Samples of ~10 cm3 were disaggregated by boiling in 20 wt% H2O2 containing a 1 wt% solution of tetrasodium pyrophosphate. The disaggregated sediment was washed through a 44-µm sieve, dried, and retreated twice by boiling in the above solution. Calcareous components are dissolved by adding 10 wt% HCl, and the residues were rinsed. The microfossils were evenly pipetted onto labeled glass slides with an eyedropper, and the accompanying water evaporated without boiling. When completely dry, air is expelled from the skeletons by the addition of a few drops of xylene. The preparations are mounted in Canada balsam. Samples with high siliceous microfossil density were separated by sieving into three size fractions: 44-63 µm, 63-150 µm, and coarser than 150 µm (Sanfilippo et al., 1985). Slides were made from each fraction for ease of viewing the radiolarians, with a minimum of interference from abundant sponge spicules.
Estimates, based on one slide, of total radiolarian abundance in each sample are expressed as trace (T; <150), very rare (VR; >151 to <300), rare (R; >301 to <1000), few (F; >1001 to <3000), and common (C; >3001). In some cases, the total number of radiolarians has been counted (Table T1). Abundances of individual taxa in Table T1 are given as present (P) or absent (-). Grades of preservation have been noted as the following:
One sample per core from Hole 1128C was studied for diatoms, between Core 182-1128C-8H (upper Oligocene or lowermost Miocene) and 26X (lower Oligocene). Samples (~1 cm3) were boiled in HCl and H2O2. The residues were rinsed by washing in distilled water and decanted after 8 hr; this cycle was repeated three times. Strewn slides were prepared by sampling the suspended residue with a pipette and spreading it on a 22 mm x 22 mm coverslip, which was air dried and mounted in Naphrax. At least one entire slide for each sample was scanned under the light microscope at 500x. Identification of species was checked at 1250x. Diatoms were identified using previous illustrated reports of Eocene and Oligocene diatoms from the middle to high latitude of the Southern Hemisphere, such as Hajós (1976), Fenner (1978, 1985), Desikachary and Sreelatha (1989), and Gombos and Ciesielski (1983). Results are reported in Table T2.
Abundance of diatoms in each sample is expressed as abundant (A), C, F, R, VR, or barren (B). Preservation is reported as good (G), moderate (M), poor (P), or very poor (VP). The presence of individual taxa in Table T2 are recorded as present (P).