北海道菊面沢の上部白亜系におけるイノセラムス・有孔虫化石の対応

概要

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The Kikume-zawa, a branch of the River Ikushumbetsu in central Hokkaido, is celebrated for the occurrence of inoceramids and ammonites of the "Upper Urakawan", which consists of the Zone of Inoceramus (Platyceramus) japonicus above and the Zone of I. amakusensis below. Foraminiferal assemblages of the mudstone samples from representative localities of the two zones have been examined, with results shown in Tables 1 and 2. The beds with I. japonicus exposed at Ik 8014 (type locality of I. japonicus hokkaidoensis) and Ik 8013 contain planktonic foraminiferal species referable to the Globotruncana arca Assemblage-zone, suggesting a Campanian age. The bed with I. amakusensis at Ik 8021 contains the benthic foraminiferal faunule of the Silicosigmoilina futabaensis-S. ezoensis Concurrent-range-zone and planktonic species referable to the Dicarinella concavata Acme-zone to Marginotruncana canaliculata-M. marginata Acme-zone and is probably of early Santonian age. As I. higoensis Noda has been separated from I. japonicus, the foraminifera from the beds with I. higoensis in Kyushu should be carefully investigated.
日本古生物学会の論文
1988-06-03