北海道小平地域北東部上部白亜系の化石層序学的研究

概要

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This paper gives an account of some new biostratigraphical information about the Upper and Middle Yezo Groups (the Upper Cretaceous deposits) in the north-east part of the Obira district, Hokkaido. In this studied area, the Upper and Middle Yezo Groups are featured by predominant mudstone and simple geological structure. We distinguished nine Inoceramus zones and show them with some columnar sections. Some inoceramid species which have not been reported in Japan were obtained from the Cenomanian, e.g., I. cf. duneganensis, I. cf. scalprum, I. sp. A, and I. gradilis. On Ammonoidea, Tragodesmoceroides which indicates Turonian was obtained from the Upper Cenomanian, and Eupachydiscus haradai (Upper-Middle Santonian) was obtained from the lowermost Santonian. Some species of Ammonoidea, which are important to correlation with other areas, were also obtained, e.g., Vascoceras aff. durandi, Calycoceras spp., Turrilites cf. acutus and Marshallites spp. The stratigraphical levels of these ammonoids are shown with other domestic species in some tables.
日本古生物学会の論文
1985-06-11