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Tonokawa Formation Shimazu and Tateishi, 1993

• Type locality: Tonokawa river, Yuzawa city, Minamiuonuma county, Niigata prefecture
• Type locality:
• Volcanic rocks
• Miocene

• Lithofacies: Quartz-bearing andesite, Dacite welded tuff

• Thickness: 500 m or thicker
• Upper limit: Unconformity (3rd stage products, 4th stage products)

• Distribution: Tonokawa river - Kassa dam, Yuzawa city, Minamiuonuma county, Niigata pref.

• Shimazu and Tateishi (1993) Geology of the Naebasan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 90p. (in Japanese with English abstract 5p.)