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El Mreiti Gr

El Mreiti Gr

Period: 
Stenian

Age Interval: 
Stenian


Province: 
Taoudeni Basin

Type Locality and Naming

This formation is mainly in the eastern portion (e.g., Hank sub-basin) 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

The El Mreiti Gr is composed of the upward succession of 8 formations (Khatt Fm, En Nesoar Fm, Aguelt el Mahba Fm, Gouamir Fm, Tenoumer Fm, Ligdam Fm, and Eib Nous Fm). It is characterized by alternating carbonates and shale sections at the base which transition into intercalation of sandstones and carbonates upwards (Martin-Monge et al., 2016). It is equivalent to the Atar Gr in the Adrar Subbasin, and the upper part of the Souroukoto Gr of the Adrar Subbasin.


Lithology Pattern: 
Clayey limestone


Relationships and Distribution

Lower contact

Unconformably (major regional D2) overlies the Douik Gr

Upper contact

Unconformably (major D3 regional D3) overlain by the Bir Amrane Gr

Regional extent

Eastern part of the Taoudeni Basin.


GeoJSON

null

Fossils


Age 

As with the Atar Gr in the Adrar sub-basin, the age span for the El Mretiti Gr is constrained by Re-Os dating of the black shales of its Tod Fm (the equivalent interval in the Hank sub-basin includes the Aguelt el Mahba Fm black shales) in its lower part, therefore the Martin-Monger et al. (2016) place these as spanning ca. 1150 to 1100 Ma in their summary diagram of the petroleum system; hence the onset of the El Mretiti Gr is arbitrarily placed as base-Stenian (1200 Ma) here; and spanning the entire Stenian. Within the Group, the component formations are scaled within this Stenian interval according to their relative schematic thicknesses on the stratigraphic figure of Martin-Monge et al. (2016). CAVEAT – All ages and age spans in the Hodh Supergroup are entirely speculative and schematic; the entire pre-Cryogenian succession awaits accurate dating!

Age Span: 

    Beginning stage: 
Stenian

    Fraction up in beginning stage: 
0.00

    Beginning date (Ma): 
1,200.00

    Ending stage: 
Stenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
1,000.00

Depositional setting

Marine (Taylor and Giles, 2013)


Depositional pattern:  


Additional Information


Compiler:  

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

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

Kah, L. C., Bartley, J. K., and Stagner, A. F. (2009): Reinterpreting a Proterozoic enigma: Conophyton-Jacutophyton stromatolites of the Mesoproterozoic Atar Group, Mauritania. International Association of Sedimentologists, Special Publication, 41: pp. 277-295

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