Arlit Fm
Period:
Permian
Province:
Iullemmeden Basin - Tim Mersoï Sub-basin
Type Locality and Naming
Upper cycle of the Tagora Gr (Upper Tagora)
References: Abdoul Aziz, 1968; Fabre et al., 1983; Broutin et al., 1990; Coquel et al., 1995; Fabre, 2005; Billon et al., 2016; Alfidja et al., 2021.
Synonym: Grès argileux d’Arlit
Lithology and Thickness
This unit is represented by medium to fine clayey sandstone, with brown or green argillite beds. Its thickness is average of 5 to 10 m (0-32 m).
Lithology Pattern:
Clayey sandstone
Relationships and Distribution
Lower contact
Underlying unit is the Madaouela Fm or the Tarat Fm when the Madaouela is absent (Alfidja et al., 2021).
Upper contact
Overlying unit is the Izégouande Fm (Izégouandane Gr).
Regional extent
GeoJSON
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Fossils
Silicified wood at the top
Age
Middle Permian (most likely Wordian). It has long been assumed to be of Upper Carboniferous (Pennsylvanian) age. However, Broutin et al. (1990) have established an Early Permian age (equivalent to the Kungurian of the Global Stages) to possibly(?) early Middle Permian (Roadian) for the upper portion of the Tarat Formation (now the Madaouela Fm) based on palynological data. (See Fig. 1 in Tarat Fm entry). This has also been confirmed by Coquel et al. (1995). The above directly affects the age of the Arlit Formation, which is now also included in the Middle Permian, just above the Madaouela Fm. Accordingly, Fabre (2005; page 333) displays a section with the upper portion of the Tarat Fm (or Madaouela Fm) and the Arlit Fm included in the Permian (not illustrated here but similar to what is seen in Fig. 1.)
Age Span:
Beginning stage:
Wordian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
269.21
Ending stage:
Wordian
Fraction up in the ending stage:
1.0
Ending date (Ma):
264.34
Depositional setting
Fluvial, lacustrine, alluvial
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)