Overview of the Neoproterozoic Sedimentary Series Exposed Along Margins of the Congo Basin - Geology and Resource Potential of the Congo Basin - page 48

3.4.2 Regional Correlations

sequence related to the break-up of Rodinia (Tack et al.
2001 ; Thi ´ blemont et al. 2009 ), while the West Congolian
Group appears to represent passive margin siliciclastic and
carbonate platform deposits preserved in the foreland
domain of the WCB. The Sansikwa Subgroup represents
continued pre-glacial continental rifting (Frimmel et al.
2006 ). The time-equivalent Roan and BII groups are
interpreted as lacustrine or lagoonal systems (Cailteux
et al. 2007 ; see also Delpomdor et al. 2014 ), while the
Roan Group from Zambia appear to be marine. The
Musindozi and Mosso groups correspond, respectively, to
continental and lacustrine deposition, and the Kibago Group
to shallow-water molasse sediments in a foreland basin. The
Sturtian-equivalent glaciogenic and associated deposits
(well constrained at 715-680 Ma from IUGS Terminal
Neoproterozoic Subcommission 2005) accumulated in the
most part of basins, except in the Malagarazi-Bukoban
Basin. In the western margin of the CS, the Bouenza
Group represents a fluvio-lacustrine and pre-glacial environ-
ment (Alvarez 1995 ), and the upper part of the Haut-
Shiloango Subgroup is interpreted as a open-marine carbon-
ate unit recording a transgression on a passive margin, fol-
lowing a rift stage (Frimmel et al. 2006 ). The time-
equivalent Ituri Group represents lagoonal or shallow marine
platform type systems (Daly et al. 1992 ). A second global
glacial event, coeval with the Marinoan glaciation (well
constrained at 660-635 Ma from IUGS Terminal
Neoproterozoic Subcommission 2005) is marked by several
diamictites in each Neoproterozoic basins (Tait et al. 2011 ),
except in the SMLL Basin (Delpomdor et al. 2013 ). The
Schisto-Calcaire (Sub) Group and Bangui Group record a
transgressive marine system including distal to proximal
outer shelf, offshore barriers and lagoonal facies submitted
to hypersaline shallow subtidal and supratidal conditions,
with lagoonal setting colonized by stromatolites and
cyanobacterial mats (Alvarez 1992 ; Pr´at et al. 2010 ).
Locally, continental and fluvial environments are observed
at the top of these groups (Alvarez 1995 ; Lepersonne 1973 ).
The Upper Dja Series bas been recently reinterpreted as
Gaskiers-equivalent lacustrine or lagoonal systems in a
graben-like syn-rift basin, with limited sediment input and
episodic marine invasion (Caron et al. 2010 ). The Mpioka
Subgroup, Schisto-Gr´seux Group, Aruwimi and
Kundelungu groups accumulated in continental, lacustrine
to fluvio-deltaic semi-arid environments, and all are
interpreted as Pan African-related late-orogenic molasse
deposits (Frimmel et al. 2006 ; Cailteux et al. 2007 ; Heijlen
et al. 2008 ). In the light of more recent works, however, the
Inkisi Group and Biano Group are considered to be red-bed
sequences of post-Pan African and pre-Karoo age (Tait et al.
2011 ; see also de Wit and Linol 2014 ).

Available stratigraphic and geochronological data support
regional correlation (Fig. 3.7 ). The late Mesoprotero-
zoic-early Neoproterozoic BI Group has no stratigraphic
equivalent in Central Africa. Nevertheless, the ' Gr´so-

P ´ litique unit of the Lower Dja series is estimated between

1167 Ma and 850 Ma in age (Vicat et al. 1997 ), but no
correlation to date is possible with the BI Group of the
Mbuji-Mayi Supergroup. The 1000-910 Ma Zadinian and
Mayumbian groups are compatible in terms of age with the
Mabouin´ and Mayumba complexes in the hinterland
domain from Gabon (Thi ´ blemont et al. 2009 ). However,
the upper part of the Mayumba Complex, dated at 904

'

6
Ma (U-Pb ages on zircon from gabbro) may be correlated
with the 912 7 Ma Sansikwa Subgroup of the DRC

(Frimmel et al. 2006 ). The lack of age constraints does not
allow precise correlations between the Sansikwa Subgroup,
Loukoula and Terreiro groups and stratigraphic references.
Nonetheless, on the basis of lithological observations, the
Lower Diamictite Formation of the DRC and Angola may be
Sturtian in age, and correlated with the M Beia Formation,

reported to the Lower Tilloid Formation by D´vigne ( 1959 ).
In the southern and eastern margins of the CS, the isolated
Itombwe and Malagarazi-Bukoban supergroups also cannot
be correlated due the lack of age constraints. However, the
emplacement of intrusive sills of basalts in the Musindozi
and Mosso groups, dated between ca. 815 14 Ma and
709

'

2 Ma (De Paepe et al. 1991 ; Deblond et al. 2001 )
may be correlated with the 888.2 8.8 Ma dolerite sills at

the BI/BII Group transition or with the second igneous
sequences overlying the Mbuji-Mayi Supergroup
(Delpomdor et al. 2013 ); and with the magmatic rocks
(Kafue rhyolites [879 Ma]; Nchanga Granite [877 Ma];
Lusaka Granite [865 M]) and the 760-735 Ma Mwashya
Subgroup (Key et al. 2001 ) of the Katanga Supergroup.
The BII Group time-equivalent to the Upper Mines and
Dipeta subgroups of the Katanga Supergroup (Delpomdor
et al. 2013 ) is supported by C-isotopic and geochronological
data (Cahen et al. 1974 ; El Desouky et al. 2010 ; Bull et al.
2011 ; Delpomdor et al. 2013 ). The Kabele and Kabenga
conglomerates, considered as coeval with the Grand
Conglom´rat Formation (Cahen and Mortelmans 1947 ),
may be correlated with the Sturtian-equivalent Tshibangu
Formation and the Bandjia Tillitic Complex.
In Gabon, the Louila Formation in the internal domain, is
a lateral equivalent unit of the Bouenza Formation
(Thi´blemont et al. 2009 ), and is a correlative of the Haut-
Shiloango Subgroup (Chevallier et al. 2002 ), consistent with
a post-Sturtian deposition for the latter. Previously, it was
suggested that the base of the Lindi Supergroup, i.e. the Ituri