相良・掛川地域上部新生界の石灰質超微化石層序

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Late Cenozoic marine sequences, the late Miocene to early Pliocene Sagara Group and the middle Pliocene to early Pleistocene Kakegawa Group develop in the hilly and coastal area facing to Suruga Bay and Enshunada Sea. These marine sediments are coming into notice for establishment of the late Cenozoic standard section in Japan by many biostratigraphers, chronostratigraphers and magnetostratigraphers because of their continuous deposition and well-preserved fossil occurrences. The present writer clarified the calcareous nannoplankton flora in the Sagara and Kakegawa Groups with a scanning electron microscope technique and distinguished three calcareous nannoplankton zones : the Reticulofenestra pseudoumbilica Zone, the Reticulofenestra japonica Zone and the Reticulofenestra pacifica Zone in ascendidg order. A revised zonation and zonal nomenclature are presented based on the Japanese data. The Reticulofenestra pseudoumbilica Zone - the interval from indefinite base to the lowest level of Gephyrocapsa caribbeanica. The Reticulofenestra japonica Zone - the interval from the lowest level of Gephyrocapsa caribbeanica to the lowest level of Gephyrocapsa oceanica. The Reticulofenestra pacifica Zone - the interval from the lowest level of Gephyrocapsa oceanica to the lowest level of Gephyrocapsa protohuxleyi. The Gephyrocapsa oceanica Zone - the interval from the lowest level of Gephyrocapsa protohuxleyi to the lowest level of Emiliania huxleyi. The Emiliania huxleyi Zone - the interval from the lowest level of Emiliania huxleyi to dominant Emilliania huxleyi. The Sagara Group is characterized by common occurrence of Reticulofenestra pseudoumbilica and assigned to the lower half of the Reticulofenestra pseudoumbilica Zone. The Kakegawa Group extends from the middle part of the Reticulofenestra japonica Zone to the upper part of the Reticulofenestra pacifica Zone. The Tamari Formation belongs to the lower part of the Reticulofenestra japonica Zone. Calcareous nannoplankton flora of the Tamari Formation is clearly distinguished from that of the Sagara Group. The calcareous nannoplankton assemblage of the Tamari Formation is characterized by rare occurrence of Reticulofenestra pseudoumbilica and common occurrence of Pseudoemiliania lacunosa. Pliocene-Pleistocene boundary in this area is confirmed in the upper part of the Hosoya Tuff in the Horinouchi Formation based on the occurrence of Gephyrocapsa oceanica.
奈良教育大学の論文
1978-11-25

相良・掛川地域上部新生界の石灰質超微化石層序

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