Integrated geophysical study of Mesozoic distribution in northeastern continental margin of the South China Sea

Abstract

From the sixties of last century, a series of geophysical surveys had been launched in northeastern continental margin of the South China Sea (SCS) and a lot of study of geological structure features about Mesozoic in this zone had been carried out. Many researchers have presented the view of existance of Mesozoic, and made certain the reflection beneath the one of Cenozoic in the seismic sections to be Mesozoic, which was thought as the product of early rift. In the early acquisition of seismic data, most of the settings of acquisition time and parameters were aimed at Cenozoic. Great limitation exists in such sections to reveal the Mesozoic strata, and just in some sections Mesozoic can be identified. This situation makes it very difficult to depict the feature of Mesozoic completely through seismic data. Chen Bing (2004) calculated the thickness of Mesozoic in Chaoshan Depression through the inversion of gravity data in the restrain of seismic data, which promoted the study of Mesozoic in this area. But the cognition of Mesozoic in northeastern continental margin of SCS should be known from a larger scope. In recent years, geophysical data (gravity, magnetic and seismic) have been newly acquired in northeastern of SCS. The quality of seismic sections has gained great improvement, with the enhancement of the technique of gathering and processing. Bottom of Mesozoic can now be identified in some sections. Studies also reveals that (Liu Zhaoshu et al., 2002), in Pearl River Mouth Basin, magnetic basement is basically consistent with the basement of basin, except some shallow interference of magnetic body. Thus, we can calculate the distribution of thickness of Mesozoic in this key zone through joint inversion of gravity and magnetic data, in the restrain of Mesozoic bottom revealed from those seismic sections with high quality.