Stable isotopic records of the glacial deep-water properties in the South China Sea

Based on the oxygen and carbon stable isotopic records of benthic foraminifera in nine deep-sea cores of the South China Sea (SCS), the bathymetric profiles of δ 18O and δ 13C since the last glacial maximum (LGM) are preliminarily established. The bathymetric gradients of deep-water δ 18O and δ 13C in the SCS are obviously greater during the LGM than during the Holocene, showing the existence of the deep thermocline and nutricline at water depth of about 2 000 m. Particularly, the differences in δ 18O and δ 13C between the LGM and Holocene, from which the ice-volume effect and the global mean shift have been subtracted respectively, are positive values at water depths of 1 000-2 500 m in the SCS. This indicates the existence of deep-water mass with relatively cool temperature or higher salinity, better ventilation and more δ 13C within the water depth range of the SCS during the LGM, which is distinctly different from that at present. These changes further confirm the existence of the glacial "North Pacific Deep Water" which, however, is possibly confined to the water depth range of 1 000-2 500 m.