Dev-F3 Formation

Dev-F3 Fm

Period:

Devonian

Age Interval:

Eifelian – Givetian.

Province:
Illizi Basin

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: F3 member.

References: Dardour et al., 2004; Benvegnù, 2020

Lithology and Thickness

The F3 Fm. is divided into four cycles (I to IV) of alternating shale, siltstone and sandstone (Benvegnù, 2020). The lower part of the sequence is made up of neritic to coastal deltaic cycles (Dardour et al., 2004).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

It conformably overlies the F4-5 Fm.

Upper contact

It is unconformably overlain by the F2 Fm.

Regional extent

Illize Basin of SE Algeria. Corresponds to the Aouinet Ouenine Fm in the Ghadames Basin (Benvegnù, 2020)

GeoJSON

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Fossils

Age

Age Span:

Beginning stage:

Eifelian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

394.30

Ending stage:

Givetian

Fraction up in the ending stage:

1.0

Ending date (Ma):

378.90

Depositional setting

Neritic to coastal deltaic environment - barrier island environment (Benvegnù, 2020).

Depositional pattern:

Additional Information

: Concerning the petroleum exploration, the uppermost part of Aouinet Ouenine Fm. is important because in Ghadames-Illizi Basin corresponds to an organic-rich level, due to particular highstand conditions including rise of the sea level and a warmer climate, which is considered a significant source rock with TOC value ranging between 2% and 14% (Benvegnù, 2020).

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 An unpublished MSc thesis at Universita’ degli Studi di Padova.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