QUATERNARY HISTORY OF CALCIUM-CARBONATE FLUCTUATIONS IN THE WESTERN EQUATORIAL INDIAN-OCEAN (SOMALI BASIN)

A study of the Quaternary history of calcium carbonate fluctuations in the equatorial Indian Ocean, based on the Swedish Deep-Sea Expedition Core 154 demonstrates that the Calcite Compensation Depth (CCD) was s hallower during interglacial periods than during glacials. Higher perc entages of calcium carbonate, lower percentages of dissolution-resista nt planktonic foraminifera and lower values of the Berger dissolution index, suggesting better calcium carbonate preservation, are recorded during glacial periods and/or at glacial/interglacial transitions. In contrast, interglacial periods are marked by stronger calcium carbonat e dissolution. The data indicate that dissolution is the main controll ing factor of calcium carbonate in the western equatorial Indian Ocean . Higher dissolution during interglacial periods and enriched deltaC-1 3 are due to higher noncarbonate productivity and enhanced Antarctic B ottom Water (AABW) ventilation in the equatorial Indian Ocean.