Nakanogawa Gr
Period:
Paleogene
Age Interval:
Province:
Hokkaido
Type Locality and Naming
Hidaka Belts (Yubetsu-Nakanogawa Sub-belt)
Synonym: 中の川
Lithology and Thickness
It is characterized by turbidites accompanied by minor red and green hemipelagic mudstone, with local occurrences of mélange containing blocks of oceanic rocks such as basalt, limestone and chert (Kontani 1978; Nanayama 1992b).
Lithology Pattern:
Clayey sandstone
Relationships and Distribution
Lower contact
No data.
Upper contact
No data.
Regional extent
The Nakanogawa Group occurs on the easter foothills of the Hidaka Mountains in south-central Hokkaido.
GeoJSON
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Fossils
See “age” section.
Age
Red and green mudstones and the melange matrix yield Paleocene radiolarians (Nanayama 1992b), and felsic tuff beds have been dated as Early Eocene in age using fission track (Nanayama & Ganzawa 1997).
Age Span:
Beginning stage:
Danian
Fraction up in beginning stage:
0
Beginning date (Ma):
66.04
Ending stage:
Bartonian
Fraction up in the ending stage:
0
Ending date (Ma):
41.03
Depositional setting
Depositional pattern:
Additional Information
Nanayama (1992a) and Nanayama et al. (1993) divided the Nakanogawa Group into petro-province zones I to III based on paleo-current and sandstone clastic compositions.
Zone I in the south is characterized by lithic sandstone richer in andesite clasts derived from the SSE and east, and the petrographic characteristics resemble those of the Nemuro Gr and Saroma Gr of the paleo-Kuril arc.
Zone III sandstones are richer in quartz and felsic volcanic clasts, in common with Yezo Group and Hidaka Super Gr sediments belonging to the NE Japan Arc.
Zone III and transitional Zone II rocks were transported from the north. Nanayama et al. 1993) also reported palaeomagnetic data which suggests clockwise rotation after sedimentation. They proposed that the Nakanogawa Group was deposited in sediment-flooded trenches at the junction of the Kuril and NE Japan arcs: Zone III was originally in the east adjacent to the Kuril Arc; Zone I was closer to the NE Japan Arc in the west; and Zone II lay somewhere between zones I and III.
The Nakanogawa Group is also known as the major protolith of the upper crustal parts of the Hidaka Metamorphic Belt. Western parts of the Nakanogawa Group are intruded by granites and metamorphosed to biotite hornfels, which grade into biotite schist of the Hidaka Metamorphic Belt westwards. Bedding planes and fold axes are obliquely overprinted by the metamorphic foliation.
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.