Kumaneshir Gr
Period:
Cretaceous
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Rebun-Kabato Sub-belt
Synonym:
Lithology and Thickness
The Kumaneshiri Group in the Kabato Mountains near Sapporo consists mainly of mudstone, volcaniclastic sandstone and tuff, with formations dominated by volcanic conglomerate, tuff breccia, pillow lava and dykes (Nagata et al. 1986; Kondo 1991). Volcanic rocks are high-K basalt to andesite, including both tholeiitic and calc-alkaline series, with low-TiO2 island-arc characteristics (Nagata et al. 1986; Kondo 1993).
Lithology Pattern:
Volcanic_ash
Relationships and Distribution
Lower contact
Oshima accretionary clastics Fm (unconformable)
Upper contact
No data.
Regional extent
in the Kabato Mountains near Sapporo of the Rebun-Kabato Sub-belt.
GeoJSON
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Fossils
Early Cretaceous radiolarians from mudstones (Nagata et al. 1986; Kondo 1991) and a 101.3 + 2.7Ma Ar-Ar age from a volcanic rock clast (Kondo 1991) have been reported.
Age
Age Span:
Beginning stage:
Valanginian
Fraction up in beginning stage:
0
Beginning date (Ma):
137.70
Ending stage:
Cenomanian
Fraction up in the ending stage:
0
Ending date (Ma):
100.50
Depositional setting
Depositional pattern:
Additional Information
Clasts of Permian fusulina limestone (Hashimoto et at. 1960) and of siliceous sedimentary rocks with Jurassic radiolarians (Kondo 1991) in conglomerates suggest that parts of the sedimentary clasts were supplied from Jurassic accretionary complex materials in addition to arc volcanoes.
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.