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Sanbongi Formation Kitagawa, 1941 ex Kitamura et al., 1981

Synonym: Sambongi Formation

• Type locality: Meguriyama, Sanbongi, Osaki city, Miyagi prefecture
• Coherent formation
• Pliocene
• Contemporaneous heterotopic facies: lower Onoda Formation, Mukaiyama Formation

• Lithofacies: Sandstone, Tuffaceous siltstone
• Lithofacies (Minor): Tuff, Lignite
• Lithofacies (Bottom): Sandstone, Conglomerate
• Sedimentary structures: Cross stratification

• Thickness: 50 - 70 m
• Upper limit: Conformity (Miyatoko Tuff Member), Unconformity (Higashihara Formation)
• Lower limit: Unconformity (Tatsunokuchi Formation)

• Distribution: Meguriyama - Konnaisan - Kayakari - Iga, Sanbongi, Osaki city, Miyagi pref.; Komaba - Furuimatsu, Ohira city, Kurokawa county, Miyagi pref.
• Fossils (Shellfishes): Corbicula leana
• Fossils (Plants): Acer sp., Fagus crenata, Sequoia japonica, Stewartia monadelpha

• Kitamura et al. (1983) Geology of the Yoshioka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 50p. (in Japanese with English abstract 5p.)
• Kitamura et al. (1981) Geology of the Furukawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 32p. (in Japanese with English abstract 4p.)