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Dev-F4-5 Formation
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Dev-F4-5 Fm base reconstruction

Dev-F4-5 Fm

Period: 
Devonian

Age Interval: 
Emsian


Province: 

Type Locality and Naming

“Devonian rocks consist of interbedded marine sandstone and mudstone. Sandstone members within the Devonian section are each given a code, F2 to F6 with F6 being the oldest and F2 the youngest. These sandstone members are principal oil and gas reservoirs in the Illizi Province.” (USGS-Klett, 2000). [NOTE: For clarity, the prefix “Devon” is added in this Lexicon to these units, and the interbeds of “unnamed” marine mudstone between the “F-sands” are considered as the upper portion of that “F” member; except for F2-sand which ends this succession.]]

Synonym: F4 member, F5 member

References: Benvegnù, 2020


Lithology and Thickness

This succession accumulated during the first stage of a new transgression in a shallow marine environment consisting of fine to medium sandstone, siltstone and dolomites with subtidal facies variations and alternations of sands, silts and shales (Benvegnù, 2020).


Lithology Pattern: 
Clayey sandstone


Relationships and Distribution

Lower contact

It conformably overlies the F6 Fm.

Upper contact

It is conformably overlain by the F3 Fm.

Regional extent

Illize Basin of SE Algeria. Laterally corresponds to the Ouan Kasa Formation in the Ghadames Basin.


GeoJSON

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Fossils


Age 


Age Span: 

    Beginning stage: 
Emsian

    Fraction up in beginning stage: 
0.00

    Beginning date (Ma): 
410.51

    Ending stage: 
Emsian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
394.30

Depositional setting

Shallow marine (Benvegnù, 2020).


Depositional pattern:  


Additional Information


Compiler:  

Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024) - Stratigraphic Lexicon compiled from the following books:

Benvegnù I. (2020): Thermal Evolution of Paleozoic and Triassic Reservoir Rocks in the Ghadames-Illizi Basin (Algeria). An unpublished MSc thesis at Universita’ degli Studi di Padova.

T.R. Klett (2000): Province, Algeria, Tunisia, and Libya - The Tanezzuft-Oued Mya, Tanezzuft-Melrhir, and Tanezzuft-Ghadames. U.S. Geological Survey Bulletin, 2202-C.