Quaternary carbonate record from the equatorial Indian Ocean and its relationship with productivity changes

Abstract

The CaCO sub(3) content in Quaternary deep-sea sediments from Pacific and Atlantic oceans have been suggested to respond differently to glacial/interglacial cycles; CaCO sub(3), contents are highest during glacials in Pacific but highest during interglacials in the Atlantic Ocean. It is not yet clear as to whether a Pacific or an Atlantic pattern of CaCO sub(3) fluctuations dominates the Indian Ocean. The Ocean Drilling Program (ODP) Site 709A from the western equatorial Indian Ocean for the last 1370 ka to determine the relationships between percentages and fluxes of CaCO sub(3) and Quaternary paleoclimatic changes is analysed. The coarse (> 25 mu m) and fine (less than 25 mu m) fractions of CaCO sub(3) in an attempt at estimating the influence of differences in productivity of foraminifera and calcareous nannofossils in shaping the CaCO sub(3) record is also analyzed. Carbon isotopes and Ba/Al ratios were used as indices of productivity. Percentages and fluxes of CaCO sub(3) in the total sediment and less than 25 mu m fraction do not show any clear relationships to glacial/interglacial cycles derived from delta sup(18)O of the planktonic foraminifera Globigerinoides ruber. This indicates that CaCO sub(3) fluctuations at this site do not show either a Pacific or an Atlantic pattern of CaCO sub(3) fluctuations. Fluxes of CaCO sub(3) (0.38 to 2.46 g cm sup(-2) ka sup(-1)) in total sediment and Ba/Al ratios (0.58 to 3.93 g cm sup(-2) ka sup(-1)) show six-fold variability through the last 1370 ka, which points out that productivity changes are significant at this site