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Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework1

M. Riedel,2 E.C. Willoughby,3 M.A. Chen,3 T. He,4 I. Novosel,5
K. Schwalenberg,6 R.D. Hyndman,3 G.D. Spence,4 N.R. Chapman,4 and R.N. Edwards7


Integrated Ocean Drilling Program Expedition 311 is based on extensive site survey data and historic research at the northern Cascadia margin since 1985. This research includes various regional geophysical surveys using a broad spectrum of seismic techniques, coring and logging by the Ocean Drilling Program Leg 146, heat flow measurements, shallow piston coring, and bottom video observations across a cold-vent field, as well as novel controlled-source electromagnetic and seafloor compliance surveying techniques. The wealth of data available allowed construction of structural cross-sections of the margin, development of models for the formation of gas hydrate in an accretionary prism, and estimation of gas hydrate and free gas concentrations. Expedition 311 established for the first time a transect of drill sites across the northern Cascadia margin to study the evolution of gas hydrate formation over the entire gas hydrate stability field of the accretionary complex. This paper reviews the tectonic framework at the northern Cascadia margin and summarizes the scientific studies that led to the drilling objectives of Expedition 311 Cascadia gas hydrate.

1Riedel, M., Willoughby, E.C., Chen, M.A., He, T., Novosel, I., Schwalenberg, K., Hyndman, R.D., Spence, G.D., Chapman, N.R., and Edwards, R.N., 2006. Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework. In Riedel, M., Collett, T.S., Malone, M.J., and the Expedition 311 Scientists. Proc. IODP, 311: Washington, DC (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.311.109.2006

2Expedition 311 Scientists' addresses. Correspondence author:

3Pacific Geoscience Centre, Geological Survey of Canada, 9860 West Saanich Road, PO Box 6000, Sidney BC VSL 4B2, Canada.

 4Earth and Ocean Sciences, University of Victoria, Victoria BC V8W 2Y2, Canada.

 5Hydrocarbon Systems—EP Solutions, Shell International Exploration and Production, Inc., 200 North Dairy Ashford Street, Houston TX 77079, USA.

 6Federal Institute for Geosciences and Natural Resources (BGR), Geozentrum Hannover, Hannover D-30655, Germany.

 7Department of Physics, University of Toronto, Toronto ON M5S 1A7, Canada.

Publication: 28 October 2006
MS 311-109