Arato Fm
Period:
Jurassic
Age Interval:
Middle Jurassic (Bajocian), (8e)
Province:
South Kitakami Belt-Western Sub-belt
Type Locality and Naming
Shizugawa (Shizukawa)-Hashiura Sub-belt; Shizugawa area
Synonym:
Lithology and Thickness
It comprises bedded mudstone with alternating beds of sandstone and mudstone
Lithology Pattern:
Clayey sandstone
Relationships and Distribution
Lower contact
The Arato Fm and its equivalents conformably rest on the Aratozaki Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Sodenohama Fm
GeoJSON
null
Fossils
The Arato Formation yielded upper Bajocian ammonoids (Sam 1962; TakahashiI969)
Age
Middle Jurassic (Bajocian)
Age Span:
Beginning stage:
Bajocian
Fraction up in beginning stage:
0.5
Beginning date (Ma):
169.54
Ending stage:
Callovian
Fraction up in the ending stage:
1.0
Ending date (Ma):
161.53
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.