Tonohetsuri Formation

[ Top ] [ Japanese ]

Tonohetsuri Formation (Masuda et al., 1974) Yamamoto, 1999

Type locality: Aga river, Yunokami - Yagoshima, Shimogo city, Minamiaizu county, Fukushima prefecture
Volcanic rocks
Collapse caldera-fill deposit
early Pleistocene

Sedimentary facies: Terrestrial
Lithofacies (Top): Interbedded sandstone and siltstone
Lithofacies (Lacustrine): Sandstone, Conglomerate, Siltstone
Lithofacies (Lacustrine, Minor): Breccia, Dacite pyroclastic rocks
Lithofacies (Debris avalanche): Breccia
Sedimentary structures (Lacustrine): Graded bedding, Reversed graded bedding, Parallel stratification

Thickness (Overall): ca. 1,000 m
Thickness (Lacustrine): ca. 350 m
Upper limit: Unconformity (Narioka Formation, Kasshiasahidake volcano, Futamatayama volanoc, Kamafusayama Pyroclastic Flow Deposit)
Lower limit: Unconformity (Oto Formation, Late Cretaceous granodiorite, Jonoirizawa Formation, Ono Formation)

Tonohetsuri Formation
[ Upper ]
~~~~~~~~~~~~~~
Nagurasawa Pyroclastic Flow Deposit = Post-caldera stage
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Kasshi Volcanic Rocks / Oshiromoriyama Lavas / Lacustrine deposit = Post-caldera stage
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Ashino Pyroclastic Flow Deposit = Caldera-forming stage
~~~~~~~~~~~~~~
[ Lower ]

Tonohetsuri caldera
[ Upper ]
~~~~~~~~~~~~~~
Tonohetsuri Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Aga river, Yunokami - Yagoshima, Shimogo city, Minamiaizu county, Fukushima pref.; Kasshi, Nishigo city, Shirakawa county, Fukushima pref.
Fossils: Plants

Yamamoto (1999) Geology of the Tajima District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 85p. (in Japanese with English abstract 8p.)