Naizawa complex Fm
Period:
Permian, Triassic, Jurassic, Cretaceous
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Sorachi-Yezo Belt (Western Idonnappu Zone)
Synonym:
Lithology and Thickness
The Naizawa Complex is dominated by oceanic rocks composed of basalt, Permian-Triassic limestone (Igo et al. 1974; Hashimoto et al. 1975; Ishizaki 1979; Sakagami & Sakai 1979; Kato et at. 1986) and Triassic-earliest Cretaceous chert (Kato et at. 1986; Igo et al. 1987; Kato & Iwata 1989; Kiyokawa 1992; Sakakibara et al. 1997a, B; Ueda et al. 2001), associated with hemipelagic mudstone and terrigenous clastic rocks of middle Early Cretaceous ages (Kato et al. 1986; Igo et al. 1987; Tumanda & Sashida 1988; Kato & Iwata 1989; Tumanda 1989; Kiyokawa 1992; Ueda et at. 2001).
Lithology Pattern:
Chert
Relationships and Distribution
Lower contact
No data.
Upper contact
Regional extent
Sorachi-Yezo Belt (Western Idonnappu Zone)
GeoJSON
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Fossils
Age
Age Span:
Beginning stage:
Capitanian
Fraction up in beginning stage:
0
Beginning date (Ma):
264.34
Ending stage:
Valanginian
Fraction up in the ending stage:
0.451
Ending date (Ma):
135.40
Depositional setting
Depositional pattern:
Additional Information
Basaltic rocks consist of two distinct chemical types: depleted tholeiite identical to the lower Sorachi Group; and oceanic-island basalts. Ueda et al. (2000) interpreted the complex as having been formed by tectonic mixing of subducted seamounts with the upper plate ophiolite (Sorachi Group) forming the inner trench slope.
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.