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In-Depth Information
a
Dekese
Gilson
Samba
Mbandaka
Isosurface 2400 m/s
Isosurface 3600 m/s
NORTH
Isosurface 4200 m/s
b
337 km
360 km
North
185 km
South
Mbandaka (well log)
Samba (core)
Gilson (well log)
Dekese (core)
C SfSmS cS Gr P
C S
fS mS cS Gr P
C S
fS mS cS Gr P
C
SfSmS
cS
Gr
P
0 m
0 m
0 m
0 m
D1
S1
Kalahari Group
M1
100 m
100 m
100 m
100 m
G1
D2
S2
200 m
200 m
200 m
200 m
M2
S3
Cretaceous red-beds
G2
Fig. 10.11
(continued)
Gilson-1 and Mbandaka-1 wells (Fig.
10.11b
), based on
freshwater ostracods (
Potamocypris?
sp.,
Eucypris
sp.,
Cyprinotus
sp. and
Cypridopsis
sp.) and charophytes
(
Grambastichara
) that can be tentatively correlated to the
'
have been derived also from the calcretized Kalahari cara-
pace (
'
Polymorph Sandstones
'
).
10.5
Regional Correlation and Synthesis
Polymorph Sandstones
'
(Colin
1981
; Colin and Jan du
Ch
ˆ
ne
1981
).
In summary, seismic and borehole correlations identify a
vast extent of fluvial sediments of the Kalahari Group in the
center of the CB. This succession contains relatively abun-
dant pebbles of silcrete and calcrete, similar
Across the central Kalahari (in Botswana and Namibia), a
distinct, condensed sequence (10-100 m thick) of calcretes
(the Nxau-Nxau and Etosha Calcrete Formations) cap a
regional unconformity across Precambrian basement, the
(Carboniferous-Triassic) Karoo Supergroup, and Upper
to those
observed in the Kwango Valley, and which we interpret to
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