New Regional Correlations Between the Congo, Parana´ and Cape-Karoo Basins of Southwest Gondwana - Geology and Resource Potential of the Congo Basin - page 254

may possibly reflect a general (global) cooling and subse-
quent drying during the Cenozoic.

3. A Late Jurassic to Early Cretaceous phase of intracon-
tinental subsidence is most pronounced in the CB [Phase
3: 25 m/Ma], where it corresponds to deposition of the
fluvial-marine Stanleyville Group and the aeolian Dekese
Formation (~0.5 km thick). This relatively short phase of
subsidence is also distinct in the PB with the Botucatu
Formation (Milani et al. 2007 ), but is not uniformly wide-
spread in the CKB, where instead sedimentation is confined
to Jurassic-Cretaceous rift basins within the Cape Fold Belt
(e.g. the intramontain Enon Formation; Dingle et al. 1983 ).
In the CB, this phase of subsidence terminates by an epi-
sode of uplift at 120-140 Ma that coincides with active
rifting and shoulders uplift in the central South Atlantic
(Heine et al. 2013 ) and the onset of the Kalahari epeirogeny
in southern Africa, ca. 80-120 Ma (de Wit 2007 ).
4. Mid- to Late Cretaceous subsidence is restricted to the CB
[Phase 4: 10 m/Ma], corresponding to deposition of the
fluvial-lacustrine Loia, Bokungu and Upper Kwango
Groups (Linol 2013 ; Chap. 8 , this topic). This phase of
subsidence terminates by an episode of uplift at 30-50 Ma,
probably linked to the onset of doming along the EARS and
the Angolan Highland (e.g. Pik et al. 2008 ;Walfordand
White 2005 ).
To summarize, the related subsidence histories of the CB,
PB and CKB of southwest Gondwana indicate initial early
Paleozoic subsidence along the southwestern (paleo-Pacific)
margin of the supercontinent, followed by a Carboniferous
to Triassic cycle of subsidence (i.e. transgression and regres-
sion) common to all three basins and then, two final, Late
Jurassic and mid-Cretaceous short episodes of subsidence
best recorded in the CB (Fig. 13.15 ). This northward propa-
gation of subsidence shows progressively increasing uplift
of southwest Gondwana during the late Mesozoic.

13.5 Tectonic Subsidence Analysis

The calculated tectonic subsidence of basement of the CB,
PB and CKB (Zalan et al. 1990 ; Milani and de Wit 2008 ;
Chap. 11 , this Topic) are compared to test their interdependence
in the framework of a larger Central West Gondwana Basin
(CWGB) complex. Together, these three curves show the
existence of four main phases of rapid subsidence

(Fig. 13.15 ):
1. A first, Ordovician to Devonian phase of subsidence [Phase
1: 5-20 m/Ma] is most pronounced in the CKB (~2 km)
where it corresponds to deposition of the shallow marine
Cape Supergroup (Johnson et al. 2006 ). It is also visible in
the PB (~0.5 km), but is absent in the CB, suggesting an
episode of non-deposition and/or erosion in central Africa.
At this early Paleozoic time, the greatest regional subsi-
dence is focused along the southwestern margin of
Gondwana, as also recorded in the foreland basins of
Bolivia and Argentina flanking the Sierra de la Ventana
Fold Belt (e.g. Milani and de Wit 2008 ). In the PB and
CKB, this subsidence terminates more or less abruptly at
about 350 Ma with the onset of the Dwyka glaciation.
2. Carboniferous to Triassic accelerated subsidence [Phase
2: 10-15 m/Ma] is remarkably similar in all three basins
(Fig. 13.15 ). This second and longest (~150 million years)
phase of subsidence comprises, generally transgressive
Carboniferous-Permian glacial and deglaciation
sequences (e.g. the Dwyka and Lower Ecca Groups)
deposited during relatively low subsidence rates
[5-10 m/Ma], overlain by thicker and regressive
Permian-Triassic sequences (e.g. the Upper Ecca and
Beaufort Groups), deposited during increased subsidence
rates [10-20 m/Ma]. This regional phase of subsidence
across the CWGB complex overlaps in time with the
accretion of Gondwana to Laurentia to form Pangea,
during the Mauritanian-Variscan orogen at ca.
275-325 Ma (Lefort 1989 ; Dabo et al. 2008 ; Kroner and
Romer 2013 ), and extensive subduction-accretion pro-
cesses along the southwestern margin of Gondwana,
resulting in, for example, the Cape-de la Ventana orogen,
ca. 250 Ma (Trouw and de Wit 1999 ; Newton et al. 2006 ).
In the Karoo of southern Africa, this subsidence
terminates at about 180-200 Ma with aeolian sedimenta-
tion (the Eliot Formation; Johnson et al. 2006 ) and the
outpouring of the Karoo LIP during the initial break-up
between East and West Gondwana (e.g. Jokat et al. 2003 ).

Summary and Conclusion
Since the pioneer stratigraphic work of Du Toit ( 1926 ,
1927 , 1937 ), Robert ( 1946 ) and Cahen ( 1954 ) in south-
central Africa, and Keidel ( 1916 ) and Schneider et al.
( 1974 ) in Argentina and southeastern Brazil, it is now
established that the CB, PB and CKB episodically shared
tectonic continental-scale processes and climatic stabil-
ity, during and following the period of amalgamation of
Gondwana and Pangea, and during the subsequent period
of break-up of these two mega-continents. Comparison of
the stratigraphic records and subsidence histories of these
three large basins of Central West Gondwana (e.g.
CWGB complex) is consistent with interpretation that
all these basins were significantly influenced by far-field
processes during the evolution of long-lived mountain
systems along the southwestern margin of Gondwana--
Gondwanides (Fig. 13.4 ).