Development and Formation Mechanism of Cenozoic Tectonics in the East Area of Liaodong Bay Depression

Based on three dimensional seismic reflection data,this paper described the plane and section characteristics of Cenozoic fault system in the eastern area of Liaodong Bay Depression and analysed the structure styles reflected from the fault system.The paper discussed the evolution and development mechanism of tectonics combined with regional geodynamic setting.The results indicate that the structures in Paleocene and Eocene mainly consist of the extensional NNE trending faults and the structure styles in Oligocene have obvious strike-slip effect.The vicinity of main faults has significant stress-increasing area and stress-decreasing area resulted from strike-slip,and the flower-liking structure and " Y"-type structure style can be observed in the seismic profiles.The secondary faults are presented as NEE trending en-echelon structure style.In Neogene,the fault system is still manifested as en-echelon faults,while conjugate shear fracture and antiform-negative flower structure style appear in this period.The development and evolution of the structure reflects the superimposition and transformation between extension tectonic system and strike-slip tectonic system in Cenozoic.The evolutionary stages of the eastern Liaodong Bay Depression can be divided into the weak strike-slip-strong extension period(Paleocene-Eocene),the weak extension-strong strike-slip period(Oligocene)and the weak compression-weak strike-slip period(Neogene).