Overview of the Neoproterozoic Sedimentary Series Exposed Along Margins of the Congo Basin - Geology and Resource Potential of the Congo Basin - page 41

continental siliciclastic and rift-related volcanic
980-920 Ma Sansikwa Subgroup (Frimmel et al. 2006 ;
Straathof 2011 ); (ii) the 800-700 m-thick siliciclastic and
carbonate 800-650 Ma Haut-Shiloango Subgroup (Frimmel
et al. 2006 ; Poidevin 2007 ; Delpomdor and Pr´at 2013 ); (iii)
the 1,000-m-thick carbonate 575-550 Ma Schisto-Calcaire
Subgroup including cap carbonates, stromatolites and oolites
(Delhaye and Sluys 1923 ; Bertrand-Sarfati 1972 ; Frimmel
et al. 2006 ; Poidevin 2007 ; Straathof 2011 ; Delpomdor and
Pr´at 2013 ); and the approximately 1,000 m-thick red-bed
siliciclastic 566

1992 ) with cap carbonates and stromatolitic bioherms
(Bertrand-Sarfati and Milandou 1989 ); and (iv) red-coloured
siliciclastic Schisto-Gr´seux Group (Fig. 3.2D ).

3.3.1.4 The Angola Basin, Angola
Lying unconformably on the Lulumba and Uonde Eburnean
metasediments, and on the granitoids and gneisses of the
northwest Angola, the poorly constrained West Congo
Supergroup (Fig. 3.2E ) comprises from the youngest to
oldest (Stanton et al. 1963 ): (i) 2,400 m-thick siliciclastic
Terreiro Group; (ii) approximately 1,250 m-thick
siliciclastic and carbonate Alto-Chiloango Group; (iii)
approximately 2,000 m-thick carbonate sequence of the
Xisto-Calcario Group starting by 10-80 m-thick diamictitic
succession of the Upper Tilloid Formation capped by a cap
carbonate unit; (iv) and 3,250 m-thick exclusively
siliciclastic Xisto-Gresoso Group subdivided into M

42 Ma Ma Mpioka Subgroup (Frimmel
et al. 2006 ). Up to two diamictite units, i.e. the 400 m-thick
Lower Diamictite and the 200 m-thick Upper Diamictite
formations (Cahen and Lepersonne 1981 ), were interpreted,
respectively, as Sturtian (U-Pb age: 694 4 Ma; Straathof

2011 ) and Marinoan in ages. The overlying red-bed
siliciclastic Inkisi (Sub)Group (I) is reported late Paleozoic,
altough

' Pioka

the youngest detrital zircon grain yielded and Inkisi formations.

Neoproterozoic U-Pb ages of 851 56

Ma, respectively (Straathof 2011 ; Frimmel et al. 2006 ), or
Permian (Alvarez 1995 ) in ages.

18 Ma and 558

3.3.2 The Northern Margin of CS

3.3.1.2 The Nyanga-Niari Basin, Gabon
The Nyanga-Niari Basin comprises two distinct geologic
domains from west to east, i.e. the metasedimentary hinter-
land domain deposited on c. 1000-850 Ma magmatic
Mabouin´ and Mayumba complexes, and the poorly
constrained unmetamorphosed sedimentary foreland domain
(Thi ´ blemont et al. 2009 ). The hinterland domain comprises
the Loukoula Group, fluvio-glacial sedimentary M

The Neoproterozoic sedimentary rocks exposed on northern
margin of CS, are recognized in the Ubangui and
Fouroumbala-Bakouma basins of the south-western CAR,
and in the Lindi Basin of the northeastern DRC (Fig. 3.3A ).
Trompette ( 1994 ) considered all these basins to be part of the
Lindi Basin. Correlation is problematic due to limited num-
ber of studies, poor or non-existent age constraints, poor
outcrop conditions and accessibility. Diamictite units have
been recognized in all three basins. The best studied is the
Lindi Basin described in detail by Verbeek ( 1970 ), the
stratigraphy of which is summarized below.

' beia and

metasedimentary 713 49 Ma Louila formations ( idid ).

The unmetamorphosed internal domain (Fig. 3.2C ), i.e. the
Nyanga syncline, is divided into (G ´ rard 1958 ; Dadet 1969 ):
(i) the 100 m-thick fluvial Bouenza Formation resting on an
Archean basement (Prian 2008 ); the 0 m to 8 m-thick fluvio-
glacial Niari Group (B´chennec et al. 1981 ; Alvarez 1995 ;
Prian et al. 2009a ); (iii) the 400 m-thick dominantly carbon-
ate Schisto-Calcaire Group including a cap carbonate
(

3.3.2.1 The Lindi Basin, DRC
The Neoproterozoic Lindian rocks, up to 2,500 m in thick-
ness, rest unconformably upon the crystalline Archean and/
or Early Proterozoic basement and have undergone little or
no metamorphism. As summarized by Verbeek ( 1970 ) and
Trompette ( 1994 ), the Lindi Supergroup (Fig. 3.3B )is
divided into three groups, from base to top, as follows: (i)
the

), lithoherms, stromatolites and
oolites (Alvarez 1992 ; Prian et al. 2009a , b ; Pr ´ at et al.
2010 , 2011 ; Delpomdor and Pr´at 2013 ); and (iv) the red-
bed siliciclastic Schisto-Gr ´ seux Group.

' Dolomie de Bongolo '

100 m-thick marine carbonates (Daly et al. 1992 )of
the Ituri Group reported as terminal Riphean (Poidevin
2007 ); (ii) the unconformable

>

3.3.1.3 The Sangha-Comba basins, RC (Republic of
the Congo)
Lithostratigraphically, the West Congo Supergroup is
divided into, from oldest to youngest: (i) approximately
400 m-thick

500 m-thick siliciclastic
Lokoma Group starting with the 40 m-thick Akwokwo
Tillite capped locally by carbonaceous argillites interbedded
of cap carbonate lenses; and (iii) the 1,500 m-thick
siliciclastic Aruwimi Group, interbedded with oolitic
limestones and dolomitic lenses. The overlying

>

' '

Group
deposited directly on the Neoproterozoic Mayumbian Com-
plex in the western basin (Mayumbe) or on an Archean-
Paleoproterozoic basement in the eastern basin (Niari); (ii)
unconformable

Diamictites and Lower Sandstones

1,000 m-
thick red-bed siliciclastic Banalia Group, which apparently
conformably overlies the Aruwimi Group, is correlated with
the Inkisi Group of the Lower Congo region (Tait et al.
2011 ).

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600 m-thick carbonate Schisto-Calcaire
Group (Babet 1935 ; Scolari 1965 ; Dadet 1969 ; Alvarez

>