徳島県穴吹川上流，木屋平の地質と地形

The Mikabu and Chichibu belts in the Anabukigawa arre were studied with respect to their composition，
boundaries and the relation with landslides. The main body of the Mikabu Greenstones is composed of the
MORB-type tholeiite, and the Hawaiian and Polynesian-type alkaline basalts. The greenstones are dominated by
dolerite intrusions into bedded-cherts. The coincidence of the chemical composition attributes the Taigo and
Nakano greenstone bodies to the Mikabu Greenstones. The limestone phyllite of the Mt. Tsurugi was dated by
the occurrence of Late Carboniferous conodonts. The co-occurrence of conodonts and crinoids suggests that the
limestone originates from the tropical reef settings.The Fujinoike-dani Valley and the southern slope along the
Anabukigawa River are characterized by the frequent occurrence of landslides and collupse of forest road-cuts.
Because the faults，that cut the North Chichibu Belt，an d bounds from the Mikabu Greenstone Belt as well as the
Kaminirogawa-Akuigawa Fault that obliquely cut them later，are concentrated in the Fujinoike-dani Valley and
the southern slope along the Anabukigawa Riiver.The landslides are concentrated along the valley walls of the
Anabukigawa River where Mikabu Greenstones and the Sanbagawa green and pelitic schists occur. The
distribution of landslides in the area is controlled by the lithology (distribution of greenstone and schists)，the
coincidence of their dipping with valley wall, the contents of swelling clay minerals in the weathered materials，
and the changes in rock properties of pelitic schists due to weathering.