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Okachigawa Formation Ozawa et al., 1979

• Type locality: Okachi river, Innai, Yuzawa city, Akita prefecture
• Volcanic rocks
• Miocene
• Contemporaneous heterotopic facies: Iizawa Formation, Sarakawa Formation

• Sedimentary facies: Marine (Shellfishes)
• Lithofacies (Main part): Pyroxene andesite tuff breccia, Volcanic breccia, Volcanic conglomerate, Lapilli tuff, Conglomerate
• Lithofacies (Main part, Minor): Andesite lava, Acidic tuff, Lapilli tuff

• Thickness: 300 - 550 m
• Thickness (Lower): 100 - 200 m
• Upper limit: Unconformity (Daisenyama Formation)
• Lower limit: Unconformity (Yunosawagawa Formation)

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

• Distribution: Okachi river - Mount Eboshi, Innai, Yuzawa city, Akita pref.; Iwadai, Ugo city, Okachi county, Akita pref.
• Fossils: Shellfishes

• Ozawa et al. (1979) Geology of the Yuzawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 64p. (in Japanese with English abstract 4p.)