Tectonic subsidence and its mechanism of the Liyue Basin, South China Sea

In order to further understand the tectonic evolution of the Liyue Basin, we systematically rebuilt the tectonic subsidence history for 43 representative stations selected from existing drill holes with reprocessed 2D seismic data. The results suggest that the Cenozoic tectonic subsidence are characterized by rapid, slow and rapid tectonic subsidence responding to the three tectonic evolutionary stages of synrift, drift and subsidence, respectively, and the total tectonic subsidence is mainly controlled by the thinning crust. In the Reed Bank, the accumulated tectonic subsidence since Late Oligocene has reached a figure from 580 m to 900 m. However, the thickness of the reef deposits not only depended on tectonic subsidence, but also related to the thickness of the underlying Cenozoic deposits. Further analyses suggest that the tectonic subsidence history of the Liyue basin is featured by a slow early subsidence followed by a rapid subsidence, while the deficit of tectonic subsidence during the margin breakup and drift stages might be caused by the buoyancy of the upwelling thermal asthenosphere material driven by seafloor spreading. Since Middle Miocene, with the cessation of seafloor spreading in the South China Sea, the upwelling of deep hot material became so weak that could not provide enough buoyancy to support the overlying Liyue basin, episodic rapid subsidence thus occurred for compensating the earlier deficit of subsidence.