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Jonoirizawa Formation (Masuda et al., 1974) Yamamoto, 1999
- Type locality: Jonoiri creek, Ashinohara, Shimogo city, Minamiaizu county, Fukushima prefecture
- Volcanic rocks
- Collapse caldera-fill deposit
- Miocene
- Intruded by: Dacite, Andesite, Granodiorite porphyry, Tonalite
- Sedimentary facies: Terrestrial
- Lithofacies (Lacustrine): Sandstone, Conglomerate, Siltstone
- Lithofacies (Debris avalanche): Breccia
- Sedimentary structures (Lacustrine): Graded bedding, Parallel stratification
- Thickness: 600 m or thicker
- Thickness (Lacustrine): ca. 200 m
- Upper limit: Unconformity (Tonohetsuri Formation)
- Lower limit: Unconformity (Oto Formation, Late Cretaceous granodiorite)
- Jonoirizawa Formation
- [ Upper ]
- ~~~~~~~~~~~~~~
- Lacustrine deposit = Post-caldera stage
- --------------
- Tsurunumagawa Pyroclastic Flow Deposit / Debris avalanche deposit = Caldera-forming stage
- ~~~~~~~~~~~~~~
- [ Lower ]
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Jonoiri creek, Ashinohara, Shimogo city, Minamiaizu city, Fukushima pref.; Odaira, Tenei city, Iwase county, Fukushima pref.
- Fossils: Plants
- Yamamoto (1999) Geology of the Tajima District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 85p. (in Japanese with English abstract 8p.)