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Les Gres Formation
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Les Gres Fm base reconstruction

Les Gres Fm

Period: 
Ordovician

Age Interval: 
Tremadocian – Darriwillian


Province: 
Reggane Basin

Type Locality and Naming

SW Algeria. Named from its composition (sandstone = Grès)

Synonym: Les Grès Fm

References:

[Figure 1: Map showing the six assessment units (AUs) in the Reggane Basin Province, Algeria (USGS, 2018).]

[Figure 2: Paleozoic litho-stratigraphic, sequence stratigraphy, and tectonic framework of the north peri-Hoggar basins (North African Saharan Platform) (Perron et al., 2020).]

[Figure 3: Geodynamic synthesis and lithostratigraphy of the Central Sahara and the Ouagarta Chain with major tectonic events (Kracha, 2011).]

[Figure 4: Geographical map of the basins of North Africa – showing the Reggane Basin (Carte SONATRACH, Division Exploration, in Akkouche, 2007).]


Lithology and Thickness

It is made up of fluvial sandstones that occur locally (Perron et al., 2018).


Lithology Pattern: 
Sandstone


Relationships and Distribution

Lower contact

It conformably overlies the Les Gres Des Ajjers Fm.

Upper contact

It is conformably overlain by the In Tahouite Fm.

Regional extent

SW Algeria.75,000 Km2


GeoJSON

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Fossils


Age 


Age Span: 

    Beginning stage: 
Tremadocian

    Fraction up in beginning stage: 
0.2

    Beginning date (Ma): 
484.90

    Ending stage: 
Darriwilian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
467.17

Depositional setting

Fluvial


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.