Cenozoic

Mesozoic

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Kome Formation

Kome Fm

Period:

Cretaceous

Age Interval:

Cenomanian-Turonian (Doba basin) or Cenomanian-Santonian (Doseo basin)

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 formation is predominantly sandstone, with secondary amounts of shale/mudstone (Fig. 9 of Lenhardt et al., 2025). The Kome Formation is mainly lacustrineto delta sandstone, and is about 400-700 m thick (Dou et al., 2022)

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

Koumra Fm, unconformably

Upper contact

Miandoun Fm, conformably in the Doba Basin (equal to upper Kome Fm in the Doseo Basin; where its top is overlain by the K2 Fm.

Regional extent

Doba Basin and Doseo Basin, Southern Chad.

GeoJSON

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Fossils

Age

Cenomanian-Turonian in Doba Basin; and the facies extends through Santonian in Doseo Basin. [In the Doba Basin, the claystone facies of the Miandoun Fm is the Coniacian-Santonian portion]. Doba Basin span is used here for graphic purposes to emphasize the upper clay-rich interval of the Miandown Fm equivalent.

Age Span:

Beginning stage:

Cenomanian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

100.50

Ending stage:

Turonian

Fraction up in the ending stage:

1.0

Ending date (Ma):

89.39

Depositional setting

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