Ratio of coccolith CaCO3 to foraminifera CaCO3 in late Holocene deep sea sediments

On the basis of measurements of the relative amounts of CaCO 3 in the less than 20‐ μ m and the greater than 20‐ μ m size fractions in open ocean core tops, we find that the coccoliths contribute about half the calcite present in late Holocene deep sea sediments which have experienced little or no dissolution. Although this ratio is of importance to the understanding of the ocean's CaCO 3 cycle, we can find only a few quantitative estimates of their relative contribution to currently forming marine sediments. As dissolution of foraminifera calcite takes place more rapidly than that of coccolith calcite, coccoliths dominate the CaCO 3 in sediments which have experienced sizable dissolution. Although coccoliths contribute 40–60 of the CaCO 3 in tropical sediments, higher‐latitude sediments and those adjacent to continental margins often have larger proportions of coccolith CaCO 3 .