Drivers of focused fluid flow and methane seepage at south hydrate ridge, offshore Oregon, USA

Journal article (2013)

Authors

Gareth J. Crutchley GEOMAR Helmholtz Center for Ocean Research
Christian Berndt GEOMAR Helmholtz Center for Ocean Research
S. Geiger Heriot-Watt University
Dirk Klaeschen GEOMAR Helmholtz Center for Ocean Research
Cord Papenberg GEOMAR Helmholtz Center for Ocean Research
Ingo Klaucke GEOMAR Helmholtz Center for Ocean Research
Matthew J. Hornbach Southern Methodist University
Nathan L.B. Bangs Jackson School of Geosciences
Christine Maier Heriot-Watt University
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Published Date

2013

Language

English

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Abstract

Methane seepage at south Hydrate Ridge (offshore Oregon, United States), one of the best-studied examples of gas venting through gas hydrates, is the seafloor expression of a vigorous fluid flow system at depth. The seeps host chemosynthetic ecosystems and release significant amounts of carbon into the ocean. With new threedimensional seismic data, we image strata and structures beneath the ridge in unprecedented detail to determine the geological processes controlling the style of focused fluid flow. Numerical fluid flow simulations reveal the influence of free gas within a stratigraphic unit known as Horizon A, beneath the base of gas hydrate stability (BGHS). Free gas within Horizon A increases the total mobility of the composite water-gas fluid, resulting in high fluid flux that accumulates at the intersection between Horizon A and the BGHS. This intersection controls the development of fluid overpressure at the BGHS, and together with a well-defined network of faults, reveals the link between the gas hydrate system at depth and methane seepage at the surface.