Fluctuations of terrestrial and marine biomarkers in the western tropical Pacific during the last 23,300 years


  • N. Ohkouchi,

  • K. Kawamura,

  • A. Taira


A sediment core collected from Caroline Basin, western tropical Pacific was analyzed for lipid class compounds (aliphatic hydrocarbons, long-chain alkenones, fatty alcohols, sterols, and fatty acids) to reconstruct changes in paleoenvironments during the last 23.3 kyr. Around the boundary between the glacial and deglacial periods (19 ka), mass accumulation rates of terrestrial biomarkers, C25-C35 n-alkanes, C24-C28 fatty alcohols, and C23-C34 fatty acids, were found to decrease significantly and stayed in low levels during the deglaciation, suggesting a reduction of atmospheric transport of continental materials during that time. In the same period, mass accumulation rates of C17-C20 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 biological productivity in the western tropical Pacific may be caused by a reduced supply of nutrients from upwelling which is associated with decreased wind velocity and/or caused by a shift of upwelling zone.