Hikoroichi Fm
Period:
Carboniferous
Age Interval:
Tournasian, (8c)
Province:
South Kitakami Belt-the Hikoroichi-Setamai district
Type Locality and Naming
Synonym:
Lithology and Thickness
Shale, Acidic tuff, 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 Nakazato Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Shittakasawa Fm
Regional extent
GeoJSON
null
Fossils
The Hikoroichi Formation and its equivalents yield a rich fauna of corals, brachiopods and trilobites.
Age
Its lower-middle part and upper part are dated as Tournaisian-lower Visean and upperVisean, respectively (Mori & Tazawa l980; Kawamura 1983; Tazawa l984). But to fit in schematic strat-column, it is adjusted to base of Tournasian here.
Age Span:
Beginning stage:
Tournaisian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
359.30
Ending stage:
Tournaisian
Fraction up in the ending stage:
0.5
Ending date (Ma):
353.02
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.