Abstract
At the lower margins of steep slopes forming three levels of erosion surfaces in Chugoku mountains there developes pediment topography. The longitudinal width of the pediment is about 1500m and their inclination is from 7° to 9° in most cases. The more marginal a pediment is, the more gentle is the inclination. The pediments are covered with strata of cobbles, boulders and coarse sands, but in those strata bedding and sorting are not remarkable. The inclination of escarpments behind is 24° to 30° or 35° in rare occasions. Transitional slope between the escarpments and the pediments are zonal. The escarpment foot has not a zigzag outline but a straight one. The developments has already stopped and they have been dissected by streamlets.
In Chugoku mountains pediments are mostly found on granite area with hardrock cover, where local base-level was rather stable and relief was rather high. All pediments are on granite and a part or all of back hill in formed with hard rocks. Though all districts where pedimants can develop have a similar climatic condition, actual development of pediment is distinctly controlled by kinds of rocks. It seems that the collapse of granite is more similar to that of rocks under arid or semiarid climate than other rocks. The pediments are formed by parallel retreat of escarpment, which is caused by weathering, gravitation and rainfall. And, they are modified by sheet wash.
It can not be known under what climatic condition the pediments develop. Inferring from the strata on, the pediments, the climate must have been more arid than that of the present.
