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doi:10.2204/iodp.proc.314315316.203.2011

Methods and materials

Samples were requested postcruise and were initially selected evenly spaced throughout the gravel intervals. Some samples were taken at different places than those requested because of voids, sample depletion, and the local poor condition of the core. Bulk 4 cm long intervals were requested. Samples 316-C0007D-12R-5, 15.5–19.5 cm; 12R-5, 39.5–43.5 cm; and 12R-5, 55–59 cm, had volumes of 120 cm³; Samples 12R-CC, 7–11 cm, and 12R-CC, 51–55 cm, had volumes of 50 cm³ and all other samples had volumes of 20 cm³. Some of the samples from Core 12R contained some mud matrix that was removed by washing the sample on a 2 mm mesh sieve. It is possible that some intraformational soft mud fragments were washed away during sieving and others may have disintegrated into smaller pieces. Intraformational mud fragments were counted although it is possible that some fragments may have been unintentionally broken into smaller pieces during handling prior to counting. It should also be noted that significant disturbance of the gravels during drilling and retrieval of core may have occurred.

A subsample was poured from each of the 19 sample bags from Core 316-C0007D-12R into a 2.5 cm diameter plastic cylindrical cup. Blue-stained epoxy resin was poured into the container and allowed to harden. One thin section was made for each of these samples. Only two thin sections were made from Core 316-C0007C-17H; one each from Samples 17H-1, 34–38 cm, and 17H-2, 49–53 cm. These two thin sections were made from a grain mount consisting of selected different clast types rather than an unsorted subsample, as was the case for all the thin sections from Core 316-C0007C-12R. Thin sections were made at the University of Wollongong (Australia) by standard thin section techniques.

After an extensive initial examination of the samples, a common set of clast categories was determined for all samples from Core 316-C0007C-17H and a slightly different set of categories was used for all samples from Core 316-C0007D-12R. This is because the gravels from Core 316-C0007D-12R are finer grained and it is more difficult to distinguish some clast types, such as chert, from very fine-grained sedimentary rock fragments. For each sample, clasts were divided into categories and clasts were counted. Identification of clasts types was assisted by using a binocular microscope and/or hand lens. All samples are poorly sorted and samples from Core 316-C0007D-12R include many sand-sized grains that were not removed by sieving through a 2 mm mesh sieve because of their angularity. Grains on the boundary between very coarse sand and granule grades (i.e., 2.0–2.5 mm) were not counted. Counts of clast types were undertaken on thin sections for samples from Core 316-C0007D-12R. Use of a transmitting light microscope enabled more categories of clast types to be used.

Grain size measurements of maximum grain diameters of 64–204 clasts were determined from all nine samples from Core 316-C0007C-17H.

Six larger clasts, representative of different clast types, from Sample 316-C0007C-17H-CC, 5–9 cm, were analyzed for major elements by X-ray fluorescence (XRF) at the School of Earth and Environmental Sciences, University of Wollongong (analyst Paul Carr).

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