Cenozoic

Mesozoic

Paleozoic

Neoproterozoic

Paleoproterozoic

Upper Diamictite Formation

Upper Diamictite Fm

Period:

Neoproterozoic

Age Interval:

latest Cryogenian

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 sedimentary West Congo Supergroup (or West Congo Group in Base-Congo) comprises two main sedimentary successions: pre-Pan-African-orogeny passive-margin platform sequences (ca. 4000 m in Bas-Congo of the Sansikwa Gr, Haut-Shiloango Gr, Schisto-Calcaire Gr; with Cryogenian glacial deposits of the Lower Diamictite Fm and Upper Diamictite Fm) and a late- to post-Pan-African molasse sequences (Mpioka Gr) followed by mid-Paleozoic red beds of the Inkisi Gr. (Delpomdor and Préat, 2013, in de Wit et al., eds.)

Synonym: Upper Mixtite; Niari Fm (Niari Tillite Fm) in Gabon. For the Angola Basin, some stratigraphic systems assign the Upper Diamictite as the basal 10-80 m of the 2,000 m-thick carbonate sequence of the Xisto-Calcario Gr. Upper Tillite Fm or Niari Gr (RC – Comba-Sangha basins).

References: Cailteux et al. (2015), de Wit et al. (eds.; 2015),

[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. 7a. 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. 7b. Synthetic stratigraphic log of West Congolian Group in Angola. cc cap carbonates; SG Sturtian Glaciation, MG Marinoan Glaciation.] [Fig. 7c. Synthetic stratigraphic log of West Congolian Group in the RC (modified after Alvarez 1995)]

[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

Glacial diamictite. In DRC Lower-Congo basin, it is up to 150 m of poorly sorted mud-supported conglomerates with angular and rounded clasts. In the Angola Basin, it is 10 to 80 m thick.

Lithology Pattern:

Glacial till

Relationships and Distribution

Lower contact

Overlies the Alto-Chiloango Gr (Angola Basin) or Haut Shiloango Gr (DRC Lower-Congo Basin). Same name, Chiloango is Portuguese and Shiloango is a German version.

Upper contact

Overlain by the Xisto-Calcario Gr (Angola Basin) or Schisto-Calcaire Gr (DRC Lower-Congo Basin). Same name, one is Portuguese and the other is a French version.

Regional extent

Extends in the Western Margin of the Lower Congo Basin. DRC Lower-Congo basin, Angola Basin, RC Sangha-Comba basins, etc.

GeoJSON

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Fossils

Age

latest Cryogenian. The "Upper Diamictite Fm in the West Congo Belt and the Kyandamu Fm (Petit Conglomérat Fm) diamictite in the Central Africa Copperbelt is interpreted of the same age as for the ± 635 Ma Marinoan Ghaub Fm diamictite in Namibia (Hoffmann et al., 2004; Kampunzu et al., 2009)." [Cailteux et al., 2015]

Age Span:

Beginning stage:

Cryogenian

Fraction up in beginning stage:

0.9

Beginning date (Ma):

643.50

Ending stage:

Cryogenian

Fraction up in the ending stage:

1.0

Ending date (Ma):

635.00

Depositional setting

Glacial

Depositional pattern:

Additional Information

Compiler:

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

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

Cailteux, J.L.H., Delpomdor, F.R.A. Ngoie Ndobani, J-P., 2015. The Neoproterozoic West-Congo “Schisto-Calcaire” sedimentary succession from the Bas-Congo region (Democratic Republic of the Congo) in the frame of regional tentative correlations. Geologica Belgica, 18(2-4): 126-146.

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: Basin Research (2011) 23, 499–527, doi: 10.1111/j.1365-2117.2011.00500.x