Characteristics and Its Role in Basin Controlling of Strike-slip Faults in Cenozoic Qikou Sag,Huanghua Depression

Based on the newly obtained high resolution 3D seismic data,we analysed the characteristics of strike-slip faults in Cenozoic Qikou sag and its controlling role in basin evolution.There develop two group strike-slip faults with three branches in Cenozoic Qikou sag,the dextral Lankao-Liaocheng strike-slip fault system coastal strike-slip fault zone and Yangerzhuang strike-slip fault zone,and the sinistral Zhangjiakou-Penglai strike-slip fault system Haihe strike-slip fault zone.Characteristics and spatial distribution of Yangerzhuang strike-slip fault zone suggested that the strike-slip fault zone should be the main branch of the dextral Lankao-Liaocheng strike-slip fault system but not the costal branch as another view.One major result of the strike-slip tectonic is the sharp increase in number of extensional faults.The Cenozoic strike-slip tectonic can divided into two episodes of late Shahejie Formation episode and Minghuazhen Formation episode.The strike-slip tectonics originated from the collisions of surrounding plates.The late Shahejie Formation episode movement is corresponding to the opening of South China Sea at about 34Ma,and the Minghuazhen Formation episode movement is corresponding to the Tibet plateau fast uplifting at about 5 Ma.Strike-slip fault zone divided the Qikou sag into three blocks with different structure style.Due to the strike-slip tectonic the evolution of Qikou sag is distinct from classical extensional basin.In the rifting episode,there were several subsidence centers and one main subsidence center,meanwhile the depocenter,the main subsidence center and the fault activity center of different evolution stages migrated toward Northeast.In the thermal subsidence episode,the rate of deposit and subsidence and fault movement sped up,and the intensity center of fault movement migrated toward Northeast.