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Stratigraphic and structural controls on the location of active methane seeps on Posolsky Bank, Lake Baikal
Naudts, L.; Khlystov, O.; Granin, N.; Chensky, A.G.; Poort, J.; De Batist, M. (2010). Stratigraphic and structural controls on the location of active methane seeps on Posolsky Bank, Lake Baikal, in: Naudts, L. Manifestations and geological characteristics of bubble-releasing methane seeps in the Black Sea, in the SW Pacific Ocean and in Lake Baikal. pp. 145-162
In: Naudts, L. (2010). Manifestations and geological characteristics of bubble-releasing methane seeps in the Black Sea, in the SW Pacific Ocean and in Lake Baikal. PhD Thesis. Ghent University, Department of Geology and Soil Science: Gent. 195 pp., more

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Keyword
    Marine
Author keywords
    Methane seeps; flares; seismic reflection data; multibeam; gas-hydrate stability; Posolsky Bank; Lake Baikal

Authors  Top 
  • Naudts, L., more
  • Khlystov, O.
  • Granin, N.
  • Chensky, A.G.
  • Poort, J., more
  • De Batist, M., more

Abstract
    The distribution and origin of shallow gas seeps occurring at the crest of the Posolsky Bank in Lake Baikal have been studied based on the integration of detailed seismic, multibeam and hydro-acoustic water-column investigations. In total 65 acoustic flares, indicating gas-bubble release at the lake floor (seepage), have been detected within the 630 km² area of the Posolsky Bank. All seeps are located on the Posolsky Fault scarp near the crest of the Posolsky Bank or on similar locations in water depths of -43 m to -332 m. Lake Baikal is the only fresh-water basin in the world where gas hydrates have been inferred from BSRs on seismic data and have been sampled. Our seismic data also portray BSRs occurring up to water depths of -300 m, which is much shallower than the previously reported -500 m water depth. Calculations for hydrate stability, heat flow and topographic effect based on the BSR occurrence and multibeam bathymetry allowed the determination of a methane-ethane gas mixture and heat-flow values wherefore gas hydrates could be stable in the lake sediments at the given ambient conditions. None of the seeps associated with the Posolsky Bank have been detected within this newly established gas-hydrate stability zone. Our observations and data integration suggest that the seeps at the crest of Posolsky Bank occur where gas-bearing strata are cut off by the Posolsky Fault. These gas-bearing layers could be traced down the Posolsky Bank to below the base of the gas-hydrate stability zone (BGHSZ), suggesting that the detected seeps on the crest of the Posolsky Bank are mainly fed by gas coming from below the BGHSZ.

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