Geology Reference
In-Depth Information
250
200
150
100
50
0
(Ma)
TRIASSIC
JURASSIC
CRETACEOUS
PALEOGENE
NEOGENE
MIOCENE
PALEOCENE
EOCENE
OLIGOCENE
PLIO.
PLEIST.
SEDIMENTS
Kalahari Sands (
Kasai - Kwango Plateaus
) - Batéké Sands (
Batéké Plateaus
)
“Grès polymorphes”
“Sables ocres”
LEPERSONNE (1974)
Yangambi
Central “Cuvette”
deposits
PLANATION SURFACES
GONDWANA Surface
POST-GONDWANA Surface
AFRICAN Surface
POST-AFRICAN Surface
KING (1962)
Subsaharian Africa
[
highs of Western Highlands Cameroon and Western East African Rift
]
Western Highlands Cameroon, Adamawa and Ouadda Plateaus, Gabon highs, most W East African Rift
]
LAT E CARBONIFEROUS (315-310 Ma)
Surface III
Surface V Surface IV
time-equivalent Karoo basins
Surface II
Surface I
JESSEN (1936)
FEIO (1946)
Angola Plateau
MID-TERTIARY Peneplain
END T. P.
VEATCH (1935)
Congo Cuvette
above
”Sables ocres”
(= ”Grès polymorphes”)
LA
TE CRETACEOU
S Surface
below ”Grès polymorphes”
MID-TERTIARY Surface
above ”Grès polymorphes”
below “Sables ocres”
END T. S.
CAHEN & LEPERSONNE (1948) - CAHEN (1954)
LEPERSONNE (1949, 1956, 1978)
Congo Cuvette
above
”Sables ocres”
KISIBA
SALABWE S.
ALEXANDRE-PYRE (1971)
ALEXANDRE & ALEXANDRE-PYRE (1987)
ALEXANDRE (2002)
Congo Cuvette - Katanga
MITWABA Surface
LUBUMBASHI Surf.
KYOBO S.
(dated by analogy with Western Africa weatherings)
above ”Grès polym.”
below “Sables ocres” (= Intermediate Surface)
(= High Glacis)
(= Middle
Glacis)
MINIM-MARTAP
BAMILEKE Surfaces
MEIGANGA MANDAR
BAMOUN Surfaces
CAMEROON INTERIOR Surface
SEGALEN (1967)
Cameroon
(= King's Gondwana I)
(= King's Gondwana II or Post-Gondwana)
(= King's African I)
LIM-BOCARANGA Surface
BOUAR-BABOUA Surface
CENTRAL AFRICAN Surface
BOULVERT (1985, 1995)
Central African Republic
(= Minim-Martap Bamiléké S.)
(= Meiganga Mandar Bamoun S.)
(= Cameroon Interior Surface)
LIM-BOCARANGA Surface
BOUAR-BABOUA Surface
CENTRAL AFRICAN S.
PIEDMONTS
TARDY & ROQUIN (1998)
Western Africa - Central African Republic
CHARDON et al. (2006)
BEAUVAIS et al. (2008)
BEAUVAIS & CHARDON (2013)
Western Africa - Burkina Faso
(= Intermediate Surface)
(= High Glacis)
(= Middle
Glacis)
BAUXITIC Surface
AFRICAN Surface
INTERMEDIATE
Surface
HIGH
Glacis
MEDIUM
Glacis
LOW
Glacis
(radiometric dating of laterites:
39
Ar-
40
Ar plateau ages of K-Mn oxides)
THIS STUDY
1:
“Grès polymorphes” Fm
/
2:
Upper P. Surf. 1
4:
Low. Surf.
/ 5:
Pedim. VW
6:
Pediments X - Y - Z
3:
Upper Surface 2
Fig. 14.2
Summary of the previous stratigraphic and geomorphologic studies carried out in the CB and surrounding highs—comparisons with the
dated planation surfaces of West Africa and the results of this study
”
based on fossils (ostracodes, gastropods and characeans)
found in silicified lacustrine carbonates (Katanga and
Kasai). The ages provided by Leriche (
1925 1926-1927
,
1927
—summary in Polinard,
1931-1932
) were inconsistent:
changing from Cenozoic (Late Pliocene to Quaternary—on
gastropods in 1925), but then revised to Purbeckian
(Jurassic-Cretaceous boundary—on characeans in
1926-1927). A subsequent biostratigraphic study (Grekoff
1958
) on ostracodes, attributed an Eocene to Oligo-Miocene
age to the
“
Gr
`
s polymorphes
The only dated sediments are the
14.2
Previous Studies
Three successive Cenozoic sedimentary units are defined
in the CB (e.g. Lepersonne
1974
—Fig.
14.2
): (1)
“
Gr`s
polymorphes
(Neogene
before Late Pliocene) and (3) Yangambi and Lodja-Salonga
Beds (Plio-Pleistocene to Neogene). The first two, grouped
as the Kalahari Sands (Maufe
1928-1929
; Cahen and
Lepersonne
1952
; Polinard
1954
)orBat
´
k
´
Sandstones
(Le Mar´chal
1966
; Giresse and K
”
(Paleogene), (2)
“
Sables ocres
”
Vadec
1971
), crop out
in the southern (Katanga, Kasai and Kwango Plateaus) and
western (Bat´k´ Plateaus) parts of the CB, while the third
ones are restricted to the central part of the CB. These three
lithological units are all incised by rivers during Pleistocene
times (e.g. Lepersonne
1974
).
'
. Later still, Colin (
1994
)
confirmed an Eocene age on the basis of characeans occur-
rence. In Angola, some isolated outcrops ascribed to the
“
Gr`s polymorphes
”
were dated as Pleistocene based on
gastropods,
“
Gr`s polymorphes
”
ostracodes
and
characeans
(Mouta
and
Dartevelle
1954
).
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