Horobetsugawa complex Fm
Period:
Cretaceous
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Sorachi-Yezo Belt (Eastern Idonnappu Zone)
Synonym: 幌别川
Lithology and Thickness
The Horobetsugawa Complex is dominated by Late Cretaceous (Campanian) clastic sedimentary rocks with minor tectonic sheets of basalt, and chert and pelagic red mudstone of mid-Cretaceous (Albian-Cenomanian) age (Kiyokawa 1992; Ueda et at. 2001). The basalts are intensely sheared and show MORB chemistry (Ueda et at. 2000). Repetition of these lithologies suggests an imbricate structure.
The complex also locally contains sedimentary mélange containing blocks of presumably Naizawa Complex origins, and a Paleocene clastic sequence presumed to represent trench-slope basin deposits. The structurally lowermost parts of the complex underwent greenschist facies metamorphism, and are overthrust by the Poroshiri Ophiolite and Hidaka metamorphic rocks.
Lithology Pattern:
Aus Conglomerate
Relationships and Distribution
Lower contact
No data.
Upper contact
No data.
Regional extent
Sorachi-Yezo Belt (Eastern Idonnappu Zone)
GeoJSON
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Fossils
Age
Age Span:
Beginning stage:
Albian
Fraction up in beginning stage:
0.442
Beginning date (Ma):
107.59
Ending stage:
Maastrichtian
Fraction up in the ending stage:
0
Ending date (Ma):
72.17
Depositional setting
Depositional pattern:
Additional Information
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.