Evidence of paleo-cold seep activity from the Bay of Bengal, offshore India

We report evidence of paleo-cold seep associated activities, preserved in methane-derived carbonates in association with chemosynthetic clams (Calyptogena sp.) from a sediment core in the Krishna-Godavari basin, Bay of Bengal. Visual observations and calculations based on high-resolution wet bulk de...

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Bibliographic Details
Published in:Geochemistry, Geophysics, Geosystems
Main Authors: Mazumdar, A., Dewangan, P., Joaeo, H. M., Peketi, A., Khosla, V. R., Kocherla, M., Badesab, F. K., Joshi, R. K., Roxanne, P., Ramamurty, P. B., Karisiddaiah, S. M., Patil, D. J., Dayal, A. M., Ramprasad, T., Hawkesworth, C. J., Avanzinelli, R.
Format: Article in Journal/Newspaper
Language:English
Published: Amer Geophysical Union 2009
Subjects:
methane hydrate
cold seep
authigenic carbonate
Bay of Bengal
AMO
chemosynthetic community
Methane hydrate
Online Access:https://archimer.ifremer.fr/doc/00218/32911/31414.pdf
https://doi.org/10.1029/2008GC002337
https://archimer.ifremer.fr/doc/00218/32911/
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Summary:We report evidence of paleo-cold seep associated activities, preserved in methane-derived carbonates in association with chemosynthetic clams (Calyptogena sp.) from a sediment core in the Krishna-Godavari basin, Bay of Bengal. Visual observations and calculations based on high-resolution wet bulk density profile of a core collected on board R/V Marion Dufresne (May 2007) show zones of sharp increase in carbonate content (10-55 vol%) within 16-20 meters below seafloor (mbsf). The presence of Calyptogena clam shells, chimneys, shell breccias with high Mg calcite cement, and pyrite within this zone suggest seepage of methane and sulfide-bearing fluid to the seafloor in the past. Highly depleted carbon isotopic values (delta(13)C ranges from -41 to -52% VPDB) from these carbonates indicate carbon derived via anaerobic oxidation of methane. Extrapolated mean calendar age (similar to 58.7 ka B. P.) of the clastic sediments at a depth of 16 mbsf is close to the upper limit of the U-Th based depositional age (46.2 +/- 3.7 and 53.0 +/- 1.6 ka) of authigenic carbonates sampled from this level, thereby constraining the younger age limit of the carbonate deposition/methane expulsion events. The observed carbonate deposition might have resulted from the flow of methane-enriched fluids through the fracture network formed because of shale diapirism.

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