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Biostratigraphic results of this study demonstrate that the extinct volcanoes in the Emperor chain show a northward linear increase in age. These results agree with K-Ar data (Dalrymple et al., this volume) which confirm a northward plate motion, as predicted by the hot-spot hypothesis. The reef deposits at Suiko in the north contain lower and middle Paleocene planktonic foraminifers such as Globorotalia pseudobulloides and G. angulata, and the deposits at öjin and Nintoku in the south contain G. aequa, G. velascoensis, G. marginodentata, and abundant specimens of Discocyclinai, suggesting that these seamounts are upper Paleocene and lowermost Eocene(?). The reef facies recovered at the three sites (430, 432, and 433) suggest a warm shallow-water environment compatible with a recent atoll; keeled planktonic foraminifers and larger foraminifers indicate a subtropical surrounding watermass. The sedimentary sequences at all drilled sites, including öjin, Yömei, and Nintoku, encompass an Eocene-Pliocene hiatus, and at Suiko, an Eocene-Oligocene and a middle Miocene hiatus. Furthermore, at Suiko, the Paleocene through Pleistocene benthic foraminifers comprise four main ecologic assemblages, and indicate different depth stages related to vertical motion of the seamounts. The Neogene planktonic foraminifers reveal paleoceanographic conditions experienced by the seamounts. At present, however, the tops of all four seamounts lie above the CCD (carbonate compensation depth), but the eastern flank of Suiko, at a depth greater than 5000 meters, lies below the CCD, and is accumulating only siliceous sediments at the sea floor.

Biostratigraphic and Paleoenvironment Analyses of the Sediments at the Emperor Seamounts, DSDP Leg 55, Northwestern Pacific: Cenozoic Foraminifers