Late-quaternary biogenic productivity and organic carbon deposition in the eastern Arabian sea

Abstract

Paleoproductivity variations in the eastern Arabian Sea, during the late Quaternary period (~42 ka BP to present), have been studied using accumulation rates of sedimentary biogenic components: organic carbon (C_org), nitrogen (N), CaCO₃, Sr and Ba. Such a multi-proxy approach reveals decreased surface productivity during the last glacial-interglacial transition. The observed change of surface water productivity during the last glacial-interglacial period is in antiphase to those observed in other low- and mid-latitude upwelling areas, however, consistent with some of the upwelling regions like NW Africa and NW Mexico. Sedimentary C_org and N are found to be decoupled from surface productivity trend, with significant enrichments in C_org and N during the Last Glacial Maximum (LGM). This is interpreted in terms of increase in sedimentation rates (by a factor of 3-4) resulting in the better preservation of C_org during the LGM.