Neoproterozoic to Lower Paleozoic Sequences of the Congo Shield: Comparisons Between the Congo and Its Peripheral Basins - Geology and Resource Potential of the Congo Basin - page 98

assigned to the late Precambrian (Cahen et al. 1960 ; Verbeek
1970 ; Lepersonne 1974 ), although some researchers
recognized parts could also be early Paleozoic in age (Evrard
1957 ). Subsequently many authors have tried to define the
Neoproterozoic-Paleozoic transition in the basins
surrounding the CB on the basis rather of structural criteria
in Katanga and West Congo; and on the basis of lithological
correlations with the Lindian Supergroup (Kampunzu and
Cailteux 1999 ; Porada and Berhorst 2000 ; Master et al.
2005 ; Tack et al. 2008 ; Tait et al. 2011 ).
In West-Congo and Katanga, where these Redbeds occur
along the tectonic fronts of the West-Congo and Lufilian
fold belts, and from there extend towards the CB into their
foreland, structural relations with reference to a supra-
regional late Pan-African unconformity have been used to
distinguish the red sandstones as both pre- and post-dating
Pan-African deformation. In the West-Congo belt, for exam-
ple, the Pan-African deformation has been dated at

566 42 Ma, the age of metamorphism of a dolerite sill

that intrudes the Haut Shiloango Subgroup and the Inkisi
Subgroup redbeds (Alvarez 1999 ; Tack et al. 2001 ; Frimmel
et al. 2006 ). The Inkisi Subgroup is therefore considered as
of latest Neoproterozoic to early Paleozoic age (Alvarez
et al. 1995 c; Tack et al. 2008 ; Tait et al. 2011 ). Recently,
Moni´ et al. ( 2012 ) determined that the West Congo belt of
Angola underwent two main deformation events of amphib-
olite grade at c. 540 and 490 Ma, followed by tectonically
assisted exhumation.
Similarly, in the Katanga basin, the sub-horizontal
siliciclastic sequences of the Biano (Plateaux) Subgroup
(uppermost subgroup of the Kudelungu Group) discordantly
overlie the folded Katanga units and are considered therefore
to be post Pan-African in age (Batumike et al. 2007 ;
Kampunzu and Cailteux 1999 ). The Lufilian Arc formed
during collision between the Congo and Kalahari Shields
between 650 and 530 Ma, with deformation peaking at ca.
550 Ma (Porada 1989 ; Hanson et al. 1993 ; Kampunzu and
Cailteux 1999 ; Porada and Berhorst 2000 ; John et al. 2004 ;
Frimmel et al. 2006 ). Detrital muscovites from the Biano
Subgroup have a maximum Ar/Ar age of 573

Fig. 6.2 ( a ) Seismic-stratigraphy of sequence on a section of seismic
profile R5, showing six depositional sequences, two unconformities and
the calibrated trace of Mbandaka-1 well as identified in this chapter.
TWT: Two Way Travel-time (TWT in seconds). Vertical black line :
position of the well, red crosses : base of the seismic sequences
(corresponding depth in Table 6.2a ). CDP 2231: Common Depth
Point location. ( b ) Time-Depth curve obtained from the CDP location
2231 along line R05, near the Mbandaka-1 projected trace well. The
curve shows the bottom limit of the different seismic sequences and the
well TD (4,350 m). Crosses: CDP data from Table 6.1a . The
depth-time curve was constructed by a polynomial interpolation of
the CDP data. Empty squares: depth-time plot of the base of the
seismic sequences from data of Table 6.2a

5 Ma at the
top of the Katanga Supergroup (Master et al. 2005 ), while
the minimum age of the Biano Subgroup is estimated as
younger than 540 Ma (Kampunzu and Cailteux 1999 ). This
suggests that at least some of the Biano sequences may have
been deposited during the Cambrian (Kipata 2013 ).
In the sub-horizontal intracratonic Lindian Supergroup
along the northern margin of the CB, no clear angular dis-
cordance has been observed within the Aruwimi Group, but
the Banalia red sandstones that form the upper part of this
group, have been correlated lithostratigraphically with the
Inkisi Group in West-Congo and the Biano (Plateaux) Sub-
group in Katanga (Alvarez et al. 1995 ; Tack et al. 2008 ; Tait
et al. 2011 ), but there are no direct age constraints.

Clearly throughout the Congo Shield, robust correlations
between RedBeds

sequences require more precise

chronostratigraphy.

6.3 Structure and Stratigraphy of the Deep

CB Based on Geophysics and Well Data

Since most of the CB is not accessible to direct observations,
geophysical investigations can complement the surface geo-
logy observations described above. Here we summarise