莱州湾地区郯庐断裂带的构造特征及其新生代演化

郯庐断裂带中段分东西两支从莱州湾进入渤海,在莱州湾地区的构造特征与演化历史一直鲜为人知。通过对横穿研究区的两条地震测线的解释和分析,揭示了该区郯庐断裂带中段在研究区的构造差异,研究表明郯庐断裂带东西两支在该研究区表现出不同的断裂性质,西支断裂表现为正断层,东支断裂表现为走滑断层。郯庐断裂是本研究区的主控断裂,通过对本地区地层形态及其组合、断层的剖面形态和空间展布规律的深入研究,揭示了郯庐断裂带在莱州湾地区新生代以来的构造演化历史:古新世—始新世的伸展阶段、渐新世—中新世早期的挤压和右行走滑阶段、中新世中晚期至今的稳定发展阶段,这几个不同时期的演化阶段主要受太平洋板块运动的方向和速度变化的控制。

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.