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Yashiki Formation (Fujimoto et al., 1946) Saito et al., 1962

• Type locality: Kiyokawa river, Yashiki, Iiyama city, Nagano prefecture
• Volcanic rocks
• early Pleistocene
• Contemporaneous heterotopic facies: Minochi Formation

• Sedimentary facies: Under water deposit
• Lithofacies: Augite hypersthene andesite Tuff, tuff breccia, Lapilli tuff, Volcanic breccia
• Lithofacies (Minor): Hornblende andesite pyroclastic rocks, Volcanic conglomerate, Conglomerate, Tuffaceous sandstone, Tuffaceous mudstone, Pumice tuff
• Sedimentary structures: Parallel stratification, Cross stratification, Graded bedding

• Thickness: 300 - 400 m
• Upper limit: Unconformity (Kitahata Landslide Deposits, Mure Debris Avalanche Deposit, Takaoka Sand and Silt Member)
• Lower limit: Unconformity (Ogawa Formation)

• Distribution: Kiyokawa river - Sara river - Shizuma - Hasu - Shinden - Nanzenji, Iiyama city, Nagano pref.; Kitanagae - Kamiimai - Oyakawa, Nakano city, Nagano pref.; Akashio, Iizuna city, Kamiminochi county, Nagano pref.

• Yanagisawa et al. (2000) Geology of the Iiyama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 144p. (in Japanese with English abstract 6p.)
• Akahane et al. (1992) Geology of the Nakano District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 106p. (in Japanese with English abstract 4p.)