Provenance of deep-sea sediments in the eastern South China Sea since Marine Isotope Stage 5 (MIS 5) and implications for climate change and volcanic activity

Abstract

The South China Sea deep-sea basin receives large amounts of marine sediments and volcanic materials from the surrounding continents and islands, and it is an ideal region to study the effects of climate change and volcanic activity on sediment provenance. Core K2 was collected in a water depth of 4078 m in the eastern South China Sea and is mainly composed of diatoms, tephra, volcanic glass and slag. The results of a total of 102 analysed grains show that the depositional processes were dominantly suspension, uniform suspension and overbank-pool facies suspension, with no rolling. Six accelerator mass spectrometry (AMS) 14C ages from planktonic foraminifers and fifty-four δ18O data points of G. ruber suggest that the age of Core K2 is 125 kyr before present (BP). Forty-four clay mineralogical data points show that the clay minerals in the sediments are mainly illite+chlorite (24.3%–49.7%), with a small amount of smectite (2.6%–11%), suggesting a sediment source mainly from Taiwan with a small amount of sediment from Luzon. Forty-five samples yield 143Nd/144Nd and 87Sr/86Sr ratios ranging from 0.512250 to 0.512769 and from 0.704383 to 0.710690, respectively, indicating that sediments in K2 represent a mixture of volcanic inputs from in or around Luzon and sediments from Taiwan and Luzon. Based on calculations of clay minerals and SrNd isotopic data, the relative proportions of sediments from Taiwan and Luzon and volcanic input vary from 8% to 88%, from 1% to 23% and from 0% to 91%, respectively, and the average proportions of sediments from Taiwan and Luzon and volcanic input are 55%, 12% and 33%, respectively. Significant temporal changes in SrNd isotopes are attributed to variations in the volcanic eruption intensity or distance to the sampling location. Moreover, high εNd values and low 87Sr/86Sr ratios of the sediments in Core K2 during interglacial periods could represent volcanic eruptions.