism by combining structural characteristics and evolution.Finally,the reliability of the previous theoretical analysis is verified by structural physical simulation,which lays the foundation for further oil and gas exploration.main findings:（1）The east-west boundary faults F₁and F₂are subjected to extensional and strike-slip structural deformation,which controls the formation and evolution of BD North Uplift.There are three main structural styles in the study area,namely,extension,strike-slip and inversion.According to the characteristics of fault combination,the extensional structural styles are subdivided into graben,horst,Y-shaped combination,fault terrace and rollover anticline.Strike-slip structural styles include flower-like structure and multi-level Y-shaped structure.（2）The tectonic evolution of BD North Uplift can be roughly divided into four stages:the Kongdian-Shasi period is the initial extension and rifting period,and the Tanlu fault zone shows regional extension,forming the early basic structural framework of the North Uplift and its adjacent areas;The third member of Shahejie Formation is a period of intense rifting.The Bohai Bay Basin is undergoing regional tectonic uplift activities,and the Tanlu fault is undergoing dextral strike-slip activities,which leads to the vertical uplift and denudation of the North Uplift.The formation of the North Uplift divides Bozhong Depression and Bodong Depression,forming a graben structural framework.The Second member of Dong Formation is still in the Paleogene rifting stage,and the northern uplift of BD began to decline and accept deposition;The Neogene-Quaternary BD North Uplift and its adjacent areas entered the stage of depression development as a whole,with thermal subsidence as the main factor and unified evolution.（3）During the period of Kongdian-4th member of Shahejie Formation in BD North Uplift,it was mainly influenced by Pacific plate,Indian plate and Tanlu fault,and NW-SE extension was carried out in the study area;During the third member of Shahejie Formation,due to the activities of Pacific plate and Indian plate,mantle upwelling and lateral flow,the regional stress of the north uplift is NW extension and NE strike-slip;During the second period of Dong Formation,the Pacific plate subducted and India plate collided,and the regional stress of the north uplift was near SN extension and NE strike-slip.The Neogene-Quaternary north uplift was mainly subjected to NE strike-slip stress,and at the same time,due to the upwelling of mantle and the thickening of lithosphere,the north uplift was completely subsided.