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Operations during Integrated Ocean Drilling Program Expedition 341 recovered cores from off the coast of the Gulf of Alaska (Fig. F1; see the “Expedition 341 summary” chapter [Jaeger et al., 2014]). In this study, we used flow-through permeability tests to measure the permeability of five whole-round core samples from Site U1417 and six whole-round core samples from Site U1418. Subsamples from the core used for permeability testing were divided for grain size, biogenic silica, and clay mineral analyses. The uppermost sample at Site U1417 consists of distal Surveyor Fan sediments, and the other four samples from this site consist of pre-Surveyor Fan sediments. The samples from Site U1418 represent proximal Surveyor Fan sediments.

The objective of the testing was to help characterize the sediments that are being carried toward the Aleutian Trench on the incoming Pacific plate (Fig. F1). The permeability of sediments entering subduction zones can greatly affect fluid pressures during shallow subduction, and this work provides some of the first permeability results from the incoming plate in this region. Analysis of amorphous silica and clay mineral content provides information on hydrous sedimentary minerals that can dehydrate during subduction or accretion and increase fluid pressures (Screaton, 2010).