Geology of the Miharaiyama District, Yabu-gun, Hyogo Prefecture, Japan, with Special Reference to the Triassic Miharaiyama Group : A Study on the Stratigraphy and Geologic Structure of the "Maizuru Zone" (Part 2)

Abstract

The Paleozoic rocks which occur in the Miharaiyama district belong to the Minamitani group., They are correlated with the rocks of Kuma series (Upper Permian), which are typically expose in Kumamoto Pref., The Minamitani group contains special deposits such as the so-called Yasuba conglomerate., The Mesozoic Miharaiyama group is correlated with the lower part of the Inai series and is considered Scythian in age., It is subdivided as follows: Gannosudani formation G3 bluish grey siltstone -200m G2 bluish grey sandstone -80∼95m G1 conglomerate-50∼80m Niikuradani formation N2 bluish grey sandstone -30∼60m N1 basal conglomerate -15∼30m Minamitani group (Upper Permian) The Niikuradani formation contains no fossils, but the Gannosudani formation, especially G2 is rich in fossils which are listed below., G3: Nuculana sp., Myophoria aff., laevigata G2: Neobakevellia kambei M., S., M., aff laevigata (abundant) Neob., kambei sakaigawensis M., S., Nuculana sp., Rhynchonella sp., Terebratula? sp., etc., (rare) An unconformity was discovered between the Miharaiyama group and the underlying Paleozoic rocks., The Lower Triassic formations in Japan are local and very limited in occurrence., They are generally jammed into others formations by faults., Previously, the disconformable relation of the Lower Triassic with the Upper Permian Series (≒Kuma series), had beenknown only in the Kitakami Mountains, Miyagi Prefecture., The discovery of the unconformity mentioned above may be important in the study of the late Paleozoic crustol movement in Japan.,