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Omata Formation (Inoue and Fujioka, 1948) Kano et al., 2012

Invalid synonym: Obonai Formation

• Type locality: Omata river, Ani river, Koyawatari - Arase, Ani, Kitaakita city, Akita prefecture
• Volcanic rocks
• early Miocene (21.7 Ma, FT)
• Correlation: Obonai Formation, Nozoki Formation
• Intruded by: Dacite, Hornblende biotite granite

• Sedimentary facies (Top): Under water
• Sedimentary facies: Terrestrial
• Lithofacies (Top): Rhyolite hyaloclastite
• Lithofacies: Dacite volcanic lapilli tuff, Tuff, Dacite welded tuff
• Lithofacies (Minor): Basaltic andesite- andesite pyroclastic rocks, Andesite scoria volcanic lapilli tuff, Tuffaceous sandstone, Conglomerate, Tuff, Clay stone
• Sedimentary structures: Graded bedding

• Thickness: 150 - 1,400 m
• Upper limit: Bottom of the bed intercalating conglomerate and sandstone
• Upper limit: Conformity (Makibuchi Formation, Kunimitoge Formation), Unconformity (Osarubegawa Formation, Iwaya Formation, Torisakagawa Formation, Yamayakawa Formation, Yoroibata Formation, Miyata Formation)
• Lower limit: Unconformity (Taiheizan Granodiorite)

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

• Distribution: Ani river, Koyawatari - Arase, Ani, Kitaakita city, Akita pref.; Utto river - Kodakura creek - Tsunagi creek - Shibuchinai creek, Ani, Kitaakita city, Akita pref.; Yukuchinai, Animizunashi, Kitaakita city, Akita pref.; Mount Taiheizan - Mount Babamedake, Akita city, Akita pref.; Onaminai creek, Nishiki town, Senboku city, Akita pref.
• Fossils (Aniai flora): Betula sp., Carpinus heigunensis, Carpinus subcordata, Tilia hommashinichii, Ulmus takayasui

• Kano (2018) Jour. Geol. Soc. Japan, vol.124, no.10, pp.781-803 DOI
• Ozawa et al. (1981) Geology of the Taiheizan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 69p. (in Japanese with English abstract 4p.)
• Sumi and Moritani (1973) Geology of the Yonaizawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 46p. (in Japanese with English abstract 4p.)
• Ozawa and Sumi (1958) Tazawako, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 23p. (in Japanese with English abstract 4p.)
• Ozawa and Sumi (1957) Moriyoshiyama, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 42p. (in Japanese with English abstract 5p.)