Primary age control points were provided by calcareous nannofossil, diatom, and radiolarian biostratigraphy, integrated in some sites with magnetostratigraphy. The calcareous nannofossil assemblages show a clear difference between the northern and southern sites, with an important decrease in diversity to the south. Datums previously calibrated in middle- and low latitude areas were used for the Pleistocene time interval. A more accurate age model will provide the possibility to recalibrate these events and estimate their synchronism or diachronism. The Pliocene-Eocene time interval offers the opportunity to generate a new biostratigraphic scheme for the Southern Ocean, as well as to correlate these events with low-latitude data. Furthermore, cyclicity and assemblage alternations of the calcareous nannofossils are observed in abundance at all sites and ages, offering a potential tool for paleoceanographic investigations.

Paleoceanographic reconstructions using foraminifer-based stable isotopic results will be possible for most sites. Although the absolute abundance of both planktonic and benthic foraminifers is low in many cases, particularly at the southernmost deep-water sites, the high sedimentation rates in these areas have clearly increased the preservation of foraminifers. Radiolarian assemblages sharply change along the latitudinal transect, which makes it possible to clarify temporal and spatial distributions of radiolarian assemblages from mid- to high-latitude regions. Also, abundant radiolarians from high-resolution sites may allow us to obtain detailed paleoceanographic information such as opal productivity and sea-surface temperature (SST) changes. A detailed late Pliocene to Pleistocene biostratigraphic diatom zonation developed for subantarctic waters could be applied throughout almost the entire transect (Gersonde and Barcena, 1998). Diatom analyses of Leg 177 material provide a great potential to improve the diatom biostratigraphic zonation for the Southern Ocean. In particular, the diatom record of the Miocene-Eocene time interval, tied to a nearly continuous undisturbed paleomagnetic record, will provide a unique biostratigraphic zonation for the Paleogene epoch. Recovered material from the two southernmost sites located within the opal belt will allow reconstructions of paleoenvironmental parameters such as SST, by means of diatom transfer functions, and sea-ice occurrence, by diagnostic diatom taxa.

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