岡山県井原北西および金川地域の舞鶴層群の放散虫生層序

Radiolarian biostratigraphy of the Permian Maizuru Group of the Maizuru Belt was examined in the northwest of Ibara and Kanagawa areas in the easten part of the Okayama Prefecture, Southwest Japan.
The Maizuru Group in the west of Ibara area is composed of the Lower, Middle and Upper Formations.
The Lower Formation consists of mainly basic volcanic rocks intercalating red bedded cherts and black mudstones. The Middle Formation consists of chiefly black mudstone with intercalated sandstones, acidic tuffs. The Upper Formation is mainly composed of altemating beds of sandstone and mudstones and shales, which are sheared and phyllitic. Radiolarian assemblages, corresponding to the Pseudoalbaillella longtanensis, Follicucullus monacanthus and F. scholasticus Assemblages which range from Middle to early Late Permian occur from the Middle Member of the Maizuru Group.
The Maizuru Group in the Kanagawa area consists of the a formation mainly composed of sandstone and the b formation consisting of chiefly mudstone. Follicucullus monacanthus and F. scholasticus Assemblages occur from the b formation.
The Maizuru Group in the northwest of Ibara area has different lithologic feature from that in the further eastem Maizuru Belt. The Maizuru Group in the northwest of Ibara area includes red bedded cherts associated with basic volcanic rocks, which may indicate difference of sedimentary environment of the Paleo-Maizuru sea basin among the areas of the Maizuru Belt.