Tanezzuft Formation

Tanezzuft Fm

Period:

Silurian

Age Interval:

Telychian – Sheinwoodian

Province:
Murzuq Basin, Ghadames Basin, Al Kufrah Basin

Type Locality and Naming

Ghat Province. The formation was formally introduced by Desio (1936b) after Wadi Tanezzuft about 65km NE of Ghat. Its type section was measured by Klitzsch (1963) at Takharkhouri pass 35km south of Ghat.

Synonym: Tannezuft or Gotlandian (French for Silurian) shale (Selley); Tanezrouft Fm.

References: Desio, 1936b; Klitzsch, 1963; Grubic et al., 1991; Pierobon, 1991; Aziz, 2000; Hallett, 2002

Lithology and Thickness

It has proven to be one of the major source rocks of North Africa and its distribution and extent are therefore of prime importance (Hallett, 2002). The Tanezzuft Formation is a sequence of dark grey to black, graptolitic shales with intercalations of siltstone and fine-grained sandstones, often forming rhythmical alternations. It is easily recognized in the field because of its typical relief with rounded and heavily dissected predominantly greyish to pink coloured hills (Alkhalas, 2006). The Tanezzuft Formation has a maximum thickness of about 50 m (Page et al., 2013).

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

It unconformably overlies the Mamuniyat Fm. (Page et al., 2013) in both the Al Kufrah and Murzuq Basins, while it conformably overlies the Bir Tlacsin Fm. in the Ghadames Basin (Bora and Dubey, 2015).

Upper contact

It is unconformably overlain by the Akakus Fm. (Page et al., 2013). This is sometimes termed the “Taconic unconformity”, although it far from the Taconic region.

Regional extent

The Tannezuft Fm. is present in the Murzuq, Ghadames, and Al Kufra Basins.

GeoJSON

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Fossils

Graptolites – Normalograptus sp. 2 (ex gr. ajjeri), Glyptograptus tariti, Neodiplograptus cf. imperfectus, N. cf. fezzanensis, Metaclimacograptus sp. (Fello et al., 2006)

Age

Global flooding after the Hirnantian glaciation. Extends through the Telychian (according to Google Gemini review of literature through Aug 2026).

Age Span:

Beginning stage:

Rhuddanian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

443.07

Ending stage:

Telychian

Fraction up in the ending stage:

1.0

Ending date (Ma):

432.93

Depositional setting

Depositional pattern:

Additional Information

Primary petroleum source rock and regional seal for major Paleozoic hydrocarbon systems in North Africa. Lower “Hot” Shale (early Rhuddanian) is the main high-carbon interval, followed by “Cold” Shale.

Compiler:

Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024) - Stratigraphic Lexicon compiled from the following books: