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The southernmost record of Maestrichtian pelagic carbonate sedimentation was recovered from ODP Leg 113 Holes 689B and 690C, drilled on the Maud Rise in the eastern Weddell Sea sector of the Southern Ocean (65°S). Well pre­ served and abundant planktonic foraminifers occur throughout Maestrichtian cores from both holes, providing a nearly complete biogeographic and biostratigraphic history of this region. Diversity is low compared to tropical and subtropi­ cal assemblages, with a maximum within sample diversity of 16 planktonic foraminifer species and a diversity total for the Maestrichtian of 24 species. The assemblages are dominated throughout by Heterohelix, Globigerinelloides, and a new species of Archaeoglobigerina, whereas keeled taxa are completely absent from the lower Maestrichtian and rare in the middle through upper Maestrichtian sediments. Three planktonic foraminifer species are described as new and are recognized as being endemic to the Austral Prov­ ince. These include Archaeoglobigerina australis n. sp., Hedbergella sliteri n. sp., and Archaeoglobigerina mateola n. sp. The former two species were previously illustrated in reports on Late Cretaceous foraminifers from the Falkland Pla­ teau and the northern Antarctic Peninsula. Two keeled and five non-keeled planktonic foraminifers, previously not found in high latitude Maestrichtian sediments, first appeared at the Maud Rise during the late early and late Maes­ trichtian. Correlation with their stratigraphic ranges in low latitude sequences shows that their first appearance datums are considerably younger at the Maud Rise than in the lower latitudes. The most likely explanation for this observation is that there was a warming in the south polar region during the late early and late Maestrichtian and a concomitant poleward migration of stenothermal taxa. However, oxygen isotopic paleotemperature results from Sites 689 and 690 (Barrera and Huber, this volume) show a long-term cooling trend throughout the Maestrichtian, indicating that other factors may have played a more important role than temperature in the distribution of Maestrichtian planktonic fora­ minifers. A new biostratigraphic scheme is proposed for the Antarctic because of the absence of thermophilic planktonic for­ aminifers used to identify existing low to middle latitude zones. The Globigerinelloides impensus Partial Range Zone is defined for the late Campanian-Maestrichtian, the Globotruncanita havanensis Partial Range Zone is redefined for the early to late early Maestrichtian, and the Abathomphalus mayaroensis Total Range Zone is recognized. Good quality magnetic polarity data obtained from both Maud Rise sites (Hamilton, this volume) enables magnetobiostratigraphic correlation of twelve foraminifer datums with the geomagnetic polarity time scale of Haq et al. (1987). The geochronol­ ogy thus obtained is crucial for accurate cross-latitudinal correlation and interpretation of the paleoceanographic his­ tory of the Antarctic region during the Maestrichtian time period.

Maestrichtian Planktonic Foraminifer Biostratigraphy of the Maud Rise (Weddell Sea|Antarctica): ODP Leg 113 Holes 689B and 690C