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Tokachi Pyroclastic Flow Deposit

Invalid synonym: Tokachi Welded Tuff, HR-6 (Unit I), HR-5 (Unit II)

• Type locality: Osobetsu river, Shibecha city, Kawakami county, Hokkaido
• Tephra
• Pleistocene (1.46 - 1.18 Ma, K-Ar; 1.4 Ma, FT)

• Lithofacies: Pyroclastic flow deposit
• Lithofacies: Rhyolitic, Dacitic
• Lithofacies: 2 cooling units
• Lithofacies (HR-5, HR-6): Glassy crystalline ash

• Source: Tokachidake volcano
• Thickness (Unit II): 100 m
• Thickness (Unit I): 150 m
• Thickness (HR-5 = Unit I): ca. 2 cm
• Thickness (HR-6 = Unit II): 50 - 60 cm
• Upper limit: Unconformity? (Iwamatsu Formation)
• Upper limit: Unconformity (Tokachimitsumata Pyroclastic Fall Deposit)
• Upper limit (HR-6 = Unit I): Unconformity (Ak14-f)
• Upper (HR-5 = Unit II): Unconformity (Ak14-c)
• Lower limit (HR-6 = Unit I): Unconformity (Ak14-g)
• Lower limit (HR-5 = Unit II): Unconformity (Ak14-d)

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Furano - Asahikawa - Upper stream of Tokachi river, Hokkaido
• Distribution (HR-5, HR-6): Kuchoro river, Osobetsu river, Shisetsuri river, Hokkaido

• Hasegawa et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.7, pp.366-381 DOI
• Ishii et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.7, pp.348-365 DOI
• Hasegawa and Nakagawa (2007) Jour. Geol. Soc. Japan, vol.113, no.2, pp.53-72 DOI