Abstract:

The South China Sea (SCS) is a typical marginal sea whose northern continental slope has a high sedimentation rate, which provides ideal material for research on sub orbital scale climate variability. In this study, samples from sediment core MD12-3432 (19°16.88′N，116°14.52′E, water depth 2125 m) retrieved from the lower northern continental slope, northern South China Sea, are selected as the major research material. By applying multiple paleo environmental poxies analysis, including benthic foraminifera abundance, coarse fraction percentage, specific environment indicators percentage and abundance as well as relevant results from previous studies, the paleoceanographic history of the northern South China Sea is reconstructed, with emphasis on the variability of surface primary productivity and bottom water dissolved oxygen content. Different from previous studies, the results indicate that from Marine Isotope Stage 11(MIS 11, approximately 400 ka B.P.) the primary productivity in the northern SCS is high in warm interglacial period and low in cold glacial period, and it is mainly influenced by the intensity of precipitation controlled by the East Asian Summer Monsoon. During MIS 7 and MIS 9, the rise in the abundance of a low productivity and high dissolved oxygen indicator, the epifaunal Cibicidoides wuellerstorfi, coincides with high productivity indicators records. This inconsistency implies a possible intrusion of oxygenenriched bottom water in both warm time periods.

Key words: the northern South China Sea, benthic foraminifera, primary productivity, dissolved oxygen content