TECTONIC CHARACTERISTICS AND DYNAMIC BACKGROUND OF THE NE TRENDING FAULT ZONE IN SHANDONG COASTAL AREA

Through the field geological investigation of the northeast fault zone and the adjacent basin in Shandong coastal area, the characteristics of the fault zone and the strata in the basin are comprehensively described. The structural characteristics such as joints, folds and scratches are comprehensively used for measurement and analysis. At the same time, the understanding of the unconformity of the late Mesozoic Wangshi Group-Qingshan Group outcrop in Jiaolai Basin is summarized. It is believed that the nature of the NE-trending fault zone is generally characterized by compression and torsion, and its Mesozoic tectonic evolution activity includes two main strike-slip stages : the left-lateral strike-slip stage at the end of Qingshan and the right-lateral strike-slip stage at the end of Wangshi. The scale of left-lateral strike-slip is much larger than that of right-lateral stage. At the same time, zircon U-Pb dating was carried out on the tuff above the unconformity surface at the end of the Qingshan period. The dating results provide an age basis for the time node of left-lateral strike-slip. Finally, the geodynamic background of different stages corresponding to the stress field transformation of different active periods of the fault zone is summarized and recognized. The present tectonic framework of the Tan-Lu fault zone is the result of the change of subduction angle and velocity of the Paleo-Pacific plate and the Indian plate to the Eurasian plate in different periods. Its kinematic characteristics can be used as an indirect evidence of the strike-slip activity of the Tan-Lu fault zone.