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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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Assedjefar Formation

Assedjefar Fm

Period:

Carboniferous

Age Interval:

Early Carboniferous (Late Mississippian, Serpukhovian) (9)

Province:
Djado Basin

Type Locality and Naming

The type locality was designated by Collomb (1962) 80 km west of Awaynat Wanin in the Adrar Uan Assedjefar Hill (28°30′N, 11°30′E). It was defined by Lelubre (1952b) as a sequence of deltaic and shallow marine rocks conformably overlying the Marar Fm in the Hamadat Tanghirt area of west Libya.

References: Lelubre, 1952b; Plauchut & Faure, 1959; Collomb, 1962; Jacqué, 1963; De Rouvre, 1984; Lababidi et al., 1985; Mergl et al., 2001; Fabre, 2005; Tawadros, 2011; Shalbak, 2015; Hallett, 2002, 2016.

Lithology and Thickness

Made up of green shales, often with gypsum beds alternating with calcareous levels. Its thickness is 140 m at the Type Locality (Fig. 1; Fig. 2; Fig. 3). Its thickness is 160 m in the Djado (Fabre (2005), thinning southward to 60 m.

[Figure 1: Stratigraphic column of the Assedjefar Formation at the Type Locality in Libya (Source: Shalbak, 2015)]

[Figure 2: Isopach map of the Assedjefar Formation]

[Figure 3: Lithostratigraphic column of the Assedjefar Formation]

Lithology Pattern:

Gypsiferous claystone

Relationships and Distribution

Lower contact

Conformable onto the Marar Fm

Upper contact

Overlying unit is the Dimbabah Fm

Regional extent

Djado Basin

GeoJSON

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Fossils

The restricted marine to lacustrine environment is indicated by algal stromatolites and concretionary limestones ("Collenia" horizons and Caliche layers). The sequence contains a rich marine fauna of brachiopods (characterized by the large syringothyrid Syringothyris jourdyi and the terebratulid Beecheria, as well as Streptorhynchus, the productids Antiquatonia, Flexaria, Ovatia, Rhipidomella, Composita, Syringothyris, Anthracospirifer and small rhynchonellids), pelecypods, corals and foraminifera plus abundant silicified wood.

Age

Age Span:

Beginning stage:

Serpukhovian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

330.34

Ending stage:

Serpukhovian

Fraction up in the ending stage:

1.0

Ending date (Ma):

323.40

Depositional setting

It represents a low-energy lagoonal to shallow shelf environment where dolomitic limestones, siltstones and ferruginous and gypsiferous sandstones were deposited. These facies indicate a retreat of the sea.

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)