Shirataki Formation

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Shirataki Formation

Type locality: Mineokaasama, Kamogawa city, Chiba prefecture
Coherent formation

Sedimentary facies: Marine
Sedimentary facies: Pelagic sediments
Lithofacies: Chert, Calcareous chert
Lithofacies (Minor): Siliceous marl, Limestone, Tuff, Shale

Thickness: 80 m or thicker
Upper limit: Conformity (Hatcho Formation), Unconformity (Fukawa Formation)
Lower limit: Conformity (Sanno Formation)

Mineoka Group
[ Upper ]
::::::::::::::
Nagime Formation
--------------
Enokibatake Formation
--------------
Hatcho Formation
--------------
Shirataki Formation
--------------
Sanno Formation
?--?--?--?--?-
[ Lower ]

Mineoka Belt (Boso peninsula)
[ Upper ]
~~~~~~~~~~~~~~
Awa Group / Minamiboso Group
~~~~~~~~~~~~~~
Hota Group
::::::::::::::
Mineoka Group
?--?--?--?--?-
[ Lower ]

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

Distribution: Mineokaasama - Fukawa, Kamogawa city, Chiba pref.
Fossils (Limestone, Foraminifera): Globorotalia sp., Orthomorphica sp., Pararotalia sp.
Fossils (Chert, Radiolarians): Calocyclas sp., Melitosphara sp., Stichocapsa sp.

Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.375-395, DOI
Nakajima et al. (1981) Geology of the Kamogawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 107p. (in Japanese with English abstract 7p.)