Quantitative Reconstruction Of The Cenozoic Deformation Of The Bohai Bay Basin,North China

Plate tectonics serves as a feasible theory for explaining geological phenomena related to lithospheric deformation.Even though plate deformation is known to be significant,deep-time plate motion models have traditionally followed a classical rigid plate approach,so that the effect of plate deformation is underestimated or even ignored 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.However,due to the lack of comprehensive constraints and effective representation methods,building quantitative models of basin kinematics and deformation remains challengingThe Bohai Bay Basin(BBB)is an important manifestation of the destruction of the North China Craton,and records the plate deformation and 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.The reconstruction model was built by using ArcGIS and GPlates software.Our reconstruction suggests that the basin formation process was composed of six periods and 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 predicted tectonic topography,including isostatic topography driven by lithospheric extension and mantle convection-driven dynamic topography,fits the backstripped topography from well-logsThe 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.Its eastern part had a transtensional pattern due to oblique strike-slip movements controlled by the Lan-Liao Fault Zone and the Tan-Lu Fault Zone,while its western part developed a rifting pattern with limited strike-slip movements due to the intense normal faulting of the Taihang Mountains Piedmont FaultWe 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.