徳島県南部，大木屋崩壊地の地形・堆積物の特徴と形成時期の推定

抄録

The Ogoya Landslide is a large failure of 8.6 ha area in south Tokushima Prefecture, southwest Japan. Both re-sedimented humic soil and tephric loess overlie the slide deposits composed of angular boulders of sandstone. The tephric loess intercalates a thin deformed humic soil layer with AMS ¹⁴C age of 4,050±40 yrs BP, and contains entirely volcanic glass shards of the 26-29 ka Aira-Tanzawa Tephra (AT).This stratigraphy suggests that the landslide predate to 26-29 ka. Average incision rate of the upper reach of Kaifu River after the failure is estimated to less than 1.0 mm/yr.