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Nakanosawa Formation (Tokunaga and Otsuka, 1930) Masatani, 1950

• Type locality: Nakanosawa, Tomizawa - Tatenosawa, Koike, Soma city, Fukushima prefecture
• Coherent formation
• Late Jurassic, Kimmeridgian - Tithonian (Ammonoids, Sr isotopes)

• Sedimentary facies: Shallow marine
• Lithofacies: Sandstone, Limestone

• Thickness: 160 - 300 m
• Upper limit: Bottom of quartz arenite bed
• Upper limit: Conformity (Tomizawa Formation), Unconformity (Kameoka Formation)
• Lower limit: Bottom of marine facies horizon bearing shellfish fossils and bioturbation
• Lower limit: Transitional (Tochikubo Formation)

• Distribution: Nakanosawa, Tomizawa - Tatenosawa, Koike, Soma city, Fukushima pref.; Koyamada, Kashima ward, Minamisoma city, Fukushima pref.; Ogai - Oshigama, Haramachi ward, Minamisoma city, Fukushima pref.; Nitta river, Ohara, Haramachi ward, Minamisoma city, Fukushima pref.; Aratozawa - Ishigami, Haramachi ward, Minamisoma city, Fukushima pref.
• Fossils: Fishes (superfamily Holostei), Bivalves, Echinoids (Cidaridae), Crinoids
• Fossils (Chondrichthyes): Hybodus sp. (Teeth), Asteracanthus sp. (Teeth)
• Fossils (Ammonoids): Aspidoceras sp., Aulacosphinctoides cf. steigeri, Aulacosphinctoides tairai, Haploceras sp., Holcophylloceras sp., Hybonoticeras sp., LIthacoceras sp., Neumayriceras cf. callicerum, Subdichotomoceras chisatoi, Taramelliceras sp., Virgatosphinctes sp.
• Fossils (Bivalves): Aequipecten kotsudu, Astarte ogawensis, Camptonectes sp., Ctenostreon proboscideum, Gervillia tatenosawensis, Grammatodon takiensis, Lima (Ctenoides) tosana, Lima (Plagiostoma) sp., Myophorella sp., Opis (Trigonopsis) torinosuensis, Parallelodon koikensis, Protocardia tosensis, Pteria masatanii, Somapecten kamimanensis
• Fossils (Corals): Acanthogyra sp., Aplosmilia somaensis, Aplosmilia? tochikuboensis, Astrocoenia sp., Enallhenia nipponoca somaensis, Gonicora? sp., Latomeandra? equchii, Latomeandra somaensis, Montlivaltia? sp., Myriophyllia sp., Stylina (Convexastrea) somaensis, Thamnasteria 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.)
• 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.)