One of the strategies of Ocean Drilling Program (ODP) Leg 178 was to establish a biostratigraphic framework for the Antarctic continental rise that is also applicable to the shelf, in order to reconstruct the late Cenozoic Antarctic glacial history (Barker, Camerlenghi, Acton, et al., 1999). Fossil diatoms are one of the key microfossil groups that provide age constraints for the shelf basin sediments (Quilty, 1995; Barker and Camerlenghi, 1999). Many authors have published Neogene diatom biostratigraphies for the Southern Ocean (e.g., Weaver and Gombos, 1981; Gersonde and Burckle, 1990; Baldauf and Barron, 1991; Harwood and Maruyama, 1992; Gersonde and Bárcena, 1998; Winter and Iwai, Chap. 29, this volume). However, there are uncertainties in the isochroneity of individual biostratigraphic events (Ramsay and Baldauf, 1999). These uncertainties may result from biostratigraphic diachroneity, varied taxonomic concepts, or incorrect magnetostratigraphic correlation arising from a large number of apparent hiatuses. It is important to maintain a rigorous treatment of taxonomy for biostratigraphic and paleoceanographic studies (e.g., Iwai, 2000a, 2000b, 2001; Winter and Iwai, Chap. 29, this volume).
Biostratigraphic studies in the Pacific sector of the Southern Ocean have been completed by McCollum (1975) and Schrader (1976) using material cored during Deep Sea Drilling Project (DSDP) Legs 28, 29, and 35. Several additional biostratigraphic studies have also been completed (Akiba, 1982; Koizumi, 1982). However, most of the biostratigraphically useful species were described in the 1990s by Yanagisawa and Akiba (1990), Gersonde (1990, 1991), Baldauf and Barron (1991), Harwood and Maruyama (1992), Bodén (1993), and Gersonde and Bárcena (1998).
The purpose of this paper is to provide a taxonomic framework useful not only for biostratigraphic (Winter and Iwai, Chap. 29, this volume) and paleoceanographic (Iwai, 2000a, 2001) studies from ODP Leg 178, but for future research projects in the Southern Ocean as well.