The Tectonic Stress Field Numerical Simulation Of Extensional Structures Since Late Mesozoic In Western Shandong

By choosing the Western Shandong as the research target, and integrating the West Shandong Uplift and the Jiyang Depression as a whole, this paper researches the characteristics of geometry and kinematics and evolutionary series by field geological survey and core observation. The structure style of the Western Shandong is an extensional structural system since Late Mesozoic. The high-angle faults constitute the main part of the extensional fault system. In the fault zone, there are tectonic breccias, fault clay making up signs of faulting activity. The low-angle décollement faults are found between Lower Cambrian and Archean and between Ordovician and Carboniferous. There are folds and shatters near the décollement surface, accompanied by dynamic metamorphism. Meanwhile, the seismic profiles and drilling wells reveal that the strata of the décollement structures is often found in northeastern and southern part of the Jiyang Depression. The analysis shows that the décollement structures mainly head to NW, NNW and NNE, composing the typical structure style of the Western Shandong with high-angle faults.On the basis of outcrop information and core data, the numerical simulation of tectonic stress since Late Mesozoic is set up using ANSYS10.0 in plane and profile; hence, the evolution and stress mechanism in Western Shandong is obtained. Western Shandong has experienced Late Jurassic to Early Cretaceous, Paleocene to Early Eocene and Middle Eocene to Oligocene since Late Mesozoic. In Late Jurassic to Early Cretaceous, the extensional orientation was NE-SW. A large number of thrust faults in Indo-Chinese Epoch developed tectonic inversion, and the décollement faults started up. In Paleocene, the extensional orientation was SN, and the activity of NW faults continued. Meanwhile, a series of NE faults developed during this period. In Eocene, the main extensional orientation was NW-SE. The NE faults's activity reached its peak, and the NW faults tended to stop. Large area of décollement faults developed in Western Shandong during this area. The study perfects the research of tectonic stress in research area, and gives structural data to the further exploration.