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Aramachi Formation

• Type locality: Aramachi, Nobesawa, Obanazawa city, Yamagata prefecture
• Coherent formation
• Miocene

• Sedimentary facies: Marine
• Lithofacies (Upper): Sandy shale
• Lithofacies (Lower): Interbedded shale and sandstone
• Lithofacies (Bottom): Tuff breccia

• Thickness: 150 - 300 m
• Upper limit: Bottom of the sandstone bed
• Upper limit: Conformity (Kodaira Formation)
• Lower limit: Bottom of the tuff breccia bed
• Lower limit: Conformity (Fukazawa Formation), Unconformity (Toyotateyama Agglomerate)

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

• Distribution: Aramachi, Nobesawa - Minegishi, Hosono, Obanazawa city, Yamagata pref.
• Fossils (Shellfishes): Serripes? sp., Thyasira bisecta

• Tokunaga (1958) Obanazawa, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 32p. (in Japanese with English abstract 6p.)