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Itaya Formation (Minakawa, 1960) Furukawa et al., 2018
Invalid synonym: Itaya Tuff, Osawa Formation, Toge Formation, Odaira Formation
- Type locality: Haguro river - Mekawa river, Yonezawa city, Yamagata prefecture
- Volcanic rocks
- Itaya caldera fill deposit
- late Miocene (9.3, 6.1 Ma, FT; 7.9 Ma, K-Ar)
- Intruded by: Rhyolite, Dacite
- Sedimentary facies: Terrestrial, Lacustrine
- Sedimentary facies (Upper): Caldera lake fill deposit
- Sedimentary facies (Middle): Pyroclastic flow deposit, Intrusive rocks
- Sedimentary facies (Lower): Caldera-collapse deposit
- Lithofacies (Upper): Tuffaceous mudstone, Mudstone
- Lithofacies (Middle): Biotite rhyolite
- Lithofacies (Middle): Pumice lapilli tuff
- Lithofacies (Middle, Minor): Tuff, Tuffaceous mudstone
- Lithofacies (Lower): Breccia
- Thickness: 350 m or thicker
- Upper limit: Unconformity (Hachimoriyama Formation)
- Lower limit: Unconformity (Granodiorite)
- Itaya caldera
- [ Upper ]
- ~~~~~~~~~~~~~~
- Itaya Formation
- ~~~~~~~~~~~~~~
- [ Lower ]
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Haguro river - Mekawa river - Mizukubo dam - Kariyasu river, Yonezawa city, Yamagata pref.; Matsukawa river, Fukushima city, Fukushima pref.
- Furukawa et al. (2018) Geology of the Azuma Yama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 74p. (in Japanese with English abstract 3p.)
- Hasegawa et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.33-48 DOI