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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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Fachi Formation

Fachi Fm

Period:

Cretaceous

Age Interval:

Lower Cretaceous (Albian?) (8a)

Province:
East Niger Rift Basin - Bilma Sub-basin

Type Locality and Naming

Fachi is an oasis surrounded by the Ténéré desert and the dunes of the Erg of Bilma in eastern Niger. Faure, 1966; Village of Fachi (Fig. 1).

References: Faure, 1966; Fabre et al., 1983.

Equivalent(s): Achegour Fm, Dibella Fm

[Figure 1. The Fachi Formation near the village of Fachi (Source: Modified from Faure, 1966, p. 215).]

Lithology and Thickness

Light sandstones, coarse or fine, with stratification in large beds, oblique or cross-bedded.

~30 m: Fine sand with ferruginous intercalations
150 m: Fine or medium-grained with cross-bedded stratification comprising a level of traces of Vegetables.
20 m: Coarse or heterogeneous conglomeratic sandstone, with cross-bedded stratification.
A reddish surface of discordance with slightly rolled debris of quartz.

Thickness: ~200 m (see the 100 m section in Fig. 2)

[Figure 2. A 100-m section of the Fachi Fm at Nagaba-Kao Boula (Source: Faure, 1966, p. 218).]

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

Underlying is Precambrian

Upper contact

Overlying unit is the Ezerza Fm

Regional extent

GeoJSON

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Fossils

Traces of plants are scarce; generally tender, they are often silicified in the vicinity of faults.

Age

Lower Cretaceous (Albian?)

Age Span:

Beginning stage:

Aptian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

117.30

Ending stage:

Albian

Fraction up in the ending stage:

1.0

Ending date (Ma):

100.50

Depositional setting

Continental

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)