Coupled C-S-Fe geochemistry in a rapidly accumulating marine sedimentary system: Diagenetic and depositional implications
Date
2015Author
Peketi, A.
Mazumdar, A.
Joao, H.M.
Patil, D.J.
Usapkar, A.
Dewangan, P.
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In the present study, we have investigated the C-S-Fe systematics in a sediment core (MD161-13) from the Krishna-Godavari (K-G) basin, Bay of Bengal he core covers the late Holocene period with
high overall sedimentation rate of 573 cm kyr 21 . Pore fluid chemical analyses indicate that the depth of
the present sulfate methane transition zone (SMTZ) is at 6 mbsf. The (DTA 1 DCa 1 DMg)/DSO 22
4 ratios
suggest that both organoclastic degradation and anaerobic oxidation of methane (AOM) drive sulfate
reduction at the study site. The positive correlation between total organic carbon content (TOC) and chro-
mium reducible sulfur (CRS) content indicates marked influence of organoclastic sulfate reduction on sulfid-
ization. Coupled occurrence of 34 S-enriched iron sulfide (pyrite) with 12 C-enriched authigenic carbonate
zones is the possible records of paleo-sulfate methane transition zones where AOM-driven-focused sulfate
reduction was likely fueled by sustained high methane flux from underlying gas-rich zone. Aluminum nor-
malized poorly reactive iron (Fe PR /Al) and La/Yb ratios suggest increasing contribution from Deccan basalts
relative to that of Archean-Proterozoic granitic complex in sediment flux of Krishna-Godavari basin during
the last 4 kyr
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