Late Cretaceous-oligocene Tectonic Deformation And Mechanism In The Oujiang Sag,East China Sea Continental Shelf Basin

Deformation of the East China Sea Shelf Basin,which is successively controlled by Pacific tectonic domain and Tethyan tectonic domain,records the interaction of ocean and continent,and is the key to understand the tectonic evolution of the eastern South China,subduction of the Pacific Ocean Plate and so on.Meanwhile,Late Cretaceous-Oligocene is an important continental margin transition period from Andeans-type continental margin to Japanese-type continental margin.Oujiang Sag,in which the Meso-Cenozoic strata are well developed,is an important sag of the East China Sea Shelf Basin,and completely records the deformation of the basin.Based on the latest geophysical data acquired in recent years and based on the research results of Mesozoic and Cenozoic predecessors,this paper uses seismic profiling to analyze fine structures,reveal important interfaces and make balanced profiles.With the Oujiang Sag as the research area and the key anatomical regions During the multi-stage tectonic movement of the Oujiang Depression,the deformation and mechanism of late Cretaceous-Oligocene tectonic deformation are discussed.Some achievements and understandings are obtained:(1)Based on drilling data and 2D seismic interpretation results,the sequence and tectonic layer of the Mesozoic and Cenozoic seismogenic zones in the study area are divided and a unified stratigraphic framework is established.Five types of tectonic styles are summarized in detail: extensional tectonic style,extrusion tectonic style,Slippery structure style,reverse structural style,the end of the split structure style;further can be divided into graben and basement,half-graben and compound half graben,domino-style,tilted ramp,extrusion anticline,Eleven structures,echelon structures,inverted structures and diapirs.(2)In the plane,the tectonic maps,faults and magmatic distribution maps are used to analyze the faults and igneous rocks in the study area.The fractures are mainly distributed along the NE-NNE and NW directions,and a small number of small-scale faults developed along the EW direction are developed.The magmatic rocks have the characteristics of multi-stage activities,mainly Yanshan period and Himalayan period.In addition,the fault has a good correlation with magmatic rocks.Both of them are in close contact with each other in terms of development period and distribution direction,which reflects a more uniform formation mechanism.(3)The analysis of the regional structure,balanced cross-section analysis and physical simulation,the comprehensive results of previous studies,to construct new generation in Oujiang sag evolution stages are analyzed,the tectonic evolution in the study area is classified into the following 3 periods: the late Cretaceous Paleocene Eocene rifting stage,depression stage in new depression.The world has regional subsidence stage.