渤海秦南凹陷新生代断裂体系与构造演化

Cenozoic fault system and tectonic evolution of Qinan Sag in Bohai Sea

运用丰富的三维地震资料,精细刻画秦南凹陷新生代断裂体系平面和剖面发育特征,并结合区域构造运动背景,探讨了该区构造演化阶段与成因机制。结果表明:古新世—始新世,一系列NNE向或NE向伸展断层组成了秦南凹陷的断裂体系;渐新世,该区断裂体系表现为伸展-走滑性质,主断裂处发育大量多级"y"形、似花状构造样式,同时在弯曲段部位产生走滑增压区、释压区,次级断裂多表现为NEE向雁列状;新近纪时期断裂体系以马尾状和雁列状断裂为主,并发育"背形负花"状构造。结合新生代区域构造运动背景,将研究区构造演化划分为3个阶段:强伸展-弱走滑期(古新世—始新世)、强走滑-弱伸展期(渐新世)、弱走滑-弱挤压期(新近纪)。

Based on the plenty of 3D seismic data,this paper described in detail the plane and section characteristics of Cenozoic fault systems in the Qinnan Sag,and discussed the evolution and development mechanism of tectonic combined with regional geodynamic setting.The results indicate that the fault systems of the Qinnan Sag in the Paleocene and Eocene mainly consist of extensional NNE and NE trending faults.The fault systems in the Oligocene have the extensional and strike-slip characteristics.The vicinity of main faults has"y"-type structure style and the flower-liking structure style in the seismic profiles.Stress increasing area and stress-decreasing area resulted from strike-slip can be observed in the bending section.The secondary faults are presented as NEE trending en-echelon structure style.In the Neogene,the fault systems mainly consist of horsetail-like and en-echelon faults,and antiform-negative flower structure style appears in this period.Combined with dynamic evolutionary mechanism of the Bohai Bay Basin,the evolutionary stages of the Qinnan Sag can be divided into the strong extension and weak strike-slip period(Paleocene-Eocene),the strong strike-slip and weak extension period(Oligocene)and the weak compression and weak strike-slip period(Neogene).