Distribution of organic carbon in surface sediments along the eastern Arabian Sea: a revisit

Abstract

One hundred twelve surface sediment samples along the western continental margin of India were analyzed for organic carbon (OC). Elevated OC concentrations are associated with sediments deposited in areas where productivity is moderate to high. Very high OC concentrations, as reported in earlier studies even for regions where productivity is comparatively low, could not be confirmed. The re-analysis of selected samples by coulometry shows that OC concentrations determined previously by the wet oxidation method may be too high by up to more than a factor of two. A broad similarity in the distribution of OC and bioproductivity is observed, which is in accordance with other productivity proxies, such as the abundance of planktonic foraminiferal species G. bulloides and hydrogen indices (HI). Our results indicate the importance of bioproductivity for OC accumulation along the western continental margin of India, even though low dissolved oxygen concentrations in the water column, sedimentation rate, sediment texture, clay mineral content, dilution by quartz and carbonate, as well as topography are considered responsible for the general OC distribution in this area.