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Kusso Formation Shikumi River Collaborative Research Group, 1991

Formerly included in Uonuma Group.

• Type locality: Kusso, Tsunan city, Nakauonuma county, Niigata prefecture
• Volcanic rocks
• Pleistocene
• Contemporaneous heterotopic facies: Torikabuto volcano
• Correlation: Tomaru Formation, Mitsuyama Formation

• Sedimentary facies: Terrestrial, Lacustrine
• Sedimentary facies: Volcanic mudflow deposit (a few flow units)
• Lithofacies (Lower, Minor): Volcanic ash, Lapilli, Volcanic sands

• Source: Torikabuto volcnao
• Thickness: ca. 200 m
• Upper limit: Unconformity (Nunoiwayama Lava)
• Lower limit: Unconformity (Maeko Member, Higashinosawa Formation, Maekura Lava and Pyroclastics)

• Distribution: Kusso, Tsunan city, Nakauonuma county, Niigata pref.; Kitano river - Kamakawa river - Yokotaira? river, Sakae city, Shimominochi county, Nagano 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.)