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Koike Limestone Member Masatani, 1950

• Coherent formation
• Late Jurassic, Tithonian (Sr isotopes)

• Sedimentary facies: Marine
• Lithofacies: Limestone
• Lithofacies: Interbedded oolite and micrite

• Thickness: 0 - ca. 50 m
• Distribution (Length): 25 km or longer
• Distribution (Width): 250 m or wider
• Upper limit: Bottom of quartz arenite bed
• Upper limit: Conformity (Tomizawa Formation)
• Lower limit: Transitional

• Distribution: Nakanosawa, Tomizawa, Soma city, Fukushima pref.; Oshigama, Haramachi ward, Minamisoma city, Fukushima pref.
• Fossils: Echinoids, Crinoids, Stromatoporoids, family Pinnidae (Trichites sp.), Gastropods (Nerinea sp.)
• Fossils (Ammonoids): Aspidoceras sp., Aulacosphinctoides cf. steigeri, Lithacoceras sp., Neumayriceras cf. callicerum, Virgatosphinctes sp.
• Fossils (Bivalves): Aequipecten kotsubu, Astarte ogawensis, Camptonectes sp., Ctenostreon proboscideum, Gervillia tatenosawaensis, Grammatodon takiensis, Lima (Ctenoides) tosana, Lima (Plagiostoma) sp., Myophorella sp., Opis (Trigonopsis) torinosuensis, Parallelodon koikensis, Protocardia tosensis), Pteria masatanii, Somapecten kamimanensis, Trichites sp.
• Fossils (Brachiopods): Terebulatula sp., Terebulatularia sp., Rhynconella sp.
• Fossils (Corals): Acanthogyra sp., Aplosmilia somaensis, Aplosmilia? tochikuboensis, Astrocenia sp., Enallhenia nipponica somaensi, Gonicora? sp., Latomeandra? eguchii, Latomeandra somaensis, Montlivaltia? sp., Myriophyllia sp., Stylina (Convexastrea) somaensis, Thamnastria abukumaensis, Thamnasteria torinosuensis, Thecosmilia tosaensis

• Taketani and Osozawa (2013) Jour. Geol. Soc. Japan, vol.119, Supplement, pp.68-81 DOI
• 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.)
• Kubo et al. (1990) Geology of the Haramachi and Omika District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 138p. (in Japanese with English abstract 7p.)