Evidence of shallow- and deep-water gas hydrate destabilizations in North Atlantic polar continental margin sediments

Mienert, Jürgen; Posewang, Jörg

doi:10.1007/s003670050101

Cited by 56 publications

(34 citation statements)

References 13 publications

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“…1). The gas hydrate stability field depths for the Barents Sea region has been calculated (Andreassen et al, 1990;Long et al, 1998;Vogt et al, 1999;Mienert and Posewang, 1999), considering parameters such as pore water salinity, gas composition, water depth (pressure), geothermal gradient and bottom water temperature. Assuming a methane-water system and bottom-water temperature of 2 1C, Laberg et al (1998) estimated that the minimum water depth for methane hydrate to be stable is 300 m. Laberg et al (1998) also estimated the depth of the GHSZ under the presence of small amounts of higher order hydrocarbon gases.…”

Section: Geology Tectonic Setting and Gas-hydrate Studies Of The Barmentioning

confidence: 99%

Gas hydrate stability zone modelling in areas of salt tectonics and pockmarks of the Barents Sea suggests an active hydrocarbon venting system

Chand

Mienert

Andreassen

et al. 2008

Marine and Petroleum Geology

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Section: Geology Tectonic Setting and Gas-hydrate Studies Of The Barmentioning

confidence: 99%

Gas hydrate stability zone modelling in areas of salt tectonics and pockmarks of the Barents Sea suggests an active hydrocarbon venting system

Chand

Mienert

Andreassen

et al. 2008

Marine and Petroleum Geology

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“…Multibeam and side-scan sonar surveys by Vogt et al (1997Vogt et al ( , 1999 revealed the morphology and sediment textures. Biogeochemical, geophysical, and biological studies were conducted by Eldholm et al (1999), Lein et al (1999), Mienert and Posewang (1999), Milkov et al (1999Milkov et al ( , 2004, Pimenov et al (1999), and Vogt et al (1999), among others.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of mud flows, chemoautotrophic communities, and biogeochemical habitats at Håkon Mosby Mud Volcano

et al. 2007

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Marine mud volcanoes are significant source locations contributing to the marine methane cycle. Enhanced heat flow, unique chemoautotrophic communities, occurrence of massive gas hydrates and large gas plumes are direct evidences of elevated methane concentrations and the dynamic environment of mud volcanoes. Related to the high concentrations and large inventories of CH 4 in surface sediments only a fraction of the methane is exported to the bottom water. This is mainly due to chemoautotrophic communities oxidizing methane and proving a "microbial filter" reducing CH 4 fluxes. Although these processes were studied for several mud volcanoes still little is known about the spatial pattern and the areas covered by chemoautotrophic communities or by present mud flows.For this purposes the Håkon Mosby Mud Volcano (HMMV), which is located at the continental slope of the Barents Sea, was studied by several dives with the Remotely Operated Vehicle Victor6000. During these dives a high resolution microbathymetric map, with a footprint of 25 × 25 cm and a vertical resolution of better than 10 cm was derived. Furthermore, video streams of the bottom camera were converted into georeferenced mosaics, providing a detailed image about the spatial distribution of seafloor features as bacterial mats, pogonophorans, both indicating methane oxidation, or mud flows. Based on visual inspection of 2310 georeferenced mosaics covering an area of 46,160 m 2 , different biogeochemical habitats were identified and quantified on a m 2 -basis. By application of geostatistic techniques as indicator kriging the distribution of different biogeochemical habitats was quantified and mapped for the entire HMMV.Considering the flat and hummocky area of HMMV, approximately 16% (115,165 m 2 ) of the flat centre is nearly void of any benthic communities. This area is considered as a region of high methane discharge into bottom water. An area of 5% (38,244 m 2 ), located in the south-eastern part, is densely inhabited by Beggiatoa. The hummocky outer part is colonised dominantly by pogonophoran tube worms (37.3%; 276,121 m 2 ) and only occasional by Beggiatoa. Source locations and drainage directions for current mud flows were identified by computation of trend surfaces and consideration of temperature data. This suggests that present mud flow ascend close to the northern edge of the flat unit of HMMV, and that the drainage pattern of mud flows shifted from a westward to a south-south-eastern direction.

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“…in pockmarks or crater fields (Ginsburg, 1998;Miller et al, 2015), or by more focused escapes along shallow faults (Freire et al, 2011;Mienert & Posewang, 1999;Suess et al, 1999).…”

Section: Gas Hydrates Backgroundmentioning

confidence: 99%

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

et al. 2017

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Empty elliptical vesicles are observed in outcrops of Barremian very fine clayey sandstone to siltstone lacustrine slurry deposits of the Pitanga Member (Maracangalha Formation), exposed in the Maré Island, Southern Recôncavo Basin, Brazil. These sedimentary features have been traditionally interpreted as water escape structures triggered by the diapirism of the underlying shales of the Candeias Formation. This work proposes that vesicles were generated during massive gas hydrate dissociation as a result of tectonic activity in a paleolake system. Tectonic uplift would have triggered both the reduction of the confining pressure as well as an increase in lake bottom temperature, resulting in the instability of gas hydrate and causing intense release of both methane -or carbon dioxide (CO 2 ) -and water. On one hand, this proposal has a strong impact on paleoenvironmental interpretations, giving support to the current hypothesis that rocks related to the Pitanga Member would have been deposited under water columns deep enough for gas hydrate formation and subsequent dissociation. On the other hand, it provides new insights on the genesis of fluid escape structures in sedimentary rocks, both lacustrine and marine, providing a paleobathymetric indicator.KEYWORDS: Fluidization; Gas hydrates; Maracangalha Formation; Pitanga Member; Recôncavo Basin; Vesicles. Recôn-cavo, uma RESUMO: Vesículas elípticas ocas são observadas em afloramentos de arenitos argilosos muito finos e siltitos lacustrinos do Membro Pitanga da Formação Maracangalha, expostos na Ilha de Maré, sudeste da Bacia do Recôncavo, Estado da Bahia, Brasil. Essas rochas foram depositadas em condições subaquosas e são consideradas depósitos gravitacionais do tipo slurry. Essas feições têm sido tradicionalmente interpretadas como sendo estruturas de escape de água, resultado da ação do diapismo de folhelhos sotopostos da Formação Candeias. Este trabalho propõe que as vesículas foram geradas durante uma intensa dissociação de hidratos de gás em resposta à atividade tectônica existente naquele sistema lacustre. O soerguimento tectônico do fundo do lago teria propiciado a redução da pressão confinante nos poros sedimentares, bem como o aumento de temperatura nas águas de fundo, resultando na instabilidade dos hidratos de gás contidos nas porções rasas dos sedimentos e causando uma violenta liberação de metano -ou gás carbônico (CO 2 ) -e água. Se correta, esta proposta tem um grande impacto na interpretação paleoambiental da Bacia do INTRODUCTIONDiscussions regarding the formation and dissociation of gas hydrates in oceans, seas and permafrost environments are widely described in the literature (Collett, 2002;Freire, 2010;Haacke et al., 2009;Hyndman & Davis, 1992;Matsumoto, 2005;Matsumoto et al., 2009). However, studies concerning fossil gas hydrate formation and dissociation in both marine and lacustrine environments are rare, since the evidences of such processes are not based on direct observations, as those of present day gas hydrate occurrences. ...

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Evidence of shallow- and deep-water gas hydrate destabilizations in North Atlantic polar continental margin sediments

Cited by 56 publications

References 13 publications

Gas hydrate stability zone modelling in areas of salt tectonics and pockmarks of the Barents Sea suggests an active hydrocarbon venting system

Gas hydrate stability zone modelling in areas of salt tectonics and pockmarks of the Barents Sea suggests an active hydrocarbon venting system

Spatial distribution of mud flows, chemoautotrophic communities, and biogeochemical habitats at Håkon Mosby Mud Volcano

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

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