南部北上帯日頃市地域の大野層から産出した前期デボン紀放散虫化石

概要

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The following four species of Early Devonian radiolarians have been discovered from felsic tuff of the lower part of the Ohno Formation in the Hikoroichi area of the South Kitakami Belt, Northeast Japan : Protoholoeciscus hindea Aitchison, Protoholoeciscus triangularis (Wakamatsu, Sugiyama and Furutani), Glanta sp. cf. G. fragilis Wakamatsu, Sugiyama and Furutani, and Tlecerina horrida Furutani. The radiolarian fauna is correlated with the Tlecerina-Glanta Assemblage recognized in the Devonian of the Kurosegawa Belt, Southwest Japan. This fauna is no older than Lochkovian or Pragian and is no younger than Emsian, considering comparisons to other Devonian radiolarian assemblages. This age assignment is consistent with macroinvertebrate age constraints of the Ohno Formation and the stratigraphic relationship to the overlying Eifelian Nakazato Formation. Based on the occurrence of these radiolarians, the Ohno Formation can be correlated with the Nakahata Formation of the Kurosegawa Belt.
2005-03-15