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Kamitamatagawa Volcanic Rocks Nakano and Tsuchiya, 1992

It has been considered as a part of Okawa Formation

• Volcanic rocks
• late Miocene - early Pliocene (6 - 5 Ma, K-Ar)
• Miocene (Andesite member) (5.9 Ma, K-Ar)
• Miocene (Acidic pyroclastic rocks member) (4,7 Ma, K-Ar)
• Intruded by: Dolerite, Andesite

• Lithofacies (Andesite member): Augite andesite, Hypersthene augite andesite lava, Volcanic breccia, Tuff breccia, Hyaloclastite
• Lithofacies (Andesite member, Minor): Augite bsalt lava, Pyroclastic rocks, Rhyolite lava, Acidic tuff, Mudstone
• Lithofacies (Acidic pyroclastic rocks member): Rhyolite - Dacite tuff breccia, Lapilli tuff, Pumice tuff
• Lithofacies (Acidic pyroclastic rocks member, Minor): Tuffaceous conglomerate, Sandstone

• Thickness (Acidic pyroclastic rocks member): 500 m or thicker

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Kamitamata river - Osawa river, Chokai town, Yurihonjo city, Akita pref.; Hayasetachi river, Sakata city, Yamagata pref.

• Nakano and Tsuchiya (1992) Geology of the Chokaisan and Fukura District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 138p. (in Japanese with English abstract 7p.)