Tsunakizaka Fm
Period:
Triassic
Age Interval:
Middle Triassic (Aalenian), (8h)
Province:
South Kitakami Belt-Central Sub-belt
Type Locality and Naming
the Karakuwa-Oshika Sub-belt
Synonym:
Lithology and Thickness
It consists of mudstone in its main part and alternating beds of sandstone and mudstone in the uppermost part. It is about 400 m in thickness at the NE part of its outcrop, thins to about 200 m towards the west and south.
Lithology Pattern:
Claystone
Relationships and Distribution
Lower contact
Regionally, the schematic strat column indicates the next older unit as Kosaba Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Ishiwaritoge Fm
Regional extent
GeoJSON
null
Fossils
It has yielded a rich fauna of Bajocian ammonoids (Sato 1962, 1972)
Age
Shown as Middle Triassic-lowermost Cretaceous hence placed 50% up in Aalenian
Age Span:
Beginning stage:
Aalenian
Fraction up in beginning stage:
0.5
Beginning date (Ma):
172.80
Ending stage:
Aalenian
Fraction up in the ending stage:
1.0
Ending date (Ma):
170.90
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.