Dev-F2 Formation

Dev-F2 Fm

Period:

Devonian

Age Interval:

Frasnian – Famennian.

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 lower portion of that “F” member.]

Synonym: F2 member.

References: Benvegnù, 2020

Lithology and Thickness

Sandstone and shales, with these sandstones considered a good reservoir in the Illizi Basin (Benvegnù, 2020).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

It unconformably overlies the Dev-F3 Fm.

Upper contact

It is conformably overlain by the Carb-A-B-C Fm.

Regional extent

Illize Basin of SE Algeria

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[7.82,29],[8.33,29.15],[8.78,29.13],[9.38,28.9],[9.38,28.08],[9.2,27.76],[9.32,27.57],[9.23,27.3],[9.03,27.06],[8.55,26.85],[8.25,27.02],[7.98,27.01],[7.69,26.81],[7.42,26.83],[7.07,27.35],[6.78,27.6],[6.59,27.43],[6.45,27.42],[6.2,27.78],[5.99,28.41],[6.33,28.67],[6.52,28.95],[6.58,28.74],[6.69,28.73],[6.86,28.91],[7.33,29.05],[7.63,29.13],[7.82,29]]]]}}

Fossils

Age

Age Span:

Beginning stage:

Frasnian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

378.90

Ending stage:

Famennian

Fraction up in the ending stage:

1.0

Ending date (Ma):

359.30

Depositional setting

Shallow marine and deltaic conditions with continental influences (Benvegnu, 2020).

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 An unpublished MSc thesis at Universita’ degli Studi di Padova.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