Lower Dja Fm

Named after the Dja river in the Sembé-Ouesso Basin CAR, Northeastern RC, the southeastern Cameroon and the southwestern CAR. Lower unit of the Dja Gr.

Synonym: Sembé-Ouesso series, Sembe-Ouesso series, Lower Dja Series

References: Alvarez 1995; Chochine 1950; Cahen 1982; Gre`s and Legras 1967; Lasserre and Soba 1976; Jaunatre 1969; Poidevin and Pin 1986; Vicat and Vellutini 1987; Vicat and Pouclet 1995; Vicat et al. 1997; Sonet 1958

[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: 4MmapGeology 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 (see text).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]

Consists of ±1,500 m-thick Schisto-Quartzitic, ±700 m-thick pelites and about ±100 m-thick Tillites. In the northeastern RC, the Lower Dja series, previously called Sembé-Ouesso series, was divided into three sub-series (Chochine 1950; Sonet 1958; Gre`s and Legras 1967; Jaunatre 1969), and grouped into two sub-series as follows, from youngest to oldest (Vicat et al. 1997):

(i) the ±1,500 m-thick Schisto-Quartzitic sub-series (Bolé series in southwestern CAR and southeastern Cameroon; Poidevin 1985); and

(ii) the unconformable ±700 m-thick 1167–850 Ma ‘Gréso-Pélitique’ sub-series (‘Grès de Douma’ in the Sembe´ sub-basin, and the ‘Grès de Séka-Nzoulabout in the Ouesso sub-basin; Vicat and Vellutini 1987; Vicat et al. 1997) including the ±100 m-thick Dja Tillitic Complex in the northeastern RC and the Bandjia Tillitic Complex in southwestern CAR and Cameroon (Cahen 1982; Poidevin and Pin 1986; Vicat and Vellutini 1987; Vicat and Pouclet 1995; Alvarez 1995).

Tonian through Sturtian glacial of lower Cryogenian