Cenozoic

Cretaceous

Jurassic

Triassic

Permian

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Ayukawa Formation

Ayukawa Fm

Period:

Jurassic

Age Interval:

Jurassic (Tithonian), (8j)

Province:
South Kitakami Belt-Central Sub-belt

Type Locality and Naming

the Karakuwa-Oshika Sub-belt; Oshika Peninsula

Synonym:

Lithology and Thickness

consists of arkose and mudstone with rare conglomerate, and is divided into the Kiyosaki, Kobitawatashi, Futawatashi and Domeki members in ascending order (Takizawa el al., 1974)

Lithology Pattern:

Aus conglomerate

Relationships and Distribution

Lower contact

The Ayukawa Fm conformably covers the Oginohama Fm

Upper contact

Regionally, the schematic strat column indicates the next younger unit as Oshika Gr

Regional extent

GeoJSON

null

Fossils

The lower part of the Kobitawatashi Member has yielded the Berriasian ammonoid

Berriasella (Takizawa 1970), whereas the upper part (and Futawatashi Member) yields Valanginian ammonoids (Takizawa I970; Obata 1988). The Kiyosaki and Domeki members are considered to be continental deposits because they have no marine fossils and contain rich plant fragments and coaly mudstones

Age

Shown as Jurassic-lowest Cretaceous, hence placed Base of Tithonian

Age Span:

Beginning stage:

Tithonian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

149.24

Ending stage:

Tithonian

Fraction up in the ending stage:

1.0

Ending date (Ma):

143.10

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.