Development characteristics and formation mechanism of two-phase transfer zone during rifting in Wushi Sag, Beibuwan Basin, South China Sea

Based on the three-dimensional seismic dataset, we consider a key area in Beibuwan Basin, South China Sea, combined with quantitative analysis method, in order to define the features of transfer zone, and its temporal spatial development mechanism is revealed. The two boundary faults in the study area constitute an S-type fault system which does not connect. During the Paleogene rifting, the fault systems and Structuralstratigraphic characteristics between Eocene and Oligocene rifting sequences are different, the ways and quantities of transfer displacement are also distinctly different: (1) The two-phase of Eocene and Oligocene generally developed transfer zones, which were controlled by the structure background and boundary conditions, the formation mechanism of the transfer zone was different in time and space, the distribution of the transfer zone was distinctly different; (2) The Ailaoshan-Honghe strike slip fault, the extension derived from the expansion of the South China Sea have a significant impact on the transfer zone formation and characteristics. The segmented growth of the fault has a direct impact on the formation of the transfer zone. This study reveals the formation mechanism of the transfer zone of superimposed basins in China offshore, which is beneficial to hydrocarbon accumulation in Eocene and Oligocene sequences.