--> ABSTRACT: Headless Submarine Canyons and Fluid Flow: Cascadia Accretionary Prism, Offshore Oregon, by Brian G. McAdoo, Daniel Orange, Elizabeth Screaton, Robert Kayen, and Homa Lee; #91019 (1996)

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Headless Submarine Canyons and Fluid Flow: Cascadia Accretionary Prism, Offshore Oregon

Brian G. McAdoo, Daniel Orange, Elizabeth Screaton, Robert Kayen, and Homa Lee

"Headless" submarine canyons are maintained by internally driven failure due to elevated fluid pressures at the canyon's base. Intercanyon regions are stabilized as indentations on the slope attract fluids to the inflection point of the canyon. Elevated fluid pressures reduce the effective stress assisting in failure. An Alvin dive program to the toe of the Cascadia Accretionary Prism offshore Oregon studied a series of headless submarine canyons on the flanks of anticlines landward of the trench. We found all fluid venting associated with canyons, although not all canyons appear to be actively venting. Near surface variations in permeability control the location of fluid venting and hence failure. The fluid pressures observed around venting communities were not reat enough to produce active failures, and are therefore taken as steady state. We believe the magnitude and occurrence of fluid seeping and slope failure to be transient. Once the steady state is defined, we can determine the type and magnitude of transients required to induce failure. Such transients may include earthquakes and tsunamis, and possibly seasonal currents and tides.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California