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Les Argiles d’El Gassi Formation
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Les Argiles d’El Gassi Fm base reconstruction

Les Argiles d’El Gassi Fm

Period: 
Ordovician

Age Interval: 

Province: 
Ahnet Basin, Mouydir Basin

Type Locality and Naming

It was penetrated in the MJB-1 well (van Dijk et al., 2019).

Synonym: El Gassi Fm

References: van Dijk et al., 2019.


Lithology and Thickness

The El Gassi Fm is about 207m thick, and it is made up of shales which are black, grey-dark grey, silty, hard micaceous and slightly pyritic with intercalations of white, grey colored sandstones (van Dijk et al., 2019).


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

It conformably overlies the Zone des Alternances Fm.

Upper contact

It is conformably overlain by the Les Gres d’El Atchane Fm.

Regional extent

75,000 Km2


GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[-0.96,26.84],[1.04,27.54],[2.69,28.22],[5,28.22],[5.81,27.21],[5.81,26.5],[5.13,25.47],[4.05,24.96],[3.51,24.55],[2.83,23.98],[2.29,23.89],[1.42,23.98],[0.66,25.06],[0.12,25.88],[-0.96,26.84]]]]}}

Fossils

Brachiopods.


Age 


Age Span: 

    Beginning stage: 
Tremadocian

    Fraction up in beginning stage: 
0.3

    Beginning date (Ma): 
483.92

    Ending stage: 
Tremadocian

    Fraction up in the ending stage: 
0.7

    Ending date (Ma):  
480.01

Depositional setting

Marine (van Dijk et al., 2019).


Depositional pattern:  


Additional Information


Compiler:  

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

Wendt J., Kaufmann B., Belka Z., Korn D (2008): Carboniferous Stratigraphy and Depositional Environments in the Ahnet Mouydir Area (Algerian Sahara). In: Facies. DOI 10.1007/s10347-008-0176-y

Wendt J., Kaufmann B., Belka Z., Klug C. & Lubeseder S. (2006): Sedimentary evolution of a Palaeozoic basin and ridge system: the Middle and Upper Devonian of the Ahnet and Mouydir (Algerian Sahara). Geol. Mag. 143 (3) pp. 269–299. doi:10.1017/S0016756806001737

Derder M, E.M., Henry B., Amenna M., Bayou B., Djellit H., Guemache M. A., Hemmi A. (2009): New structural implications for the central Sahara (Algeria), from the revisited Upper Carboniferous “Hassi Bachir” Formation: Paleomagnetic constraints. Tectonophysics, 463: pp.69–76.

Perron P., Guiraud M., Vennin E., Moretti I., Portier E., L. Le Pourhiet, M. Konaté (2018): Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi basins, Hoggar Massif). Solid Earth, 9: pp.1239-1275.