Reconstruction of the Cenozoic deformation of the Bohai Bay Basin, North China

A well-constrained plate deformation model may lead to an improved understanding of sedimentary basin formation and the connection between subduction history and over-riding plate deformation. Building quantitative models of basin kinematics and deformation remains challenging often due to the lack of comprehensive constraints. The Bohai Bay Basin (BBB) is an important manifestation of the destruction of the North China Craton, and records the plate kinematic history of East Asia during the Cenozoic. Although a number of interpretations of the formation of the BBB have been proposed, few quantitative basin reconstruction models have been built to test and refine previous ideas. Here, we developed a quantitative deformation reconstruction of the BBB constrained with balanced cross-sections and structural, stratigraphic, and depositional age data. Our reconstruction suggests that the basin formation process was composed of three main stages: Paleocene-early Eocene (65-42 Ma) extension initiation, middle Eocene-early Oligocene (42-32.8 Ma) extension climax, and post-Oligocene (32.8-0 Ma) post-extensional subsidence. The deformation of the BBB is spatially heterogeneous, and its velocity directions rotated clockwise during the basin formation process. The reconstruction supports the interpretation that the BBB formed via strike-slip faulting and orthogonal extension and that the basin is classified as a composite extensional-transtensional basin. We argue that the clockwise rotation of the basin velocity field was driven by the counter-clockwise rotation in the direction of Pacific Plate subduction. The kinematics of the BBB imply that the Pacific Plate may have been sufficiently coupled to the over-riding East Asian Plate during the critical period of Pacific Plate reorganization. The new reconstruction provides a quantitative basis for studies of deformation processes not only in the vicinity of the BBB but more broadly throughout East Asia.