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Oyakejima Formation (Inai and Takahashi, 1940) Murata and Shimoyama, 1979

• Type locality: Oyake island, Ogatsu town, Ishinomaki city, Miyagi prefecture
• Coherent formation
• Permian
• Correlation: Tenjinnoki Formation

• Sedimentary facies: Shallow marine
• Lithofacies: Sandstone, Sandy siltstone
• Lithofacies (Minor): Limestone, Usuginu Conglomerate
• Sedimentary structures: Bioturbation

• Thickness: 110 - 200 m or thicker
• Upper limit: Transitional (Toyoma Formation)

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Oyake island - Kobama - Hatezaki - Naburi, Ogatsu town, Ishinomaki city, Miyagi pref.
• Fossils: Trilobites (Phillipsia sp.), Corals (Michelinia? sp.), Crinoids, Stromatoporoids (Fenestella sp., Coeloconus sp.), Fuzulinids (Lepidolina kumaensis, Verbeekina japonica), Bryozoans (Fistulipora? sp.)
• Fossils (Ammonoids): Stacheoceras sp., Protocycloceras sp.
• Fossils (Shellfishes): Cryptocardinia? sp., Myophoria subelegans, Nuculites kimurai, Palaeoneilo ogachiensis
• Fossils (Brachiopods): Camarophoria humbeltonensis, Chonetes molengraffii, Compressoproductus sp., Cytospirifer? sp., Derbyia sp., Dielasma cf. biplex, Gratiosina gratiosa, Leptodus richthofeni, Linoproductus sp., Marginiferidae gen. et sp. indet, Martinia sp., Neophricadothyris? sp., Orthotelina sp., Phricodothyris? sp., Productus cancriniornis, Productus cf. cora, Productus flemingii, Productus puvei, Reticularia sp., Reticulariidae gen. et sp., indet, Rhynchonella sp., Richthofenia sp., Rhynchopora sp., Spirifer sp., Spiriferella sp., Spiriferellina sp., Squamularia cf. waageni, Stenoscisma humbletonensis, Waagenites sp.
• Fossils (Sponges): Amblysiphonella dichotoma, Coelocladia spinosa major, Thamnopora? sp., Thamnopora? nipponica, Thamnopora? chaetetoidea

• Kamada and Takizawa (1992) Geology of the Osu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 69p. (in Japanese with English abstract 4p.)
• Takizawa et al. (1990) Geology of the Toyoma District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 126p. (in Japanese with English abstract 8p.)