We examined biostratigraphic age inferences based on planktonic foraminifera and calcareous nannoplankton and documented the faunal associations of benthic foraminifera during the Quaternary in core PC311 taken from the top of a seamount (1,370 m water depth) in the Magellan Seamounts (western Pacific Ocean). Six and five biostratigraphic datums were recognized by planktonic foraminifera and calcareous nannofossils, respectively. In the lower part of the core, a planktonic foraminiferal datum occurred at the depth corresponding to 2.332 Ma, whereas the two datums of calcareous nannofossils were observed at 2.76 Ma and 2.78 Ma. As a result, we propose two age models. The diversity measures of benthic foraminifera declined gradually from similar to 1.3 Ma to the present. Stilostomellidae and Pleurostomelidae also decreased gradually after similar to 1.3 Ma and disappeared at similar to 0.7 Ma, as taxa went extinct across the Mid-Pleistocene Transition. In contrast, Pseudoparrella obtusa, a possible phytodetritus species, increased intermittently after similar to 1.3 Ma. In the lower part of the core, Globocassidulina subglobosa-Globocassidulina ryukyuensis plexus were abundant before similar to 1.5 Ma, whereas Globocassidulina obtusa became common after similar to 1.4 Ma. The faunal transition in core PC311 from the seamount top in the western Pacific Ocean appears to be related to the enhanced zonal gradient of sea surface temperature between the eastern and western Equatorial Pacific Ocean at similar to 1.3 Ma as well as the changes in global deep-water circulation including the persistent North Pacific Deep Water and/or the Upper Circumpolar Deep Water from the Southern Ocean-originated deep water.
The Hauterivian coral fauna of Oshima Island (Miyagi, Japan) is taxonomically revised on the basis of the type and additional materials. The fossil localities are no longer accessible. Sixteen species from 13 genera and seven families are described. Not all originally described species could be revised either because the type material could not be found or owing to the poor state of preservation of the corals. The coral fauna from Oshima shares most species with the species-rich Hauterivian coral fauna of the Paris Basin (France). Four genera undergo a range extension: Calamophylliopsis, ?Eohydnophora, Siderohelia and Palaeosiderofungia.
