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Detailed calcareous nannofossil range charts for the Oligocene-Pleistocene sections from high-latitude Ocean Drilling Program Sites 747, 748, and 751 in the southern Indian Ocean are presented in this report. Calcareous nannofossils are generally low in abundance in Pliocene-Pleistocene sediments, whereas they are very abundant throughout the Miocene and Oligocene. Species diversity, however, is low compared with assemblages in the lower latitudes. Nannofossil reworking is extensive in the middle Miocene at Site 751, less extensive in the lower Miocene at Site 748, and negligible for the entire Neogene at Site 747. Six nannofossil datums, which have previously been correlated with magnetostratigraphy in the Southern Ocean, were recognized in the upper Oligocene-Pleistocene sequence at Site 747. Three such nannofossil datums are available for the Neogene at Sites 748 and 751. A new subspecies, Coccolithus pelagicus floralis, is described. INTRODUCTION Neogene calcareous nannofossils were recovered only at three sites (747, 748, and 751) from Ocean Drilling Program (ODP) Leg 120 (Fig. 1). However, these assemblages provide an important bridge between those sampled between 50° and 52°S during ODP Legs 114 and 119, and those from 63° and 65°S recovered during Legs 113 and 119 (Ciesielski, Kristoffersen, et al., 1988; Barron, Larsen, et al., 1989; Barker, Kennett, et al., 1988). As such, the Leg 120 sites provide a unique sequence of transitional sites across which changes in the diversity and composition of nannofossil assemblages can be traced in reference to latitude. Located well south of the present-day Polar Front, the Leg 120 sites studied lie at fairly shallow depths (water depths range from 1298 to 1634 m), and primarily for this reason Leg 120 succesfully recovered for the first time long sequences of Pliocene-Pleistocene carbonate sediments at these high latitudes (Schlich, Wise, et al., 1989). Among the 11 sites drilled on the Kerguelen Plateau during Legs 119 and 120, Hole 751A was a dedicated Neogene site chosen specifically to yield an expanded carbonate-rich section, at least for the Miocene. The expected high sedimentation rates would provide the basis for a high-resolution biostratigraphy, magnetostratigraphy, and chemostratigraphy of these high-latitude sites. This report provides a description of the distribution of the Neogene nannofossil assemblages recovered at Sites 747, 748, and 751. Extensive Neogene sediments were recovered in only one hole at each site. The range chart for Hole 747A was extended down into the upper Oligocene to link up with the distribution chart for Paleogene assemblages (Aubry, this volume) for that site. Additional discussion and interpretation of the Neogene nannofossil assemblages, key datums, and their correlations with magnetostratigraphy at theses sites as well as at other Southern Ocean sites are given in Wei and 1 Wise, S. W., Jr., Schlich, R., et al., 1992. Proc. ODP, Sci. Results, 120: College Station, TX (Ocean Drilling Program). 2 Department of Geology, Florida State University, Tallahassee, FL 32306, U.S.A. 3 Present address: Geological Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, U.S.A. Wise (this volume) and in Harwood et al. (this volume). Leg 120 Paleogene nannofossil assemblages are discussed by Aubry (this volume) and Wei et al. (this volume). MATERIALS AND METHODS Smear slides were made directly from unprocessed samples and were routinely examined using a light microscope at magnifications of either ×650 or ×133O (for the identification of small coccoliths such as Emiliania huxleyi in the latter case). At the lower magnification, the abundance of calcareous nannofossils in each slide was estimated using the following criteria: V = very abundant (more than 10 specimens per field of view); A = abundant (1-10 specimens per field of view; C = common (1 specimen per 2-10 fields of view); F = few (1 specimen per 11—50 fields of view); R = rare (1 specimen per 51-200 fields of view); and B = barren (no specimen was found in 200 fields of view). Preservation of the calcareous nannofossil assemblage is recorded as G = good (little evidence of etching or overgrowth); M = moderate (etching or overgrowth is apparent); and P = poor (there is significant etching or overgrowth and identification of some species is impaired). Calcareous nannofossil species considered in this paper are listed in the Appendix and are arranged alphabetically by generic epithets. Bibliographic references for these taxa can be found in Loeblich and Tappan (1966, 1968, 1969, 1970a, 1970b, 1971, 1973), Heck (1979a, 1979b, 1980a, 1980b, 1981a, 1981b, 1982a, 1982b, 1983), or Steinmetz (1985a, 1985b, 1986, 1987a, 1987b, 1988a, 1988b, 1989). Stratigraphically important occurrences and selected species are illustrated in Plates 1 and 2. The upper Oligocene is zoned using the high-latitude nannofossil zonation of Wei and Thierstein (1991). The last occurrences (LOs) of Reticulofenestra bisecta and Chiasmolithus altus used for subdivision of the upper Oligocene have previously been correlated with magnetostratigraphy (Wei and Wise, 1989, 1990) and Wei and Thierstein (1991). For reference to lower latitude stratigraphies, combined Neogene zones are tentatively indicated according to the zonation of Okada and Bukry (1980). Most of the index taxa of Okada and Bukry (1980) are absent at these high latitudes, but a few nontraditional datums are useful for stratigraphic subdivision at these sites. These nontraditional datums include the LO of

Oligocene-Pleistocene Calcareous Nannofossils from Southern Ocean Sites 747, 748, and 751