FLUCTUATIONS OF TERRESTRIAL AND MARINE BIOMARKERS IN THE WESTERN TROPICAL PACIFIC DURING THE LAST 23,300 YEARS

A sediment core collected from Caroline Basin, western tropical Pacifi c was analyzed for lipid class compounds (aliphatic hydrocarbons, long -chain;alkenones, fatty alcohols, sterols, and fatty acids) to reconst ruct changes in paleoenvironments during the last 23.3 kyr. Around the boundary between the glacial and deglacial periods (19 ka), mass accu mulation rates of terrestrial biomarkers, C-25-C-35 n-alkanes, C-24-C- 28 fatty alcohols, and C-17-C-20 fatty acids, were found to decrease s ignificantly and stayed in low levels during the deglaciation, suggest ing a reduction of atmospheric transport of continental materials duri ng that time. In the same period, mass accumulation rates of C-17-C-20 n-alkanes, pristane, cholesterol, and dinosterol which are thought to be mainly derived from marine organisms also decreased, suggesting a significant drop of marine biological productivity. The decreased biol ogical productivity in the western tropical Pacific may be caused by a reduced supply of nutrients from upwelling which is associated with d ecreased wind velocity and/or caused by a shift of upwelling zone.