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Unit 1

Invalid synonym: Ua, Ub

• Coherent formation
• Yezo forearc basin
• Late Cretaceous, Coniacian? (Foraminifera)

• Sedimentary facies: Marine
• Depth of water: Continental shelf
• Depth of water: Middle - Upper bathypelagic (Foraminifera)
• Lithofacies (Main): Sandy mudstone
• Lithofacies (Minor): Tuff
• Lithofacies (KY-5): Tuffaceous sandstone, Tuff

• Thickness: ca. 500 m
• Upper limit: The boundary between the sandy mudstone bed of Unit 1 and the overlying mudstone bed of Unit 2
• Lower limit: The boundary between the sandstone bed of Saku Formation and the overlying sandy mudstone bed of Kashima Formation

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

• Distribution: Mayachi creek, Mayachi, Yubari city, Hokkaito; downstreams of Porosaru creek, Mukawa city, Yufutsu county, Hokkaido
• Fossils: Inoceramus uwajimensis, Foraminifera
• Tephra: KY-5

• Hayashi et al. (2011) Jour. Geol. Soc. Japan, vol.117, no.1, pp.14-34 DOI