Widespread occurrence of methane seeps in deep-water regions of Krishna-Godavari basin, Bay of Bengal

Dewangan, P.; Sriram, G.; Kumar, Aditya; Mazumdar, Aninda; Peketi, A.; Mahale, V.; Reddy, S.S.C.; Babu, Anu K.

doi:10.1016/j.marpetgeo.2020.104783

Cited by 21 publications

(20 citation statements)

References 116 publications

(179 reference statements)

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“…Repeated occurences of authigenic carbonates (Figures 8A-K; Table 1) from 45 to 219 cmbsf in core SSD-045/Stn-9/GC-01 indicate the episodic events of intense AOM due to enhanced methane flux. This also show the variability in past methane fluxes could be due to episodic ventilation of deep-seated methane gas or dissociation of gas hydrates or opening/closing of fault/fracture system driven by neo-tectonic activity (Dewangan et al, 2020).…”

Section: Correlation Between Magnetic Parameter and Mean Grain Sizementioning

confidence: 78%

“…The seep occurs due to deformation structures (fault/fractures and diapirs) formed due to shale tectonism in K-G basin (Dewangan et al, 2010;Sriram et al, 2020). A high-resolution seismic data beneath the seep sites showed the presence of acoustic chimneys, and the overburden is heavily faulted (Dewangan et al, 2020). Deeprooted faults provide a conducive environment for the migration of methane from deep-seated gas reservoir and led to the development of a cold seep ecosystem and formation of shallow fracture-filled gas hydrate deposits at the studied site (Dewangan et al, 2020;Mazumdar et al, 2019;Sriram et al, 2020).…”

Section: Introductionmentioning

confidence: 89%

“…A high-resolution seismic data beneath the seep sites showed the presence of acoustic chimneys, and the overburden is heavily faulted (Dewangan et al, 2020). Deeprooted faults provide a conducive environment for the migration of methane from deep-seated gas reservoir and led to the development of a cold seep ecosystem and formation of shallow fracture-filled gas hydrate deposits at the studied site (Dewangan et al, 2020;Mazumdar et al, 2019;Sriram et al, 2020). High methane flux and favourable P-T conditions supported the accumulation of gas hydrates (Mazumdar et al, 2019).…”

Section: Introductionmentioning

confidence: 89%

“…High magnetic susceptibility in the bottom most sediment interval containing massive gas hydrate deposit (MZ-3) can be attributed to the survival of detrital magnetic grains due to both hinderance of diagenetic reactions due to trapping of H 2 S within hydrate (Housen and Musgrave, 1996;Riedinger et al, 2005) and rapid burial and preservation of the detrital magnetic grains due to higher sedimentation events (Badesab et al, 2019). Such gas hydrates requires efficient methane migration from deep-seated reservoir through the fracture system as evident from the existence of seismic chimneys beneath this site (Dewangan et al, 2020). Some active faults may even transport methane to seafloor, which is observed as methane gas flares (Mazumdar et al, 2019).…”

Section: Evolution Of Active Cold Seep System In Krishna-godavari Basmentioning

confidence: 98%

“…Repeated occurences of authigenic carbonates from 45 to 219 cmbsf in core SSD-045/Stn-9/GC-01 support multiple episodes of AOM intensification in the past. The opening/ closing of fault/fractures due to neo-tectonic activities allowed migration of methane from deep-seated gas reservoir (Dewangan et al, 2011;Sriram et al, 2013;Dewangan et al, 2020;Mazumdar et al, 2019). Upon entering the shallow depths and encountering conducive P-T conditions, gas hydrates started crystallizing within the faults and fractures where methane concentration exceeded the solubility limit (You et al, 2019).…”

Section: Evolution Of Active Cold Seep System In Krishna-godavari Basmentioning

confidence: 99%

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Magnetic Mineral Diagenesis in a Newly Discovered Active Cold Seep Site in the Bay of Bengal

2020

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Diagenetically formed magnetic minerals at marine methane seep sites are potential archive of past fluid flow and could provide important constraints on the evolution of past methane seepage dynamics and gas hydrate formation over geologic time. In this study, we carried out integrated rock magnetic, and mineralogical analyses, supported by electron microscope observations, on a seep impacted sediment core to unravel the linkage between greigite magnetism, methane seepage dynamics, and evolution of shallow gas hydrate system in the K-G basin. Three sediment magnetic zones (MZ-1, MZ-2, and MZ-3) have been identified based on the down-core variations in rock magnetic properties. Two events of intense methane seepage are identified. Repeated occurences of authigenic carbonates throughout the core indicate the episodic intensification of anaerobic oxidation of methane (AOM) at the studied site. Marked depletion in magnetic susceptibility manifested by the presence of chemosynthetic shells (Calyptogena Sp.), methane-derived authigenic carbonates, and abundant pyrite grains provide evidences on intense methane seepage events at this site. Fracture-controlled fluid transport supported the formation of gas hydrates (distributed and massive) at this site. Three greigite bearing sediment intervals (G1, G2, G3) within the magnetically depleted zone (MZ-2) are probably the paleo-gas hydrate (distributed-type vein filling) intervals. A strong linkage among clay content, formation of veined hydrate deposits, precipitation of authigenic carbonates and greigite preservation is evident. Hydrate crystallizes within faults/fractures formed as the methane gas migrates through the gas hydrate stability zone (GHSZ). Formation of authigenic carbonate layers coupled with clay deposits restricted the upward migrating methane, which led to the formation of distributed-type vein filling hydrate deposits. A closed system created by veined hydrates trapped the sulfide and limited its availability thereby, causing arrestation of pyritization and favored the formation and preservation of greigite in G1, G2, G3.

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Section: Correlation Between Magnetic Parameter and Mean Grain Sizementioning

confidence: 78%