Seabed morphology and gas venting features in the continental slope region of Krishna–Godavari basin, Bay of Bengal: Implications in gas-hydrate exploration

Dewangan, P.; Ramprasad, T.; Ramana, M.V.; Mazumdar, Aninda; Desa, M.; Badesab, Firoz

doi:10.1016/j.marpetgeo.2010.03.015

Cited by 70 publications

(66 citation statements)

References 33 publications

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“…Smectite bearing Godavari Clay Formation constitutes the Holocene-Pleistocene deposit of the K-G basin (Rao, 2001). The seismic reflection data off K-G basin (Collett et al, 2008;Dewangan et al, 2010;Shankar and Riedel, 2010) show regional presence of gas hydrates manifested in the form of bottom simulating reflectors (BSR) observed at depth of 125 mbsf (water depth: 945m) to 220 mbsf (water depth 1146 m). BSRs represent a phase boundary, where the low-velocity, gas-charged sediments occur below the high-velocity gas hydrate bearing sediments (Singh and Minshull, 1993).…”

Section: Geological Settingmentioning

confidence: 99%

“…BSRs represent a phase boundary, where the low-velocity, gas-charged sediments occur below the high-velocity gas hydrate bearing sediments (Singh and Minshull, 1993). Ramana et al (2007) and Dewangan et al (2010) have reported various shale tectonics induced structures like bathymetric mounds, deep seated shale diapirs and toe thrust faults from the K-G basin. Both coring sites (MD161-8 and 15) are located on the top of bathymetric mounds.…”

Section: Geological Settingmentioning

confidence: 99%

“…Bright spots, acoustic blanking/turbidity and drop in P-wave velocity below BSR testify the presence of free gas (Dewangan et al, 2010;Shankar and Riedel, 2010).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

“…Shale tectonics (diapirism) induced deep fault system has been amply demonstrated from the K-G Basin (Mazumdar et al, 2009b;Dewangan et al, 2010;Shankar and Riedel, 2010;Riedel et al, 2010;Choudhury et al,2011). Shale tectonic is driven by the downward movement of thick sediment mass over a deeply buried over pressured shale strata (Damuth, 1994;Wu and Bally, 2000).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

“…Shale tectonic is driven by the downward movement of thick sediment mass over a deeply buried over pressured shale strata (Damuth, 1994;Wu and Bally, 2000). The perturbation of the over pressured strata induces folding, faulting and upthrusting of the overburden strata thereby creating prominent bathymetric mounds and ridges (Rao and Mani, 1993;Dewangan et al,2010).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

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

Joshi¹,

Mazumdar²,

Peketi³

et al. 2014

Marine and Petroleum Geology

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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 δ 13 C spikes are recorded during the marine isotope stages MIS-4 and at the transition of MIS-5 to 4. Occurrence of highly 13 C depleted (average δ 13 C = -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 13 C 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 δ 13 C 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.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

“…Bright spots, acoustic blanking/turbidity and drop in P-wave velocity below BSR testify the presence of free gas (Dewangan et al, 2010;Shankar and Riedel, 2010).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

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

Joshi¹,

Mazumdar²,

Peketi³

et al. 2014

Marine and Petroleum Geology

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Coupled C–S–Fe geochemistry in a rapidly accumulating marine sedimentary system: Diagenetic and depositional implications

Peketi

Mazumdar

Joao

et al. 2015

Geochem Geophys Geosyst

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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. The core covers the late Holocene period with high overall sedimentation rate of ∼573 cm kyr−1. Pore fluid chemical analyses indicate that the depth of the present sulfate methane transition zone (SMTZ) is at ∼6 mbsf. The (ΔTA + ΔCa + ΔMg)/ ΔSO42− 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 chromium reducible sulfur (CRS) content indicates marked influence of organoclastic sulfate reduction on sulfidization. Coupled occurrence of 34S‐enriched iron sulfide (pyrite) with 12C‐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 normalized poorly reactive iron (FePR/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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Controls on evolution of gas‐hydrate system in the Krishna‐Godavari basin, offshore India

Badesab

Dewangan

Usapkar

et al. 2017

Geochem Geophys Geosyst

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In this study, we integrate environmental magnetic, sedimentological, and geochemical records of sediment core of Hole NGHP-01-10D overlying methane hydrate deposits to decipher the controls on the evolution of fracture-filled gas-hydrate system in the Krishna-Godavari (K-G) basin. Four distinct sedimentary units have been identified, based on the sediment magnetic signatures. An anomalous zone of enhanced magnetic susceptibility (Unit III: 51.9-160.4 mbsf) coinciding with the gas hydrate bearing intervals is due to the presence of magnetite-rich detrital minerals brought-in by the river systems as a result of higher sedimentation events in K-G basin and has no influence over hydrate formation. A strong to moderate correlation between magnetite concentration and chromium reducible sulfur (CRS) content indicates significant influence of sulfidization on the magnetic record and could be further exploited as a proxy to decipher paleo-H 2 S seepage events. Analysis of high-resolution seismic, bathymetry, and subbottom profiler data reveals the existence of a regional fault system in K-G basin. The opening and closing dynamics of the faults facilitated the migration and trapping of required gas concentrations resulting in accumulation of gas hydrates at the studied site. The seismic data provides support to the rock-magnetic interpretations. The observed variations in magnetic and geochemical properties have resulted from the episodic flow of methane and sulfide-enriched fluids through the fracture-filled network formed as a result of shale-tectonism. Our study demonstrated the potential of using an enviro-magnetic approach in combination with other proxies to constrain the evolution of gas-hydrate system in marine environments. Key Points:Magnetic signatures of detrital and diagenetic processes associated with evolution of gas-hydrate system. Changes in magnetic and geochemical properties controlled by underlying gas-hydrates. Magnetic proxy to decipher paleo-H2S seepage events in marine sediments.

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Seabed morphology and gas venting features in the continental slope region of Krishna–Godavari basin, Bay of Bengal: Implications in gas-hydrate exploration

Cited by 70 publications

References 33 publications

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

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

Coupled C–S–Fe geochemistry in a rapidly accumulating marine sedimentary system: Diagenetic and depositional implications

Controls on evolution of gas‐hydrate system in the Krishna‐Godavari basin, offshore India

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