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Kajrahat Formation
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Kajrahat Fm base reconstruction

Kajrahat Fm

Period: 
Statherian

Age Interval: 
late-middle Statherian


Province: 
Proterozoic N.India Vindhyan Basin east

Type Locality and Naming

Lower formation (2 of 5) of Lower Vindhyan Gr in East


Lithology and Thickness

Upward succession of Arangi Shale Member and Kajrahat Limestone Member. The Kajrahat Limestone Member contains stromatolites, and its upper part shows large fan-fabrics. The Arangi Shale Mbr is carbonaceous in places; and is generally poorly exposed. Kajrahat Lms Mbr (ca. 250 m thick) has a lower dolomite (intertidal), middle alternating dolomite and limestone bands (shallow lagoon with evaporitic conditions), and upper limestone with large stromatolites alternating with microbial laminate (Supratidal to subtidal).


Lithology Pattern: 
Shallow-marine marl


Relationships and Distribution

Lower contact

Underlain by Deoland Fm sandstone

Upper contact

Overlain by Porcellanite Fm volcanics. Uppermost Kajrahat Lms Mbr has abundant dissiccation craks.

Regional extent

Son Valley area. Bhagwanpura Limestone Mbr (lower Sands Fm) in the Rajasthan sector (west Vindhyan basin) is considered to be the stratigraphic equivalent of the Kajrahat Limestone Member (upper Kajrahat Fm) of the Son Valley (east Vindhyan basin)


GeoJSON

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Fossils


Age 

Date of 1720 +/- 90 Ma in lower Kajrahat Lms Mbr. See discussion in Lower Vindhyan Gr; for graphic purposes 1700-1640 Ma.

Age Span: 

    Beginning stage: 
Statherian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
1,700.00

    Ending stage: 
Statherian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
1,640.00

Depositional setting

The Kajrahat Limestone Member "is considered to be deposited under subtidal to supratidal conditions. Presence of intraformational conglomerates suggest repetitive transgression and regression. Gypsum layers are also reported from this unit which indicates an evaporative condition."


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.