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Gassan volcano
- Type locality: Yamagata prefecture
- Volcanic rocks
- late Pleistocene (? - 20 ka)
- Lithofacies: Hypersthene series, High-alumina basalt magma
- Lithofacies: Hypersthene augite andesite, Dacite
- Lithofacies (Pyroclastic flow deposit): Hornblende hypersthene augite andesites
- Lithofacies (Older volcanic products): Hypersthene augite andesite, Volcani ash
- Thickness: a few dozen - 100 m
- Lower limit: Unconformity
- Gassan volcano
- [ Upper ]
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- Volcanic mudflow deposit
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- Pyroclastic flow deposit
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- Older volcanic products
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- [ Lower ]
- Gassan volcano
- [ Upper ]
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- Gassanchuo volcano
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- Ohama volcano
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- Ubagadake volcano
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- Yudonosan volcano
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- Early volcano
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- [ Lower ]
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution (Volcanic mudflow deposit): Mount Kawadai - Tashiro - Matsugaoka, Haguro town, Tsuruoka city, Yamagata pref.
- Distribution (Pyroclastic flow deposit): Toge - Nakakawadai, Haguro town, Tsuruoka city, Yamagata pref.
- Distribution (Older volcanic products): Mount Haguro - Hagurokaitaku, Tsuruoka city, Yamagata pref.
- Tsuchiya et al. (1984) Geology of the Tsuruoka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 77p. (in Japanese with English abstract 5p.)