Upward flow of North Pacific Deep Water in the northern South China Sea as deduced from the occurrence of drift sediments

Abstract

Reflection seismic profiles show that drift sediments occur in the depth range of 1200–2800 m on the continental margin off Southeast China. These drift deposits were generated by upward flow near the Dongsha Islands of the North Pacific Deep Water (NPDW), which enters the South China Sea via the Bashi Channel (sill depth >2500 m). This flow results in deposition of slope sediments resuspended off East and South Taiwan on the slope southeast of the Dongsha Islands. At 1200 m water depth, this upward flow probably terminates and the NPDW mixes with the surface water. Sediment ages from ODP site 1144 southeast of the Dongsha Islands show that this process started at least 1.1 m.y. ago. Indications for mass wasting in the area of upslope water flow document the simultaneous occurrence of current‐ and gravity‐controlled sedimentation processes. However, bottom current‐related drift sedimentation dominates.