Yokokurayama Gr

Cenozoic

Cretaceous

Jurassic

Triassic

Permian

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Yokokurayama Gr

Period:

Silurian, Devonian

Age Interval:

Sheinwoodian-Frasnian, (15a)

Province:
Kurosegawa Belt- Shikoku

Type Locality and Naming

Kurosegawa Belt-central Shikoku

Synonym:

Lithology and Thickness

It is divided into the Gomi, Fukata, lchiyama, Joryu, Nakahata and Ochi formations, in ascending order. The stratigraphic relationships among the first three formations are conformable, whereas there are hiatuses between the other formations based on the ages of radiolarians (Umeda 1998b, c)

[Figure 1: Stratigraphy of the Paleozoic of the Kurosegawa Belt in the central part of Shikoku, Southwest Japan (after M. Ehiro et al., 2016)]

Lithology Pattern:

Relationships and Distribution

Lower contact

Regionally, the schematic strat column indicates the next older unit as Ochi Fm

Upper contact

Regionally, the schematic strat column indicates the next younger unit as Buntoku Fm

Regional extent

Kurosegawa Belt-central Shikoku. The Okanaro Group (lchikawa et al., 1956; Umeda 1994) in western Shikoku, the Suberidani Group (Hirayama er al. 1956) in eastern Shikoku and the Gionyama Formation (Hamada 1959c) in Kyushu are equivalent strata, but exclude the equivalent of the Ochi Formation.

GeoJSON

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Fossils

Age

Sheinwoodian-Frasnian

Age Span:

Beginning stage:

Sheinwoodian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

432.93

Ending stage:

Frasnian

Fraction up in the ending stage:

1.0

Ending date (Ma):

371.10

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Moreno, T., WALLIS, S., Kojima, T. & Gibbons, W. (Eds) 2016. The Geology of Japan. Geological Society. London. 1-24.