SEISMIC REFLECTION CHARACTERISTICS OF NANWEI UPLIFT ZONE IN NANSHA AND THEIR APPLICATION TO STRUCTURAL UNIT DIVISION

A large number of continental margin rifting basins are well developed on the Nanwei uplift of Nansha Waters, which bears great oil and gas potentials. The region experienced a complex evolutionary history in Cenozoic period, including extensional rifting from Late Mesozoic to Paleogene and seafloor spreading in Late Eocene. A high-resolution single-channel seismic line Nan-1, acquired in the Nansha by the trial vessel "Shiyan 2" of the South China Sea Institute of Oceanology in 2013, is interpreted and analyzed in this study. As well, some previous seismic profiles and drilling data are studied. The seismic reflection characteristics of the Nanwei uplift in the southern margin are summarized and outlined briefly. Results show that the Nanwei uplift zone is mainly composed of two structural units, the southern belt of subsidence and the northern belt of buried volcanic uplift. Compared to the previous reflection seismic data in this area, some main seismic reflection layers are divided. The belt of buried volcanic uplift is about 63 km wide, and the neighboring subsidence belt 58 km wide both in SE direction. The distribution of sporadic epicenters stronger than 4 magnitude earthquakes suggest that the entire Nanwei uplift is still a relatively stable tectonic body since Pliocene.