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[MIS13-P05] Sandstone dikes within pelagic cherts of the Permian Yoshii Group in Southwest Japan and its deformation structure
Keywords:ductile deformation, Permian, radiolaria, pelagic chert, sandstone dike, Akiyoshi terrane
We discovered ductilely- and brittlely-deformed chert blocks within sandstone dikes of the Yoshii Group in the Mihara area. The ductilely-deformed chert blocks and the clay minerals within the sandstone dikes are elongated and have slightly preferred orientation.
Pseudoalbaillella sp. cf. P. longtanensis Sheng et Wang was obtained from a chert bed just below the sandstone dike. Pseudoalbaillella longtanensis is characteristic species of the P. longtanensis Assemblage-Zone corresponding tentatively to the Kungurian (Cisuralian: Lower Permian).
The presence of the ductilely-deformed cherts suggests that the siliceous deposits had yet been unconsolidated when the sandstone dikes intruded. The sandstone dikes might be originated in terrigenous clastic, which is a component of chert-clastic sequences of the Yoshii Group in the Mihara area. The Permian chert had kept unconsolidated more than 10 My in this case.