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Oyama Formation Omura, 1937

Invalid synonym: Wakinomachi Formation, Washima Formation

• Type locality: Yukyuyama park, Oyama town, Nagaoka city, Niigata prefecture
• Coherent formation
• middle Pleistocene
• Correlation: Hirote Formation, Shimizusawa Formation, Otsubo Formation

• Sedimentary facies: Lacustrine or fluvial
• Lithofacies: Sands, Mud
• Lithofacies (Minor): Gravels, Humic soils
• Sedimentary structures (Minor): Cross stratification

• Thickness: 10 - 50 m or thicker
• Upper limit: Unconformity (Higher I Terrace Deposits)
• Lower limit: Unconformity (Uonuma Formation)

• Distribution: Oyama town, Nagaoka city, Niigata pref.; Mimitori town - Myosho town, Mitsuke city, Niigata pref.; Higashiyama, Nagaoka city, Niigata pref.
• Fossils: Plants
• Fossils (Diatoms): Melosira solida, Stephanodiscus carconensis

• Kobayashi et al. (2010) Jour. Geol. Soc. Japan, vol.116, no.11, pp.XVII-XVIII
• Ikeda and Yamaji (2008) Jour. Geol. Soc. Japan, vol.114, no.8, pp.405-414 DOI
• Kobayashi et al. (2002) Geology of the Sanjo District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 98p. (in Japanese with English abstract 4p.)
• Kobayashi et al. (1991) Geology of the Nagaoka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 132p. (in Japanese with English abstract 6p.)