Pore water profiles and authigenic mineralization in shallow marine sediments above the methane-charged system on Umitaka Spur, Japan Sea

Snyder, G. T.; Hiruta, Akihiro; Matsumoto, Ryo; Dickens, Gerald R.; Tomaru, Hitoshi; Takeuchi, Ryota; Komatsubara, Junko; Ishida, Yukisato; Yu, Ho‐Shing

doi:10.1016/j.dsr2.2007.04.001

Cited by 111 publications

(117 citation statements)

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“…The presence of manganese-bearing carbonate cement filling ostracode shells suggests reducing environmental conditions, typical of methane seep environments (Snyder et al, 2007), as well as in stratified anoxic bottom water lake. Major negative excursions in δ 13 C values occurring together with increases in benthic temperature, as well as lake or sea-level lowering events that reduce hydrostatic pressure, may provide plausible clues to the past behavior of gas hydrates (Haq, 1998).…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…Authigenic carbonate formation will not affect the sulfate and methane concentrations and does not fractionate carbon isotopes [Teichert et al, 2005]. Authigenic carbonate formation, however, may decrease the DIC concentration in the sediment column [Sivan et al, 2007] and reduce the upward diffusive flux of DIC into the SMT [Snyder et al, 2007], changing the d 13 C-DIC profile. At Site U1325 there is clear evidence of upward DIC flux, as shown by an increase in measured alkalinity (a proxy for DIC [Claypool et al, 2006]) that reaches a maximum well below the SMT at about 30 mbsf .…”

Section: Authigenic Carbonate Formationmentioning

confidence: 99%

“…[16] The model does not include authigenic carbonate formation, which would decrease the DIC concentration [Sivan et al, 2007;Snyder et al, 2007]. We consider the implications of this assumption in the sensitivity analysis.…”

Section: Modelingmentioning

confidence: 99%

“…[2] Methane-bearing continental margin sediments have characteristic near-seafloor geochemical profiles, schematically illustrated in Figure 1 [e.g., Claypool and Threlkeld, 1983;Borowski et al, 1996Borowski et al, , 2000Burns, 1998;Moore et al, 2004;Treude et al, 2005;Claypool et al, 2006;Sivan et al, 2007;Snyder et al, 2007;Kastner et al, 2008a;Pohlman et al, 2008;Ussler and Paull, 2008]. These profiles are strongly influenced by microbially mediated sulfate reduction processes that oxidize methane and more complex organic compounds to carbon dioxide.…”

Section: Introductionmentioning

confidence: 99%

“…[7] In this study, we apply reaction-transport diagenetic modeling [Berner, 1980;Boudreau, 1997] to determine the combination of OSR and AOM that matches the basic geochemical observations from a site drilled in the northern Cascadia margin (Integrated Ocean Drilling Program (IODP) Site U1325 ). The modeling compares concentration gradients of sulfate and methane to estimate the relative importance of OSR and AOM, as done in previous studies [Niewöhner et al, 1998;Borowski et al, 2000;Moore et al, 2004;Treude et al, 2005;Snyder et al, 2007]. We also compute the concentration and d 13 C of DIC to determine how they are affected by the balance of OSR and AOM.…”

Section: Introductionmentioning

confidence: 99%

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Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?

Malinverno

Pohlman

2011

Geochem. Geophys. Geosyst.

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[1] The sulfate-methane transition (SMT), a biogeochemical zone where sulfate and methane are metabolized, is commonly observed at shallow depths (1-30 mbsf) in methane-bearing marine sediments. Two processes consume sulfate at and above the SMT, anaerobic oxidation of methane (AOM) and organoclastic sulfate reduction (OSR). Differentiating the relative contribution of each process is critical to estimate methane flux into the SMT, which, in turn, is necessary to predict deeper occurrences of gas hydrates in continental margin sediments. To evaluate the relative importance of these two sulfate reduction pathways, we developed a diagenetic model to compute the pore water concentrations of sulfate, methane, and dissolved inorganic carbon (DIC). By separately tracking DIC containing 12 C and 13 C, the model also computes d 13 C-DIC values. The model reproduces common observations from methane-rich sediments: a welldefined SMT with no methane above and no sulfate below and a d 13 C-DIC minimum at the SMT. The model also highlights the role of upward diffusing 13 C-enriched DIC in contributing to the carbon isotope mass balance of DIC. A combination of OSR and AOM, each consuming similar amounts of sulfate, matches observations from Site U1325 (Integrated Ocean Drilling Program Expedition 311, northern Cascadia margin). Without AOM, methane diffuses above the SMT, which contradicts existing field data. The modeling results are generalized with a dimensional analysis to the range of SMT depths and sedimentation rates typical of continental margins. The modeling shows that AOM must be active to establish an SMT wherein methane is quantitatively consumed and the d 13 C-DIC minimum occurs. The presence of an SMT generally requires active AOM.

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Pore water geochemistry at two seismogenic areas in the Sea of Marmara

Ruffine

Germain

Polonia

et al. 2015

Geochem Geophys Geosyst

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Within the Sea of Marmara, the highly active North Anatolian Fault (NAF) is responsible for major earthquakes (Mw 7), and acts as a pathway for fluid migration from deep sources to the seafloor. This work reports on pore water geochemistry from three sediment cores collected in the Gulfs of Izmit and Gemlik, along the Northern and the Middle strands of the NAF, respectively. The resulting data set shows that anaerobic oxidation of methane (AOM) is the major process responsible for sulfate depletion in the shallow sediment. In the Gulf of Gemlik, depth concentration profiles of both sulfate and alkalinity exhibit a kink-type profile. The Sulfate Methane Transition Zone (SMTZ) is located at moderate depth in the area. In the Gulf of Izmit, the low concentrations observed near the seawater-sediment interface for sulfate, calcium, strontium, and magnesium result from rapid geochemical processes, AOM, and carbonate precipitation, occurring in the uppermost part of the sedimentary column and sustained by free methane accumulation. Barite dissolution and carbonate recrystallization have also been identified at deeper depth at the easternmost basin of the Gulf of Izmit. This is supported by the profile of the strontium isotope ratios ( 87 Sr/ 86 Sr) as a function of depth which exhibits negative anomalies compared to the modern seawater value. The strontium isotopic signature also shows that these carbonates had precipitated during the reconnection of the Sea of Marmara with the Mediterranean Sea. Finally, a first attempt to interpret the sulfate profiles observed in the light of the seismic activity at both sites is presented. We propose the hypothesis that seismic activity in the areas is responsible for the transient sulfate profile, and that the very shallow SMTZ depths observed in the Gulf of Izmit is likely due to episodic release of significant amount of methane.

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Pore water profiles and authigenic mineralization in shallow marine sediments above the methane-charged system on Umitaka Spur, Japan Sea

Cited by 111 publications

References 65 publications

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

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

Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?

Pore water geochemistry at two seismogenic areas in the Sea of Marmara

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