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Okawa Formation Taguchi, 1962
Okawa Formation had been defined as a member of Aosawa Formation.
A part of this formation was separated as Kamitamatagawa Formation.
Invalid synonym: Komatagawa Altered Green Tuff Breccia Member, Myojinzawa Green Tuff Member, Honmaru Green Tuff Breccia, Irimizuzawa Green Tuff, Budozawa Green Tuff
- Type locality: Myojin creek - Osawa river (Okawa river), Mamurogawa city, Mogami county, Yamagata prefecture
- Volcanic rocks
- middle Miocene
- Contemporaneous heterotopic facies: Aosawa Formation, Sugota Formation
- Intruded by: Granodiorite (Neogene), Quartz diorite (Neogene), Quartz porphyry (Neogene), Rhyolite (Neogene), Dolerite
- Sedimentary facies: Marine
- Lithofacies: Augite andesite - Hypersthene augite andesite lava, Volcanic breccia, Tuff breccia
- Lithofacies (Minor): Mudstone, Basalt lava, Pyroclastic rocks, Rhyolite lava, Acidic lapilli tuff, Pumice tuff, Welded tuff
- Fukura, Yamagata pref.
- [ Upper ]
- --------------
- Kusanagi Formation
- --------------
- Okawa Formation
- ?--?--?--?--?-
- [ Lower ]
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Mount Tokami, Chokai town, Yurihonjo city, Akita pref.; Myojin creek - Osawa river (Okawa river) - Omata river - Mount Arisawa - Ishifutagari creek, Mamurogawa city, Mogami county, Yamagata pref.
- Fossils (Foraminifera): Hopkinsina morimachiensis
- 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.)
- Tsuchiya (1989) Geology of the Osawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 85p. (in Japanese with English abstract 6p.)