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Usp Tephra Collaborative Research Group for Eastern Marginal Hills of Niigata Plain, 1990

Abbr.: Usp

• Type locality: Urase river, Urase town, Nagaoka city, Niigata prefecture
• Tephra
• Pleistocene (1.8 Ma, FT)

• Lithofacies: Pumiceous vitreous volcanic ash (2 units)

• Host: Uonuma Formation
• Thickness (Upper): ca. 300 - 750 cm
• Thickness (Lower): ca. 150 cm

• Distribution: Urase river, Urase town, Nagaoka city, Niigata pref.; Hokake river - Miyaji river, Nagaoka city, Niigata pref.

• Kobayashi et al. (1991) Geology of the Nagaoka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 132p. (in Japanese with English abstract 6p.)