Calcareous nannofossil assemblages from the samples in Holes 910A, 910C, and 911A were studied in order to estimate the age of the sediments drilled at the Yermak Plateau in the Arctic Ocean. Although the abundance and species diversity of calcareous nannofossil flora were poor, eight of twelve Quaternary calcareous nannofossil events were detected in Hole 911A. This indicates that the Quaternary datum planes defined by Takayama and Sato (1987) are applicable to the Arctic Ocean.
  The late Pliocene new datum plane A, defined by the floral change from Reticulofenestra ssp. (small) assemblage to Coccolithus pelagicus assemblage, is placed in the late Gauss Normal Epoch in the successions at both the Japan Sea side of Japan and the Arctic Ocean. This horizon is also assigned to that of increased dropstones in Holes 910C and 911A. These facts indicate that the datum plane A in the late Gauss Normal Epoch is strongly related to heavy glaciation in the high northern latitudes.

Date of initial receipt: 6 July 1995
Date of acceptance: 11 December 1995

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