辽东湾坳陷东部地区新生代断裂体系与构造演化

Cenozoic Fault System and Tectonic Evolution of the Eastern Liaodong Bay Depression

断裂体系发育特征是辽东湾坳陷东部地区新生代构造演化的重要表现形式,运用丰富的三维地震资料,详细刻画了研究区断裂体系平面和剖面特征。断裂体系特征分析表明:研究区古新世-渐新世的断裂体系主要由NNE向的拉张正断层组成;渐新世时期的断裂体系则表现出走滑断裂的性质,主干断裂附近出现走滑效应产生的增压区和释压区,同时发育似花状构造和多级"y"字型构造,次级断裂多表现为雁列状的NEE向断裂;新近纪时期断裂体系仍以雁列状断裂为主,发育共轭状剪切破裂以及"背形负花"状构造。断裂体系的研究明确了研究区新生代走滑构造系统与伸展构造系统的叠加改造过程,结合研究区构造动力学背景,将辽东湾坳陷东部地区的构造演化阶段划分为古新世-始新世的弱走滑强拉张期、渐新世的弱拉张强走滑期以及新近纪的弱挤压弱走滑期。

Development characteristics of a fault system are an important manifestation of the structural evolution of the easternLiaodong Bay Depression in the Cenozoic period. Based on plenty of three dimensional seismic data, this paper describes the horizontaldecreased and sectional characteristics of fault systems in detail in the study area and analyzes the formation mechanism of the faultsystems. The result shows that the fault systems in the Paleocene and the Eocene mainly consist of NNE trending extensional faults.And the fault systems in the Oligocene have the strike-slip characteristics. The vicinity of main faults has significantly stress-increasedarea and stress-decreased area due to the strike-slip effect. The flower-liking structures and＂Y＂-type structures can be observed in theseismic profiles. The secondary faults mostly consist of NEE trending en-echelon faults. The main faults and the secondary faults canform strike-slip duplex. In Neogene, the secondary faults are still manifested as NEE trending en-echelon faults and the fault systemshows characteristics of weak strik-slip. And conjugate shear fractures and antiform-negative flower structures began to appear in thisperiod. The study of the fault system illustrates the superimposition and transformation between extension tectonic systems andstrike-slip tectonic systems in the eastern Liaodong Bay Depression in the Cenozoic. Combined with dynamic evolutionary mechanism of the Bohai Bay Basin, the evolutionary stages of the eastern Liaodong Bay Depression can be divided into the weak strike-slip-strongextension period（Paleocene-Eocene）, the weak extension-strong strike-slip period（Oligocene）, and the weak compression-weakstrike-slip period（Neogene）.