Provenance and weathering of sediments in the deep basin of the northern South China Sea during the last 38 kyr

Abstract

Deep-sea sediments are ideal recorders for studying the provenances and relevant chemical and physical weathering of adjacent lands. Major, trace (Fe, K, Al, Ti, V, Rb, Th, and Cr), and rare earth elements (REEs), grain size, and AMS 14C ages were studied on a 4-m-long core CS11 collected from a deep basin in the northern South China Sea (SCS). Core CS11 sediments were mainly derived from southwestern Taiwan Island and transported by the southward bottom current during most of the study periods, except from 37 to 35 kyr BP, when northern Luzon inputs temporarily had influence. For the past 35 kyr, the stacked chemical weathering index (SCWI) correlated well with the worldwide Younger Dryas (YD), Heinrich 1 (H1), Heinrich 2 (H2), and Heinrich 3 (H3) events, indicating global climate control on weathering intensity in this area. However, the SCWI showed the strongest chemical weathering intensity during the low sea level at the Last Glacial Maximum (LGM) when Taiwan-derived sediments were subaerially exposed on the shelf, chemically weathered and increasingly transported to the deep basin of the SCS. The major factors influencing chemical weathering intensities for sediments in the deep basin of the northern SCS varied on different geological time scales, with climate changes on millennial scales and sea-level changes on orbital scales.