Lisa E. Osterman


  The benthic foraminiferal record of Ocean Drilling Program (ODP) Site 910 can be divided into four assemblage zones, from oldest to youngest: the Cassidulina spp. zone, the Elphidium spp. zone, the Elphidium albiumbilicatum zone and the Elphidium excavata forma clavata zone. The Pliocene benthic foraminifers in the three lower zones of Site 910C, 102.8-504.7 meters below sea floor (mbsf), indicate warm conditions that cool progressively from 2.7 to 1.6 Ma. Based on the number and diversity of planktonic foraminifers and the high benthic foraminiferal abundances, the lowermost Cassidulina spp. zone indicates the warmest water conditions within the Pliocene at this locality. The Elphidium spp. zone of Site 910C indicates warm but cooling conditions with decreasing foraminiferal diversities and abundances, which end with the initiation of glacial dropstones at 208.7 mbsf. The presence of species described from Pacific deposits in both lower zones suggests a Pacific Ocean influence during the late Pliocene at this site. However, climatic conditions change when Atlantic species begin to dominate the uppermost Pliocene sediments. The uppermost Pliocene sediments of the E. albiumbilicatum zone indicate glacial-marine conditions with warm episodes.
  The uppermost E. exacavatum f. clavata, zone (0-102.8 mbsf), of Quaternary age, records glacial and interglacial climatic fluctuations, including one or more instances of grounded glacial ice (or episodes of severe ice-rafting) and ice-free interglacial deposits.
  It appears to be possible to correlate the Pliocene benthic foraminiferal assemblages in Hole 910C with the isolated pockets of Arctic Pliocene sediment that have been previously described (Brouwers et al., 1991; Brigham-Grette and Carter, 1992; Feyling-Hanssen, 1990; Feyling-Hanssen et al., 1982).

Date of initial receipt: 1 July 1995
Date of acceptance: 12 December 1995

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