Interior structure of gravitationally deformed bodies on the left slope of Azusa River, Kamikochi, Nagano Prefecture, central Japan

Abstract

Geological investigation on the left slope of the Azusa River,　Kamikochi revealed structure of gravitationally deformed　bedrocks composed mainly of mudstone of the Jurassic　accretionary complexes in the Mino Belt. Bedding planes of the　rocks strike NNE-SSW subparallel to the trend of main dividing　ridge, and dip steeply to the west; the slopes form underdip　cataclinal structure where the bedding planes dip steeper than　the slope. In the upper part of slopes, dip of bedding planes is　gentle by the loosening of rock mass, while in the lower part, the　bedding planes dip eastward. The geologic characteristics show　the bedding planes of the deformed rock bodies have S-shaped　geologic structures. Elastoplastic buckling or plastic flow　probably formed the deep-seated gravitational slope deformation　structures and affected over 100 m in depth.