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Jumara Formation
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Jumara Fm base reconstruction

Jumara Fm

Period: 
Jurassic

Age Interval: 
Callovian-Oxfordian (mid-Jurassic)


Province: 
W.India Kutch Basin

Type Locality and Naming

The type area lies along across country travel along village Jumara over Jumara Dome (Biswas, 1977)

[Fig. Geological and structural map of Kutch, also showing the onshore and offshore wells drilled for oil exploration. (Map by Rasoul Sorkhabi in GeoExpro Dec2014, based on various sources including S.K. Biswas, Current Science, 25May2005)]


Lithology and Thickness

Claystone with an uppermost Oolite. In the type section it consists of Khaki, gypsiferous shale with thin marl bands. Towards top a thin fossiliferous, conglomeratic, oolitic marl band is present. Top of the formation is marked by Dhosa oolite member, which is also conglomeratic in nature. In subsurface bottom unit contains alternating micaceous shale, clay, impure limestone and calcareous shale. In the type section it is 273.5 m, in subsurface 121 to 725 m.


Lithology Pattern: 
Gypsiferous claystone


Relationships and Distribution

Lower contact

Defined by shale –limestone contact to underlying Jhurio Fm limestone.

Upper contact

Its uppermost Dhosa oolite member is unconformably overlain by the Jhuran Fm sandstone.

Regional extent


GeoJSON

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Fossils

Brachiopods, Lamellibranches, Gastropods, corals are very common. The microfauna observed are Tewari kutchensis P.R.Z., and Proteonina diffugiformis- Astracolus anceps assemblage zone and Epistomina majungaensis R.Z. in the type section (Pandey and Dave, 1993).


Age 

Callovian-Oxfordian (Middle to Upper Jurassic)

Age Span: 

    Beginning stage: 
Callovian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
165.29

    Ending stage: 
Oxfordian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
156.13

Depositional setting

Deposited in littoral (?) transgressive environment


Depositional pattern:  


Additional Information


Compiler:  

Modified from Jitendriya Mishra (2009) Kutch-Saurasthra Basin, Chap. 17 in ONGC Bull 44