Sanyama Formation

Coherent formation
late Aptian - Albian, Late Cretaceous

Lithofacies (Upper): Shale
Lithofacies (Upper, Minor): Sandstone, Conglomerate
Lithofacies (Lower): Interbedded shale and sandstone
Lithofacies (Basal): Conglomerate, Sandstone
Lithofacies (Basal, Minor): Shale
Sedimentary structures (Upper): Cross stratification, Flute cast
Sedimentary structures (Lower): Gradded bedding

Thickness (Upper): 100 - 650 m
Thickness (Lower): 100 - 700 m
Upper limit: Lithofacies boundary
Lower limit: Unconformity (Sebayashi Formation)

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

(Invalid name) Sancyu 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: Sanyama - Kawarazawa, Ogano city, Chichibu county, Saitama pref.
Fossils: Ammonoids (Desmoceras sp., Marshallites? sp., Neohibolites sp.), Belemnoids, Echinoids (Washitaster? sp.), Plants
Fossils (Bivalves): Aphrodina cfr. pseudoplana, Astarte cfr. minor, Cerithium? sp., Dentalium sp., Inoceramus cfr. hobetsuensis, Nucula? sp., Ostrea sp., Pecten? sp., Propeamussium cowperi var. yubarensis, Pterotrigonia hokkaidoana, Solemya cfr. angusticaudata, Trigonia sp., Trochus? sp.

Matsui et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.6, pp.261-266, DOI
Terabe and Matsuoka (2009) Jour. Geol. Soc. Japan, vol.115, no.3, pp.130-140 DOI
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.)