Cenozoic

Mesozoic

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Koumra Formation

Koumra Fm

Period:

Cretaceous

Age Interval:

Late Albian

Province:
Chad S

Type Locality and Naming

Doba Basin and Doseo Basin. The Southern Chad Basin (consists of the Bongor, Doseo, Doba, and Salamat basins)

References: Lenhardt et al., 2025; Dou et al., 2022

[Fig. 1: Simplified map of the West and Central African Rift System showing the major basins (from Lenhardt et al., 2025).]

[Fig. 2: Stratigraphy of the basins of the Central African Rift System (from Lenhardt et al., 2025)]

[Fig. 3: Composite stratigraphic column of the Doseo Basin. R_t– resistivity; GR – natural gamma (Fig 4. of Dou et al., 2022)]

[Fig. 4: Comprehensive column of sedimentary strata in the Doseo Basin of the Southern Chad Basin (from Hong et al., 2024)]

Lithology and Thickness

The Koumra Fm is predominantly made up of sandstone, with a few intercalating shales (Fig. 9 of Lenhardt et al., 2025). The thickness of the Koumra Formation is 300–600 m, and the sand-to-formation ratio is about 45%–60% (Dou et al., 2022). Sand bodies became more prominent as the lake level began to fall again during the late stage of deposition of the Koumra Formation (Zhang et al., 2024a).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Doba Fm, unconformably

Upper contact

Kome Fm, unconformably

Regional extent

Doba Basin and Doseo Basin, Southern Chad

GeoJSON

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Fossils

Age

Late Albian

Age Span:

Beginning stage:

Albian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

106.85

Ending stage:

Albian

Fraction up in the ending stage:

1.0

Ending date (Ma):

100.50

Depositional setting

Lacustrine-fluvial-delta sandstone and mudstone in a highstand systems tract (Dou et al., 2022). Lacustrine to fluvial-delta sandstones and mudstones (Gao et al., 2023).

Depositional pattern:

Additional Information

Compiler:

Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024) - Stratigraphic Lexicon compiled from the following books:

Lenhardt, N., Omietimi, E. J., Edegbai, A. J., Schwark, L., Catuneanu, O., Fairhead, J. D., Gotz, A. E. (2025): Traversing the rift: A review of the evolution of the West and Central African Rift System and its economic potential. Earth-Science Reviews, 261: pp. 1-39

Dou L.. Xiao K., Du Y., Wang L., Zhang X., Cheng D., Hu Y. (2022): Exploration discovery and hydrocarbon accumulation characteristics of the Doseo strike-slip and inverted basin, Chad. Petroleum Exploration and Development, 49 (2): pp.247-256.