Neoproterozoic to Lower Paleozoic Sequences of the Congo Shield: Comparisons Between the Congo and Its Peripheral Basins - Geology and Resource Potential of the Congo Basin - page 95

crystalline basement comprises Archean to Mesoproterozoic
igneous and metamorphic rocks of the Congo Shield (see de
Wit and Linol, Chap. 2 , this Topic). Scarce outcrops, limited
geological data and stratigraphic age constraints still prevent
a detailed reconstruction of the Neoproterozoic history of the
CB. Nevertheless, many authors have attempted to decipher
the Neoproterozoic geological evolution of Central Africa
and the CB in particular (Cahen 1954 ; Evrard 1960 ;
Lawrence and Makazu 1988 ; Daly et al 1991 , 1992 ; Kadima
2011 ; Kadima et al. 2011a , b ; Linol 2013 ; see also Chaps.
2 to 5 , this Topic).
Here, we re-examine the largely hidden Neoproterozoic
to lower Paleozoic sequences of the CB near the centre of the
Congo Shield and compare its evolution with the
surrounding and partially exposed marginal sedimentary
basins.

observed into these basins (Vicat and Vellutini 1987 ; Vicat
et al. 1989 ; Key et al. 2001 ; Tack et al. 2001 ; Johnson et al.
2007 ; de Waele et al. 2008 ). A brief summary of the strati-
graphy of these marginal basins is given below, in clockwise
order as depicted in Fig. 6.1 :
1. The West Congo basin contains rhyolites and felsic
volcanoclastics dated at 950 Ma (Tack et al. 2001 ) and
intruded by granitoids (e.g. in the West Congo Super-
group and the Sangha-Comba Aulacogen). These
volcano-magmatic series have been considered to repre-
sent a continental rift sequence related to the break-up of
Rodinia and the opening of the Adamastor Ocean with the
deposition of passive margin sediments (Alvarez 1995a ,
b ; Tack et al. 2001 ). These sequences are overlain by the
Ediacaran-Cryogenian West Congo Group comprising a
succession of siliciclastics interbedded with diamictites
and carbonates (Frimmel et al. 2006 ; see also Delpomdor
et al., Chap. 3 , this Topic).
2. The Semb´-Ouesso basin exposed in the Republic of the
Congo (Congo-Brazzaville) contains sequence of schist
and quartzite, overlain by a pelitic and sandstone
sequence, and in turn by the Dja tillite, estimated at ca.
950 Ma (Vicat and Vellutini 1987 ). Dolerites intrude all
these sequences; and their emplacement is interpreted to
be related to crustal extension leading to basin subsidence
in a failed rift (Vicat and Vellutini 1987 ; Vicat et al. 1989 ;
Vicat and Pouclet 1995 ).
3. The Fouroumbala-Bakouma and Bangui basins in the
Central African Republic (CAR), the Liki-Bembian,
Lindian, Itombwe syncline in the Democratic Republic
of Congo (DRC), as well as the Malagarazi-Bukoban
basin in Burundi and Tanzania all have been recognized
to be Neoproterozoic in age, based on limited radiometric
dating and lithostratigraphic correlations (Alvarez 1995a ,
b , 1999 ; Poidevin et al. 1980 /1981; Poidevin 1985 , 2007 ;
Deblond et al. 2001 ). The age of the Bakouma Formation
was first estimated at ca. 840

6.2 Neoproterozoic to Lower Paleozoic

Sequences of the Congo Shield Flanking
the CB

In Central Africa, the Neoproterozoic geological evolution is
marked by a succession of major events initiated by the
break-up of the Rodinia supercontinent and opening of rift-
basins (e.g. West Congolian, Semb ´ -Ouesso, Mbuji-Mayi,
Katanga, Zambian basins), and terminating by the amalgam-
ation of Gondwana and the filling of associated foreland
basins (e.g. de Waele et al. 2008 ). Traces of these events
can be observed within the Congo Shield (sensu Stankiewicz
and de Witt 2013 ) and particularly in marginal sedimentary
basins surrounding the CB (Fig. 6.1a ), such as the West
Congo, Semb ´ -Ouesso, Bangui and Liki-Bembian basins to
the West and Northwest; the Fouroumbala-Bakouma and
Lindian basins to the North and Northeast; the Itombwe
and Malagarazi-Bukoban basins to the East; the Katanga,
Zambian and Mbuji-Mayi basins to the Southeast 50 Ma (Poidevin 1996 ),

although Alvarez ( 1999 ) obtained a whole rock Rb-Sr
date for these rocks of ca. 683

(Fig. 6.1b ).
Studies based on shear-wave tomography (Crosby et al.
2010 ; Priestley et al. 2008 ; Ritsema and van Heijst 2000 ),
admittance models (Downey and Gurnis 2009 ; Hartley and
Allen 1994 ; Hartley et al. 1996 ;P ´ rez-Gussiny ´ et al. 2009 ),
kimberlite data (Crosby et al. 2010 ; Batumike et al. 2009 ),
subsidence modelling (Kadima et al. 2011b ; Kadima 2011 )
and heat flow estimations (Kadima et al. 2011b ; see also
Lucazeau et al., Chap. 12 , this Topic) suggest that the CB and
surrounding Lindian and Mbuji-Mayi basins are underlain
by a thick mantle lithosphere (200 km or more), with an
equivalent elastic thickness of ca. 100 km (for further details
see Raveloson et al., Chap. 1 , this Topic).
Evidence of Rodinia break-up as main mechanism of
formation for some of the sedimentary basins surrounding
the CB is supported by the age of magmatic intrusions

11 Ma. Magmatic
intrusions have been documented, in particular in the
Fouroumbala-Bakouma, Bangui, Itombwe and
Malagarazi-Bukoban basins (Waleffe 1988 ; Poidevin
1976 , 1979 ; De Paepe et al. 1991 ; Tack 1995 ; Deblond
et al. 2001 ). Amygdaloid lava belonging to the
Malagarazi Supergroup has been dated at 795 7Ma

50 Ma,
intrude sediments filling the Itombwe basin (Villeneuve
1983 ).
4. The Katangan and Zambian basins, now part of the
Lufilian (Arc) fold-and-thrust belt, developed during
two magmatic events between 880 Ma and 750 Ma
(Porada 1989 ; Armstrong et al. 2005 ; Johnson et al.
2005 ), and were subsequently deformed during the Pan-

(Deblond et al. 2001 ). Syenite, dated at 700