FLUCTUATIONS OF CARBONATE CONTENT AND ITS CONTROL FACTORS IN THE WESTERN PHILIPPINE SEA FOR THE LAST 150KA

The carbonate content of bulk samples was analyzed for the sediment cores of MD06-3050 taken from Benham Rise, western Philippine Sea. The fluctuations in carbonate content for the past 150 ka show a general pattern of the "Atlantic type" of carbonate cycle, i.e. lower in glacials and higher in interglacials. Both sediment coarse fractions and foraminifera fragment ratios were used as indicators of the dissolution intensity of carbonate, and show a similar pattern to carbonate content change since 150 ka. TOC content in bulk samples was also measured, which showed a good consistency with carbonate content. In contrast, the primary productivities derived from the relative abundance of coccolith species F.profunda, yield significantly different trend. By comparison of above proxies, it is inferred that there may be multiple factors controlling the variation in carbonate content, but dissolution is certainly the most important. This dissolution pattern maybe related to the Corg/CaCO₃ rain ratio and the ventilation of deep water.