Calcareous Nannofossils in Surface Sediments of the Central and Northern Parts of the South China Sea

Abstract. Taxonomic composition and quantitative distribution of calcareous nannofossils in the nothern and central parts of the South China Sea were studied in 146 samples of surface sediments taken from estuary, continental shelf, continental slope and deep-water basin. This paper reports distribution patterns of nannofossils in the area, including nannofossil abundance, species, assemblages and specimen size. Abundance increases from shelf to slope, with a decrease from the lower part of the slope towards the abyssal plain. The assemblages are dominated by Emiliania huxleyi, Gephyrocapsa oceanica and Florisphaera profunda. Ecologically the effects of water temperature, and nutrient inputs can be detected in the distribution of nannofossils, while dilution by terrigenous materials and deep sea carbonate dissolution influence the sedimentological aspect of the samples. The composition of the South China Sea nannofossil assemblage enables it to be grouped with the central zone of the North Pacific in biogeographic zonations of nannoplankton.