三疊系荒倉層及び荒倉期について : 舞鶴地帯の層序と構造-その7

概要

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The Arakura formation, composed mostly of black shales and sandy shales more than 70m thick, is overlain disconformably by the Sakawan (≒ Carnian) Nabae group. The Arakura is referred to be earliest Carnian or Ladino-Carnian in age by the following animal fossils and from the stratigraphical view point: "Monophyllites" arakurensis NAKAZAWA MS., Monophyllites? sp., Halobia? sp., Palaeoneilo sp., Nuculopsis (Palaeonucula?) sp., Psioidea spp. α, β, Spiriferina sp.. "Monophyllites" arakurensis belongs probably to a new genus derived from the Monophyllites-stock like Mojsvarites. Psioidea sp. α resembles especially P. conjuncts (HECTOR) from the Oretian (≒ lower Carnian) in New Zealand. The Arakura is surely later in age than the Zohoin group, the type of the Fujinohiran, which is characterized by typical Ladinian molluscs such as Daonella kotoi, D. sakawana, Monophyllites cf. wengensis and Protrachyceras aff. archelaus, although the stratigraphical relation between the two cannot be ascertained. Therefore, the Arakura formation represents the new stage between the Fujinohiran and the Sakawan. Here, the Arakuran age (= earliest Carnian or Ladino-Carnian) is proposed.
地学団体研究会の論文
1958-02-28