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Oishigawa Scoria Kawachi, 1974

Abbr.: OS

• Type locality: 1,020 m above sea level of Oishi river, Sakuho city, Minamisaku county, Nagano prefecture
• Tephra
• Strombolian
• early Pleistocene
• Interfingered with debris flow deposits and fluvial deposits

• Lithofacies: Augite olivine basalt scoria, Volcanic lapilli (20 units or more)

• Source: Yabashira volcanoes
• Source: Upper reaches of Otake river
• Thickness: 15 - 40 m
• Thickness (A unit): ca. 10 cm
• Upper limit: Transitional (Kasuga Volcanic Rocks), Unconformity (Chojabaru Gravels, Yachiho Mudflow Deposit, Usonokuchi Gravel Bed, Kaize Formation, Miyanoshita Formation, Ikenotairabokujo Lava)
• Lower limit: Transitional (Uryuzaka Formation)

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

• Distribution: 1,020 m above sea level of Oishi river, Sakuho city, Minamisaku county, Nagano pref.; Yachiho - Usonokuchi, Sakuho city, Minamisaku county, Nagano pref.; Odagiri - Yuharashinden - Maeyama, Saku city, Nagano pref.
• Tephra: Shindai Volcanic Ash

• Nishiki et al. (2007) Jour. Geol. Soc. Japan, vol.113, no.5, pp.193-211 DOI
• Kawachi and Aramaki (1979) Geology of the Komoro District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 39p. (in Japanese with English abstract 2p.)
• Kawachi (1974) Geology of the Tateshinayama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 114p. (in Japanese with English abstract 5p.)