Rohtas Fm
Period:
Calymmian
Age Interval:
earliest Calymmian
Province:
Proterozoic N.India Vindhyan Basin east
Lithology and Thickness
Upward succession of Rampur Shale Member and Rohtas Limestone Member. The Rohtas Limestone shows rhythmite-like intercalations between thin bedded limestone and shale. Poorly developed columnar stromatolites are also reported.
Lithology Pattern:
Clayey limestone
Relationships and Distribution
Lower contact
Overlies the Kheinjua Fm
Upper contact
Major unconformity. Overlain by Lower Quartzite member at base of Kaimur Fm (base of Upper Vindhyan Gr in East)
Regional extent
GeoJSON
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Fossils
Age
1599 +/- 8Ma in middle of Rampur Shale Mbr. See discussion in Lower Vindhyan Gr; for graphic purposes 1600-1580 Ma
Age Span:
Beginning stage:
Calymmian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
1,600.00
Ending stage:
Calymmian
Fraction up in the ending stage:
0.1
Ending date (Ma):
1,580.00
Depositional setting
The Rohtas Limestone Member was deposited under subtidal to intertidal conditions.
Depositional pattern:
Additional Information
Compiler:
Main sources: S. Sarkar and S. Banerjee (2020), A Synthesis of Depositional Sequence of the Proterozoic Vindhyan Supergroup in Son Valley, Springer Geology, https://doi.org/10.1007/978-981-32-9551-3_2
Basu, P., and Chakrabarti, R. 2020. Origin and evolution of the Vindhyan Basin: A geochemical perspective. Proc. Indian Natn. Sci. Acad., 86: 111-126.