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Agueni Formation
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Agueni Fm base reconstruction

Agueni Fm

Period: 
Calymmian

Age Interval: 
Late Calymmian


Province: 
Taoudeni Basin

Type Locality and Naming

This formation is mainly in the western portion (e.g., Adrar and Hohd sub-basins) of the Taoudeni Basin, which a vast intracratonic sedimentary basin spanning parts of Mauritania, Mali, Algeria, Burkina Faso and Guinea.

Synonym:

References: Martin-Monge et al., 2016

[Fig. 1: Location of the Taoudeni Basin Province and the four assessment units defined in the study by Brownfield et al. (2015)]

[Fig. 2: The Taoudeni Basin (Taupin et al., 2017)]

[Fig. 3: Abolag-1 well, R well and Atar Group type section stratigraphy, facies description and correlation in the Taoudeni Basin, and organic richness profile in the Abolag-1 well (Claue,1981; Rooney et al.2009; Trompette,1973; Albert-Villanueva et al. 2016).]

[Fig. 4: Generalized stratigraphy of the Taoudeni Basin in Mauritania. Lithostratigraphic name equivalences are provided for the Adrar, Hank and Hodh depocentres. The major discontinuities are numbered and reference to global glacial and tectonic events is provided. (From Martin-Monge et al. (2016) as modified after Lahondere et al., 2003, 2005]


Lithology and Thickness

Consists predominantly of coarse to fine grained, thick to very thick bedded (0.8 to 4.0 m), quartz arenites and local accumulations of arkosic sandstones. Beds commonly exhibit large-scale cross-bedding and mud-draped wave or current ripples at bed tops. A thin (0.5 m) basal conglomerate or conglomeratic sandstone is locally present at the base and shows evidence of aeolian erosion (Pitfield et al., 2004). The quartz arenite beds are interbedded with massive, purple-red mudstone beds (up to 4 m thick) that contain white to pale greenish-gray reduction spots. Basal mudstone contacts are sharp and upper contacts are gradational. Sandstone beds become thin-bedded moving up-section and mudstone beds become more common (Taylor and Giles, 2013). The total thickness of the Agueni Fm is about 150m (Pitfield et al., 2004).


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

Non-conformably overlies the Archaean and Paleoproterozoic Basement Complex (Martin-Monge et al., 2016)

Upper contact

conformably overlain by the Azougui Fm (Taylor and Giles, 2013)

Regional extent

This formation is mainly in the western portion (e.g., Adrar-Hohd sub-basin) of the Taoudeni Basin


GeoJSON

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Fossils


Age 

See Hohd Super Gr entry for discussion of age assignments to Neoproterozoic units. The legend to the USGS regional map (Bradley et al., 2015) indicates that the onset of the lowest units begins shortly after 1600 Ma. Temporarily, the onset is arbitrarily set here as 1500 Ma (mid-Calymmian); with its lower Char Gr plus Foum Chor Fm (and regional equivalents) arbitrarily placed as upper Calymmian through lower Ectasian (1500 to 1300 Ma), then the major regional "D2" regional unconformity. Formations within the Char Gr are scaled following their relative proportions in the stratigraphic figure from Martin-Monge et al. (2016)

Age Span: 

    Beginning stage: 
Calymmian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
1,500.00

    Ending stage: 
Calymmian

    Fraction up in the ending stage: 
0.85

    Ending date (Ma):  
1,430.00

Depositional setting

In general, the Agueni Formation marks a transgressional sequence from continental, to coastal, and eventually to shallow marine depositional environments (Pitfield et al., 2004).


Depositional pattern:  


Additional Information


Compiler:  

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

Wenzhe, G. (2009): Hydrocarbon generation conditions and exploration potential of the Taoudeni Basin, Mauritania. Pet. Sci., 6: pp.29-37

Taylor, C. D. and Giles, S. A. (2013): Mineral Potential for Sediment-Hosted Copper Deposits in the Islamic Republic of Mauritania: Phase V, Deliverable 75. U.S. Geological Survey, Reston, Virginia

Martin-Monge, A., Baudino, R., Gairifo-Ferreira, L. M., Tocco, R., Badali, M., Ochoa, M., Haryono, S., Soriano, S., El Hafiz, N., Mez, J. H., Chacon, B., Brisson, I., Grammatico, G., Varade, R., and Abdallah, H. (2016): An unusual Proterozoic petroleum play in Western Africa: the Atar Group carbonates (Taoudeni Basin, Mauritania). In: Sabato Ceraldi, T., Hodgkinson, R. A. & Backe, G. (eds) Petroleum Geoscience of the West Africa Margin. Geological Society, London, Special Publications, 438, http://doi.org/10.1144/SP438.5

Bradley, D. C., Motts, H. A., Horton, J. D., Giles, Stuart, and Taylor, C. D. (2015): Geologic Map of Mauritania (Phase V, Deliverables 51a, 51b, and 51c), Chap. A1 of Taylor, C. D., ed., Second Projet de Renforcement Institutionnel du Sector Minier de la Republique Islamique de Mauritanie (PRISM-II): U.S. Geological Survey Open-File Report 2013-1280-A1, 3 pl., http://dx.doi.org/10.3133/ofr20131280