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Yokomuki Formation Yamamoto, 1994

• Type locality: Bonten river, Inawashiro city, Yama county, Fukushima prefecture
• Volcanic rocks
• Yokomuki caldera fill sediments
• Intrusive rocks: late Miocene (5.3 Ma, K-Ar)
• Pyroclastic flow deposit: late Miocene (5.0 Ma, FT)
• Intruded by: Orthopyroxene clinopyroxene dacite, Orthopyroxene clinopyroxene andesite, Basalt
• Contemporaneous heterotopic facies: Fujitoge Formation

• Sedimentary facies: Terrestrial, Lacustrine
• Sedimentary facies (Upper): Caldera lake-fill deposit
• Sedimentary facies (Lower): Pyroclastic flow deposit, Debris avalanche deposit
• Lithofacies (Upper): Sandstone, Conglomerate, Interbedded sandstone and mudstone
• Lithofacies (Lower): Breccia, Hornblende biotite ryolite pyroclastic flow deposit
• Sedimentary structures (Upper): Graded bedding, Reversed graded bedding, Parallel stratification, Current ripples

• Thickness: 1,300 m or thicker
• Thickness (Upper): ca. 100 m
• Thickness (Lower): ca. 300 m
• Distribution (Intrusive rocks, Diameter): ca. 2 km
• Upper limit: Unconformity (Nishikarasugawa Andesite, Numajiri Pyroclastic Flow Deposit, Iogawa Lava)
• Lower limit: Unconformity (Kijigoya Formation, Tsuchiyutoge Formation)

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

• Distribution: Bonten river - Takamori river, Inawashiro city, Yama county, Fukushima pref.

• 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.)
• Hasegawa et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.33-48 DOI
• Sakaguchi (1995) Geology of the Nihonmatsu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 79p. (in Japanese with English abstract 4p.)