The Present Day Drainage Patterns of the Congo River System and their Neogene Evolution - Geology and Resource Potential of the Congo Basin - page 323

Table 15.3 The fluvial changes of in the Congo basin during the Neogene and Quaternary. The timing of events is based on age estimates
reported by phylogeographic studies.
Period Geomorphic event and time estimate Phylogenetic evidence

Neogene
Early to middle
Miocene

(1) Diversion of north eastern Congo of the
Aruwimi River headwaters drainage towards the Nile

(1a) “ Haplochromic ” species “Yaekama” is distributed in the
north eastern CRS near Kisangani but groups with Lake Victoria
superflocks (Schwarzer et al. 2012 ).
(1b) A sistergroup of modern haplochromines found in Lake
Kivu occurs in Lake Victoria (Schwarzer et al. 2012 )

(2) Major drainage re-organisations of central CRS
drainage flowing off the southern escarpment with:
(i) severance of connections between the Fwa, Inkisi
and Kiwul Rivers (rivers presently adjacent to
one another in south western CB);
(ii) disruption of the Sankuru-Lukemie system,
with diversion of present day Sankuru flowing into
the Kasai system

(2a) Close phylogenetic relationship of “ Haplochromis ” species
haplotypes of the Fwa-Inkisi-Kwilu Rivers (Schwarzer et al.
2012 )
(2b) Genetic markers of the Fwa “ Haplochromis ” closely related
to these in the mid-Kasai and mid-Kwango Rivers and; Fwa
haplochromides closely relates to “ H. ”cf bakongo and “ H. ”
snoeki from the lower CR system (Schwarzer et al. 2012 )

Late Neogene

(3) Partial re-arrangement across the headwaters of the
Lufira, Kwango and Cuanza (an Angolan coastal basin)
systems; capture of Zamnezian headwaters by the Lufira

(3) Hybrid taxa of northern and southern Oreochromic
torrenticolo and Serranochromis sp. “red scales” that presently
occur either side of the Congo-Cuanza and Congo-Zambezi
divides (Schwarzer et al. 2012 )

(4) Approximately 4 Ma: Establishment of water flow
across the modern day lower rapids of the CR connecting
the CRS to the Atlantic Ocean (established by 5 Ma?)

(4) High level of cichlid flocks ( Steatocranus and Nanochromis )
diversification in the lower CR; these cichlids are endemic to
rapids (Schwarzer et al. 2011 )

(5) 3.1 Ma : Disruption of drainage between Lake
Tanganyika and Lake Victoria/East Africa drainage

(5) Phylogenetic dating of the timing of divergence of
Hydrocynus tanzania and H. vittatus (Goodier et al., 2011 )

Quaternary
Pleistocene (6) 2.5-1.5 Ma: Establishment of the 'modern', sickle

shape of CR is established in the region of the Equator

(6a) Divergence date between chimpanzees occurring on the
northern and eastern banks of the Congo River with bonobos
restricted to an area inside the arc of the CR. Dates of 2.5-1.5 Ma
(Pr¨fer et al. 2012 ). See Fig. 15.8a
(6b) Divergence age between western and eastern gorillas of the
CB calculated to have been at 1.75 Ma (Scally et al. 2012 ). See
Fig. 15.8a

(7) 2.0 Ma: Separation of the Bangweulu and Lufubu
drainage systems from the upper-western CR tributaries

(7) Founding of Hydrocynus “clade B”, and “Clade C” diverges
from “Clade D” and H. vittatus ca. 2.0 Ma (0.8-3.0 Ma)
(Goodier et al. 2011 )

(8a) Speciation of Pseudocranilabrus “lufubu” (1.4-2.3 Ma)
(Koblm ¨ ller et al. 2008 ).
(8b) Divergence of Synodontis nigromaulata 2 from S.
nigromaculata3 (1.0-2.7 Ma) (Day et al. 2009 )

(8) 1.8 Ma: The Lufubu system is isolated from the
Bangweulu river system and flows into Lake Tanganyika

(9) 1.7 Ma: Major south to north flowing tributaries of
the Cuvette Central region are in place i.e. Lomami
River

(9) Two genetic markers of the guenons populations
( Cercopithecus lomamiensis and C. hamlyni) have been
estimated to be 1.7 Ma (3.2 Ma-0.5 Ma at 95 % confidence level)
and 2.8 Ma (4.3 Ma-0.6 Ma at 95 % confidence). C. lomamiensis
is separated from C. hamlyni by both the Congo and Lomami
rivers (Hart et al. 2012 ). See Fig. 15.8b

(10) 1.5 Ma: isolation of Lake Taganyika from the CRS,
with consequent establishment of the Lukuga River
outflow

(10a) Phylogenetic dating of the Hydrocynus population in Lake
Tanganyika compared populations in the Bangweulu system
(Goodier et al. 2011 )
(10b) Lukuga River appears to from a partial barrier between
two chimpanzee population (see Fig. 15.8a )

(11) 0.8 Ma: Establishment of the modern day Ogou´
River sands (Seranne et al. 2008 )

(11) Divergence date between southern and northern mandrills
(Telfer et al. 2003 ). See Fig. 15.8b