Terrigenous-n-alkane input in the South China Sea:high-resolution records and surface sediments

Abstract

Molecular abundances of n-nonacosane are reported for a suite of 44 surface sediments and four deep sea cores distributed throughout the South China Sea (SCS), covering the last 220 ky at different time resolutions. The patterns of glacial to interglacial variability of the concentrations of this terrigenous marker are parallel for all cores, taking values linearly inversely correlated to the UK′37 index sea surface temperatures (SST), with high concentrations during cold-glacial intervals and low concentrations during warm-interglacial periods. The oscillations of this terrigenous marker likely result from the emergence and flooding of the shelves caused by sea-level variations which, together with SCS SSTs, have a clear dependency on the Northern Hemisphere climate evolution. Calculation of accumulation rates for the northernmost core together with the modern distribution of n-nonacosane concentrations in surface sediments evidences the complexity of sedimentation patterns in the northern SCS. In particular, and in agreement with recent studies, terrigenous materials deposited there might originate from areas different than the highly loaded Pearl River. For paleoceanographic purposes, the noticeable general pattern of the n-alkane concentration down-core profiles for the four cores studied, a parameter apparently unaffected by changes in sedimentation rates, prompts its use as a tracer of variations in terrigenous input into this basin over glacial to interglacial times.