STRUCTURAL FEATURES AND CENOZOIC EVOLUTION OF THE TAN-LU FAULT ZONE IN THE LAIZHOU BAY,BOHAI SEA

The middle portion of Tan-Lu fault zone is divided into two branches(the east and west faults) and enters the Laizhou Bay of the Bohai Sea,according to the interpretation and analysis results of the seismic lines across the study area.The structural characters of the middle portion of the Tan-Lu fault zone are little reported due to lack of seismic data.During this study,we discuss the tectonics and evolution of the Tan-Lu fault in the Laizhou Bay by using the latest seismic data.The research result shows that the two faults are different in kinematical characters in the study area: the west fault is a normal fault while the east is a strike-slip one.The Tan-Lu fault zone is the main fault in the study area.After careful researches on the stratigraphic distribution and combination,sectional shape and dimensional distribution features of the faults in the study area,the Cenozoic tectonic evolution history of the middle portion of the Tan-Lu fault zone is divided into three stages: Paleocene-Eocene extension,Oligocene-early Miocene extrusion and dextral strike-slip,middle Miocene to the present stable depression,which are mainly controlled by direction and velocity changes of the Pacific plate.