COCCOLITHOPHORE RECORDS AND THEIR RESPONSE TO PALEOCLIMATIC AND PALEOENVIROMENTAL CHANGES IN SULAWESI SEA FROM THE LAST DEGLACIAL

To reconstruct the variation in paleoproductivity and nutricline of sea water over the last 20 ka, we analyzed the relative abundance of coccolithophores in deep sea core MD98-2178 (3.62°N,118.70°E), Sulawesi Sea. Three coccolihophores species, Emilania huxleyi, Gephyrocapsa oceanica and Florisphaera profunda, representing 80%~90% relative abundance, dominate the coccolith assemblage. Owing to the absolutely different ecological niche between G.oceanica and F. profunda, they experienced inverse variation trend, the former being sensitive to nutritive material in sea water and representing high productivity, and the latter indicating low productivity and deep nutricline. We suggest that two models can be attributed to coccolihophores responding to paleoenvironment around the timing 13.5 ka in the deglacial. Before 13.5 ka coccolihophores and their productivity mainly responded the nutritive material that transported by run-off, and after 13.5 ka they responded to the intensity of hydrology between sea water and atmosphere. Centennial scale oscillations of F. profunda% are found in the Holocene period, being agreement with solar activity in 100~260 years cycles. We infer that long-term ENSO-like conditions and solar activities could force the variation of nutricline in Holocene.