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Gas hydrate destabilization and methane release events in the Krishna-Godavari Basin, Bay of Bengal

DRS at CSIR-National Institute of Oceanography

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Title Gas hydrate destabilization and methane release events in the Krishna-Godavari Basin, Bay of Bengal
 
Creator Joshi, R.K.
Mazumdar, A.
Peketi, A.
Ramamurty, P.B.
Naik, B.G.
Kocherla, M.
Carvalho, M.A.
Mahalakshmi, P.
Dewangan, P.
Ramana, M.V.
 
Subject gas hydrate
global warming
tectonic
carbon isotope
 
Description Methane release events have been linked to global warming, alteration of the carbon cycle and influence on biota. However, unequivocal evidence of paleomethane release events are limited. We report several negative carbon stable isotope excursions in planktic and benthic foraminifera in a core (MD161-8) from the Krishna-Godavari (K-G) Basin, Bay of Bengal. The most negative 13C spikes are recorded during the marine isotope stages MIS-4 and at the transition of MIS-5 to 4. Occurrence of highly 13C depleted (average 13C = -48±2.4 ‰ VPDB) authigenic high magnesian calcite are also reported within this time window from the core MD161-8. In the present work an unequivocal explanation for the observed 13C depletion in the marine planktic and benthic foraminifera is difficult to achieve solely from the optical/ electron microscopy or C-O stable isotope ratio analyses due to possible influence of diagenetic alteration. We attribute the observed episodic methane expulsion events, as inferred from the negative 13C excursions and earlier reports on the occurrence chemosynthetic bivalves and Mo concentration anomaly to the destabilization of the base of gas hydrate stability zone (BGHSZ). Sea level drop and shale tectonics induced focused fluid flow are the two possible causes of hydrate destabilization discussed here. Shale tectonics were possibly responsible for creating fault systems which acted as the conduit for gas flow through the sediment column and subsequent seepage. Shale and salt tectonics in the passive continental margins being a globally observed phenomenon, its role as an important driving force for enhanced methane emission needs detailed investigation to understand the climatic perturbations through geologic time. Additional evidence of methane emission from site MD161-15 further supports the link between shale tectonics and methane emission.
 
Date 2015-01-08T08:50:25Z
2015-01-08T08:50:25Z
2014
 
Type Journal Article
 
Identifier Marine and Petroleum Geology, vol.58; 2014; 476-489
http://drs.nio.org/drs/handle/2264/4673
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2014] Elsevier
 
Publisher Elsevier