Plate convergence controls long-term full-depth circulation of the South China Sea

Abstract

How plate tectonics may affect full-depth ocean/sea circulation is not well understood. We used seismic data plus drilling/core and geomorphologic data to examine the influence of regional tectonics on South China Sea circulation. The features of four contourite depositional complexes across the sea, continental shelf to abyssal plain, indicate that plate convergence has controlled circulation within this marginal sea since the beginning of its closure, primarily via Luzon Strait changes. Initially (late Miocene), South China Sea circulation was open, as a part of North Pacific ocean circulation. Later (Pliocene to early Pleistocene) creation of the Luzon Strait reversed the direction of South China Sea surface circulation but not its deeper circulation. Subsequent (middle Pleistocene to present) narrowing and shallowing of the strait weakened surface, intermediate, and bottom flows within the sea but strengthened deepwater flow. This contourite-based approach to elucidating tectonic effects on surface-to-bottom paleo-circulation can be applied to other marine basins within an active tectonic setting.