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Nichioji Formation (Imamura, 1966) Suzuki et al., 2009

• Type locality: Nichioji, Okayama city, Okayama prefecture
• Coherent formation
• early Miocene
• Correlation: Bihoku Group, Katsuta Group

• Sedimentary facies: Marine
• Lithofacies (Upper): Sandstone
• Lithofacies (Middle): Conglomerate
• Lithofacies (Lower): Conglomerate

• Thickness: ca. 20 m
• Altitude: 255 - 275 m
• Lower limit: Unconformity (Yagane Formation, Kibi Group)

• Distribution: Nichioji, Okayama city, Okayama pref.
• Fossils: Brachiopods, Echinoids, Balanus sp., Bryozoans
• Fossils (Bivalves): Saccella sp., Acar cf. congenita, Striarca (Estellarca) uetsukiensis, Barbatia lima, Barbatia sp., Anadara valentula, Anadara sp., Septifer (Mytilisepta) sp., Modiolus? sp., Anomia? sp., Chlamys cf. arakawai, Chlamys sp., Ostrea sp., Mantellum sp., Cardita sp., Diplodonta? sp., Conchocele cf. nipponica minor, Conchocele sp., Thyasira sp., Lucinoma sp., Laevicardium sp., Callista? sp., Mercenaria otutumiensis, Ruditapes sp., Leukoma? sp., Verenolpa sp., Veneridae gen. et sp., indet, Oxyperas osawanoensis, Macoma sp., Angulus sp., Solen tanozawaensis, Solen sp., Cuspidaria cf. fluctuosa, Cuspidaria sp.
• Fossils (Scaphopods): Dentalium sp.
• Fossils (Gastropods): Haliotis sp., Emarginula sp., Scutus? sp., Clypidina (Montfortula) sp., Penepatella sp., Tectus cf. japonicus?, Phasianella? sp., Turritella filiola, Turritella sp., Calyptraea yokoyamai, Calyptraea sp., Natica sp., Conus (Asperella) sp.
• Fossils (Foraminifera): Miogypsina kotoi, Lenticulina nichiojiensis, Robulus lucidus, Textularia sp.

• Suzuki et al. (2009) Jour. Geol. Soc. Japan, vol.115, Supplement, pp.139-151 DOI