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Ryozen Formation (Fujita and Oka, 1954) Yamamoto, 1996
Invalid synonym: Aoba Conglomerate and Sandstone Member, Ryozen Volcanic Rocks
Probably same as Lower Member of Kaneyama Formation.
- Type locality (Fall deposit): Ryozenan - summit of Mount Ryozen, Ryozen town, Date city, Fukushima prefecture
- Type locality (Lava and lahar deposit): Mano river, Yubune, Iidate city, Soma county, Fukushima prefecture
- Type locality (Lahar and fluvial deposit): Mount Shiote, Soma city, Fukushima prefecture
- Volcanic rocks
- Stratovolcano and relating alluvial fans
- middle Miocene (16.3, 15.5, 14.8 Ma, K-Ar)
- Correlation: Tenmyosan Volcanic Rocks
- Sedimentary facies: Lacustrine, Fluvial, Terrestrial
- Sedimentary facies: Stratovolcano, Pyroclastic cone, Volcanic-fan, Dammed lake
- Lithofacies: Low-K tholeiite series
- Lithofacies: Olivine basalt, Clinopyroxene olivine basalt, Olivine clinopyroxene basalt
- Lithofacies: Lava, Pyroclastic fall deposit, Lahar deposit
- Lithofacies: Aa lava, Scoria, Volcanic sands
- Lithofacies (Lahar): Tuff breccia, Lapilli tuff, Volcanic conglomerate
- Lithofacies (Lahar, Minor): Sandstone
- Lithofacies (Fluvial): Conglomerate, Sandstone, Siltstone
- Lithofacies (Lacustrine): Sandstone, Interbedded sandstone and siltstone
- Sedimentary structures (Lahar): Pararell stratification, Scour-fill cross-stratification, Low-angle cross-stratification
- Sedimentary structures (Fluvial): Trough cross-stratification, Parallel stratification
- Sedimentary structures (Lacustrine): Graded bedding, Parallel stratification
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Mount Ryozen, Ryozen town, Date city, Fukushima pref.; Yubune - Mano river - Matsugadaira, Iidate city, Soma county, Fukushima pref.; Mount Shiote, Soma city, Fukushima pref.; Hippo - Ouchi, Marumori city, Igu county, Miyagi pref.; Mount Iboishi, Kawamata city, Date county, Fukushima pref.; Iitoi, Iitate city, Soma county, Fukushima pref.
- Fossils (Plants): Betula mioluminifera, Betula nathoristi, Betula oobae, Carpinus jobanensis, Carpinus konnoi, Carya sp., Fothergilla ryozenensis, Liquidambar japonica, Ostrya subvirginiana, Populus kobayashii, Quercus hanagaii, Salix varians, Sequoia sp., Zelkova elongata, Zelkova ungeri
- Kubo et al. (2015) Geology of the Kawamata District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 86p. (in Japanese with English abstract 4p.)
- Yanagisawa et al. (1996) Geology of the Somanakamura District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 114p. (in Japanese with English abstract 9p.)