Sea surface salinity and bottom water oxygenated conditions in western equatorial Pacific marginal seas during the last glaclal age

Abstract

Based on Core GGC-6 from the South China Sea (SCS) and Core GGC-29 from the Sulu Sea, planktonic and benthic foraminifera and organic carbon measurements were used to evaluate the water mass conditions in these sea areas during the last glacial age. The results show that the higher organic carbon contents in the SCS and Sulu Sea during the last glacial period were mainly caused by low dissolved oxygen concentrations in bottom waters and that in the last glacial to Holocene, the fluctuation of dissolved oxygen in the bottom waters was large in the SCS and relatively stable in the Sulu Sea. In addition, increased precipitation reduced surface water salinities, which caused the water column to be more stratified in the SCS and Sulu Sea during the last glacial period. This process lowered dissolved oxygen concentrations in bottom waters, which resulted in better preservation of organic matter in both basins.