Abstract
A large-scale cross-stratified sediments of about 5.5 meter thickness which consist mainly of sands and gravels, crop out facing the Amano River, at Kisaichi on the northwestern margin of Ikoma Mountains. This is regarded as deposits formed in an artificial raising process of river bed. The upper part of silty layer beneath this sediments, was dated at 602±59yB(A. D.1290-1424). These facts indicate that the beginning of artificial raising of Amano River bed doesn't date back to the end of the 13th century. And this is an important data suggested too that the historical event of Ikoma active fault estimated by Togo(2000), is after the latter period of Kamakura era.
