Shibganj Trapwash Fm
Period:
Cretaceous
Age Interval:
Late Aptian
Province:
Bangladesh NW
Type Locality and Naming
Local? Details not given.
Lithology and Thickness
Clayey sandstone. A relatively thin cover of the weathered product of volcanic rocks consisting of red ferruginous sandstone and mudstone. It is composed of red clay, claystone and greenish sandstone (trapwash), and dominant white sandstone elsewhere. Thickness not given.
Lithology Pattern:
Soil
Relationships and Distribution
Lower contact
Conformable on Rajmahal Traps Fm
Regional extent
Shibganj Trapwash is subsurface in the shelf area of northern Bangladesh. The upper part probably is coeval with the Bolpur Fm in West Bengal.
GeoJSON
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Fossils
Age
The spore-pollen of the partly coeval Bolpur Fm indicates an Early Cretaceous to early part of the Late Cretaceous age. [Immediately overlies the Rajmahal Traps Fm, so pending a better age for the termination of those eruptions, then this erosion product assigned as the ca. 5 Myr immediately following the assigned age for those Traps.]
Age Span:
Beginning stage:
Aptian
Fraction up in beginning stage:
0.7
Beginning date (Ma):
115.66
Ending stage:
Albian
Fraction up in the ending stage:
0.5
Ending date (Ma):
106.85
Depositional setting
Local erosion products = alluvial and soil
Depositional pattern:
Additional Information
Compiler:
Partly copy-pasted from Banglapedia (National Encyclopedia of Bangladesh as compiled by several geologists; http://en.banglapedia.org/index.php/Geological_Group-Formation; 2015)