CARBONATE PRESERVATION VARIATION IN THE CAROLINE BASIN DURING THE LAST 330 KYR

The carbonate content of two cores from the West Caroline Basin in the western equatorial Pacific was examined during the last 330 kyr. The results show that carbonate content varied greatly in core C4402, whic h was taken from a water depth of 4,402 m between the present-day lyso cline and the Carbonate Compensation Depth (CCD), whereas the content in core NGC34 which was recovered from a water depth of 2,188 m, displ ays no distinct glacial-interglacial difference. The fluctuations obse rved in core C4402 are ascribed to dissolution induced by change in se awater chemistry rather than by changes in local rain rate of organic carbon. The degree and pattern of carbonate preservation in the West C aroline Basin differ from that observed in cores from the Ontong Java Plateau although both areas are within the western equatorial Pacific. The chronostratigraphy for cores C4402 and NGC34 is based on delta(18 )O records to the SPECMAP stack record and on coccolithophorid stratig raphy. We chose delta(18)O records as the second variable in a cross-s pectral analysis of delta(18)O versus the preservation degree. No sign ificant differences were found even when we used a stacked delta(18)O record. Spectral comparison of carbonate preservation and delta(18)O r ecords shows high coherencies at the 100-kyr and 41-kyr periodicities, but low coherency at the precessional period (23-kyr). We interpret t he high coherencies as evidence that deep-water circulation changes, d riven by high-latitude climatic forcing in the North Atlantic, are the principal source of variability in the carbonate preservation record of the West Caroline Basin. Carbonate preservation is in phase with de lta(18)O at the 100-kyr period, indicating a rapid response of the dis solution intensity in Pacific deep and/or bottom water to changing cli mate.