Hosokojigawa Lava

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Hosokojigawa Lava

Type locality: Hosokoji river, Saku city, Nagano prefecture
Volcanic rocks
early Pleistocene (0.89 Ma, K-Ar)

Lithofacies: Dacite
Lithofacies: Lava (a flow unit)
Lithofacies (Minor): Pyroclastic rocks

Source: Mount Futago
Eruptive volume: 0.4 km³
Thickness (A unit): ca. 40 m
Upper limit: Unconformity (Amazakai Pyroclastic Flow Deposit, Ryugamine Lava)
Lower limit: Unconformity (Byobuiwa Lava, Kasuga Volcanic Rocks)

Fukinotaira Volcanic Rocks
[ Upper ]
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Hosokojigawa Lava
~~~~~~~~~~~~~~
Byobuiwa Lavas
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[ Lower ]

Byobuiwa volcanic body
[ Upper ]
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Fukinotaira Volcanic Rocks
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[ Lower ]

Yabashira volcanoes
[ Upper ]
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Kengamine volcanic body
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Byobuiwa volcanic body
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Yabashirayama volcanic body
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Ryugamine volcanic body
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Tokin-no-iwa volcanic body
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[ Lower ]

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

Distribution: Hosokoji river - Hacchoji river, Saku city, Nagano pref.

Nishiki and Takahashi (2012) Jour. Geol. Soc. Japan, vol.118, no.8, pp.499-515 DOI
Kawachi (1974) Geology of the Tateshinayama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 114p. (in Japanese with English abstract 5p.)