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NA7 Tephra

Abbr.: NA7

• Type locality: Niigata prefecture
• Tephra
• Pliocene - Pleistocene (2.8, 2.38 Ma, FT)

• Lithofacies: Rhyolite vitreous volcanic ash

• Host: Minagawa Formation
• Thickness: 40 cm

• Distribution: Nobe river, Ojiya 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.)
• Yanagisawa et al. (1986) Geology of the Ojiya District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 177p. (in Japanese with English abstract 6p.)