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doi:10.2204/iodp.proc.331.102.2011

Biostratigraphy

Microfossil recovery and preparation

Large microfossils (>63 µm fraction)

A total of 20–25 cm³ samples from the core catcher and a smaller selection of 5 cm³ sediment samples submitted from the Petrology group were collected for microfossil analyses. Sediment samples were disaggregated in tap water and washed under flowing water through a nest of sieves with mesh sizes of 1 mm (18 mesh), 150 µm (100 mesh), and 63 µm (230 mesh) until the water passing through the 63 µm (230 mesh) sieve was clean (i.e., the silt-clay fraction had been removed). The immobilized samples (>1 mm, 150 µm–1 mm, and 63–150 µm) were then washed from the sieves using a stream of tap water into Whatman No. 2 filter paper and dried at 100°C for 2 h.

Fossils from each sample/size fraction were screened using a Zeiss Discovery V.12 stereomicroscope. Samples of representative dominant foraminifers from Site C0014 were also selected for examination with a scanning electron microscope (SEM). Samples for SEM examination were hand-picked from a petri plate using a wet toothpick. Samples were then immobilized on an SEM sample holder using double-sided carbon tape for coating and imaging.

Small microfossils (<63 µm fraction)

Smear slides were prepared by first producing an ~10% (v/v) suspension of material from the core catcher samples (i.e., 0.1 cm³ sediment + 0.9 mL distilled water in a 1.5 mL microcentrifuge tube). The suspension was allowed to settle for 1 min to sediment sand-sized material at the bottom of the tube, producing a supernatant with a slightly milky consistency. A small drop of this suspension was screened for the presence of coccoliths using phase-contrast light microscopy and cross-polarized light; positive samples were spread across a coverslip and dried using a hot plate for SEM.

Imaging using scanning electron microscopy

Microfossil preparations were Pt coated using a JEOL JFC-1800 nano fine coater and imaged using a JEOL JCM-5700 SEM operating at an accelerating voltage of 5 kV for secondary electron imaging.

Species diversity and abundance

To determine species diversity and species abundance, specimens were identified and counted along a linear axis until ~250 specimens from each group (i.e., foraminifers) were enumerated (where possible). Abundance, preservation, zonal data, and SEM micrographs of dominant or representative taxa for each sample investigated were recorded in the J-CORES database. Foraminifers were identified in relation to the work done by Keller (1980a, 1980b) and Thompson (1980). Coccoliths were identified based on the compilation by Winter and Siesser (1994). Radiolarians were keyed based on the regional work by Sakai (1980).

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