Late Quaternary paleoceanography of western Pacific marginal basins

A series of quantitative studies of benthic and planktonic foraminifera in deep-sea sequences from South China and Sulu Sea have been used to reconstruct the late Quaternary paleoceanographic history of this region.; Sea surface temperature (SST) estimates were derived using a planktonic foraminiferal transfer function (FP-12E). The SST records from South China Sea and Sulu Sea indicate that during the Last Glacial Maximum, South China SST dropped by 2{dollar}spcirc{dollar}C in summer and by 5-7{dollar}spcirc{dollar}C in winter. Sulu Sea SST dropped by 1{dollar}spcirc{dollar}C in summer and by 2-3{dollar}spcirc{dollar}C in winter. Variations in the intensity of the monsoon system and surface water exchange rates between basins are the major factors controlling glacial-interglacial SST fluctuations in the South China Sea and Sulu Sea. The primary factor influencing the accuracy of our SST estimates is the quality of preservation of planktonic foraminiferal assemblages.; Surface sediment samples collected from the South China and Sulu Seas were examined to determine the bathymetric distribution of benthic foraminifera in these two basins and the factors responsible for these distributions. Four faunal assemblages were identified for each basin by Q-mode principal component analysis. A correlation between various environmental and benthic foraminiferal variables indicates that organic carbon content and oxygen penetration depth in sediments appear to play important roles in determining the distribution of benthic foraminifera in both basins.; The study of distributions of benthic foraminifera in both basins for the last 25,000 years is based on the time slice and time series benthic foraminiferal data. Benthic foraminiferal abundances (BN) in glacial and deglacial-age sediments were more than twice that of the present day in the South China Sea and Sulu Sea. In the South China Sea, B. aculeata and Uvigerina were most important at water depths above 3,000 m in the South China Sea during the last glacial. In the Sulu Sea, glacial assemblages were dominated by P. sphaera and B. robusta at water depth above 3000 m. Two paleoceanographic implications can be drawn from our observations: (1) an increase in surface productivity and (2) a decrease in the level of carbonate undersaturation occurred during the last glacial in the both basins.