Geology Reference
In-Depth Information
Dekese
well
Samba
well
Lindi / E
margin
Age at
base (Ma)
Sed.
units
Stratigraphy
Kalemie
Lithology
Environment
Couches A
(
22
m
)
Quaternary
Superficial dep.
Fluviatile to
lacustrine
1,8
Couches 1
(69-86 m)
Neogene
23
O. Sands
Loose sand
Grès
Po
l
ymo
r
phe
Siliceous
sandstone
s
Basin closed by
m
a
r
gina
l
upl
i
f
t
Paleogene
65
Recent
erosion
E
r
osion
Erosion
Erosion
Erosi
o
n &
wea
t
hering
80
Senonian
Couches 2
(
82-107m)
Continental to
lacustrine
Late Cret.
Kwango
Tur. Ceno -
man
i
an
Loose sandstones
100
Unconfo
rm
ity
Local
tectonic Unconfo
rm
i
t
y
Late Albian -
Cenomania
Couches B
(439 m)
Couches 3
(372 m)
Sandstones -
siltstones
Continental to
lacustrine
Bokungu
112
Early- Mid.
Cretaceous
Undiff.
Cretaceous
Early Apt. -
Late Albian
Couches C
(
254
m
)
Couches 4
(280 m)
Sandstones -
mudstones
Aolian & shallow
lacustrine
Loia
145
Middle
Jurassic
Aalenian -
Bathonian
Couches 5
(
323
m
)
Stanleyville
(
4
70
m
)
Bituminous shales
& limestones
Shallow lacustrine
to lagunar - marine
161
Seismic
horizon
Base
Jurass
i
c unc
.
Fa
r
-
f
ie
l
d
tecton
i
c reactivat
i
ons
237
Red sandst. &
m
uds
t
.
E
T
B
H
L
Tropical climate
250
Tec
t
onic uncon
f
or
mi
ty ?
P.
-
T.
unc
.
Far
-
f
i
eld
t
ecton
i
c
react
i
va
t
i
o
ns ?
Seismic
horizon
Couches D-E
(146 m)
Lukuga
(coaliferous)
Coal-bearing
lacustrine basins
Perm.
Ecca
Black shales, coal
300
Pennsyl-
v
a
nian
Couches F-G
(816
m
)
Lukuga
(
l
oca
ll
y)
Lukuga
(gla
c
ia
l
)
Diamictites, varval
shales
Mountain glaciers
(3-4 oscillations)
Dwyka
318
Or
d
.
,
S
i
l
.
,
Dev.
Miss
i
ng
Se
i
smic horizon
CB in located close to South Pole
Aruwimi
Redbeds
(
1760
m)
Couches H
( >156 m)
Couches 6
(> 871 m)
Red arkoses &
black shales
Foreland basin -
Platform deposit
Early Paleozoic
542
TD: 1856 m
TD: 2038 m
Pan-
Af
r
ican
Peak of Pan-African assembly of
Gondwana
Pan-African unc.
Weak unc.
550
?
?
Lokoma
(470
m
)
Siliciclastics,
l
imestones
Ediacaran
Basement
Lagunar to marine
635
A
k
wokwo
Local un
c
.
Ituri
(130 m)
D
i
a
m
ict
i
tes
Marinoan
glacial
Possib
l
e
t
ec
t
on
i
c de
f
orma
t
ion
Cryogenian
Stromatilites,
Carbonates,
ev
a
pori
t
es
Marine?
750
Basement
Basement
Crystalline basement
Basement
Fig. 18.2
Schematic lithostratigraphy of the Congo Basin (modified from Kadima et al.
2011a
), based on the two stratigraphic wells (Samba and
Dekese) and outcrop data in in the northeastern and eastern margins of the basin
subdivided successively from base to top into: the
Galamboge arkoses and quartzites (100-150 m); the Alolo
dark carbonaceous shales (350-400 m); and the Banalia red
arkoses (up to 1,200 m), with ~ 100 m thick transitional
units between them (Verbeek
1970
). The Alolo shales are
interpreted to have been deposited in a shallow marine to
lagoonal basin (Verbeek
1970
). The Aruwimi Group is ten-
tatively correlated to the Inkisi post Pan-African fluvio-
deltaic red sandstones in the West Congo Belt (Alvarez
et al.
1995
; Tait et al.
2011
), the Biano red sandstones in
the Kundelundu foreland of the Katanga Fold Belt
(Kampunzu and Cailteux
1999
) and the red sandstones of
the lower parts of the Samba and Dekese wells (Cahen et al.
1959
,
1960
). Using refractions seismic velocities, Evrard
(
1960
) recognized the similarity between the red sandstones
in the lower part of the Samba and Dekese wells, but did not
exclude that they could be younger than the red sandstones
of the Aruwimi, Inkisi and Biano Groups. This correlation is
based on lithological similarity (quartzitic red sandstones),
taking also into consideration the fact that these series are all
post-orogenic relative to the Pan-African deformation. In the
Dekese well, the red sandstones are overlain by glacial-
interglacial and post-glacial sediments of the Lukuga
Group (from the depths of 816 m and 146 m, respectively),
dated to be Late Carboniferous-Permianin age (Cahen et al.
1960
; Boze and Kar
1978
; Cahen and Lepersonne
1978
).
The age of the Aruwimi Group is therefore constrained only
by a regional unconformity at the base, and by the Upper
Paleozoic sediments of the Lukuga Group on top, spanning
the
entire Early-Middle
Paleozoic. No
prominent
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