Cenozoic

Cretaceous

Jurassic

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Compiled by: Jacques LeBlanc (2022), Stratigraphic Lexicon: The Sedimentary Formations of The Republic of Niger, Africa. Colnes Publishing (Tallin, Estonia), 365 pp. For more information see "About"

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Farak Formation

Farak Fm

Period:

Cretaceous

Age Interval:

Upper Cretaceous (Lower Cenomanian) (1)

Province:
Iullemmeden Basin

Type Locality and Naming

Joulia, 1951

References: Joulia, 1951; Faure, 1966; Greigert, 1966; Taquet, 1976; Fabre et al., 1983; Dikouma, 1990; Rat et al., 1991.

Synonym: The former (now obsolete): In Assamed Fm and the old *Talrass Fm, *Aïn Toufayen Fm and *En Nassame Fm.

Equivalent(s): Alanlara Fm (Ezerza-Cheffadène Fm)

Lithology and Thickness

It constitutes a series of transitions between the typically continental deposits of the Tégama Gr and the distinctly marine deposits of Cenomanian-Turonian age, which begin with the Iguéllala Mountains Fm (Greigert, 1966). It is a shaly sequence with kaolin cement sandstone intercalations. In the Damergou area, it is fine-grained sandstone and massive clays bedded with coarse sandstone lenses. The deposition conditions would transition between those of the underlying Tégama Gr and the Upper Cretaceous marine formations. Faure (1962) provides the following section:

50 m: Very fine-grained sandstone and sandy shales
12 m: Lenses of coarse sandstones with oblique stratifications
15 m: Fine-grained sandstones and sandy shales
11 m: Lenses of coarse sandstones
25 m: Grey-greenish shales, massive or layered with lenses of fine sandstones.
75 m: Fine-grained white micaceous sandstones and argillaceous motley sandstones.

Thickness is 190 m.

Lithology Pattern:

Relationships and Distribution

Lower contact

Underlying unit is the Tégama Gr

Upper contact

Overlying unit is the Iguéllala Mountains Fm, Béréré Fm (Damergou Gr). The transition from the Farak Fm to the overlying marine Cretaceous is generally very gradual (Greigert, 1966). On the other hand, the Farak Fm passes eastward in the Eastern Niger Basin to the Alanlara Fm and the Ezerza Fm, both marines and located under the Neolobites zone (Faure, 1966).

Regional extent

GeoJSON

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Fossils

The top of this formation is made up of "oblique stratification" of lacustrine limestones, which gave rise to fish, crocodilians and dinosaurians (Greigert, 1966; Taquet, 1976). The Farak Formation also contains freshwater bivalves, including Unio jowikolensis, U. cretaceus. Cyrena mascula.

Age

Upper Cretaceous (Lower Cenomanian)

Age Span:

Beginning stage:

Cenomanian

Fraction up in beginning stage:

0.05

Beginning date (Ma):

100.17

Ending stage:

Cenomanian

Fraction up in the ending stage:

0.5

Ending date (Ma):

97.20

Depositional setting

Continental; transitional continental to marine.

Depositional pattern:

Additional Information

Compiler:

Jacques LeBlanc (2022), Stratigraphic Lexicon: The Sedimentary Formations of The Republic of Niger, Africa. Colnes Publishing (Tallin, Estonia), 365 pp. https://doi.org/10.47909/978-9916-9760-6-7 (or via https://sites.google.com/site/leblancjacques)