Cenozoic structural deformation and dynamic processes of the Bohai Bay basin province, China

Cenozoic structures in the Bohai Bay basin province can be subdivided into eleven extensional systems and three strike-slip systems. The extensional systems consist of normal faults and transfer faults. The normal faults predominantly trend NNE and NE, and their attitudes vary in different tectonic settings. Paleogene rifting sub-basins were developed in the hanging walls of the normal faults that were most likely growth faults. Neogene–Quaternary sequences were deposited in both the rifting sub-basins and horsts to form a unified basin province. The extensional systems were overprinted by three NNE-trending, right-lateral strike-slip systems (fault zones). Although the principal displacement zones (PDZ) of the strike-slip fault zones are developed only in the basement and lower basin sequences in some cross sections, the structural deformation characteristics of the upper basin sequences also indicate that they are basement-involved, right-lateral strike-slip fault zones. According to the relationships between faults and sedimentary sequences, the extensional systems were mainly developed from the middle Paleocene to the late Oligocene, whereas the strike-slip systems were mainly developed from the Oligocene to the Miocene. Strike-slip deformation was intensified as extensional deformation was weakened. Extensional deformation was derived from horizontal tension induced by upwelling of hot mantle material, whereas strike-slip deformation was probably related to a regional stress field induced by plate movement.