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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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Dimbabah Formation

Dimbabah Fm

Period:

Carboniferous

Age Interval:

Late Carboniferous (Middle Pennsylvanian; Moscovian) (9)

Province:
Djado Basin

Type Locality and Naming

A succession in a well in Hasi Dimbabah (28°30′N, 11°33′E) in Hamadat Tanghirt area in south Libya (Lelubre, 1952; Hallet, 2002) (Fig. 1). Named after Hassi Dimbabah well in southern Libya.

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

References: Lelubre, 1952; Plauchut & Faure, 1959; Jacqué, 1963; Lababidi et al., 1985; Mergl et al., 2000, 2001; Tawadros, 2011; Shalbak, 2015; Hallett, 2002, 2016.

Synonym: Dambabah (old spelling); Calcaires à Collenia; the former spelling of the formation was "Dembaba". The spelling was modified to its current form by Hallet (2002) after verifying the official name records of localities in Libya

Lithology and Thickness

Djado Basin: Built-up of red and white shales with few black limestones in the lower half of the unit. The upper half has a terrestrial origin and is unfossiliferous (Jacqué (1963) mentions that in Madama, the Carboniferous ends with about 100 m of unfossiliferous continental sandstones). Several evaporite levels with massive gypsum and sparse dolomite horizons are present. Jacqué (1963) mentions two horizons of stromatolites that can be followed for hundreds of kilometers from the Fezzan (Libya) to Chad, passing through Niger. Continental cross-bedded sandstones mark the final regression of the sea with chalcedonite, paleosols and red shales. Its thickness is 65 m at the Type Locality and 80-120 m at the Djado (Fabre, 2005). The maximum cumulative thickness of all Carboniferous units in the Djado Basin (Marar Fm, Assedjefar Fm and Dimbabah Fm), known from surface and subsurface, is 1000-1100 m (Figures).

[Figure 2: Lithostratigraphy column of Dimbabah Fm]

Lithology Pattern:

Gypsiferous claystone

Relationships and Distribution

Lower contact

Conformable contact onto the underlying Assedjefar Fm

Upper contact

Disconformable contact with the overlying Tiguentourine Fm

Regional extent

GeoJSON

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Fossils

Type Locality: Rich fauna of foraminifera, conodonts, corals and brachiopods. Jacqué (1963) also adds gastropods and Nautiloids. Djado Basin: The formation yielded an assemblage consisting of the chonetid Rugosochonetes cf. chesterensis (Weller) associated with Moscovian foraminifers (Mergl & Massa, 2000).

Age

Late Carboniferous (Middle Pennsylvanian; Moscovian). Lelubre, 1952.

Age Span:

Beginning stage:

Moscovian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

315.15

Ending stage:

Moscovian

Fraction up in the ending stage:

1.0

Ending date (Ma):

307.02

Depositional setting

Sabkha, lagoonal and continental. The lagoonal and continental episode during the Moscovian closed the Carboniferous in the Djado Basin. The Carboniferous Sea retreated after Moscovian time.

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)