岩手県滝名川扇状地における下層土の性質と微地形との対応

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In this paper, the relation between micro-landform and subsoil on alluvial fan is discussed for the purpose of an effective mapping of soil types. The results are summarized as follows. The studied area is the Shiwa fan, which is one of fans developing in the Kitakami Basin in northeastern Japan, and had been formed in Late Pleistocene to Early Holocene time. Tilting toward mountains, accompanied by a low-angle thrust fault at the fan apex, has affected the distribution of geomorphic units and the geologic structure. The fan was devided into eight geomorphic units of LF1 to LF8 in micro-scale. The older ones of LF1 to LF4 were situated around a distal part of the fan. The subsoils under these geomorphic units were characterized by heavy to light clay. This subsoil was a kind of buried soil which had developed on diluvial upland, and played as a impermeable layer to cause gley soil formation in the geomorphic units of LF1 to LF4. The youngest geomorphic unit of LF8 and partially younger units of LF5 to LF7 were characterized by humic subsoil. The appearance of gley subsoil around the fan apex resulted from a basin-like structure of the basal surface of Quaternary sediments.
日本ペドロジー学会の論文