Tectonic Stratigraphic Framework of the Yinggehai‐Qiongdongnan Basins and Its Implication for Tectonics Province Division in South China Sea

Abstract

AbstractThe Yinggehai and Qiongdongnan basins together form one of the largest Cenozoic sedimentary basins in SE Asia. Here we present a prominent regional tectonic revolution boundary T70 in the Paleogene filling sequence based on structure‐stratigraphic analysis of regional seismic profiles in the basins. The T70 boundary, characterized by distinct truncation and onlap seismic reflections, was dated 32~30 Ma, consistent with the onset and spreading of South China Sea oceanic ridge. This boundary separated two tectonic‐stratigraphic units in the Paleogene sediments, e.g the lower faulting‐controlled subsidence layer in the Yinggehai and Qiongdongnan basins, the upper faulting‐sag layer in the Qiongdongnan basin and the sag layer in Yinggehai basin. The tectonicstratigraphic units and tectonic revolution boundaries in the Yinggehai and Qiongdongnan basins were the original responses to reorganization of plates in SE Asia. In combination with previous work, this study suggests that SE Asia can be divided into collision‐extrusion tectonic province and proto‐SCS slab pull tectonic province. We clarify distinct structure features, different evolution histories and dynamic settings of the two tectonic provinces. They are bounded by a transform boundary of the Red River fault extending south along the Vietnamese margin and joining with the trench along the Lupar Line. Considering the dynamic deformation division in this paper, the dynamic mechanisms and their evolution models for the Yinggehai and Qiongdongnan basins have been clearly determined. Our research will improve understanding on the development and evolution of the South China Sea and its peripheral areas, and has great significance for geodynamics of the continental margins and petroleum exploration in the South China Sea.