Palaeoproductivity of the eastern Arabian Sea during the past 200 ka: A multi-proxy investigation

Two sediment cores from the eastern Arabian Sea were investigated for reconstructing the late Quaternary palaeoproductivity using a variety of proxies: the relative abundance of Florisphaera profunda in the total coccolithophore flora (%Fp), organic carbon (Corg), and calcium carbonate contents. The low abundance of Fp during glacial periods suggests a significantly enhanced primary productivity during those periods. The high Fp abundance during Terminations II and I implies that the productivity was low during deglaciation. The reduced productivity was probably a result of the intensification of the SW monsoon during the two terminations. The high Corg content documented for glacial periods (marine isotopic stages 2, 4, and 6) also suggests that productivity was high during glacial periods. The consistent results obtained from two independent proxies (%Fp and Corg) for palaeoproductivity confirm that productivity was indeed high during glacial periods, and hence the high Corg content is not just an artifact of better preservation of organic matter due to high sedimentation rate. ore variations in the CaCO3 content and δ18O show coherent fluctuations and typical glacial–interglacial cyclicity. Glacial periods were characterised by low CaCO3 and interglacials by high CaCO3 content. Interestingly, the low CaCO3 content during glacials is in contrast to the high productivity suggested by the low relative abundance of Fp and the high Corg content. Therefore, the low carbonate content during glacial periods was probably due to dilution by terrigenous material and/or increased biogenic opal production. al analysis of data on palaeoproductivity proxies shows a 23 ka periodicity indicating that the Earthʹs precessional cycle exerts a significant control on the palaeoproductivity of the eastern Arabian Sea.