Influence of the Kuroshio current intrusion on depositional environment in the Northern South China Sea: Evidence from surface sediment records

Abstract

The influence of the Kuroshio Current (KC) intrusion on the depositional environment of the northern South China Sea (SCS) is discussed based on multi-proxies of surface sediments including planktonic foraminifera, clay minerals and geochemical elements. The results reveal that four typical planktonic foraminifera ( Globigerinoides ruber, G. sacculifer, Neogloboquadrina dutertrei and Pulleniatina obliquiloculata) can be used to trace the KC flow route in the northern SCS. Globigerinoides ruber is mainly distributed in shallower water than the South China Sea Branch of the Kuroshio (SCSBK) flow route, while P. obliquiloculata is mostly distributed in deeper water than the SCSBK flow route. There are high percentages of G. sacculifer and N. dutertrei at the SCSBK flow route along the 1000-m isobath where bottom sediments consist of clayey silt and silty clay. The SCSBK also affects sediment distribution of various sources. Taiwan-sourced sediments characterized by high illite and chlorite contents are transported southwestward into the deep sea environment by the SCSBK and/or deep water current. The Pearl River sediments, characterized by high kaolinite and titanium (Ti) contents are mostly transported southwestward to be distributed in the sea environment between the Pearl River mouth and southeast of Hainan Island, but hardly entered the abyssal basin. The Luzon Island sediments, characterized by high smectite content, are generally deposited at the northwest of Luzon Island under the effect of an eddy west of Luzon Island. These sediments were hardly transported northwestward onto the northern shelf of the SCS throughout the SCSBK flow route. The sedimentary environment at the northwest of Luzon Island is relatively oxidized and higher in salinity than the northern SCS, which is probably connected with the KC intrusion through the Luzon Strait.