Argileux Formation

Argileux Fm

Period:

Silurian.

Age Interval:

Telychian – Ludfordian (?).

Province:
Illizi Basin, Ghadames Basin

Type Locality and Naming

Named after the facies

Synonym: Claystone Fm (translation of the French)

References: Hallett, 2002; Bora and Dubey, 2015; Benvegnù, 2020

Lithology and Thickness

This succession is related to ice-sheet retreat and global sea-level rise and corresponds to a transgressive system tract during which a layer of graptolitic black shales was deposited. It is the lateral equivalent of the Tanezuft Fm. and consists of dark micaceous siltstone with interbedded sandstone. In the lowermost part, this formation is also made by radioactive shales due to the presence of uranium transported by wind as volcanic ash. The upper part is characterized by a thick siltstone member showing hummocky cross-stratification separated by hardgrounds, probably representing tempestite deposits (Hallett, 2002).

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

It conformably overlies the Gara Louki Fm.

Upper contact

It is conformably overlain by the F6 Fm.

Regional extent

In addition to the Illizi Basin, this particular rock is present also in surrounding basins such as the Sirte, Hamra and Berkine (Ghadames) (Bora and Dubey, 2015).

[Just Illizi-Ghadames merger given in this GeoJSON pending making a larger one.]

GeoJSON

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Fossils

Graptolites

Age

Age Span:

Beginning stage:

Telychian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

438.59

Ending stage:

Ludfordian

Fraction up in the ending stage:

1.0

Ending date (Ma):

422.73

Depositional setting

Marine (Benvegnù, 2020). This succession is related to ice-sheet retreat and global sea-level rise and corresponds to a transgressive system tract

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 An unpublished MSc thesis at Universita’ degli Studi di Padova.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.