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Muhaiwir Formation
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Muhaiwir Fm base reconstruction

Muhaiwir Fm

Period: 
Jurassic

Age Interval: 
Middle Jurassic, Iq (2,3)


Province: 
Iraq

Type Locality and Naming

Columns: Central Iraq, Rutba Uplift (W Iraq)

Synonym:


Lithology and Thickness

Divided into two parts. The lower part comprises clayey, sandy, and oolitic limestone and sponge detritus overlain by 3m of sandstone with lenses of limestone and 1m of sandy oolitic limestone. The upper part comprises 9m of fine-grained limestone with chert nodules overlain by a soft marl, 12m of sandstone and clayey limestone with beds of oolitic and coralline limestone, and 14m of well-bedded and clayey limestones. 48m thick at type section.


Lithology Pattern: 
Oolitic limestone


Relationships and Distribution

Lower contact

Regionally, the schematic strat column indicates the next older unit as Alan Fm

Upper contact

Regionally, the schematic strat column indicates the next younger unit as the deeper-water Sargelu Fm; but the Rutba Uplift (W. Iraq) continues with the shallow-water Muhaiwir Fm facies.

Regional extent


GeoJSON

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Fossils

The lower part comprises corals, brachiopods. The upper part comprises abundant Rhynchonella spp., Terebratula sp., echinoids, gastropods, and pelecypods


Age 

Middle Jurassic (only latest Toarcian in Central Iraq, but latest Toarcian through Callovian at Rutbah Uplift (W. Iraq) where there is no Sargelu Fm facies. Therefore, to avoid overlap, generalized here as latest Toarcian to mid-Aalenian

Age Span: 

    Beginning stage: 
Toarcian

    Fraction up in beginning stage: 
0.85

    Beginning date (Ma): 
176.13

    Ending stage: 
Aalenian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
172.80

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

From S. Z. Jassim and J. C. Goff, Geology of Iraq, 2006. pg 117, Fig. 10-1: "Stratigraphic correlation of Megasequence AP7."