AMERASIAN ARCTIC-OCEAN

Four sediment cores collected from the Northwind and Mendeleyev ridges , Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanogr aphic record extending back into the Matuyama reversed polarity chron, Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsa lis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones repres ent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at sim ilar to 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arcti c cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should p rovide important information pertaining to the Quaternary paleoceanogr aphic evolution of the Arctic Ocean.