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Osoki Formation Ueki and Sakai, 2007

• Type locality: Osoki, Ome city, Tokyo
• Coherent formation
• late Pliocene (2.3 Ma, FT)
• Correlation: Oyabe Formation, Terada Formation

• Sedimentary facies: Fluvial
• Lithofacies: Breccia, Sands, Silt
• Lithofacies (Minor): Pumiceous tephra, Lignite
• Sedimentary structures: Channel structure

• Thickness: ca. 3.5 - 10 m
• Upper limit: Unconformity (Hanno Formation)
• Lower limit: Unconformity (Nitayama Unit, Nariki Unit, Raidenyama Unit)

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

• Distribution: Kurosawa river - Kobuichi river, Osoki, Ome city, Tokyo; Nariki river, Meganuki, Hanno city, Saitama pref.; Irumagawa river, Hanno - Yaoroshi, Hanno city, Saitama pref.
• Fossils: Insects, Wood fragments, Freshwater diatoms
• Deposit: Lignite

• Ueki and Sakai (2007) Geology of the Ome District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 189p. (in Japanese with English abstract 5p.)