Bouenza Fm

Period:

Neoproterozoic

Age Interval:

late-middle Cryogenian

Province:
West Congo Margin Basins

Type Locality and Naming

Carbonate-bearing facies of the uppermost formation in the EASTERN Mayombe Gr. The Mayombe Gr consists of the upward succession of the Mossouva Fm (Subgroup), Lower Tillite Fm (Subgroup), eastern Bouenza Fm and western Louila Fm (subgroups); and overlain by the Nairi Fm glacial.

Synonym: Louila Fm is the equivalent in the

References: Fullgraf et al., 2024; de Wit et al., 2015; Dadet 1969; Frimmel et al. 2006; Ge´rard 1958; Thie´blemont et al. 2009

[Fig 1. Lithostratigraphic synthesis for the Neoproterozoic to Early Paleozoic period. Compiled after various authors (see text).Dotted lines between Banalia, Alolo and Galamboge formations: stratigraphic transition by recurrences.]

[Fig 2. 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 3. 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. 4. 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

100 m-thick fluvial Bouenza Fm. Bz0 to Bz3 are mostly shales and sandstones, while the formation Bz4 contains mostly oolithic and stromatolitic carbonates (de Wit et al., 2015).

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

Rests on the glacial Lower Diamictite Fm (Lower Tillite Fm) (regionally).

Upper contact

Unconformably overlain by the fluvio-glacial Niari Gr of Marinoan age (latest Cryogenian)

Regional extent

Extends in the Eastern part (Nyanga-Niari Basin) of the Western Margin into Gabon and Republic of Congo. Equivalent to the Louila Fm of Mayombe Chain region.

GeoJSON

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Fossils

Age

Cryogenian (between Sturtian and Marinoan glacials)

Age Span:

Beginning stage:

Cryogenian

Fraction up in beginning stage:

0.7

Beginning date (Ma):

660.50

Ending stage:

Cryogenian

Fraction up in the ending stage:

0.9

Ending date (Ma):

643.50

Depositional setting

Passive margin

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

Fullgraf, T., Callec, Y., et al. (2024) Structural architecture and metamorphism of the Mayombe Chain and Niari Basin (West Congo Belt) in Congo Brazzaville. Jour. Afr. Earth Sci., 220: article 105369.