Ainosawa Fm
Period:
Devonian
Age Interval:
Late Devonian (Frasnian), (8a)
Province:
South Kitakami Belt-Okago region
Type Locality and Naming
Nagasaka-Soma district
Synonym:
Lithology and Thickness
It consists of tuffaceous mudstone and mudstone above a basal pebbly sandstone that contains schist and granitic clasts
[Figure 1: Stratigraphy of the Palaeozoic of the South Kitakatmi Belt, NE Japan (after M. Ehiro et al., 2016)]
Lithology Pattern:
Clayey sandstone
Relationships and Distribution
Lower contact
It unconformably covers the underlying metamorphic Matsugadaira Unit Fm (Ehim & Okami 1990). Regionally, the schematic strat column indicates the next older unit as Shoboji Diorite Fm.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Tobigamori Fm
Regional extent
Nagasaka-Soma district
GeoJSON
null
Fossils
The Ainosawa Formation has also yielded Cyrtospirifer (Hayasaka & Minato 1954) and Leptophloeum (Koseki & Hamada 1988; Tazawa et al., 2006).
Age
Shown as Late Devonian, hence placed Base of Frasnian
Age Span:
Beginning stage:
Frasnian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
378.90
Ending stage:
Frasnian
Fraction up in the ending stage:
1.0
Ending date (Ma):
371.10
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.