Abstract
The extensional model of the South China Sea (SCS) has been widely studied, but is still debated. Analysis of the latest high-quality multi-channel seismic data acquired by the National Basic Research Program of China, together with existing seismic profiles and bathymetry data, reveal asymmetry between the conjugate margins of the SCS. Two interpreted strike-slip faults divide the SCS into three basins: the Zhongnan Fault separates the eastern basin (EB) from the southwest basin (SWB), and the Xinin Fault subdivides the SWB into eastern and western components (E-SWB and W-SWB). Each of these sub-basins has totally different structural features on their conjugate margins. A detachment fault is identified within the crust on the southern margin and is believed to play an important role in the Cenozoic evolution of the SCS. Referring to extant and well-recognized extension models of detachment plus pure shear, a differential extensional model is proposed for the rifting of the SCS. Because of different lateral mass transfer between the observed upper detachment fault and inferred lower ductile extensional regions, a marginal plateau (Liyue basin) and outer rise (Zhenghe massif) developed on the lower plate margin of the EB and E-SWB, respectively. Several geological and geophysical features indicate that the W-SWB may be a failed rift, with no formation of oceanic crust.