Geology Reference
In-Depth Information
3
Overview of the Neoproterozoic Sedimentary
Series Exposed Along Margins of the
Congo Basin
Franck Delpomdor and Alain Pr ยด at
3.1
Introduction
exposed on the eastern margin of the CS; (iv) the Katanga
and Mbuji-Mayi supergroups along the southern margin of
the CS.
The Neoproterozoic (1000-542 Ma) is an important Era in
the Earth history, because it records a complete cycle of
supercontinent break-up and re-assembly from Rodinia to
Gondwanaland, during which major climatic fluctuations
occurred, e.g. several recurring ice ages as part of the Snow-
ball Earth hypothesis (Kirschvink 1992 ; Hoffman et al.
1998 ; Hoffman and Schrag 2002 ) and the emergence of
Metazoans (Knoll 1992 ; Narbonne 2010 ; Erwin et al.
2011 ). The Central African Shield consists of several tec-
tonic blocks of Archean age amalgamated during the
Mesoproterozoic, whilst the margins of the Congo Shield
(CS) consist of mid-Neoproterozoic back-arc type rifts that
briefly opened and closed during this supercontinental cycle
(e.g. De Waele et al. 2008 a, b; Begg et al. 2009 ; see also de
Wit and Linol 2014 ).
In the light of this general tectonic configuration, we aim
here to synthetize the sedimentology, geochemistry and
paleogeography of the Neoproterozoic sequences flanking
the CS. The series belong to: (i) the West Congo Supergroup
that extends along the western margin of the CS from Gabon
in the north to northern Angola through the Democratic
Republic of the Congo (DRC) and the Republic of the
Congo (RC); (ii) the Lindi Supergroup of the Lindi/Ubangui
and Fouroumbala-Bakouma exposed along the northern
margin of the CS in the Central African Republic (CAR)
and DRC; (iii) the Itomwe and Malagarazi supergroups
3.2
Structural Regional Tectonic Framework
The CS (Fig. 3.1 ) comprises several Archean nuclei welded
during the Eburnean orogeny approximately between
2.1-1.8 Ga (Pinna et al. 1996 ; Noce et al. 2007 ; De Waele
et al. 2008 a, b; Delor et al. 2008 ; Begg et al. 2009 ; de Wit
and Linol 2014 ), and forming a coherent block throughout
Late Paleoproterozoic and Mesoproterozoic times (Linol
et al. 2014 ). The late Mesoproterozoic period (1.3-1.0 Ga)
is marked by the assembly of the Rodinia supercontinent
(Piper 1976 ; Bond et al. 1984 ; McMenamin and
McMenamin 1990 ; Dalziel 1991 ; Hoffman 1991 ; Karlstrom
et al. 1999 ). However, the exact configuration of various
elements, e.g. the CS, surrounding Rodinia is still not clear
(Dalziel 1997 ; Piper 2000 ; Sears and Price 2000 ). Nonethe-
less, palaeomagnetic data suggested that the CS was inde-
pendent of Rodinia in the late Mesoproterozoic (Pisarevsky
et al. 2003 ) and joined only its south-eastern margin, facing
Laurentia at c. 1.0 Ga (Hoffman 1991 ; Li et al. 2004 , 2008 ).
During this time-span, the southern and eastern margin of
the CS was characterized by the Kibaran orogen
(1.4-1.0 Ga) related to the accretion of the CS and
Tanzania-Bangweulu-Kalahari cratons (Pinna et al. 1996 ;
Fernandez-Alonso et al. 2012 ), and the amalgamation of
microcontinental belts (Southern Mozambique, Sinclair
zone, Gordonia, Namaqua) between the proto-Zambezi
orogen and the northern Kalahari Craton, ending with a
collision along the Irumide orogen at c. 1.02 Ga (De Waele
et al. 2003 ; De Waele 2005 ; Johnson et al. 2005 ; Begg et al.
2009 ). In the southeastern margin of the CS, the fragmenta-
tion of Rodinia started around 880-850 Ma with the
emplacement of magmatic rocks (Tack et al. 1984 ; Porada
and Berhorst 2000 ; Mbede et al. 2004 ; Armstrong et al.
 
Search WWH ::




Custom Search