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Niari Gr
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Niari Gr base reconstruction

Niari Gr

Period: 
Neoproterozoic

Age Interval: 
Latest Cryogenian


Province: 
West Congo Margin Basins

Type Locality and Naming

The Nyanga-Niari Basin in the northern part of the West Congo Belt on the western margin of the Congo Shield comprises two distinct geologic domains from west to east, i.e., the metasedimentary hinterland domain deposited on c. 1000–850 Ma magmatic Mabouine´ and Mayumba complexes, and the poorly constrained unmetamorphosed sedimentary foreland domain (Thie´blemont et al. (2009). The unmetamorphosed internal domain, i.e. the Nyanga syncline, had been divided into (Ge´rard 1958; Dadet 1969): Bouenza Fm, fluvioglacial Niari Gr, Schisto-Calcaire Gr and Schisto-Gre´seux Gr. The hinterland domain had comprised the Loukoula Gr, fluvio-glacial sedimentary M’beia Fm and metasedimentary 713 ± 49 Ma Louila Fm.

Synonym: Upper Diamictite Fm, Upper Tillite, Niari Tillite, Niari Fm

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

[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

It is 0 m to 8 m of fluvial-glacial deposits that consist of siliceous shales, sandstones and shales deposited as mass flows before glaciers. (de Wit et al., 2015)


Lithology Pattern: 
Glacial till


Relationships and Distribution

Lower contact

Overlies the Mayumbe Group along a regional unconformity – rests on the inter-glacial carbonate-fluvial Bouenza Fm (Nairi Basin in east) or equivalent clastic Louila Fm (Mayombe Chain in west) of late-middle Cryogenian of the uppermost Mayombe Gr

Upper contact

Overlain by the cap carbonate (Dolomie de Bongolo) basal unit of the Schisto-Calcaire Gr. This represents a return to warm climatic conditions.

Regional extent

Extends in the Western Margin into Gabon and Republic of Congo.


GeoJSON

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Fossils


Age 

Cryogenian (Marinoan glacial), the Upper Diamictite Fm in the West Congo Belt is interpreted of the same age as for the ± 635 Ma Marinoan Ghaub Fm diamictite in Namibia (de Wit et al., 2015; 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-fluvial


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.