Geology Reference
In-Depth Information
Lithostratigraphy
Biostratigraphy
C
Sf
S
m
ScSG
r
P
B
800 m
Pseudestheria malangensis
MARLIERE (1950),
Bairdestheria-Estheriella moutai
LERICHE (1932),
Glyptoasmussia luekensis
DEFRETIN (1967),
Echinestheria amrimbensis
MARLIERE (1950),
Palaeolimnadiopsis lubefuensis
DEFRETIN (1967)
Red sandstones
Massive or cross-bedded,
with mudstone intercalations
700 m
Red sandstones and
mudstones
Sporae dispersae
BOSE & KAR (1976)
Formation “transition”
Varicoloured claystones and
siltstones
Glossopteris indica
SHIMP. (abundant)
Phyllotheca australis
BRONGN.,
Gangamopteris
(rare)
600 m
Formation with coal beds
Alternations of grey mudstones
and psammitic sandstones
Glossopteris
(apparition)
Walkomiella fragilis
HOEG & BOSE,
Gangamopteris
500 m
400 m
Lukuga black shales
Massive or laminated black
shales, locally disseminated
pebbles
Cyclodendron leslii
KRAUSL. (abundant)
Gangamopteris
300 m
Upper, mainly glacial beds
Grey tillite and red-yellow
sandstones with plant remains
Gangamopteris cyclopteroides
FEISTM (abundant)
Mainly periglacial and
inter-glacial beds
Black shales with pebbles,
soft-sediment deformations,
and locally calcareous nodules
200 m
Gangamopteris cyclopteroides
FEISTM (rare)
100 m
Lower, mainly glacial beds
Tillite with matrix of grey-red
sandstones and large pebbles
and boulders, locally cross-
stratifications
0 m
Fig. 7.2
(
A
) Map of Carboniferous-Permian and Triassic sequences of
the CB, showing their vast extent in subsurface (as inferred from
borehole and seismic data), and (
B
) stratigraphic type-section along
the eastern margin of the basin (reconstructed from descriptions
summarized in Cahen and Lepersonne (
1978
) and Cahen (
1981
)); see
Figs.
7.4
and
7.10
for lithologic and biostratigraphic symbols. Seismic
profiles A-B and C-D (
thick black lines
) are re-interpreted in Fig.
7.6
and
7.8
, respectively
basement in the east (e.g. the Kibaran Belt), and is
estimated to be between 100 m to 300 m thick in total,
mainly based on the field studies of Fourmarier (
1914
),
Jamotte (
1932
) and Boutakoff (
1948
).
2. The Upper Subgroup is known in more detail because of
coal exploration and mining (Cahen and Lepersonne
1978
). It includes 120 m thick black shales (
The Lukuga Group is dated by paleobotany from the
Carboniferous to the Upper Permian (Bose and Kar
1978
).
This compares well with other records of the late Paleozoic
glaciation of Gondwana, such as the Dwyka and Ecca
Groups of southern Africa (Johnson et al.
2006
; Isbell et al.
2008
). The lowermost glacial sediments are difficult to date
accurately, however, in southern South Africa uppermost
beds (the Waaipoort Formation) underlying the Dwyka
Group contain plant remains no older than Middle
Tournaisian (350 Ma) and have dropstones and soft sedi-
ment deformation structures of glacial origin (Streel and
Theron
1999
; Opdyke et al.
2001
). Thus, the onset of the
glaciation in southern (and central) Africa is likely to be
'
the Lukuga
Black Shale
), overlain by a 20 m to 125 m thick formation
of sandstones and mudstones with thin coal beds, and then
a
'
of varicolored mudstones,
between 30 m and 65 m thick. The top of this sequence
is an erosion surface, covered by a conglomerate bed at the
base of the Haute Lueki Group.
'
Transitional Formation
'
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