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doi:10.2204/iodp.proc.314315316.224.2019

Site and sample description

Sites C0006 and C0007 are located less than ~2 km landward of the deformation front in the Nankai Trough. The region is a zone of diffuse faulting that may act as the plate boundary (Screaton et al., 2009). The main frontal thrust was not penetrated at Site C0006 but was penetrated at Site C0007 slightly trenchward (Figure F2). We tested four samples from Site C0006 (see the “Expedition 316 Site C0006” chapter [Expedition 316 Scientists, 2009a]) and one sample from Site C0007 (see the “Expedition 316 Site C0007” chapter [Expedition 316 Scientists, 2009b]), which were recovered from 192–562 meters below seafloor (mbsf) (Table T1). All samples are described lithologically as silty clay, of which the uppermost four samples belong to Unit II, representing accreted trench wedge sediments, whereas the deepest sample, 316-C0006F-19R-1 from Unit III, has been classified as accreted Shikoku Basin sediment. The samples are not from any major fault or zone of concentrated deformation and therefore represent wall rock mudstone for the frontal thrust region. Bulk composition of the samples was quantified by shipboard X-ray diffraction (see the “Expedition 316 Site C0006” and “Expedition 316 Site C0007” chapters [Expedition 316 Scientists, 2009a, 2009b]). Total clay mineral content for our tested samples ranges from 41 to 67 wt% with the remainder being quartz and plagioclase except for 5 wt% calcite observed in Sample 316-C0006F-7R-1 (Table T1).

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