莺歌海—琼东南盆地构造-地层格架及南海动力变形分区

通过对盆地地震剖面构造-地层的详细解释,在莺歌海盆地和琼东南盆地(简称莺-琼盆地)古近纪同裂陷充填序列中识别出一条区域性的构造变革界面——T70,该界面在地震剖面上表现为显著的下削上超的地震反射结构特征,发育的时代为32～30 Ma,与南海海底扩张起始和红河断裂带左旋走滑的时间一致；T70界面将莺-琼盆地的同裂陷期地层...

Tectonic stratigraphic framework of Yinggehai-Qiongdongnan Basins and its implication for tectonic province division in South China Sea

The 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, were dated at 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, i.e., the lower faulting-controlled subsidence layer in Yinggehai and Qiongdongnan basins, and the upper faulting-sag layer in Qiongdongnan basin and the sag layer in Yinggehai basin. The tectonic-stratigraphic units and tectonic revolution boundaries in Yinggehai and Qiongdongnan basins were originally responses to reorganization of plates in SE Asia. This study in Yinggehai and Qiongdongnan basins confirmed that South China Sea and its adjacent areas can be divided into collision-extrusion tectonic province and proto-SCS slab pull tectonic province, which was mostly suggested by works on southern South China Sea.In this paper we clarify distinct structure features, different evolution history and dynamic settings of the two tectonic provinces. They are bounded by a transform boundary of Red River fault extended south along the Vietnamese margin and joined with the trench along the Lupar Line. Considering the dynamic deformational division in this paper, the dynamic mechanisms and their evolution models for Yinggehai and Qiongdongnan basins have been clearly determined. Our research will improve our understanding on the development and evolution of South China Sea and its peripheral area, and has a great significance for geodynamics of the continental margins and petroleum exploration in the South China Sea.