宮城県富谷丘陵小流域における斜面崩壊発生史

概要

論文の詳細を見る
Tomiya Hills, situated in northeastern Japan, are composed of Neogene sedimentary rocks and are densely dissected by V-shaped valleys. Some of these are filled with thick sandy sediments. These sediment units are rendered conspicuous by buried humus horizons. Such sedimentary facies indicate frequent occurrences of sand flows induced by heavy rains and regolith slides. The lowermost unit of the valley-filling sediments in the investigated watershed, which appears to be deposited simultaneously with regolith sideslope slides, shows a radiocarbon age of 60 ± 20 yrs BP Therefore, this suggests that the former V-shaped valley was filled 100 years ago. The volume of the remaining sediments as a whole is approximately 2.7 × 10^4 m^3. The volume of the regolith slides, with a thickness of 0.5 m, that the Lower Sideslopes below the Postglacial Dissection Front might have caused is too small to have occurred in only 100 years. From the large volume of sediments and the slope form in the watershed, it can be inferred that the large-scale sand flows were accompanied by large regolith slides with a thickness of more than 2 m on the Upper Sideslope of the valley head above the Postglacial Dissection Front.
日本地形学連合の論文
2004-10-25