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doi:10.2204/iodp.proc.314315316.219.2012

Sample descriptions

Site C0004

We tested eight samples from the megasplay fault zone at Site C0004 (see the “Expedition 316 Site C0004” chapter [Expedition 316 Scientists, 2009a]), including two samples from the accretionary prism (hanging wall), four samples from within the megasplay fault zone, and two samples from underthrust slope sediments that comprise the footwall (Table T1). Sample depths ranged from 119.3 to 357.1 meters below seafloor (mbsf); the megasplay fault zone is located between 258.0 and 307.5 mbsf. Within the depth interval of our samples, total clay mineral content ranges between ~40 and 70 wt% and combined quartz and plagioclase content ranges from ~25 to 55 wt% (see the “Expedition 316 Site C0004” chapter [Expedition 316 Scientists, 2009a]). One hanging wall sample (from Section 316-C0004C-15X-2) and one footwall sample (from Section 316-C0004D-47R-2) were trimmed from whole-round cores and tested as intact wafers. All other samples from this site were dried at a low temperature of ~40°C (to prevent clay mineral transformation that may occur at higher temperatures), powdered with a mortar and pestle, and sieved to a uniform grain size of <106 µm. This processing was utilized because many samples, especially those from within the fault, were recovered in brecciated condition.

Site C0007

We tested eight samples from the frontal thrust region at Site C0007 (see the “Expedition 316 Site C0007” chapter [Expedition 316 Scientists, 2009b]), which were sampled from 103.6 to 437.2 mbsf. Site C0007 penetrated the accretionary prism near the trench, including three fault zones located at 237.5–259.3, 341.5–362.3, and 398.5–446.0 mbsf (see the “Expedition 316 Site C0007” chapter [Expedition 316 Scientists, 2009b]). We tested one sample from the shallowest fault zone (in Section 316-C0007D-9R-2) and two from the deepest fault zone (in Sections 316-C0007D-27R-1 and 29R-1). Other samples are from the trench-wedge facies and the lithologic equivalent of the upper Shikoku Basin facies sampled during Ocean Drilling Program (ODP) Leg 190 (Shipboard Scientific Party, 2001) (Table T1). Within the depth interval we studied, combined quartz and plagioclase content ranges from ~50 to 75 wt% at the top of the section and decreases with depth to ~30 wt%, whereas clay content is ~25–50 wt% at the top of this section and increases to nearly 70 wt% by ~360 mbsf. Three samples from this site were tested as intact wafers trimmed from whole-round cores. Other samples were tested either as powders (which were rehydrated in the sample assembly), remolded wet (cold-pressed into the sample assembly), or tested as breccia with no additional sample preparation (Table T1).

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