Abstract
Eight samples with different colors, textures, etc., were selected according to the depth in the soil profile at Mt. Katasone, Fukushima Prefecture. The minerals in the fine sand fraction in these samples were quantitatively investigated. By summarizing the distribution of the minerals in the fine sand fraction, the process of the formation of the soil profile is concluded as fallows. The fact that the xenomorphic quartz, biotite and hornblende are found in large amounts at Nos. 9,8 and 7 indicates that the materials of these layers are derived from granodiorite rock. From bipyramidal quartz, pumice, volcanic glass, hypersthene and augite at Nos. 6,5,4,3 and 2,it is proved that a part of the parent materials of the soil of these layers is composed of dasitic ash. In spite of remarkable decrease of biotite at the parts apper from No. 6,hornblende relatively increases, and some soft weathered fragments of hornblende gabbro are abundant at the coarse sands of Nos. 6,5,4,3 and 2. These prove that the materials derived from hornblende gabbro are mixed at the parts upper than No. 6 with dasitic ash. Moreover the existence of andesine with An 45%, the increase of hypersthene, augite and flack opaque minerals at Nos. 3 and 2,and abundance of pumice in these coarse sands undoubtedly shown the addition of the ash of pyroxene andesite to these layers. In brief, the weathering products of granodiorite are covered by those of hornblende gabbro mixed with ash of dacite, and further by the mixture of hornblende gabbro and ashes of both dacite and pyroxene andesite.
