Roan Gr

Katanga Basin, Southern Congo margin in DRC and Zambia. Outcrop section is exposed in Zambia. The Roan Gr is subdivided into four subgroups: (i) the ‘Roche Argilo-Talqueuse Subgroup’ (R.A.T.; undetermined thickness); (ii) the > 400 m-thick carbonate Mines Subgroup; (iii) the >1,000 m-thick carbonate Dipeta Subgroup; and (iv) the 600–800 m thick carbonate and siliciclastic ±760 Ma Mwashya Subgroup.

Synonym:

References: Armstrong et al. 2005; Brock 1961; Barron et al. 2003; Cailteux 1983; Cailteux et al. 2003; Cailteux et al. 2007; Steven 2000; Lefebvre 1975; Liyungu et al. 2001; Key et al. 2001; Lefebvre 1973; Kabengele et al., 2003; Mendelsohn 1961;

[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, Aloloand 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: Southern margin of the Congo Shield. (A) Geological sketch map of the Katanga Basin (modified after Heijlen et al. 2008). (B) Synthetic stratigraphic log combined with C and Sr isotopic curves of the Katanga Supergroup in the DRC and Zambia (modified after d ‰13 Cailteux et al. 2005). Note the declines in C estimated at 6.7 in d 1 the Lower Roan Group, followed by intervals with strong 3C enrichments, attributed to the Bitter Spring negative excursion and a d1 second negative 3C shift at the top of the Mwashia Group, reported to the Sturtian glacial events (Bull et al. 2011)]

[Fig 7: Stratigraphic correlation between the Neoproterozoic sedimentary basins in Central Africa. Correlations based on Sr isotopic data, radiometric age constraints and revised lithological relationships]

The Roan Gr is subdivided into four subgroups (Cailteux et al. 2007): (i) the ‘Roche Argilo-Talqueuse Subgroup’ (R.A.T.; undeterminated thickness) of chloritic (altered illite)-dolomitic quartz-sandstones and siltstones, with reddish lower part and the grey upper part with economic Copper-Cobalt mineralization; reported stratigraphically to the ± 880 Ma Mindola Subgroup in Zambia (Armstrong et al., 2005); (ii) the > 400 m-thick carbonate Mines Subgroup correlated with the Kitwe Subgroup in Zambia; (iii) the >1,000 m-thick carbonate Dipeta Subgroup equivalent to the Kirilabombwe Subgroup in Zambia (Cailteux 1994; Cailteux and Kampunzu 1995); and (iv) the 600–800 m thick carbonate and siliciclastic ±760 Ma Mwashya Subgroup (formerly Upper Mwashya; Armstrong 2000; Liyungu et al. 2001; Key et al. 2001; Barron et al. 2003) including mafic volcaniclastic rocks (Lefebvre 1973; Cailteux 1983; Cailteux et al. 2003; Kabengele et al. 2003) coeval with the gabbroic bodies emplaced within rocks of the Dipeta Subgroup (DRC) and Bancroft-Kanwangungu formations (Mendelsohn 1961; Lefebvre 1975; Cailteux et al. 2007).

Considered coeval with the BI Gr carbonates; therefore late Tonian (ca. 40% to base-Cryogenian glacial till)

The time-equivalent Roan Gr and BII Gr are interpreted as lacustrine or lagoonal systems (Cailteux et al. 2007; see also Delpomdor et al. 2014), while the Roan Gr from Zambia appear to be marine.