南部北上山地上八瀬地域の中部ペルム系細尾層から産出したフズリナ化石とその意義  [in Japanese] Middle Permian fusulines from the Hoso-o Formation in Kamiyasse area, southern Kitakami Mountains, Northeast Japan : Their biostratigraphic implications  [in Japanese]

南部北上山地宮城県気仙沼市上八瀬地域の中部ペルム系細尾層中の石灰質基質支持礫岩から,新たにSumatrina cf. annae, Pseudodoliolina pseudolepida, Chusenella sinensisおよびその他の有孔虫類を含むフズリナ化石群を発見した.この群集には,テチス域標準年代区分の後期MurgabianからMidianを示すS. cf. annaeが含まれる一方で,前・中期Murgabianの指標となる原始的なNeoschwagerinaやAfqhanella,および中・後期Midianを指示する進化型のLepidolinaやYabeinaが共産しない.このことは,この石灰質礫岩層が前期Midian(ペルム系標準年代層序区分の上部Wordian階)に対比されることを示唆する.この解釈は先行研究によるアンモノイド化石を用いた細尾層の年代論とも整合的である.

A fusulinid fauna, newly distinguished from the calcareous conglomerate of the Middle Permian Hoso-o Formation in Kamiyasse area, southern Kitakami Mountain, Northeast Japan, consists of Sumatrina cf. annae, Pseudodoliolina pseudolepida, Chusenella sinensis, and others. An early Midian age (late Wordian) is strongly suggestive for this fauna by the presence of Sumatrina cf. annae and the absence of both primitive forms of Neoschwagerina and Afghanella indicating an early-middle Murgabian age, and advanced forms of Lepidolina and Yabeina referable to the middle-late Midian. This age assignment of the formation by fusulinids is consistent with the previous ones by ammonoids.