Abstract
Several thin clay layers (about 1cm. to 10cm. in thickness) are found in the Miocene sedimentary rocks which are composed of fine alternation of the mudstone and sandstone strata, in the midstream district of the Kakizaki-Gawa (River). They are very tender and parallel to the bedding planes, and show apparently intraformational disturbance. It is concluded from the above-mentioned observations that the thin clay Layers were due to flexural slip folding.
On the other hand, there are many Landslide areas in this district. Therefore, it is thought that the several of them and the thin clay layer were closely related.
Consequently, it may be unavoidable to recognize the following conclusion: A basic factor of the several primary landslides in this district was flexural slip folding with thin clay layers.
