Samples were collected by the Shipboard Scientific Party during Leg 162. Each sample was placed in a 250-mL beaker, then left on a hot plate for 5 min before adding diluted hydrogen peroxide to disaggregate the sediment and remove organic matter. Hole 982B samples averaged 90% calcium carbonate in composition; therefore, hydrochloric acid was added to remove it (this step was not necessary for Hole 907B samples). Once the reaction ceased, the beaker was filled with distilled water and left overnight to settle. The fluid was then decanted, and the residue was placed in 50-mL plastic centrifuge tubes in distilled water. This was centrifuged and decanted. The preparation phase ended with the addition of sodium pyrophosphate, centrifugation, and decanting at least three times, until most of the clays were removed through suspension (particularly for samples from Hole 907B). The residue was stored in distilled water in the same tubes, after the last decanting of sodium pyrophosphate. Whole-fraction slides were prepared from each sample, using Canada balsam as the mounting medium and 24- × 50-mm coverslips to provide a larger area for analysis and counting.
Slides were examined for silicoflagellates by traversing as many rows as needed to count at least 300 specimens. If no specimens were found in the first 11 traverses, the sample was considered barren. A maximum of 32 traverses was usually possible at the magnification used to scan the slide (250×); occasionally, the counts did not reach 300, even when the whole slide was examined. Counts are presented in table format, and abundance for the sample is given as follows: abundant (A) if counts were at least 250, common (C) between 150 and 250, rare (R) between 50 and 150, very rare (VR) lower than 50, and barren (B) if no silicoflagellates were found. The abundance of individual taxa is given by the actual number of specimens counted in the slide.
Certain taxonomic criteria were applied to try and establish a compromise between different schools of thought (see "Taxonomy" section, this chapter, for a complete discussion). The morphotypes found and counted are listed in the "Taxonomy" section, including a brief synonymy for each taxon to facilitate future comparisons and correlation with previous studies.