Abstract:

Daxing Fault is a boundary fault of Langgu Depression which is located in the northwest of Jizhong Depression in Bohaiwan Gulf Basin. It controls the sediment and structural evolution of the whole depression. According to the strike direction, Daxing Fault is divided into three segments which are northeastern segment, middle segment, and southwester segment, and the origin of their linkages has been discussed. This paper shows the triaxial geometric graph of Daxing Fault plane for the first time, and analyzes it. We consider that Daxing Fault plane is a surface which consists of several inclined planes separated by axial planes. According to the strike direction, axial planes are divided into two types， a transversal axial plane whose strike direction is parallel to the fault strike and a vertical axial plane whose strike direction is vertical to the fault strike. Daxing Fault plane is divided into 10 zones by 4 transversal axial planes and 2 vertical axial planes, and each zone has its own configuration and feature. We also have discussed the mechanism of Daxing Fault movement, and consider that Daxing Fault movement in a domino normal pattern at first, and then the fault rotated to form the fault that was flattened from top to bottom. The stratum of the hanging wall rotated with fault at first, and then moved in an inclined shear pattern to form a rollover anticline when the fault was flattened from top to bottom.

Key words:  Langgu Depression, Daxing Fault, Paleogene, domino normal fault, listric normal fault, faultbending fold