The Origin of Millennial-Scale Variations in the Sulu Sea

Dannenmann, S. 1 (518-442-4470;

Linsley, B.K. 1 (518-442-4478;

Beaufort, L. 2 ((33) 442 97 15 71;

1 Department of Earth and Atmospheric Sciences, University at Albany,

SUNY, Albany, NY 12222

2 CEREGE-CNRS, Europole Mediterranéen de l'Arbois, BP 80, 13545 Aix-

en-Provence Cedex 4 France

Preliminary evidence from deep marine late Pleistocene and Holocene sediments from the Sulu Sea basin in the Western Pacific suggests that areas in this basin contain high-resolution records of paleoceanographic change including surface ocean millennial-scale variations during several intervals. The most pronounced variations occur during the Younger Dryas Chronozone, within stages 2, and 5, and at the stage 6/5 transition. In this study we are re-examining the cause of these events in the Sulu Sea through isotopic analysis of additional planktonic foraminifera species in ODP Site 769A and through isotopic and faunal analysis of samples collected at 1cm intervals in IMAGES core MD972141 collected near the site of ODP 769A. Our goal is to determine whether the documented d18O variations are related to surface salinity changes and the East Asian monsoon. Data from stable isotopic analyses of the planktonic foraminifera Globigerinoides sacculifer and Globigerinoides ruber will be presented for ODP Site 769A over the last 150 kyr and in MD972141 across the last deglaciation and over other selected intervals. Preliminary d18O results of G. sacculifer from Site 769A agree with observed millennial-scale variations of the previously published d18O data of G. ruber. Ongoing isotopic analyses of the same two species from core MD972141 will be used to confirm and temporally define these millennial scale events.