(Invalid name) Sanchu Graben

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Synonym: Sanchu Group

Cretaceous strata distributed in a graben-shape from Gunma pref. to Saitama pref.

Coherent formation
Early Cretaceous, Hauterivian - Albian
Correlation: Monobegawa Group

Sedimentary facies: Shallow marine, Brackish

Distribution (Width): 2 - 4 km
Distribution (Length): ca. 40 km
Upper limit: Unconformity (Shirasu Formation)
Lower limit: Unconformity

(Invalid name) Sanchu Graben
[ Upper ]
?--?--?--?--?-
Sanyama Formation
~~~~~~~~~~~~~~
Sebayashi Formation
--------------
Ishido Formation
--------------
Shiroi Formation
~~~~~~~~~~~~~~
[ Lower ]

(Invalid name) Sanchu Graben (Koizumi, 1991)
[ Upper ]
?--?--?--?--?-
Sanyama Formation
--------------
Ishigami Formation
--------------
Hashizume Formation
--------------
Sebayashi Formation
--------------
Ishido Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Saku, Sakuho city, Minamisaku county, Gunma pref.; Ogano city, Chichibu county, Saitama pref.
Fossils: northern Tethyan fauna

Hara et al. (2010) Geology of the Mitsumine District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 110p. (in Japanese with English abstract 4p.)
Okubo and Horiguchi (1969) Geology of the Mamba District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 65p. (in Japanese with English abstract 5p.)