1981 Volume 33 Issue 3 Pages 18-23
Nuta and Yo-une landslide areas located in the northern part of Kouchi prefecture and belong to the Mikabu geological zone. The Mikabu zone is formed of socalled Mikabu green rocks which is composed chlolite, actinolite, epidote, felspar, calcite and quartz. The landslides of the Mikabu zone are characterized by slope inclination, land-use and slide moving type. It seems that those characterestics are caused by Montmorillonite contained in landslide debris.
Samples which were surface, subsurface soils and weathered rocks were collected in study area. Laboratry analysis of sampled soils were performed on the measurment of soil suspention apH nd X-ray diffraction for clay particle(2μ). The resulst are as follows:
1) surface soils which wrs yellowish brown contained organic matter, were commonly contained Vermiculite, Kaolinite and Chlolite expect for Montmorillonite. Soil pH value is about 5-6.
2) Subsurface soil about lm depth which was graysh green, contained Montmorillonite and Chlolite. Vermiculite was not existed in this layer. It seemed that the Vermiculite decrease with depth. Soil pH value indicated abut 7-8. These facts are used to estimate the formative enviroment of Montmorillonite.
3) Montmorillonite was not only in subsurface soils, but in weathered rocks.