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Nagaiwa Member (Takeuchi and Sakamoto, 1976) Kato et al., 1989

Invalid synonym: Nagaiwa Formation

• Type locality: Hijirigawasawa creek, Ooka, Nagano city, Nagano prefecture
• Coherent formation
• Pliocene
• Correlation: Okubo Mudstone and Sandstone Member

• Sedimentary facies: Shallow marine
• Lithofacies: Sandstone
• Lithofacies (Minor): Conglomerate, Mudstone

• Thickness: 300 - 600 m or thicker
• Upper limit: Conformity (Joshita Member), Unconformity (Hijiriyama Volcanics, Ooka Mudflow Deposit)
• Lower limit: Conformity (Komiji Formation)

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

• Distribution: Hijirigawasawa creek - Minamimaki - Tsukudami - Nagaiwa, Ooka, Nagano city, Nagano pref.
• Fossils (Trace fossils): Pipe rocks

• Kato et al. (1989) Geology of the Omachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 111p. (in Japanese with English abstract 7p.)
• Kato and Sato (1983) Geology of the Shinano-Ikeda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 7p.)