Cenozoic

Mesozoic

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Kedeni Formation

Kedeni Fm

Period:

Cretaceous

Age Interval:

Aptian

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)

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

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 Kedeni Formation is lacustrine mudstone intercalated with braided-delta or fan-delta sandstone in a lowstand-transgressive system tract, with a thickness of 600–1200 m (Dou et al., 2022). The dark mudstone in the Kedeni Formation is assumed by Dou et al., (2022) be the regional caprock. Mudstone also dominate the formation to the north (about 80%), with a layer of those mudstones reaching a thickness of 100m, but about 10-40 m to the southern margin of the basin (Dou et al., 2022). The rapid rise of the lake water level during the deposition of the Lower Kedeni Member resulted in the predominance of shale with thinly bedded sandstone (Lenhardt et al., 2025). During the Upper Kedeni Member, multiple thick layers of sandstone were deposited as a result of short-term uplifting (Zhang et al., 2024a). The sand-to-formation ratio of the upper member is about 40%–55%, and that of the lower member is about 30%–45% (Dou et al., 2022).

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

Kedeni Fm unconformably lies on the Mangara Gr,

Upper contact

Doba Fm conformably rests on the Kedeni Fm

Regional extent

Doba Basin and Doseo Basin, Southern Chad

GeoJSON

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Fossils

Age

Aptian (Lower member is Early Aptian; Upper member is Late Aptian)

Age Span:

Beginning stage:

Aptian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

121.40

Ending stage:

Aptian

Fraction up in the ending stage:

1.00

Ending date (Ma):

113.20

Depositional setting

Braided-delta or fan-delta (Dou et al., 2022)

Depositional pattern:

Additional Information

Compiler:

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

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.