Geology Reference
In-Depth Information
Table 14.5
Relative chronology, characteristics, synonymy and age of the landforms of the Katanga Plateaus and Plains
RELATIONSHIPS WITH
THE OLDEST FORM
ELEVATION
RELIEF FORM-WEATHERING (W.)
SYNONYMY AGE
Congolese Surface
(
C, Cd
)
1,700-1,400 m
(Katanga)
1,200-1,000 m
(Kasai-Lunde-
Kwango)
Top « Gr`s polymorphes» Fm planation surface, covered (veneered) by the «Sables ocres» Fm
Katanga (Kundelungu, Kibara, Biano Plateaus)—Kamina, Kasai (
Katanga to Kwango Plateaus
:
The Congolese
Surface, slightly erosional on the top of the «G`s
polymorphes» Fm is younger than those aeolian
deposits dated Paleogene and probably Eocene
(see text)
¼
Cassai in Angola), Lunde and
Kwango Plateaus
slightly domed—present-day Congo-Zambezi divide, from the Muchinga Mountains (Zambia) to
the Angolese Plateau
Detailed evolution in Katanga (Alexandre-Pyre
1971
; Alexandre and Alexandre-Peyre
1987
;
Alexandre
2002
—see Sect.
14.4.1.2
)
1. Low erosion (
10 m?) of the
“
Gr`s polymorphes
”
Fm and weathering by iron duricrust 1
(pisolitic)—degraded Kisiba Salagwe Surf
2. Low erosion, removal of most of duricrust 1 and deposition of a fluvial gravels bed (
“
cailloutis
des plateaux
)
3. Weathering by iron duricrust 2 (red shinning coating), both on the gravels bed and surrounding
basement rocks Mitwaba Surf.
4. Draping by the
”
“
Sables ocres
”
Fm
Congolese Surface
degraded by the
Lower P. Surface
(
Cdl
)
1,500-1,200 m
Same polygenic planation surface than
C
(based on maps of Alexandre and Alexandre-Peyre
1987
;
Alexandre
2002
)
- Not veneered by «Sables ocres» Fm
- Degraded by pedi-valleys and rivers of the Lower planation surface (
l
) and Pediment Xc
Biano, Kibara, Kundelungu, Mporokoso Plateaus - north of the Congo-Zambezi divide
w.
: relicts of Iron duricrusts 1 and 2
Lower degraded
Planation Surface
(
ld
)
Highly degraded pediments by incised rivers of
X
c
Possible equivalent of
ld
(difficult mapping from
the NE Mitumba Mounts)—Pediments V and W
not impossible
w.
: no published descriptions
Progressive or sharp—scarps
200-300 m
Pediments X
(
X
c
,X
f
)
Pediment systems: three large pedi-valleys
(width: 50-200 km) passing upslope to smaller
pedi-valleys (w.: 10-20 km) and then to
connected incised valleys (
X
f
) degrading the
Lower planation surface (
l
)
Kamalondo (Upemba) Depression, Lu_ra Plain,
Mweru-Luapula Plain
w.
: iron duricrust 3 (Alexandre
2002
), dark
brown shinning coating
Deply incised scarps
500 m
X
f
network extends 100 to
200 km far upstream of the pedi-
valleys
Lubumbashi
Surface
(Alexandre
2002
)
Kolwezi - Lubumbashi area
(Kawama,
Kasompi, Luishiwi): On the Congolese Surface
(
Cdl
) degraded by
l
and
X
f
, oxidized manganese
ores (
), dated by
39
K-
40
Ar (Decr
´
e
et al.
2010
), range from 10.3
0.1 Ma to
2.3
0.17 Ma (five ages: 10.3, 5.3, 3.66, 3.54,
2.30) confirmed by an U-Pb age on supergene
heterogenites at 3.1
4 Ma. That implies:
- A major uplift, before 10.3 Ma
- Minor uplifts, between 10.3 and 3.66 Ma or
between 10.3 and 5.3 Ma and 5.3 and 3.66 Ma
Our interpretation
:
Major uplift
¼
deep incision of pediment
X
c
Minor uplifts
¼
incision of
Y
c
(and may be
Z
c
)
“
cobalt cap
”
Pediments Y
(
Y
c
)
Pedi-valleys superimposed on previous
Pediments X
w.
: iron duricrust 4 (Alexandre
2002
), ochre dull
coating
Low amplitude incision
- Highest (SE Kamalondo):
50-100 m
- Lowest (Lu_ra and Mweru
Plains)
Kyobo
Surface
(Alexandre
2002
)
Incised channels
and rivers
time-equivalent of
X
c
Y
c
Z
c
- Outlets betwen two pedi-valleys (
X
c
-Y
c
)
Luvua River (between Kibara and Masseba
Plateau) Lu_ra River (between the Biano and
Kibara Plateaus)
Incision: 200-500 m
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