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doi:10.2204/iodp.proc.314315316.206.2011

Methods and materials

Samples used for this research were collected from Holes C0001E, C0001F, and C0001H at an interval of 1 to 2 samples per section. We treated 266 samples, ranging in age from Holocene to late Miocene. The stratigraphy of the present site is divided into two units. Unit I (0–198.98 m logging depth below seafloor [LSF] in Hole C0001D) is slope apron deposits mainly composed of hemipelagic clayey silt to silty clay. Unit II (198.98 m LSF to bottom of hole) is the accretionary prism consisting of siltstone with many minor faults.

Soft-sediment samples from Unit I (20 cm³) were treated with a hydrogen peroxide solution. Firm rock samples from Unit II were disaggregated using the sodium tetraphenylborate method (Hanken, 1979). After samples became macerated, each sample was wet-sieved through a 63 µm screen. Planktonic foraminiferal specimens >125 µm were observed under a binocular microscope. Semiquantitative estimates were made of species relative abundance (abundant: >16%, common: 8%–16%, rare: 4%–8%, present: <4%) for each sample that contained >100 individuals. Species from samples yielding <100 individuals were recorded as “+” in occurrence tables. Scanning electron microphotographs of selected index species were taken using a JCM-5000 (JEOL Co. Ltd., Japan).

At Site C0001, most of the marker species for Berggren et al.’s (1995) zonation are very rare or absent. Therefore, we use the planktonic foraminiferal zonation of Blow (1969). Biohorizons were quoted from Thompson et al. (1979) (biohorizon 1 of table 1), Oda (1977) (biohorizon 5), Berggren et al. (1995) (biohorizons 3, 9, and 17), Motoyama et al. (2004) (biohorizons 6 and 8), and Gradstein et al. (2004) (biohorizons 2, 4, 7, and 10–16) and converted in numerical age to the standard GTS2004 timescale (Gradstein et al., 2004).

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