Older Sanbe Tephra

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Older Sanbe Tephra

Tephra
Pleistocene

Lithofacies (Urizaka): Crystalline volcanic ash (more than 4 units)
Lithofacies (Yokomi): Clayey volcanic ash

Mode of eruption: Phreatic
Thickness (Urizaka, A unit): 70 - 90 cm
Thickness (Yokomi): 2.2 - 3 m
Upper limit: Unconformity (Sanbe Base Surge Deposits, Sanbe Pyroclastic Flow Deposits)
Lower limit: Unconformity (Granite)

Older Sanbe stage
[ Upper ]
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Kosanbe Lava
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Older Sanbe Tephra
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Moritayama Lava
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[ Lower ]

Sanbe volcano
[ Upper ]
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4th stage
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3rd stage
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2nd stage
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1st stage
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Older Sanbe stage
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[ Lower ]

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

Distribution: Urizaka, Oda city, Shimane pref.; Yokomi, Izumo city, Shimane pref.
Fossils (Pollen): Abies sp., Acer sp., Alnus sp., Carya sp., Castanea sp., Fagus sp., Lepidobalanus sp., Liquidamber sp., Pinus sp., Pterocarya sp., Quercus sp., Taxodiaceae, Tsuga sp., Ulmus sp., Zelkova sp.

Hattori et al. (1983) Geology of the Sambesan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 168p. (in Japanese with English abstract 7p.)