东海陆架盆地西湖凹陷西部斜坡带始新世"断-洼"耦合过程研究OA

As the most significant area for oil and gas exploration in the East China Sea Shelf Basin,the Xihu sag was characteried by a complex fault system during the Eocene.Investigating the"fault-sag"coupling process under multi-phase tectonic activity is crucial for palaeogeographic reconstruction and hydrocarbon exploration in this region.Based on high-resolution 3D seismic data,this study focuses on the characteristics of Eocene fault development in the western slope belt of the Xihu sag.It systematically analyzes the geometric patterns and activity history of the faults,and further investigates the"fault-sag"coupling process and its control on sedimentary systems.The results indicate that:(1)Controlled by basement structures,palaeo-uplifts,and the regional stress field,the Eocene fault system exhibits significant zonation and segmentation.The southern part of the western slope belt is characterized by single-fault and composite horst assemblages;the central part is dominated by various fault assemblages,including horst-graben and reverse fault terrace structures;while the northern part features homoclinal fault terraces and secondary horst-graben structures.(2)The Pinghu main fault,Hangzhou main fault,and Baoyunting-Wuyunting fault constitute the basin-controlling fault system.The intensity of fault activity peaked during the deposition of the lower Baoshi Member and gradually weakened throughout the depositional period of the Pinghu Formation.(3)The tectonic evolution of the basin was driven by variations in the subduction rate of the Pacific Plate.During the rifting stage,intense extensional tectonics formed a fault-controlled depositional framework,in which syn-sedimentary fault activity governed the migration and distribution of sedimentary centers.In the second rifting episode(Baoshi Formation depositional period),differential fault extension led to the development of multiple isolated sedimentary centers within the basin.During the fault-sag transition period(Pinghu Formation depositional period),the earlier palaeogeographic pattern of multiple uplifts and sags was transformed,as the isolated sedimentary centers merged and migrated southward.This study elucidates the dynamic response mechanism between faulting and sedimentation during the Eocene in the Xihu sag,providing a theoretical basis for further oil and gas exploration in the East China Sea Shelf Basin.