LATE QUATERNARY PALEOCEANOGRAPHY OF THE PERVENETS CANYON AREA OF THE BERING SEA: EVIDENCE FROM THE DIATOM FLORA

Abstract

Sediments from three gravity cores from an east-west shelf-to-slope transect along the axis of Pervenets Canyon in the northern Navarin basin, Bering Sea were analyzed for diatoms. The diatom floras present in the cores were divided into four assemblages following Sancetta (1981). The Bering Basin (deep water open ocean) and Sea Ice (ice cover at least six months per year) Assemblages were dominant in each core. The taxa that comprise the Bering Shelf Assemblage (continental shelf) indicate that downslope transport plays only a minor part in the development of the thanatocenoses. The presence (up to 10% of the total valve count) of the Productivity Assemblage, which consists mainly of poorly silicified, easily dissolved taxa, indicates that nutrient flux is relatively high in the region. Several taxa can be used as proxy indicators for specific water masses. Neodenticula seminae (Simonsen & Kanaya) Akiba & Yanagisawa is indicative of Holocene open marine (deep water) conditions. Nitzschia cylindra (Grunow) Hasle and N. grunowii Hasle are both associated with sea ice and are thought to indicate late Pleistocene conditions. The relative downcore abundance of these taxa was used to approximate the Pleistocene- Holocene boundary (recognized in Core 80–65 at a depth of about 75 cm).