Jump event of mid-ocean ridge during the eastern subbasin evolution of the South China Sea

Abstract

The South China Sea is one of the largest marginal seas in the Western Pacific region, and it has been widely accepted that the evolution of the basin and the development of its oceanic crusts is closely linked to seafloor spreading. A great controversy, however, is around whether or not there was a jump of mid-ocean ridges during seafloor spreading, particularly in the eastern South China Sea subbasin. A tectonostratigraphic interpretation using high-resolution seismic data demonstrated that: (1) a southward jump event of the mid-ocean ridge took place in the eastern subbasin during the seafloor spreading; (2) the orientation of the mid-ocean ridge had dramatically changed after the event resulting in that the abandoned mid-ocean ridge is along an east–west direction, whereas the younger one is generally east–northeast/west–southwest oriented; (3) the corresponding surface caused by the jump tectonic event and the pre-event sequence can be traced throughout the earlier formed oceanic crust; and (4) paleo-magnetic data showed that the event occurred at approximately 25–23.8 Ma. The results of this study could be used to better understand the evolution and filling of the South China Sea and other associated marginal basins.