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Iwakura Formation Yoshida et al., 1983

• Type locality: Iwakura, Nihonmatsu city, Fukushima prefecture
• Coherent formation
• Forearc basin sediments
• middle Miocene
• Correlation: Marginal facies of Tsuchiyutoge Formation

• Sedimentary facies: Marine
• Lithofacies: Biotite rhyolite
• Lithofacies: Tuff breccia, Lapilli tuff
• Lithofacies (Minor): Conglomerate, Sandstone, Siltstone

• Thickness: ca. 40 m
• Upper limit: Unconformity (Fushiogami Debris Avalanche Deposit)
• Lower limit: Unconformity (Abukuma Granitic Rocks)

• Distribution: Iwakura, Shimokawasaki, Nihonmatsu city, Fukushima pref.; Matsukawa town - Shimokawasaki, Fukushima city, Fukushima pref.
• Fossils: Plants
• Fossils (Shellfishes): Acila cf. submirabilis, Clinocardium sp., Kotorapecten kagamianus, Limatula sp., Lucinoma acutilineatum

• Kubo et al. (2015) Geology of the Kawamata District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 86p. (in Japanese with English abstract 4p.)
• Sakaguchi (1995) Geology of the Nihonmatsu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 79p. (in Japanese with English abstract 4p.)