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Pore-water sulfate concentration profiles of sediment cores from Krishna-Godavari and Goa basins, India

A. MAZUMDAR, A. L. PAROPKARI, D. V. BOROLE, B. R. RAO, N. H. KHADGE, S. M. KARISIDDAIAH, M. KOCHERLA, HILDA M. JOÄO
2007 Geochemical Journal  
Several cores from Krishna-Godavari (Western Bay of Bengal) and Goa (Eastern Arabian Sea) basins have been studied for pore water sulfate concentrations in order to understand and contrast the diagenetic processes. K-G sediments differ markedly from Goa sediments in pore water sulfate gradients and depth-integrated sulfate reduction rates. Significantly higher sulfate reduction rates in K-G sediments (3.6 to 15.8 nmol cm -2 day -1 ), compared to that in Goa sediments (0.011 to 0.94 nmol cm -2
more » ... o 0.94 nmol cm -2 day -1 ), can be attributed to higher sedimentation rates. Lower exposure time to oxygen for the organic matter in K-G sediments has preserved reactive organic compounds required for sulfate reducers and possibly methanogens. Authigenic carbonates with depleted carbon isotopic composition (δ 13 C = -48 to -50‰) at the base of the sulfate reduction zone in a core from K-G suggests anaerobic methane oxidation (AMO) process. The possibility, that the underlying methane gas hydrate zone is acting as a methane source for sulfate reduction can not be negated specially in light of the existing geophysical studies. Both methane and the fermentation products of organic matter degradation served as a substrate for sulfate reduction. However, a clear understanding of there relative importance needs further investigation.
doi:10.2343/geochemj.41.259 fatcat:j4bgkn2b7rdsfezlk7f3pwznzq