Rebun Gr
Period:
Cretaceous
Age Interval:
Early Cretaceous
Province:
Hokkaido
Type Locality and Naming
Rebun-Kabato Sub-belt
Synonym: 礼文
Lithology and Thickness
The Rebun Group in Rebun Island consists dominantly of volcanic and tuff breccia. associated with volcaniclastic conglomerate and sandstone, mudstone and dykes of dolerite-gabbro and diorite (Nagao et al. 1963; Ikeda & Komatsu 1986). Volcanic rocks are TiO2-poor basalt to andesite of tholeiitic series (Ikeda & Komatsu 1986).
Lithology Pattern:
Volcanic_ash
Relationships and Distribution
Lower contact
Oshima accretionary clastics Fm (unconformable)
Upper contact
No data.
Regional extent
Rebun Island of Rebun-Kabato Sub-belt.
GeoJSON
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Fossils
The lowermost formation has yielded Barremian ammonoids (Nagao et al. 1963 and Early Cretaceous (Valanginian-Aptian) radiolarians (Iwata et al. 1997).
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
Along the eastern marginal parts of the Oshima Belt, Early Cretaceous arc volcanic rocks and related sedimentary rocks are exposed in the Kabato Mountains (Kumaneshiri Group) and on Rebun Island (Rebun Group), and comprise a north-south-trending volcanic chain called the Rebun-Kabato Belt. The basement of these volcanogenic sequences is inferred to belong to the Oshima Belt accretionary complex, and the Rebun-Kabato Belt is therefore defined as a sub-belt of volcanic cover in the Oshima Belt (Kiminami et al. 1986a). Its southern extension is traced by an array of marine aeromagnetic anomalies (Finn 1994) connecting the belt to coastal NE Honshu (e.g. Harachiyama Formation in the Northern Kitakami Belt), where Early Cretaceous volcanogenic deposits unconformably overlie the Jurassic accretionary complex. It is notable that this volcanic zone obliquely crosses the basement architecture: it overlaps Jurassic accretionary terranes of the Oshima and Northern Kitakami belts in the central area, and the Palaeozoic terrane of the Southern Kitakami Belt in the south.s
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.