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Foraminiferal assemblages consisting of 76 genera and 145 species were recovered from Upper Cretaceous and Paleocene sediments in the James Ross Island region, northeastern Antarctic Peninsula. Open taxonomic nomenclature is used for 37 taxa and 10 new species are described, including Alveolophragmium macellarii, Spiroplectammina vegaensis, Dorothia paeminosa, Buliminella procera, Neobulimina digitata, Bolivina pustulata, Conorbina anderssoni, Cibicides nordenskjoldi, C. seymouriensis, and Anomalinoides larseni.

Three biostratigraphic range zones are recognized for interregional and regional correlation: (1) the ?mid- to upper Campanian Gaudryina healyi Zone, used to correlate the Cape Lamb (Vega Island), The Naze (James Ross Island), Snow Hill, and lowermost Seymour Island beds; (2) the upper Campanian through Maastrichtian Hedbergella monmouthensis Zone, occurring only on Seymour Island; and the Danian Globastica daubjergensis Zone, also occurring only on Seymour Island. The foraminiferal transition from Upper Cretaceous to Lower Tertiary sediments on Seymour Island is characterized by extinction of all Upper Cretaceous planktonic species and numerous benthic taxa, a lowermost Tertiary dissolution facies that is barren of calcareous microfossils, and the appearance of the Danian marker species Globastica daubjergensis with low-diversity, high-dominance calcareous assemblages just above the dissolution facies.

The stratigraphic distribution of foraminifera on Seymour Island attests to long-term environmental stability in the Upper Cretaceous sequence, in contrast to stressed environmental conditions in the lower Paleocene. Foraminiferal distributions indicate that the lowermost 250 m of the Seymour Island sequence was deposited in an inner neritic environment, and the overlying 950 m of Cretaceous and lower Danian sediments in an outer neritic setting. Foraminifera are absent from the younger Paleocene sequence, which was deposited in a relatively high-energy environment.

The foraminiferal assemblages from the James Ross Island region include a mixture of cosmopolitan and provincial species. The Campanian-Maastrichtian fauna is characterized by: (1) the conspicuous absence of specialized benthic and keeled planktonic species, which are used as index fossils in low to middle latitude regions; (2) the predominance of long-ranging, cosmopolitan taxa; and (3) the occurrence of provincial species that were restricted to the southern, extratropical latitudes. These latter taxa are included in the foraminiferal Austral Province. The biogeographic distribution of Austral Province foraminifera supports the postulated trans-Antarctic seaways between East and West Antarctica and/or a marine communication through the Antarctic Peninsula during the Late Cretaceous. The Danian assemblages are characterized by opportunistic, cosmopolitan species and one new buliminellid species, which dominates the calcareous assemblages.

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