Mesozoic Sedimentary Cover Sequences of the Congo Basin in the Kasai Region, Democratic Republic of Congo - Geology and Resource Potential of the Congo Basin - page 162

and uplift in the West Congo and Lufilian Belts (Daly et al.
1992 ). Break-up of Gondwana and the opening of the South
Atlantic Ocean resulted in an elevated rift shoulder forming
the present western boundary of the Congo Basin. Although
separation of South America from southern Africa began
during the earliest Cretaceous and continued well into the
middle Cretaceous and was followed by a major Santonian
compressional event across central African (sensu Bosworth
1992 ) and the development of the Cenozoic East African
Rift System, Daly et al. ( 1992 ) observed no evidence of the
influence of these events in the Cuvette Centrale. Sahagian
( 1993 ) and other workers suggest that following separation
in the Early Cretaceous, the Congo Basin remained largely
stable, dominated by thermal relaxation and passive
infilling, at or near sea-level for the last 100 Ma, remarkably
with no noticeable effects (e.g., deformation; regional
hiatuses; tectonic subsidence) associated with any of the
major tectonic events affecting the continent during this
interval (i.e., the Santonian compressional event; Super
Plume and East African Rift).

Mesozoic sedimentary depocenters, trending ENE-WSW
and NW-SE following the trends of the Luana, Lulua,
Bushimay (Fig. 9.2 ) and Cassange depocenters. Similar
orientations are shown by the modern drainages such as the
linear stretches of the Lubembe, Kasai, Luebo, Lulua and
Lomami rivers (Fig. 9.3 ).

9.2.3 Stratigraphy

9.2.3.1 Pre-Mesozoic Sequences (Sequences 1-4)
The greater Congo Basin (Cuvette Centrale plus margins)
preserves up to 9 km of sedimentary fill spanning the Late
Proterozoic to Quaternary (Cahen 1954 ). Based on seismic
data and cores, Daly et al. ( 1992 ) distinguished five major
stratigraphic sequences in the Cuvette Centrale that range in
age from Late Neoproterozoic to late Cenozoic. The age and
compositional make-up of basement flooring the basin varies
quite significantly across the basin, ranging from Archean
crystalline rocks (Kasai, Mbomou, Chaillu-Gabon cratons) to
Meso- to Neoproterozoic deformed sedimentary sequences
(Cahen 1954 ; Cahen and Lepersonne 1978 ; Daly et al. 1992 ).
Beyond the Cuvette Centrale on the southern margin of the
basin, the ancestry of the Kasai Craton is well indicated from
analyses of zircons recovered from Quaternary sediments
of the Luebo River, which indicate a provenance area that
included Archean-Paleoproterozoic, 3.2-2.1 Ga crustal
components (Batumike et al. 2009 ). The basement comprises
gneisses, migmatites and granulites and intrusive granitoids
that have been assigned to the Sandoa-Kapanga, Kasai-
Lomami and Dibaya Complexes (Cahen 1954 ; Delhal 1977 ;
Delhal and Li´geois 1982 ; Walraven and Rumvegeri 1993 ),
with remnant supracrustal rocks including greenstone belts
and the Lulua and Luana fault-bound grabens (Delhal et al.
1989 ; Andre 1993 ; Pereira et al. 2003 ; Perritt et al. 2011 ).
The first cover sequence in the Cuvette Centrale
(Sequence 1) recognized by Daly et al. ( 1992 ) comprises
Late Neoproterozoic (Vendian) shallow marine stromatolitic
limestones with subordinate evaporites that overlie truncated
basement reflectors, correlated with the (~645 Ma) Ituri
Group in northeastern DRC (Verbeek 1970 ). Deposition
predates, or is at least partially syndepositional with, defor-
mation interpreted during the Pan-African event. Stromato-
litic limestones are also known from the Mbuji-Mayi
Supergroup, which is an up to 4 km thick, siliciclastic-
carbonate intracratonic failed-rift basin, but these sediments
are older, constrained in age between

9.2.2 Structure

Within the Cuvette Centrale, seismic and gravity data have
permitted the recognition of a suite of major structures,
basement highs and sub-basins. The presence of an angular
unconformity between the Permian Lukuga Group and over-
lying beds in the Dekese core and in the Lukuga Valley, on
the eastern margin of the basin, provides an indication of
Late Paleozoic faulting and deformation in the basin. This
interpretation was confirmed by Daly et al. ( 1992 ) in their
seismic analysis of the Cuvette Centrale. They identified a
series of dominantly southwest verging thrust faults that
formed two major NW-SE trending subsurface basement
highs (residual gravity anomalies shown on Fig. 9.2 ),
which they called the Kiri and Lonkonia highs. Daly et al.
( 1992 ) interpret two phases of deformation, first during the
Early Paleozoic, followed by reactivation of these structures
during the Late Paleozoic.
Outside of the Cuvette Centrale, little is known about the
structural geology of the basin. Most of the structures and
deformation are interpreted to be largely constrained within
the Paleozoic sequence, whereas the Mesozoic and Cenozoic
stratigraphy are grossly characterized as uniform and un-
disturbed across the basin. Although geological structures
are not indicated on the geological map of the Belgian
Congo by Cahen and Lepersonne ( 1951 ), the distribution
of pre-Mesozoic sequences and interpretation of satellite
imagery provides some new insights into the structural geo-
logy. For instance, the southern part of the basin is character-
ized by dominant

1.1 Ga and 0.9 Ga
(Raucq 1970 ; Cahen et al. 1974 ; Kadima et al. 2011a , b ;
Delpomdor et al. 2014, in press). The Mbuji-Mayi basin is
fault-bound and trends NW-SE, and projects, based on a
residual gravity anomaly (Kadima et al. 2011a , b ), below
cover sediments towards the Dekese, Gilson and Mbandaka

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fault orientations that are inferred