Ž . Marine Geology 162 1999 91–103 www.elsevier.nlrlocatermargeo Distribution of organic carbon in surface sediments along the eastern Arabian Sea: a revisit C. Prakash Babu a,1 , H.-J. Brumsack b, ) , B. Schnetger b,2 a Geological Oceanography DiÕision, National Institute of Oceanography, Dona Paula, 403 004, Goa, India b ( ) Institute of Chemistry and Biology of the Marine EnÕironment ICBM , UniÕersity of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany Received 2 April 1998; accepted 7 April 1999 Abstract One hundred twelve surface sediment samples along the western continental margin of India were analyzed for organic Ž . 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 Ž . 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. q 1999 Elsevier Science B.V. All rights reserved. Keywords: organic carbon; Arabian Sea; Indian continental margin; productivity; preservation 1. Introduction The spatial distribution and mode of accumulation Ž . of organic carbon OC in surface sediments along Ž . the western continental margin of India WCMI is Ž still a matter of discussion Pedersen and Calvert, 1990; Paropkari et al., 1992, 1993a,b; Calvert et al., . 1995 . OC enrichments of ) 8% with maxima of up ) Corresponding author. Fax: q49-441-798-3404; E-mail: brumsack@icbm.de 1 E-mail: pbabu@csnio.ren.nic.in, pbabu@darya.nio.org. 2 E-mail: schnetger@icbm.de. Ž to 12–16% Paropkari et al., 1987, 1992, 1993a, . 1994 are reported even in areas where bioproductiv- Ž y2 y1 . ity is low to moderate - 0.50 g C m day . These findings served as a basis to emphasize the importance of oxygen-depleted waters for OC preservation. During ongoing investigations focusing on the trace metal distribution along the WCMI, we sampled and routinely analyzed 112 surface sedi- ment samples for OC. According to our database, Ž . higher OC concentrations maximum 5.3% only seem to be associated with sediments deposited in Ž areas where productivity is moderate to high 0.50– y2 y1 . 1.0 g C m day . It seems that a few erroneously 0025-3227r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0025-3227 99 00047-X