Multi-stage activity characteristics of small-scale strike-slip faults in superimposed basin and its identification method: a case study of Shunbei area, Tarim Basin

The strike-slip faults in superimposed basins usually experienced multi-stage activities. The episodic formation and evolution of strike-slip faults match with the important tectonic transformation periods of superimposed basins. Generally speaking, strike-slip fault zones converge (or stretch) in stress fields at different tectonic stages. It will result in the formation of specific associated structural styles of near-surface tectonic layers in the same period. Finally, a complete vertical tectonic sequence is formed. If the strike-slip associated structures peculiar to each tectonic layer are taken as geological records of strike-slip fault activities in the same period, the episodic activity of the strike-slip faults can be restored step by step from the present underground geological structure, and then the active periods of faults can be determined. In addition, during the episodic slip of strike-slip faults, changes in horizontal slip direction and faulted tectonic-sedimentary geological bodies often occur. These two phenomena actually reflect the core content of the kinematic characteristics of strike-slip faults, namely, the direction and distance of slip. It can also be used as an important basis for judging the active stages of strike-slip faults. Therefore, the Tarim superimposed basin is divided into five tectonic layers on the basis of the study of basin tectonic-sedimentary evolution background. On this basis, the vertical structural sequence and main associated structural styles of strike-slip fault system in the study area are determined. The geometric and kinematic characteristics of strike-slip associated structures in different tectonic layers of Tarim superimposed basin are analyzed. Two types with seven applicability techniques for distinguishing active periods of faults based on seismic data have been formed.