Koguro Fm
Period:
Ordovician
Age Interval:
Middle-Late Ordovician (Sandbian), (8b)
Province:
South Kitakami Belt- Miyamori-Hayachine-Kamaishi district
Type Locality and Naming
Synonym:
Lithology and Thickness
It consists mainly of dolerite and basalt, with intercalated thin beds of tuffaceous sandstone and mudstone, and reddish hematite-quartz rock in the upper part.
[Figure 1: Stratigraphy of the Palaeozoic of the South Kitakatmi Belt, NE Japan (after M. Ehiro et al., 2016)]
Lithology Pattern:
Granitic
Relationships and Distribution
Lower contact
Regionally, the schematic strat column indicates the next older unit as Kagura Unit Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Yakushigawa Fm
Regional extent
GeoJSON
null
Fossils
Age
Shown as Middle-Late Ordovician, hence placed Base of Sandbian
Age Span:
Beginning stage:
Sandbian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
458.18
Ending stage:
Katian
Fraction up in the ending stage:
1.0
Ending date (Ma):
445.21
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.