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Ryukawa Formation Murai, 1962

Invalid synonym: Sakamoto Formation, Sakamotogawa Formation, Lower Takinoueonsen Formation

• Type locality: middle reaches of Ryukawa river, Shizukuishi city, Iwate county, Iwate prefecture
• Coherent formation
• Miocene

• Lithofacies: Interbedded siltstone and tuff

• Thickness: ca. 300 m
• Upper limit: Conformity (Yamatsuda Formation)
• Lower limit: Conformity (Ryukawa Formation)

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

• Distribution: Ryukawa river - Sakamoto river - Koshidomae creek, Shizukuishi city, Iwate county, Iwate pref.

• Suto and Ishii (1987) Geology of the Shizukuishi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 142p. (in Japanese with English abstract 5p.)