The sediment sequences cored during Leg 167 are made up primarily of hemipelagic sediments containing a relatively continuous succession of planktonic and benthic foraminifers. These occur in sufficiently high abundances since 3.5 Ma to provide a strong base for the development of a regional late Neogene planktonic foraminiferal zonation. Sedimentation rates are relatively high in the six sites documented in this study, ranging from ~8 to ~20 cm/k.y. Samples (10 cm3) were taken at 1.5- to 3-m intervals down the length of the cores. Samples were gently washed over a 63-µm sieve and the residues dried at 50°C. Semiquantitative estimates were made of the relative abundance (abundant, common, few, and rare) of stratigraphically important taxa in the >150-µm fraction for each sample. Samples were strewn over a picking tray divided into 45 quadrants. Taxa that occurred once per quadrant were considered common, and those that occurred, on average, in every several quadrants were considered few. If a taxon was observed only once or twice per tray, it was considered rare (Table 2, Table 3, Table 4, Table 5, Table 6, Table 7).
Earlier shipboard investigations on core-catcher samples and the recognition of a biostratigraphic succession (Lyle, Koizumi, Richter, et al., 1997) enabled us to identify planktonic foraminifers of potential biostratigraphic importance. During our later, shore-based investigations we estimated the relative abundance of these forms (Table 2, Table 3, Table 4, Table 5, Table 6, Table 7). Changes in the relative abundance of other taxa were not recorded.