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Ryotsu-oki Group Okamura et al., 1955

• Coherent formation
• late Pliocene - late Pleistocene

• Sedimentary facies: Marine
• Sedimentary facies: Shoreface, Sea shore
• Lithofacies: Sands

• Upper limit: Conformity (Yotsugoya Group)

• Distribution: Japan sea floor, Niigata pref.
• Fossils: Callista sp., Trace fossils (Bichiordites monasiriensis)

• Kamoi et al. (2016) Geology of the Niigata and Uchino District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 90p. (in Japanese with English abstract 2p.)