TECTONIC EVOLUTION AND FORMING MECHANISM OF THE SOUTHERN LIAOZHONG SAG, LIAODONG BAY DEPRESSION

Based on the conventional interpretation of latest 3D seismic data, the tectonic evolution of the southern Liaozhong Sag is analyzed, and the formation mechanism discussed. The results indicate that two main types of faults, i.e. the strike-slip faults and the extensional faults, are developed in the study area. The strike-slip faults extend primarily along the strike of strata in NNE and cut through both the deep and shallow sequences, while the extensional faults are developed in the deep sequences and complicated by the formers. Under the combined influence of strike-slip shearing and extensional stress, the southern Liaozhong Sag are divided into the western half-graben slope zone, the central strike-slip zone and the eastern half-graben slope zone from west to east, and the central strike-slip zone is further sub-divided into south and north parts according to the change in the quantity and curvature of the central strike-slip faults. The Cenozoic tectonic evolution of the southern Liaozhong Sag have passed through four tectonic evolutionary stages, including the extensional stage (Ek-Es₄), tectonic transitional stage (Es₃-Es₁), strike-slip shearing + extensional stage (Ed), and strike-slip shearing + depression stage (N+Q), based on the tectonic evolution caused by temporal and spatial variation of the strike-slip shearing and extension stress. The present structural pattern of southern Liaozhong Sag is complicated under the control of the temporal and spatial variation of both the strike-slip shearing and extension instead of one stress.