Cenozoic

Mesozoic

Paleozoic

Neoproterozoic

Paleoproterozoic

Gres Polymorphes Formation

Gres Polymorphes Fm

Period:

Paleogene

Age Interval:

Early Eocene

Province:
Northern Congo Margin, Southern Congo Margin, Central Congo region

Type Locality and Naming

Lower unit in the Kalahari Gr. The type locality is situated in the northeastern margin of the Congo Basin DRC (Lindi Basin)

Synonym:

Reference: Cahen 1954; C.f. Lepersonne 1945; de Wit et al., 2015; De Ploey 1968; Kadima et al., 2011

[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, 1974) 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. Northern margin of the Congo Shield. (A) Geological sketch map of the Lindi Basin (modified after Verbeek 1970; Poidevin 1985)]

[Fig 7. Stratigraphic logs of the Lindi Supergoup in the DRC (modified after Verbeek 1970). (C and D) Stratigraphic logs of the Lindi Supergoup in CAR (modified after Poidevin 1985). cc cap carbonates, SG Sturtian Glaciation, MG Marinoan Glaciation]

[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

Consists of siliceous sandstones (Kadima et al., 2011). It is made up of massive sequence comprises 60–80 m thick extensively silicified ‘limestones’, calcareous sandstones and silcretes with chalcedony, known as the ‘Polymorphes Sandstones’ (C.f. Lepersonne 1945; de Wit et al., 2015). These rocks are often cavernous, bioturbated and fossiliferous with shells that display early silicification (De Ploey 1968).

Lithology Pattern:

Relationships and Distribution

Lower contact

Lies unconformably on the Nsele Fm of the Kwango Gr (Linde Basin), but on hiatus (during time of kimberlite emplacement; Delpomdor et al., 2009) above Bokungu Gr in the Sankuru-Mbuji-Mayi-Lomami-Lovoy Basin (DRC).

Upper contact

Overlain conformably by the Sables Ocres Fm

Regional extent

Located in the northeastern DRC

GeoJSON

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Fossils

Ostracods (Cypris farnhami, C. lerichei, Erpetocypris sp., Gomphocythere? sp., Oncocypria sp. and Stenocypris bunzaensis; Leriche 1927; Polinard 1932; Grekoff 1958; Colin 1994) and other lacustrine fossils, e.g., charophytes and gastropods (de Wit et al., 2015).

Age

middle Eocene (Linol et al., 2015, Fig. 11.4)

Age Span:

Beginning stage:

Ypresian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

56.00

Ending stage:

Lutetian

Fraction up in the ending stage:

0.5

Ending date (Ma):

44.55

Depositional setting

Aeolian depositional environment

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

Linol, B., de Wit, M.J., Guillocheau, F., Robin, C., Dauteuil, O., (2015). Multiphase Phanerozoic subsidence and uplift history recorded in the Congo Basin: A complex successor basin. In: M.J. de Wit et al. (eds.), Geology and Resource Potential of the Congo Basin, Regional Geology Reviews, DOI 10.1007/978-3-642-29482-2_11, # Springer-Verlag Berlin Heidelberg 2015

Giresse, P. (2005). Mesozoic-Cenozoic history of the Congo Basin. Jour. African Earth Sciences, 43: 301-315. doi:10.1016/j.jafrearsci.2005.07.009