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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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Wan Kasa Formation

Wan Kasa Fm

Period:

Devonian

Age Interval:

Lower Devonian (Pragian-Emsian) (9)

Province:
Djado Basin

Type Locality and Naming

Wadi Wan Kasa in southwest Libya. Borghi & Chiesa, 1940. Reference section is at Gour Iduka in Wadi Wan Kasa in the Takarkhouri Pass in southwest Libya (Figure).

References: Borghi & Chiesa, 1940; Plauchut & Faure, 1959; Jacqué, 1963; Freulon, 1964; Klitzsch, (1969; Lababidi et al., 1985; Mergl & Massa, 1992, 2000; Mergl et al., 2001; Tawadros, 2011; Shalbak, 2015; Hallett, 2002, 2016.

Synonym: Spelled Wan Kaza on the Geological Map of Libya (1977) and Ouan Kasa in the 1985 edition. The former/improper spelling of the Formation was "Ouan-Kasa". The spelling was modified to its current form by Hallet (2002) after verifying the official name records of localities in Libya. Freulon’s (1964) "Séries du Djado" is synonymous with the combined formations of Tadrat and Wan Kasa.

[Figure. Stratigraphic column of the Wan Kasa Fm at the Type Locality in Libya (Source: Hallet, 2002).]

Lithology and Thickness

At Type Locality (Figure): Gray, partly silty shale interbedded with clayey siltstone and fine-grained sandstone with minor calcareous beds. In the Djado Basin: Fine-grained sandstones and calcareous sandstones (up to 25% carbonate), with several coquina horizons, indicate wholly marine origin. Thickness: 20-170 m at the Type Locality and up to 365 m in the subsurface.

Lithology Pattern:

Fine-grained sandstone

Relationships and Distribution

Lower contact

Conformable onto the Tadrart Fm

Upper contact

Overlain by the Awaynat Wanin Fm

Regional extent

GeoJSON

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Fossils

In the type section in Libya, a rich and diversified marine fauna was collected and described, dating a Late Pragian to Emsian interval [Brachiopods, tentaculites, cephalopods and trilobites (e.g., Tropidoleptus carinatus Conrad, Chonetes orientalis Loczy var. admixta (Cowper-Reed)) as well as crinoids, corals, pelecypods, and plates from placoderm fishes.] (Mergl & Massa, 1992). A similar fauna, collected in the SW part of the Djado Basin, was also described (Mergl & Massa, 2000). The fossiliferous locality lies east of the Chirfa oasis (co-ordinates N 12°43’E 20°55’N). The distance between both localities is approximately 400 km.

Age

Lower Devonian (Pragian-Emsian at the Type Locality, and Emsian in the Djado Basin). Mergl & Massa, 1992, 2000; Mergl et al., 2001.

Age Span:

Beginning stage:

Pragian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

411.46

Ending stage:

Emsian

Fraction up in the ending stage:

1.0

Ending date (Ma):

394.30

Depositional setting

Continental to shallow marine at the Type locality; Marine in the Djado Basin. Extended regional and continuous open marine character of the late Early Devonian is well established along the western margin of the Djado Basin.

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)