Onimaru Fm
Period:
Carboniferous
Age Interval:
Late Visean, (8c)
Province:
South Kitakami Belt-the Hikoroichi-Setamai district
Type Locality and Naming
Synonym:
Lithology and Thickness
It is composed of bedded limestone and muddy limestone
[Figure 1: Stratigraphy of the Palaeozoic of the South Kitakatmi Belt, NE Japan (after M. Ehiro et al., 2016)]
Lithology Pattern:
Clayey limestone
Relationships and Distribution
Lower contact
Regionally, the schematic strat column indicates the next older unit as Mano Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Nagaiwa Fm
Regional extent
GeoJSON
null
Fossils
The Onimaru Formation is rich in corals belonging to the Kueichouphyllum fauna. It is biostratigraphically divided into the Kueichouphyllum glacial-Actinocyathus japonicus Zone, Saccaminopsis Zone, Arachnolasma~Palaeosmilia regia Zone and Barren Zone.
Age
It is dated as upper Visean (Niikawa l983a, 1983b).
Age Span:
Beginning stage:
Visean
Fraction up in beginning stage:
0.9
Beginning date (Ma):
331.98
Ending stage:
Visean
Fraction up in the ending stage:
1.0
Ending date (Ma):
330.34
Depositional setting
Depositional pattern:
Additional Information
Compiler:
Moreno, T., WALLIS, S., Kojima, T. & Gibbons, W. (Eds) 2016. The Geology of Japan. Geological Society. London. 1-24.