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Nakatsukyo Formation (Mikami, 1955) Ueki et al., 2013
- Type locality (New): Mount Bukkasan - Mount Kyogatake, Aikawa city, Aiko county, Kanagawa prefecture
- Type locality (Old): Nakatsugawa river, Mukaihara, Hanbara - Miyagase dam, Aikawa city, Aiko county, Kanagawa prefecture
- Volcanic rocks
- Trough-fill deposit at the collision boundary between Oceanic arc of Paleo-Izu-Bonin arc (Ocean crust) and Honshu arc (Island arc)
- late Miocene
- Sedimentary facies: Marine
- Sedimentary facies (Lower, Tuff facies): Pyroclastic turbidite, Debrite
- Sedimentary facies (Lower, Tuff facies): Reworked pyroclastic rocks (Epiclastic)
- Sedimentary facies (Lower, Volcanic breccia facies): Reworked pyroclastic rocks (Epiclastic)
- Lithofacies (Upper, Sandstone and mudstone facies): Tuffaceous sandstone, Mudstone
- Lithofacies (Lower, Tuff facies): Basalt - Andesite tuff, Sandstone, Mudstone
- Lithofacies (Lower, Tuff facies, Minor): Basalt - Andesite lapilli tuff, Tuffaceous sandstone, Dacite pumice tuff, Lapilli tuff
- Lithofacies (Lower, Volcanic breccia facies): Basalt - Andesit volcanic breccia, Tuff breccia, Lapilli tuff, Pyroclastic sandstone
- Lithofacies (Lower, Volcanic breccia facies, Minor): Dacite pumice tuff, Tuffaceous sandstone, Mudstone
- Thickness: 1,000 - 1,100 m or thicker
- Thickness (Sandstone and mudstone facies): ca. 150 m or thicker
- Thickness (Tuff facies): ca. 600 - 1,100 m
- Thickness (Volcanic breccia facies): ca. 450 m
- Upper limit: Minor unconformity (Sekirozan Formation)
- Lower limit: Conformity (Funazawa Formation)
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Mount Bukkasan - Mount Kyogatake - Mukaihara, Hanbara - Miyagase dam, Aikawa city, Aiko county, Kanagawa pref.; Mount Minamiyama, Sagamihara city, Kanagawa pref.; Sekidaira, Midori ward, Sagamihara city, Kanagawa pref.; Yono - Mayumi, Atsugi city, Kanagawa pref.
- Fossils: Chlamys kaneharai, Trace fossils (Cylindrichnus isp.)
- Fossils (Calcareous nannofossils): Discoaster berggrenii, Discoaster quinqueramus
- Ueki et al. (2013) Geology of the Hachioji District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 137p. (in Japanese with English abstract 6p.)
- Oka et al. (1979) Geology of the Fujisawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 111p. (in Japanese with English abstract 5p.)