The group in this area is divided, in descending order, into the following formations :
Itoshiro subgroup …Saradani shale (about 50 m thick)
Kuzuryu subgroup Kowashimizu sandstone (about 600 m thick) Sakaidera alternation of sandstone and shale (about 1, 000 m thick) Higashiamada conglomerate (about 150 m thick)
The Higashiamada conglomerate overlying the basement granodiorite consists mainly of the subangular pebbles of granodiorite. Judging from the pebbles the sediments of the conglomerate may be originated from the granodiorite mass which is extensive in the upper reach of the Asuwa River.
The Kowashimizu sandstone consisting of coarse-grained arkose was probably deposited in the shallow sea.
In the middle Kuzuryu region which includes the Asuwa district the group forms a large synclinal structure. Its axis runs from the northwest to the southeast through Mt. Daibutsuji, while in the Asuwa district the group shows a monoclinal structure.This, however, constitutes the southern wing of the synclinal structure. It is considered that this folding of the group had been completed before the Tertiary formations were deposited.
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