Sorachi Gr
Period:
Cretaceous, Jurassic
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Sorachi-Yezo Belt (Yezo Main Zone)
Synonym:
Lithology and Thickness
The Sorachi Group is generally divided into a basaltic lower part and a volcaniclastic upper part (Kito et al. 1986). The lower part consists almost entirely of pillow and massive basalt and their volcaniclastic rocks (=the basaltic section of the Horokanai Ophiolite).
See details in Upper Sorachi Gr, Lower Sorachi Gr and Horokanai Ophiolite Fm.
Lithology Pattern:
Relationships and Distribution
Lower contact
No data.
Upper contact
Lower Yezo Gr (conformable)
Regional extent
Sorachi-Yezo Belt (Yezo Main Zone)
GeoJSON
null
Fossils
No data.
Age
Age Span:
Beginning stage:
Bajocian
Fraction up in beginning stage:
0
Beginning date (Ma):
170.90
Ending stage:
Barremian
Fraction up in the ending stage:
0
Ending date (Ma):
126.50
Depositional setting
Depositional pattern:
Additional Information
The name Sorachi Group has traditionally been applied to geological units dominated by basalt and chert in the Sorachi-Yezo Belt.
However, stratigraphic and geochemical studies have revealed that they comprise a mixture of differing components with contrasting origins. Some of these components are now regarded as belonging to the accretionary complex of the Kamuikotan Zone, whereas others represent allochthonous units (klippe) derived from the Hidaka Belt and emplaced during Neogene collision. Excluding these exotic components, coherent sequences typical of the stratigraphy summarized by Kito et al. (1986) are here described as the Sorachi Group (sensu stricto).
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.