Multiphase Phanerozoic Subsidence and Uplift History Recorded in the Congo Basin: A Complex Successor Basin - Geology and Resource Potential of the Congo Basin - page 218

Groups were deposited during a second, slower main Epi-
sode B of subsidence that includes two distinctive phases of
subsidence (Fig. 11.5 ): during the Late Jurassic to Early
Cretaceous (10-50 m/Ma), and during the middle to Late
Cretaceous (10-15 m/Ma), separated by episodes of uplift at
160-180 Ma, 110-140 Ma and 30-50 Ma (Fig. 11.6 ). The
lower, shallow marine to fluvial Stanleyville Group, 320 m
thick at Samba in the northern part of the basin, and the
overlying aeolian Dekese Formation, maximum 300 m thick
at Dekese in the south-central CB, record the first phase of
regression and desertification during the Late Jurassic to
Early Cretaceous (Fig. 11.7c ). Succeeding a hiatus and/or
erosion of about 25 million years, the overlying middle and
Upper Cretaceous fluvial-lacustrine Loia, Bokungu and
Upper Kwango Groups, maximum 650 m thick in the
Samba and Mbandaka sections (Fig. 11.3 ), record the second
phase of subsidence and regression of the CB (Fig. 11.5 ). It
is terminated by a regional uplift during the early Cenozoic
that corresponds to limited preservation of the Kalahari
Group (Fig. 11.7d ), possibly linked to the Kalahari epeirog-
eny (de Wit 2007 ) and the onset of doming of the Angolan
Highland and along the East African Rift System (EARS),
ca. 30-40 Ma (e.g. Walford and White 2005 ; Pik et al. 2008 ).

subsidence of the CB possibly linked to long wavelength
flexural loading of the Gondwana continental lithosphere
related to the Mauritanian-Variscan orogen (ca.
325-275 Ma; Dabo et al. 2008 ; Van Staal et al. 2009 ;
Kroner and Romer 2013 ; Chap. 13 , this Topic) during
amalgamation of Gondwana into Pangea, and the Cape-
de la Ventana orogen (ca. 245-278 Ma; Newton et al.
2006 ), as it has been proposed for the main Karoo and
Paran ´ Basins of south-western Gondwana (e.g. Daly
et al. 1992 ; Pysklywec and Quintas 2000 ; Milani and de
Wit 2008 ; Fig. 11.8 ).
2. Two late Mesozoic phases of subsidence of the CB (at
140-160 Ma and 60-110 Ma), with calculated rates rang-
ing between 10 and 50 m/Ma, are separated by three
regional episodes of uplift at 160-180 Ma (e.g.
'

Karoo ), 120-140 Ma (e.g. Paran´-Etendeka ), and

' ' '

30-50 Ma (e.g. ). These episodic uplifts are

coeval with continental rifting and the successive out-
pouring of Large Igneous Provinces (LIPs, or hotspot
plumes) associated with the opening of the Indian and
South Atlantic Oceans during the main period of
Gondwana break-up (e.g. Jokat et al. 2003 ; Torsvik
et al. 2012 ; Heine et al. 2013 ), as well as the Late Creta-
ceous Kalahari epeirogeny (de Wit 2007 ), and the Ceno-
zoic onset of doming of the Angolan Highland and EARS
(e.g. Walford and White 2005 ; Pik et al. 2008 ).
In conclusion, this multiphase Phanerozoic history of
the CB suggests that initial basin subsidence was linked
to the Carboniferous-Permian glaciation/deglaciation of
Gondwana and its accretion to Laurentia (Europe and
North America) to form Pangea during the Mauritanian-
Variscan orogen (280-330 Ma; Dabo et al. 2008 ; Kroner
and Romer 2013 ), and further amplify by following
Permian-Triassic deformation during the Cape-de la
Ventana orogen (ca. 250 Ma;) along the southern margin
of Gondwana (Daly et al. 1992 ; Trouw and de Wit 1999 ;
Newton et al. 2006 ; Milani and de Wit 2008 ). Subsequent
(late Mesozoic) intermittent phases of subsidence
recorded in the CB most likely related to extensional
tectonic, marginal uplifts and the successive cooling of
LIPs around Africa (Fig. 11.8 ). Although it appears diffi-
cult to relate these phases of subsidence to specific events,
it is clear from this study that the initiation and develop-
ment of the CB related to both geodynamic and global
climate processes during the formation and break-up of
the Pangea supercontinent.

Ethiopian

' '

Discussion and Conclusion
A large number of driving mechanisms have been pro-
posed for the formation and development of the CB: (1)
long-lived tectonic uplift along its margins, (2) long-lived
thermal subsidence following an initial phase of late
Precambrian rifting, (3) long-lived dynamic subsidence
related to the effect of a high-density lithospheric mantle
root, (4) long-lived lithospheric delamination, and (5)
long-lived dynamic topography due to downward flow
within the mantle (Sahagian 1988 ; Hartley and Allen
1994 ; Downey and Gurnis 2009 ; Crosby et al. 2010 ;
Kadima et al. 2011 ; Buiter et al. 2012 ). All these models
assume a single long (~700 million years) and extremely
slow (ca. 2-4 m/Ma) subsidence history of the CB since
the Neoproterozoic. However, our new subsidence analy-
sis, based on revised sedimentological and stratigraphic
data from the four historic deep boreholes drilled in the
center of the basin (Fig. 11.3 ), reveal that the geodynamic
evolution of the CB is much more complex, including at
least two main episodes of rapid subsidence (ca. 5-20 m/
Ma), punctuated by multiple uplifts (Figs. 11.5 and 11.6 ):
1. Late Paleozoic to early Mesozoic accelerated subsidence
(180-350 Ma), with a calculated rate of 10-20 m/Ma,
follows a prolonged erosional hiatus in the central CB.
This long (~150 million years) erosion time-interval was
possibly associated with the successive, Ordovician and
Carboniferous Gondwana ice-sheets that covered much
of central Africa (e.g. Visser 1995 ; Ghienne 2003 ).
Thereafter, the first and most pronounced episode of

Acknowledgments We acknowledge funding through the Inkaba
yeAfrica and !Khure Africa programs, supported by the DST/NRF of
South Africa. We thank Anthony Tankard and an anonymous referee
for critical reviews that improved the chapter. This is AEON contribu-
tion number 130 and Inkaba yeAfrica contribution number 100.