Stratigraphy of the Nankai Group in the Tosayamada area, Central Kochi, and correlation with the Monobegawa Group
Kozai, Takeshi Naruto University of Education
Ishida, Keisuke University of Tokushima Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Departmental Bulletin Paper
The purpose of our study is to clarify stratigrapical correlation of the Nankai and Monobegawa Groups. This paper presents the results of srratigraphy, sedimentary facies and geologic time.
The Cretaceous System of the Chichibu Terrain in the Tosayamada area is divided into the Monobegawa and Nankai Groups. The Monobegawa Group conformably overlies the Yasuba Formation(Permian) can be subdivided into three formations which are the Ryoseki, Monobe and Hibihara Formation. The Nankai Group can be subdivided into two formation which are the Funadani and lgenoki Formations. These are bounded to the North by Suita Tectonic line with serpentinite and to the South by Permian accretionary complex.
The lower part of the Funadani Formation consists of 150m of massive conglomerate and sandstone. The upper part of this formation consists of black mudstone which bear ammonite and some bivalve fossils.
The lgenoki Formation conformably overlies the Funadani Formation. The lower part of the Igenoki Formation consists of alternate layers sandstone and mudstone in which occur abundant bivalves and ammonites. They indicate the lower part to be Aptian. Some bivalves and ammonites are obtained from black mudstone which is the upper part of this formation. lgenoki Formation lies in fault contact with Permian accretionary complex which is named Yukigamine Formation.
Stratigrafical sequences of both groups are very similar, therefore, the Nankai group is member of Kurosegawa Tarrain.
Research bulletin of Natural Sciences, Naruto University of Education
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