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Iwamizawa Formation

• Coherent formation
• Foreland basins by collision between northeast Japan island arc and Kuril island arc
• late Miocene (12.9 - 9.2 Ma, Diatoms)

• Lithofacies: Mudstone, Shale

• Lower limit: Unconformity (Kawabata Formation)

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

• Distribution: Umaoi hills, Hokkaido

• Kase et al., (2018) Jour. Geol. Soc. Japan, vol.124, no.8, pp.627-642 DOI
• Okamura et al. (2010) Jour. Geol. Soc. Japan, vol.116, no.4, pp.181-198 DOI
• Hoyanagi et al. (2007) Jour. Geol. Soc. Japan, vol.113, Supplement, pp.205-215 DOI