Isokusa Fm
Period:
Cretaceous
Age Interval:
Early Cretaceous (Berriasian-Valanginian), (8h)
Province:
South Kitakami Belt-Central Sub-belt
Type Locality and Naming
the Karakuwa-Oshika Sub-belt
Synonym: Nagasaki Fm
Lithology and Thickness
It consists mainly of sandy mudstone
Lithology Pattern:
Sandy_claystone
Relationships and Distribution
Lower contact
Regionally, the schematic strat column indicates the next older unit as Kogoshio Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Karakuwa Gr
Regional extent
The lsokusa (Nagasaki) Formation crops out on Oshima Island in Kesennuma Bay.
GeoJSON
null
Fossils
It has yielded Early Cretaceous (Berriasian-Valanginian) ammonoids (Sato 1958; Takahashi 1973; Nara et a1., 1994)
Age
Shown as Early Cretaceous, hence placed Base of Berriasian
Age Span:
Beginning stage:
Berriasian
Fraction up in beginning stage:
0.5
Beginning date (Ma):
140.40
Ending stage:
Valanginian
Fraction up in the ending stage:
1.0
Ending date (Ma):
132.60
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.