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Otaki Formation Ozawa and Sumi, 1961

• Type locality: Shione river, Mamurogawa city - Nakada river, Kaneyama city, Mogami county, Yamagata prefecture
• Coherent formation
• late Miocene
• Correlation: Onnagawa Formation, Kusanagi Formation
• Intruded by: Otaki Dolerites, Takadoyama Andesites, Yakushisan Andesites, Rhyolite, Dacite, Andesite, Basalt, Dolerite

• Lithofacies (North): Mudstone
• Lithofacies (North, Minor): Basalt, Dolerite, Andesite
• Lithofacies (South): Mudstone, Tuff
• Lithofacies (South, Minor): Rhyolite, Andesite, Basalt, Dolerite

• Thickness: ca. 400 m
• Upper limit: Bottom of the horizon mainly composed of dacitic tuff
• Upper limit: Transitional (Haruki Tuff Member, Hasshikidai Mudstone Member)
• Lower limit: Transitional (Kaneyama Formation)

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

• Distribution: Shione river, Mamurogawa city - Nakada river, Kaneyama city, Mogami county, Yamagata pref.

• Ozawa and Sumi (1961) Uzenkaneyama, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 66p. (in Japanese with English abstract 5p.)