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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Alanlara Formation

Alanlara Fm

Period:

Cretaceous

Age Interval:

Late Cretaceous (Lower Cenomanian) (5)

Province:
East Niger Rift Basin - Téfidet Sub-basin

Type Locality and Naming

Accurate location not stated, however, see Fig. 1 for a general location. Faure (1959) for the name of the nearby town of Alanlara.

References: Faure, 1959, 1966; Greigert, 1966 ; Greigert & Pougnet, 1967; Fabre et al., 1983; Meister et al., 1994; Konaté et al., 2019.

Synonym: Equivalent(s): Farak Fm; Ezerza-Cheffadène Fm.

Lithology and Thickness

Faure (1959) selects the top of the formation just below the limestone horizon with Neolobites. It begins with black limestones containing lamellibranch debris (marine), then beige to yellow, fine-grained sandstones (continental), clay-limestone silts, and ends with gastropod-rich sandy limestones (marine). 200 m thickness.

Lithology Pattern:

Relationships and Distribution

Lower contact

Underlying unit is the Tanguérat Fm (of Téfidet Gr in Téfidet Sub-basin)

Upper contact

Overlying unit is the Arentigué Fm (Zoo Baba-Arentigué Fm)

Regional extent

East Niger Rift Basin - Téfidet Sub-basin

[Figure 1: Geological map of the Téfidet Sub-Basin and surroundings (Faure, 1966). The dark green stands for the Zoo Baba Fm; the pale green for the Alanlara/Ezerza Fm. In the Téfidet Sub-Basin, the blue color is a combination of the Tanguérat, Tagrezou and Angornakouer formations (Téfidet Gr). Outside of the sub-basin, it represents the Eckhar, Elrhas and Tazolé formations (Tégama Gr)]

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[9.14,19.06],[8.85,18.85],[11.01,17.2],[11.38,17.66],[9.14,19.06]]]]}}

Fossils

Faure (1959) observed a series of clays with rare oyster debris (notably Ostrea deletrei - marine), conglomerates with bone debris of Ceratodus (freshwater), fine sandstones with Exogyra (marine), and finally sandstones and clays with vertebrate bones (Rebbachisaurus - continental). Rare molluscs, Dinosaurians.

Age

Late Cretaceous (Lower Cenomanian). Faure (1959) includes it in the Cenomanian. Greigert and Pougnet (1967) include it in the Early Cenomanian. Fabre et al. (1983) place it in the Late Cenomanian. Konaté et al. (2019) put it back in the Early Cenomanian.

Age Span:

Beginning stage:

Cenomanian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

100.50

Ending stage:

Cenomanian

Fraction up in the ending stage:

0.5

Ending date (Ma):

97.20

Depositional setting

Depositional pattern:

Additional Information

The whole is folded.

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)