Okuniikappu Complex Fm
Period:
Cretaceous, Jurassic
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Sorachi-Yezo Belt (Okuniikappu Complex)
Synonym:
Lithology and Thickness
The Okuniikappu Complex is an ophiolitic mélange consisting of slices and blocks of serpentinized peridotite, gabbro-diabase, altered volcanic rocks, earliest Cretaceous chert and mid Cretaceous (Albian-Cenomanian: Kivokawa 1992) clastic sedimentary rocks separated by sheared serpentinites.
Lithology Pattern:
Chert
Relationships and Distribution
Lower contact
No data.
Upper contact
No data.
Regional extent
Sorachi-Yezo Belt (Okuniikappu Complex). Between the Naizawa complexe Fm and Horobetsugawa complexe Fm, Ueda & Miyashita 2005) identified the ophiolitic Okuniikappu Complex which includes mid- Cretaceous clastic sedimentary rocks.
GeoJSON
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Fossils
No data.
Age
Age Span:
Beginning stage:
Oxfordian
Fraction up in beginning stage:
0.36
Beginning date (Ma):
159.10
Ending stage:
Cenomanian
Fraction up in the ending stage:
0.762
Ending date (Ma):
95.47
Depositional setting
Depositional pattern:
Additional Information
All the igneous rocks show island-arc chemical characteristics. Andesitic volcanic rocks with minor boninite are overlain by earliest Cretaceous pelagic chert intercalated with volcanogenic debris beds. Ueda & Miyashita (2005) attributed these arc rocks and andesite-chert sequences to a remnant arc behind a back-arc basin which was subducted along the Eurasian continental margin in mid-Cretaceous times, analogous to the present-day Kyushu-Palau Ridge.
Compiler:
Hayato Ueda. 2g Hokkaido. in Moreno, T., WALLIS, S., Kojima, T. & Gibbons, W. (Eds) 2016. The Geology of Japan. Geological Society. London. 201-220.