SPATIAL DISTRIBUTION OF ANCIENT SHUANGFENG-BIJIA OROGEN ON NORTHERN CONTINENTAL MARGIN OF SOUTH CHINA SEA

In order to reveal the spatial extent and the development characteristics of the folds and faults of the ancient Shuangfeng-Bijia collision orogenic belt in the northern continental margin of the South China Sea, stratigraphic and structural architectures of 22 seismic profiles are studied in details in addition to the comprehensive interpretation of lithological information from drilling holes. With the help of structural analysis, deleting the Cenozoic tectonic subsidence, the basic geometric features of the ancient Shuangfeng-Bijia collision orogenic belt are disclosed. After the integrated analysis of spatial fluctuation characteristics of the bottom boundary of the Cenozoic (seismic reflection surface of Tg), screening off the tectonic subsidence of Cenozoic, the deformation features of Pre-Cenozoic strata are observed. Spatially, the ancient Shuangfeng-Bijia collision orogenic belt is stretched in NEE direction, and the core part of the orogen is located on the southeastern slope of ocean-continent transition zone in the Pearl River Mouth Basin. It is close to 06 seismic line and next to the Qiongdongnan basin. In summary, the research results provided observation facts for reconstruction of late Mesozoic tectonic framework in the South China Sea, which is helpful for understanding the formation mechanism of the South China Sea.