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doi:10.2204/iodp.proc.333.202.2014

Site locations and lithologies

Site C0011

Site C0011 is located at the northern flank of the Kashinosaki Knoll (Figs. F1, F2). A total of 380 m of cores was obtained from Holes C0011C and C0011D (Fig. F3). Lithology is divided into two units (Units I and II) at 347.82 m core depth below seafloor, method B (CSF-B) (see the “Site C0011” chapter [Expedition 333 Scientists, 2012a]), corresponding to Shikoku Basin hemipelagites and middle Shikoku Basin volcanic sand faces, respectively (see the “Expedition 333 summary” chapter [Underwood et al., 2010]). Unit I is divided into Subunits 1A and 1B at 251.56 m CSF-B. Subunit IA is mainly composed of greenish gray silty clay with minor amounts of volcanic ash. Subunit IB comprises weakly lithified mudstone with minor altered volcanic glass and volcanic ash. The dominant lithology of Unit II is coarser grained tuffaceous sandstones and conglomerate interbedded with mudstone similar to that of Subunit IB. The dip angle of bedding is stably low, at ~10°. Moderately dipping small faults and planar shear zones are distributed in the 30–190 m CSF-B interval. Porosity determined onboard is about 0.63 in the ~20–80 m CSF-B interval and slightly increases to ~0.68 at ~80 m CSF-B. Again, porosity of 0.69 is constant to ~250 m CSF-B. Deeper than 250 m CSF-B, porosity decreases to 0.55 immediately and slightly decreases to ~0.5 to 380 m CSF-B.

Five core samples from Site C0011 were tested for velocity measurements. The locations of samples for this site are shown in Table T1 and Figure F3. Tested samples are from Sections 333-C0011D-6H-3, 14H-3, 31X-5, 40X-2, and 50X-3. All samples are silty clay or weakly lithified mudstone. Dip angles of bedding for those samples are 13°, 16°, 19°, 19°, and 10°, respectively. Those values are determined from structure data at the location closest to the analyzed samples.

Site C0012

Site C0012 is located close to the top of Kashinosaki Knoll, oceanward of Site C0011 (Figs. F1, F2). A total of 180 m of core was drilled at this site. The lithology of Site C0012 is divided into two units (Unit I Shikoku Basin hemipelagite and Unit II middle Shikoku Basin volcanic sand facies; Fig. F4). Unit I is composed of mainly dark greenish gray clay and silty clay and silt interbedded with volcanic ash and minor thin sand (see the “Site C0012” chapter [Expedition 333 Scientists, 2012b]. The boundary between Units I and II is at 151.61 m CSF-B. Unit II comprises mudstone similar to the lower part of Unit I and turbidite sands and sandstones including pebbles, coarse ash, and lapilli tuff. Lower dipping (~10°) bedding changes to higher dipping (~60°) bedding from the seafloor to 15 m CSF-B. In the interval between 15 and 85 m CSF-B, bedding dip is slightly stable around 50°–60°. Deeper than 85 m CSF-B, bedding dip decreases to about 10°–20°. Deeper than ~150 m CSF-B, bedding dip ranges from 10° to 50° to 180 m CSF-B.

Porosity is roughly constant and about 0.7 in the shallower interval between 0 and 80 m CSF-B. It decreases from 0.7 to ~0.6 from 80 to 100 m CSF-B. Again, porosity is stable at 0.6 to 130 m CSF-B, and then porosity decreases to ~0.5 to 180 m CSF-B. Porosity at Site C0012 is relatively lower at Site C0011 at the same depth (Figs. F3, F4) because porosity at Site C0011 does not change from around 0.6–0.7 to 250 m CSF-B.

Tested samples are Sections 333-C0012C-8H-1, 11H-4, and 15H-5 and Sections 333-C0012D-4H-5 and 9H-3. All samples are silty clay or weakly lithified mudstone. Dip angles of bedding for these samples are 50°, 13°, 14°, 16°, and 16°, respectively, on the basis of structural data.

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