A total of 168 named taxa from 6 sites (744, 745, 746, 747, 748, 751) from the Kerguelen Plateau were analyzed in the study (Figure 1).

Caulet (1991) provided a detailed record of faunal change (50 taxa, Figure 2A, Table 1) for the latest Miocene to late Pleistocene interval, based on 76 samples from Leg 119 Site 745. The mid Pliocene to Recent time interval is not well represented in most ODP sites recovered from the Southern Ocean and, in particular, was not studied in detail by either Lazarus (1992) or Abelmann (1992a). Although Caulet (1991) also provided less detailed data for the earlier Neogene as well, the bulk of his study is devoted to the very poorly known Southern Ocean faunas of Eocene age, that were well recovered by Leg 119 drilling. In this study, only the detailed Plio-Pleistocene data of Caulet are used, although its relative shortness (0-6 Ma, 6 m.y.) creates substantial problems in range truncation. Attempts to incorporate some of Caulet's results from older Neogene intervals were frustrated by the lack of well-resolved age models for these older sections.

Abelmann (1992a) studied radiolarian faunas from the middle and early Miocene interval of Leg 120 sediments, using 139 samples from three sites (747, 748 and 751). The total number of taxa reported (97, Figure 2B, Table 2) is relatively large, and the total time interval covered (ca. 24-10 Ma, or nearly 14 m.y.) is also substantial, but the data is complicated by the fact that many taxa were not examined in all three sites, leading to numerous range truncations, even within the composite range chart of this single author's results, due to the differing time intervals studied in each site. Preservation and abundance of radiolarians in this sample set are also relatively variable, and particularly in the earlier Miocene can be poor enough to affect observed diversity and taxon ranges.

The report of Lazarus (1992) on radiolarian faunas from both Legs 119 and 120 provides a relatively uniform data set from a large number of sites (744, 745, 746, 747, 748, 751) comprising in total 262 samples. A relatively fixed taxon checklist was used in this study which covers the entire Neogene interval, although the late Pliocene-Recent and early Miocene intervals were not as extensively examined as the early Pliocene to middle Miocene intervals. The number of taxa considered is moderately high (68 taxa were recorded, Figure 2C, Table 3), although noticably fewer taxa were recorded than in the study by Abelmann. Of the three data sources used in this study, this one is also the least affected by truncation problems, due to the relatively long time interval covered (ca. 4-20 Ma, 16 m.y.) and consistency of data recording between sites.