Geo-Marine Letters, 2016, Vol.36(3), p.165(10)
To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s00367-015-0431-5 Byline: Ingo Klaucke (1), Christian Berndt (1), Gareth Crutchley (2), Wu-Cheng Chi (3), Saulwood Lin (4), Sina Muff (1) Abstract: Within the accretionary prism offshore SW Taiwan, widespread gas hydrate accumulations are postulated to occur based on the presence of a bottom simulating reflection. Methane seepage, however, is also widespread at accretionary ridges offshore SW Taiwan and may indicate a significant loss of methane bypassing the gas hydrate system. Four Way Closure Ridge, located in 1,500 m water depth, is an anticlinal ridge that would constitute an ideal trap for methane and consequently represents a site with good potential for gas hydrate accumulations. The analysis of high-resolution bathymetry, deep-towed sidescan sonar imagery, high-resolution seismic profiling and towed video observations of the seafloor shows that Four Way Closure Ridge is and has been a site of intensive methane seepage. Continuous seepage is mainly evidenced by large accumulations of authigenic carbonate precipitates, which appear to be controlled by the creation of fluid pathways through faulting. Consequently, Four Way Closure Ridge is not a closed system in terms of fluid migration and seepage. A conceptual model of the evolution of gas hydrates and seepage at accretionary ridges suggests that seepage is common and may be a standard feature during the geological development of ridges in accretionary prisms. The observation of seafloor seepage alone is therefore not a reliable indicator of exploitable gas hydrate accumulations at depth. Author Affiliation: (1) GEOMAR Helmholtz-Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148, Kiel, Germany (2) GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand (3) Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC (4) Institute of Oceanography, National Taiwan University, Roosevelt Road, Taipei, Taiwan, ROC Article History: Registration Date: 25/11/2015 Received Date: 26/04/2015 Accepted Date: 25/11/2015 Online Date: 04/12/2015 Article note: Responsible guest editor: M. De Batist
Methane – Analysis ; Sonar Systems – Analysis ; Gas Hydrates – Analysis ; Carbonates – Analysis ; Hydrates – Analysis
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