Mayumbian Gr

Cenozoic

Mesozoic

Paleozoic

Neoproterozoic

Paleoproterozoic

Mayumbian Gr

Period:

Neoproterozoic

Age Interval:

early Tonian

Province:
West Congo Margin Basins

Type Locality and Naming

The West Congo Belt (WCB) is exposed, on 1,300 km, along the western margin of the CS. The West Congo Supergroup is divided into, from oldest to youngest, the rift-related volcanoclastic 999 ±7 Ma Zadinian and volcano-sedimentary ±910 Ma Mayumbian groups deposited on a ±2.1 Ga polymetamorphic Kimezian basement, and the overlying sedimentary West Congolian Group.

Synonym:

References: Deblond and Tack, 2001; Tack et al., 2001.

[Fig 1. Simplified geological map of the Congo Basin, compiled from various published map. The stratigraphic units have been assembled into major sequences (Late Neoproterozoic, Paleozoic and Cenozoic)]

[Fig 2. Tectonic setting of the Neoproterozoic basins of present-day Central Africa, compiled from the 1: 2M geological map of the Zaire (Lepersonne, 1974a) and the 1:4M map Geology and Major Ore Deposits of Africa (Milesi et al., 2006)]

[Fig 3. Lithostratigraphic synthesis for the Neoproterozoic to Early Paleozoic period. Compiled after various authors. Dotted lines between Banalia, Alolo and Galamboge formations: stratigraphic transition by recurrences]

[Fig 4. Lithostratigraphic columns for the Congo Basin established using data from the 4 wells in the central part of the basin and outcrops on its NE margin (Lindi-Ubangi and Kisangani-Kindu region), compared with the West-Congo and Katanga stratigraphy]

[Fig 5. Simplified geological map of Sub-Saharan Africa showing the Neoproterozoic basins on and around the Congo Shield (modified after De Waele et al. 2008). (LC) Lower Congo Basin, (Co) Comba Basin, (Sa) Sangha Basin, (Ny) Nyanga-Niari Basin, (An) Angola Basin, (SO) Semb-Ouesso Basin, (Ba) Ubangui Basin, (LiB) Likki-Bembe´ Basin, (Bk) Bakouma Basin, (Fou) Fouroumbala Basin, (Li) Lindi Basin, (It) Itombwe Basin, (Ma) Malagarazi-Bukoban Basin, (Mb) Sankuru-Mbuji-Mayi-Lomami-Lovoy Basin, (Lu) Luamba Group, (Kat) Katanga Basin, (RB) Ruwenzorian Belt, KaB) Karagwe-Ankole Belt, (RuB) Ruzisian Belt, (KiB) Kibaran Belt, (UB) Ubendian Belt, IB Irumide Belt]

[Fig. 6. Western margin of the Congo Shield. (A) Sketched geological map of the West Congo Belt (modified after Frimmel et al. 2006)]

[Fig. 7. Synthetic stratigraphic log combined with C and Sr isotopic curves of the West Congolian Group in the DRC (modified after Tait et al. 2011). Note strontium isotope ratios of the Haut-Shiloango Subgroup ranging between 0.7068–0.7072 (Frimmel et al. 2006; Poidevin 2007) and of the C3 to C5 formations of the Schisto-Calcaire Subgroup ranging between 0.7074 to 0.7084 suggesting deposition, respectively, between 800 Ma and 650 Ma and between 635 and 575 Ma (Frimmel et al. 2006; Poidevin 2007; Delpomdor and Pre´at 2013) and the negative shift of -13 ‰, consistent, in absolute values, with the negative swing of the Trezona anomaly (Halverson et al. 2007)]

[Fig. 8. Stratigraphic correlation between the Neoproterozoic sedimentary basins in Central Africa. Correlations based on Sr isotopic data, radiometric age constraints and revised lithological relationships]

Lithology and Thickness

"In Bas-Congo, the 3000-4000 m thick, predominantly felsic, volcanic-plutonic sequence described under various local names (‘Inga’ metarhyolites, in type area; Steenstra, 1973; Tack, 1975a, 1979a) is intruded by a suite of successively emplaced high-level granitic bodies with various local names and generally referred to as the ‘Lufu’ massif (Tack, 1973a,b, 1979a)." [Tack et al., 2001]

Lithology Pattern:

Volcanics

Relationships and Distribution

Lower contact

Rests on the rift-related volcanoclastic Zadinian Gr (basal age 999 ±7 Ma), which were deposited on a ± 2.1 Ga polymetamorphic Kimezian basement

Upper contact

Unconformably overlain by the Sansikwa Gr sediments of ca. 900 Ma. The onset is of the West Congo Supergroup (base of Sansikaw Gr) is the beginning of the infill of the newly formed Neoproterozoic basins on the Western margin of the Congo Shield, which was the initial stage of breakup in this part of the Rodinia supercontinent (Tack et al. 2001).

Regional extent

Extends in the western margin of the Lower Congo Basin into the DRC

GeoJSON

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Fossils

Age

early Tonian. Dated at 920 +/-8 Ma at the base and 912 +/-7 Ma at the top." (Tack et al., 2001) => rounded here to 930 to 915 Ma. [Arbitrarily equated with onset of volcanics (Nemba Complex) in northern West Margin rifting – Niari Basin; dated at ca. 915 Ma, hence 30% up in Tonian; and top also with those Nemba Complex at ca. 910 Ma (32% up in Tonian)

Age Span:

Beginning stage:

Tonian

Fraction up in beginning stage:

0.30

Beginning date (Ma):

916.00

Ending stage:

Tonian

Fraction up in the ending stage:

0.32

Ending date (Ma):

910.40

Depositional setting

Both the Zadinian Gr and Mayumbian Gr represent early Neoproterozoic magmatic events marking the initial continental rifting of the Rodinia supercontinent before its breakup (Tack et al., 2001).

Depositional pattern:

Additional Information

Compiler:

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

Geology and Resource Potential of the Congo Basin by Maarten J. de Wit, François Guillocheau and Michiel C.J. de Wit, 2015, Published Springer-Verlag Berlin Heidelberg; DOI 10.1007/978-3-642-29482-2

Deblond, A., and Tack, L. 2001. 4. Updated geologic framework of the Democratic Republic of Congo (DRC) in Central Africa. [uncertain original publication source; downloaded from https://cibaf.academia.edu/BenedictLunze]

Tack, L., et al., 2001. Early Neoproterozoic magmatism (1000–910 Ma) of the Zadinian and Mayumbian Groups (Bas-Congo): onset of Rodinia rifting at the western edge of the Congo craton. Precambrian Research, 110: 277-306. https://doi.org/10.1016/S0301-9268(01)00192-9

Structure and geological history of the Congo Basin: an integrated interpretation of gravity, magnetic and reflection seismic data by E. Kadima, D. Delvaux, S. N. Sebagenzi, L. Tack and S. M. Kabeyaz, 2011: Basin Research 23: 499–527, doi: 10.1111/j.1365-2117.2011.00500.x