Structure and kinematic analysis of the deepwater area of the Qiongdongnan Basin through a seismic interpretation and analogue modeling experiments

Abstract

Located at the northwest continental slope of the South China Sea, the Qiongdongnan Basin bears valley-shaped bathymetry deepening toward east. It is separated from the Yinggehai Basin through NW-trending Indo-China-Red River shear zone, and connected with NW subsea basin through the Xisha Trough. Along with the rapid progress of the deepwater exploration, large amounts of high resolution geophysical and geological data were accumulated. Scientific researches about deepwater basins kept revealing brand new tectonic and sedimentary discoveries. In order to summarize the structural features and main controlling factors of the deepwater Qiongdongnan Basin, a series of researches on basin architecture, fault activities, tectonic deformation and evolution were carried out. In reference to analogue modeling experiments, a tectonic situation and a basin formation mechanism were discussed. The researches indicate that: the northern boundary of the Qiongdongnan Basin is strongly controlled by No. 2 fault. The overlapping control of two stress fields from the east and the west made the central depression zone extremely thinned. Combined with the changed stress field, the segmentation of a preexisting weakness zone made the sags in the east experiencing different rifting histories from the west ones. The NE-trending west segment of the Qiongdongnan Basin experienced strong rifting during Eocene, while the roughly EW-trending sags in the east segment show strong rifting during late Eocene and early Oligocene. Local structures such as NW-trending basal fault and inherited uplifts controlled the lateral segmentation. So first order factors such as regional stress field and preexisting weakness zone controlled the basin zonation, while the second order factors determined the segmentation from east to west.