Abstract
This paper describes conformable relationship between the Mizuyagadani and Sorayama Formations in the Fukuji area, Hida-gaien Tectonic Zone, and occurrence of Middle Permian fusulinids from the matrix of limestone conglomerate of the Sorayama Formation.The Mizuyagadani Formation consists mainly of tuffaceous clastic rocks, sandstone and mudstone, whereas the Sorayama Formation is composed mainly of mafic to intermediate pyroclastic rocks. Field observations of the boundary strata between the two formations exposed in the Iranodani Valley strongly indicate the conformable relationship. The reasons are as follows ; 1) no faults exist between the two formations, 2) the Mizuyagadani Formation is stratigraphically lower than the Sorayama Formation, since the sedimentary structures observed in the Mizuyagadani Formation indicate northward facing, 3) bedding planes of the two formations are parallel to subparallel to each other, 4) the Mizuyagadani Formation is intercalated with mafic tuff layers, and felsic tuff of the Mizuyagadani Formation contains many basaltic volcanic fragments similar to the basalts of the Sorayama Formation, and 5) lithology between the two formations is gradual change.Middle Permian fusulinids (Nankinella sp., Parafusulina sp. aff. gigantea and Russiella pulchra) are found from the matrix of conglomerate in the Sorayama Formation along the Kashiatedani Valley about 1 km east of the Iranodani Valley. The age of the sedimentation of the Sorayama Formation is regarded as of the same age of fusulinids, because the felsic to intermediate tuffaceous materials similar to the matrix of conglomerate fill chambers of the most of fusulinid shells remains.
