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Meganebashi Formation (Morita, 1930 ex Yabe and Hatai, 1941) Yanagisawa and Yamamoto, 1998
Invalid synonym: Oguni Formation, Kawairi Formation, Bentozawa Formation, Koarasawa Formation, Shirabutoge Formation (Fukushima pref.), Ohisawa Formation (Lower part)
- Type locality: Megane bridge, Myozawa river, Oguni city, Nishiokitama county, Yamagata prefecture
- Coherent formation
- Half-graven deposit
- early - middle Miocene (ca. 16 Ma, FT)
- Correlation: Imaichi Formation (Okiura flora), Budozawa Formation
- Intruded by: Rhyolite dyke, Andesite dyke
- Sedimentary facies: Terrestrial
- Sedimentary facies (Upper): Fluvial, Lahar deposit
- Sedimentary facies (Upper, Minor): Overbank deposit
- Sedimentary facies (Lower): Braided river
- Lithofacies (Upper): Basalt lapilli tuff, Accretionary lapilli tuff, Basalt - Andesite lava, Volcanic conglomerate, Volcanic sandstone, Rhyolite lapilli tuff, Interbedded volcanic conglomerate and volcanic sandstone, Welded tuff
- Lithofacies (Upper, Minor): Siltstone
- Lithofacies (Middle): Conglomerate
- Lithofacies (Lower): Conglomerate, Sandstone
- Sedimentary structures (Lower): Imbrication, Cross stratification
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Hakonokuchi - Myozawa bridge - Kawairi - Uchikawa? river - Kanomizu - Shirakozawa, Oguni city, Nishiokitama county, Yamagata pref.; Yonezawa city, Yamagata pref.; north shore of Lake Hibara, Kitashiobara city, Yama county, Fukushima pref.
- Fossils (Plants): Alangium aequalifolium, Betula cf. hommashinichi
- Furukawa et al. (2018) Geology of the Azuma Yama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 74p. (in Japanese with English abstract 3p.)
- Yamanoi et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.5, pp.262-266 DOI
- Yanagisawa and Yamamoto (1998) Geology of the Tamaniwa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 94p. (in Japanese with English abstract 4p.)
- Takahashi et al. (1996) Geology of the Iidesan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 52p. (in Japanese with English abstract 3p.)