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

One hundred twelve surface sediment samples along the western continental m argin of India were analyzed for organic carbon (OC), Elevated OC concentra tions are associated with sediments deposited in areas where productivity i s moderate to high. Very high OC concentrations, as reported in earlier stu dies 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 to o high by up to more than a factor of two. A broad similarity in the distri bution of OC and bioproductivity is observed, which is in accordance with o ther productivity proxies, such as the abundance of planktonic foraminifera l species G. bulloides and hydrogen indices (HI). Our results indicate the importance of bioproductivity for OC accumulation along the western contine ntal margin of India, even though low dissolved oxygen concentrations in th e water column, sedimentation rate, sediment texture, clay mineral content, dilution by quartz and carbonate, as well as topography are considered res ponsible for the general OC distribution in this area. (C) 1999 Elsevier Sc ience B.V. All rights reserved.