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Les Gres d’El Atchane Formation
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Les Gres d’El Atchane Fm base reconstruction

Les Gres d’El Atchane Fm

Period: 
Ordovician

Age Interval: 
Tremadocian – Floian.


Province: 
Ahnet Basin, Mouydir Basin

Type Locality and Naming

Synonym: Les Grès d’El Atchane (Klett, 2000; Perron et al., 2019).

References: Klett, 2000; van Dijk et al., 2019.


Lithology and Thickness

The Les Gres d’El Atchane Fm is made up of very fine-grained quartzite sandstones which are dark grey colored, glauconitic, and show intercalations of shales and black silty-sandstones (van Dijk et al., 2019).


Lithology Pattern: 
Fine-grained sandstone


Relationships and Distribution

Lower contact

It conformably overlies the Les Argiles d’El Gassi Fm.

Upper contact

It is unconformably overlain by the Quartzites de Hamra 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


Age 


Age Span: 

    Beginning stage: 
Tremadocian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
480.01

    Ending stage: 
Floian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
475.92

Depositional setting


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.