岩手県北上市付近の火山灰土壌の生成について-1-地形と土壌生成

概要

論文の詳細を見る
The major Andosols in the vicinity of Kitakami city, Iwate prefecture, are Normal, Light-colored, and Aquic Andosols. The genesis and distribution of the soils in the study area are found to be closely related to the geomorphic development and characteristics of three Pleistocene terraces.The formation of Andosols on the Kanagasaki terrace, the youngest one (an alluvial fan formed by the Geto river), is strongly influenced by the micro-relief, variety of terrace deposits, and drainage conditions of this terrace. The parent materials of the Andosols are relatively thin volcanic ash layers (1, 000 to 5, 000 years B.P.) overlying the alluvial deposits. Normal Andosol occurs in the well-drained area from the top to the spring zone, approximately the center of the alluvial fan. Light-colored Andosol (I) (though the color of humus horizon is black, its depth is less than 25cm) occurs locally on the eminence which consists of gravel deposits. On the other hand, Aquic Andosol is widely distributed in the poorly-drained area from the spring zone to the margin of the fan.Normal Andosol and Light-colored Andosol (II) (the color of the humus horizon is brown) belonging to a truncated soil are two major Andosols on the Murasakino terrace, the younger one. This terrace occuring on the margin of the alluvial fan is slightly dissected and has a wide subhorizontal surface. The parent materials of these soils consist of volcanic ash layers (1, 000 to 20, 000 years B.P.) and Murasakino pumice bed (20, 000 years B.P. or more), indicating intermittent volcanic activity. Normal and Light-colored (II) Andosols predominate on the flat terrace surface, whereas Aquic Andosol is formed by the redistribution of eroded Andosol materials on the bottoms of the valleys dissecting the terrace surface.Light-colored (II) and Aquic Andosols predominate on the Nishine terrace, the old one, which is strongly dissected. Tephra deposits consisting of younger to very old ones are extremely thick on the terrace surface, but subjected to strong erosion owing to the development of the terrace scarp and valleys. Light-colored Andosol (II) occurs on the summit, shoulder, and back slope components. Aquic Andosol which represents redistribution of the materials occurs on the footslope and toe slope components.
日本第四紀学会の論文

岩手県北上市付近の火山灰土壌の生成について-1-地形と土壌生成

スポンサーリンク

概要

著者

関連論文

スポンサーリンク