Evolution of the tectonic stress regime in the Pearl River Mouth Basin and its constraints on the spreading of the South China Sea

Abstract

The formation and evolution of the South China Sea (SCS) have been a great concern in the academia for many years, but still are controversial. The evolution of the SCS can be constrained by studying the tectonic stress regime of the Pearl River Mouth Basin (PRMB), one of the representative basins in the northern continental margin of the South China Sea. Based on the analysis of high-resolution 2D and 3D seismic data, we discover seesaw sedimentary filling features above and below a crucial unconformity interface, the T80 reflection interface (40 Ma), which corresponds to a transformation in the tectonic stress regime of PRMB. We also find that before 40Ma (below the T80 reflection interface), the PRMB was extended in the NW-SE direction, and during 40–10.5 Ma (between T80–T32), the extension direction was nearly N-S and kept unchanged. With the constraints of tectonic stress regime of PRMB and other basins in the north of SCS, a new tectonic evolution model of the SCS is proposed. During 40–15.5 Ma, the formation of the SCS Oceanic Basin was driven by near N-S extension under conditions of pre-existing structures. The seawater depth and the seafloor geography in the SCS Oceanic Basin also can support this new model.