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Akashiba Formation Fujita, 1988

Invalid synonym: Hatsuno Formation

• Type locality: Shiinoki river - Akashiba, Soma city, Fukushima prefecture
• Coherent formation
• middle Miocene (Diatoms)
• Correlation: Yoshigasawa Formation

• Sedimentary facies (Upper): Marine
• Sedimentary facies (Lower): Talus
• Lithofacies (Top): Mudstone
• Lithofacies (Upper): Sandstone
• Lithofacies (Upper, Minor): Tuff
• Lithofacies (Lower): Breccia
• Sedimentary structures (Upper): Bioturbation

• Thickness (Upper): ca. 180 m
• Thickness (Lower): 200 m or thicker
• Upper limit: Unconformity (Kuboma Formation, Mukaiyama Formation)

• Distribution: Shiinoki river - Akashiba - Hatsuno - Kitakayakura, Soma city, Fukushima pref.
• Fossils (Shellfishes): Acila divaricata, Cardium shiobaraensis, Dentalium sp., Glycymeirs sp., Lucina meisenensis, Macoma sp., Mercenaria chitaniana, Pecten kaneharai, Pecten yanagawaensis, Turritella nipponica
• Fossils (Diatoms): Denticulopsis simonsenii, Denticulopsis vulgaris

• Yanagisawa et al. (1996) Geology of the Somanakamura District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 114p. (in Japanese with English abstract 9p.)
• Fujita et al. (1988) Geology of the Kakuda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 99p. (in Japanese with English abstract 9p.)