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Yamayakawa Formation Hosoi, 2019
Invalid synonym: Haginari Formation
- Type locality: Upper reaches of Yamaya river, Okuyama, Kakunodate town, Senboku city, Akita prefecture
- Volcanic rocks
- late Oligocene - early Miocene (25.1, 21.0 Ma, K-Ar, 24.3 Ma, FT)
- Intruded by (Haginari Formation): Nibetsu Granite
- Sedimentary facies: Terrestrial?
- Lithofacies: Andesite lava, Sill, Tuff breccia
- Lithofacies (Minor): Sandstone, Mudstone, Basalt lava, Volcaniclastic rocks, Lignite
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Yamaya river - Sotohisaichi river, Okuyama, Kakunodate town, Senboku city, Akita pref.; Haginari, Kamikoani city, Kitaakita city, Akita pref.; Hitsuzawa, Kisoishi, Taiheihatta, Akita city, Akita pref.; Koguro creek, Akita city, Akita pref.; Kagotaki creek, Kawabe, Akita city, Akita pref.; Arakawa river, Kyowa, Daisen city, Akita pref.
- Fossils (Shellfishes): Anadara sp., Crassatellites suyamensis, Ostrea sp., Paliollum peckhami, Shichiheia cf. etchuensis
- Fossils (Aniai-type flora):
- Hosoi et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.4, pp.279-295 DOI
- Tsuchiya and Yoshikawa (1994) Geology of the Kariwano District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 72p. (in Japanese with English abstract 4p.)
- 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.)
- Huzioka et al. (1977) Geology of the Akita District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 69p. (in Japanese with English abstract 5p.)