ABSTRACT

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, which was taken from a water depth of 4, 402 m between the present-day lysocline and the Carbonate Compensation Depth (CCD), whereas the content in core NGC34 which was recovered from a water depth of 2, 188 m, displays no distinct glacial-interglacial difference. The fluctuations observed in core C4402 are ascribed to dissolution induced by change in seawater chemistry rather than by changes in local rain rate of organic carbon. The degree and pattern of carbonate preservation in the West Caroline 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 δ¹⁸O records to the SPECMAP stack record and on coccolithophorid stratigraphy. We chose δ¹⁸O records as the second variable in a cross-spectral analysis of δ¹⁸O versus the preservation degree. No significant differences were found even when we used a stacked δ¹⁸O record. Spectral comparison of carbonate preservation and δ¹⁸O records shows high coherencies at the 100-kyr and 41-kyr periodicities, but low coherency at the precessional period (23-kyr). We interpret the high coherencies as evidence that deep-water circulation changes, driven 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 δ¹⁸O at the 100-kyr period, indicating a rapid response of the dissolution intensity in Pacific deep and/or bottom water to changing climate.