Abstract:

Abundant 3D seismic data were used, combined with the characteristics of seismic profile and time slices, the fault
development and basin structure of Bonan area were researched. Furthermore, characteristics of the fault system and the structural evolution were delineated. The Cenozoic Tanlu fault in Bonan area was divided to eastern, middle and western branches. These branches interact with the EW-trending, NW-trending and NE-trending were associated with the strike-slip movement of the Tanlu fault, leading to the formation of the grid structural pattern in Bonan area due to changing stress field. There fore, changes in the relative importance between extension and strike-slip occurred in Bonan area. The Cenozoic structural evolution can be classified into three evolutionary stages, i.e., left lateral slip with strong extension, right lateral slip with strong extension and weak slip and weak extension. During the first stage of Ek-Es4, the Eastern Branch moved greatly but the Middle and the Western Branch weakly. The EW-trending, NW-trending controlled the basin pattern of the Huanghekou Sag and Laizhouwan Sag. During the second stage of Es3-Ed, three branches of the strike-slip fault and the main faults of other directions became activated. The secondary faults of the NE-trending and the near EW-trending faults began to develop. The two basins underwent persistent extension and rift. During the third stage of Ng-Nm, right-lateral strike-slip changed to weak, en-echelon faults of the NE-trending faults that appeared near the Middle and Western Branch, and secondary faults were increasingly developed. Two basins were transformed into initial rift.

Key words: Tanlu fault zone, fault system, basin structure, evolutionary stage, Cenozoic, Bonan area