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Post-Gondwanan continental sedimentation, Limpopo region, southeastern Africa
Journal
of African
Vol.
Earth Sciences,
Pergamon
23, No. 2, PP. 163.187,
PII: SO899-5362(96)00060-7
0899-5362196
Post-Gondwanan continental sedimentation, Limpopo region, southeastern Africa
G. A. BOTHA’ and M. C. J. DE WIT2 ‘Council for Geoscience, 2Anglo-American
P.O. Box 900, Pietermaritzburg, 3200, South Africa Research Laboratories IPty) Ltd, PO Box 106,
Crown
Abstract-The
post-Karoo
Formation,
is currently
Singuedeze/Elefantes’ Africa,
breakup
and within
systems
active
followed
the extensional
tectonics valleys.
an eastward
sandstones
and conglomerates,
units comprising
succession
alluvial
exposed possibly
developed
within
plain.
comprising
coarse-grained off areas
in the
Olifants
sandstone,
River
units
for an indication accumulation Late
relationships
landsurface
sediments
Resume-Sit&e se partagent Formatron
formation, vastes
I’exrstence
en bordure
coalescents
La sedimentation ainsi qu’a
suggere
du continent
la tectonique
in
palaeosols on the broad
depositional
interbedded
units
with very generated
d’une
surface
des vallees proto-Limpopo
autrefois
Beds’.
majeurs
formee
associes
La Formation
de
de Sena’,
resultent
d’une
en voie de
jalonnant
a tectonique
sur de
active
du
a Cenozo’ique
precoce,
par des cones
alluviaux
d’inondation.
associee au volcanisme
la bordure
de Malonga
Ltd.
et le Zimbabwe
a des plames
eustatique
affectant
of littoral and
africain
Ce type de sedimentation,
de Piedmont
‘African’
The Eocene
sous le nom
Ces roches
tardif
during the
the
‘Formacao
du continent
dans les vallees
valley
period of
Elsevier Science
connue
de Malonga,
orientale
et au rifting
et Zambeze.
and deposition
du Sud, le Mozambique
a la longue periode de remontee d’extension
ceased with
Copyright D 1996
du Mesozo’ique
fluviatiles
apparently assocrated
Formation
Plateau
septentrional
accepted
prior to the Palaeocene.
Formation
du Gondwana.
a chenaux
layer
post-Karoo
en bordure
plain and in the Zambezi
Deposition
oti I’Afrique
au courant
and one must look to continental/
The most commonly
silcrete
et ‘Gona-re-Zhou
du Lebombo
est posterieure
stability
continuous
coastal
mountains.
appelee
taphrogenique
et des systemes
mountains
on an alluvial fan complex
stability
sedimentaire
au terme de la fragmentation les collines
planar
The homogeneous,
Calcareous
conglomerate,
of the Malonga
est maintenant
et du Zambeze,
I’interieur
ages.
of the thick
in truncation
la serie
continentale
Btendues
Limpopo
Karoo,
and minimum
de Singuedeze/Elefantes’
sedimentation
of fining-upward
Lebombo
geomorphic
is poorly constrained,
dans le bassin du Limpopo, la front&e,
of the
laterally
with deposition
high against the Lebombo
de Malvernia
Formacao
periodic
below the Mozambique
the formation
resulted
east
thinly-bedded
and overlyrng
of this system.
Zimbabwe,
during this long period of geomorphic
marine transgression estuarine
to a sequence
conglomerate
valley,
NW of South
poorly-sorted,
action,
grade
is during the Middle to Late Cretaceous. with
and
topography.
of the maximum
Cretaceous
era.
margin and within the proto-Limpopo
matrix-supported
is consistent
bedrock
of a
with Karoo vulcanicity
near Pafuri in the extreme
reaches
suggest
The Initiation of this period of sedimentation marine stratigraphic
exposed
the
channel/floodplain
to Early Cainozorc
from homogeneous,
the distal
poorly-sorted,
after
mountains
the existence
and major fluvial
uplift assocrated
to boulder
north in southeastern
of high relief
suggests
de
South
continental,
continent
in fluvial channel and floodplarn environments.
represents
thinly-bedded,
African
valleys,
fans
by sheetflood
pebble
the sedimentary
Further
alluvial
change
deposited
clast-supported
bedded silt and sand, deposited
Mozambique,
and Zambezi
Formation
lithological
Malvernia
‘Formacao
rocks represent
margin during the Late Mesozoic
The Malonga
as the
de Sena’,
of this system along the northern Lebombo
and rifting along the continental
Africa
These
of the emergent
the long period of eustatic
and Zambezi shows
borders.
margin
coalesced
close to the continental
formerly
‘Formacao
Beds in the Limpopo Basin region where
have common
Limpopo
comprising
known
Formation,
Plateau
on the eastern
the tectonically
South Africa
succession
Malonga
The wide occurrence
landsurface
Sedimentation
silty
the
and Zimbabwe
sedimentation
of Gondwana.
Piedmont
sedimentary
termed
and Gona-re-Zhou
Mozambique
taphrogenic
age
Mines 2025,
1996
Copvght o 1996 Elsever Scence Ltd Prmted m Great Bmam. All rights reserved
du continent
affleurant
et
au voisinage
S15.00
+ 0.00
G. A. BOTHA and M. C. J. DE WIT
de Pafuri
dans
I’extrbme
nord-ouest
de I’Afrique
lithologique montrant des gres homogenes, deposes
sous I’action du rurssellement
decroissante sables
comprenant
lit&s planaires,
d’inondation.
Des paleosols
sud-orientale
du Zimbabwe,
de conglomerats
tres grossiers,
Le debut de cette
pourrait correspondre
aux termes
Davantage
distaux
et de plame
d’un tel systeme.
suggerent
une stabilrte
vers le nord, dans la partie
laterale
dissemines
en intercalation
avec des depots d’un systeme
par des silts et
River, 5 I’est des
a continuite
et a elements
a granulometne
fluviatiles
sedimentaires
plaine alluviale.
periode de sedimentation
et minimal
tardif
‘Africarne’,
developpee
avec
comprenant
de minces
avec des gres
de cone alluvial forme en contrebas
les relations
et dans la vallee du Zambeze.
au Cretace
la formation
et pour en obtenir une indicatron des
stratigraphiques
continentalesimarrnes
La periode
moyen a tardif. La sedimentation
d’une
epaisse
couche
de silcrete
de depot la plus
prit fin apparemment
associee
a la peneplaine
au tours de cette longue penode de stabilite geomorphologique
La transgression
et le depot de sediments Elsevier Science
est mal contraint
il y a lieu d’etudier
du Mozambique
au C&ace
1996
de chenaux
dans la vallee de la Olifants
des unites sedimentaires
admise correspond
le Paleocene.
d’unites
galets et blocs, coiffes
au sein des unites
mal classes
par une variation
a relief prononce.
sous la plaine cot&e generalement
affleurant
de la vaste
sont compatibles
d’un soubassement
ages maximal
silteuse
developpes
periodique
a abondants
un environnement
au Mozambique,
calcaires
geomorphologique
pas&es
dans
La serie homogene
collines de Lebombo
en nappe, passant a une sequence
des conglomerats deposes
du Sud est caracterisee
mal calibres et frnement lit&s ainsi que des conglomerats,
marine Eocene engendra
littoraux
et estuariens
la troncature
surplombant
de la Formation
precedant de Malonga
les collrnes de Lebombo.
Copyright ’
Ltd.
(Received
31 January
1996:
revised
version received
6 May
19961
INTRODUCTION Research
into
the
geomorphological emphasised
post-Gondwanan
evolution
long-term
of southern
erosional
Mid-Cretaceous
Africa
processes
has
rather
than the characteristics of post-Jurassic rock suites. This is due to the limited exposure of Cretaceous terrestrial dating
deposits
and the difficulty
involved
with
the lithologies.
supposedly Elefantes’ lnstituto
the
(1 :I
National
Previous 1938;
Schutte, lithological
further
palaeoenvironments
these
rocks,
changes,
understanding The
complicated has also
of this lithological
post-Karoo
southeastern
hindered
regional in
the Plateau
Beds by Lightfoot (I 938), and subsequently the Malvernia Formation by Cox (1963). The Zimbabwean nomenclature was utilized in naming this
lithostratigraphic
context, (SACS,
in order 1983).
unit to avoid
Recently,
in the
South
proliferation however,
African of names
Barber
SACS,
(I 987)
suggested that the lithostratigraphic naming ‘Malvernia Formation’ be altered to the ‘Gona-reZhou Plateau Beds’ as the name of the town of Malvernia in Mozambique, from where the Malvernia Formation name was derived, has been changed.
1967;
of the three of Pafuri National
1983)
succession
calcareous (Lightfoot,
Sutton,
1967;
countries
de Geologia, 1991)
whose 1987; the
cover
borders
Survey,
with
emphasis
the calcareous
sand and gravel
rocks in each
meet
1981;
Zimbabwe result
north
lnstituto Geological
that
three,
incompatible representations of the geology been compiled on the International Geological of Africa
(Commission
the
depositional
in any detail. Different
(Geological
Survey,
did not describe
nor interpret
on mapping
and unconsolidated
succession
was named
1974;
has been placed
succession.
sedimentary
Zimbabwe
by several the
the
Zimbabwe
1968; Barber, 1987), western Mozambique (Barges, 1944; Rennie, 1944) and South Africa (Keyser, 1972;
names associated
name
Geologica;
1987).
of
Muirhead,
the
‘Formacao
Carta
de Geologia,
Cox, 1963;
Sena’,
de Singuedeze/
Neogene 000
rocks in southern
The proliferation with
000
descriptions
sediments in this region is due to the isolation of investigations with respect to political boundaries. of stratigraphic
de
‘Formacao
and the overlying
de Mazamba’
sedimentary
Much of the misunderstanding surrounding relationship between the post-Gondwanan
‘Formacao younger
for the Geological
have Map
Map of
the World, 1986). In order to distinguish the calcareous sedimentary succession from its decalcified weathering products
In adjacent Mozambique the same succession was initially described as the ‘Conglomerados de Lorenco Marques’ (Borges, 1944; Rennie, 1944) and
unconsolidated sediment cover, Botha deemed it necessary to redefine this lithostratigraphic unit in South Africa as the Malonga Formation. The criteria used by Botha et al. (1995) for differentiation of the lithostratigraphic unit from its weathering products
more
are
recently
was subdivided
~_____ 164 Journal of African Earth Sciences
into the Lower
to
and derived
et a/. (1995)
utilised
throughout,
even
though
the
Post-Gondwanan
continental
sedimentation,
along
Limpopo
region
the Lebombo
central
mountain
foothills
flat,
sand covered
Mozambique,
in western plateau
areas stand in stark contrast to areas with high drainage density defined by tributaries of the Limpopo, I).
Luvuvhu,
Mwenezi
The escarpment
topography calcareous plateaus
is dominated
by these
sedimentary
rocks.
covered
at elevations
Unconsolidated
Sand
400 m and 528 m
by poorly-defined streams
sand
these wide plateau Late
between
blind ephemeral
drainage
with
and spherical
and gravel
pans.
deposits
areas, concealing
Mesozoic/Early
sedimentary
plateau
in this region
asl are characterised linear,
and Lundi Rivers (Fig.
and sand-covered
cover
the underlying
Cainozoic
calcareous
rocks,
Proterozoic
and the Archaeozoic, and Palaeozoic bedrock (Fig. 2). The
high density
dendritic
tributary
low escarpments below into the post-Gondwanan the underlying
bedrock.
major rivers define
The calcareous
The wide floodplains
of the 200 m
terraces
at the northern
occur
post-Gondwanan
and Limpopo
up to 40 m
succession
in
River valleys accumulated
extremity
in close proximity
the
are incised rocks and
local base levels at about
asl and a flight of alluvial above current river level. the Luvuvhu
basins defining
flat plateaus sedimentary
of the Lebombo
to a Karoo-age
mountains
depositional
trough
controlled by extensional tectonics and basement structure along the line of the current Limpopo valley. Figure
1. Locality
map
showing
extent of post-Gondwanan correlated with the Malonga/ Formations
in
represent
IA)
Massingir
study
(in black)
Sedimentation
the
continental deposits Gona-re-Zhou /Sena
southeastern
Gona-re-Zhou,
Africa. fB1 Pafuri;
differential, followed
insets and
terminology
successions
and mapping
and Mozambique
may not draw
The objective a detailed
of this investigation
description
comprising
weathering
sediments,
and
depositional enables
an
profile
and
interpretation
of
palaeoenvironments.
southern
the
within of the
(Cox, 1970,
and felsic
volcanic
localised
defined
1989,
possibly of a hilly
sediments were deposited.
by the
Nuanetsi-Sabi
volcanic
anomaly
which
continental
and
successions fractures
could
and
represent
and thinned-
continental or oceanic crust related to the separation of east Antarctica from Africa during the breakup of Gondwana during the Late Jurassic to Cretaceous (Nairn et a/., 1991; Gwavava
et al., 1992; Cox, 1993).
The linear zones of crustal thinning in southern
Zimbabwe,
close
intersect
to the Pafuri
at 120” study
area. The geometry of these gravity highs has been described as representing a rift triple-junction with
AREA AND REGIONAL
region of southeastern
rocks,
gravity
between
Eales
erosion
areas of high relief upon
Karoo-age
the boundary
1993;
rifting, led to creation
which the post-Gondwanan area
axis
199 1). Differential
Broderick,
with
the
with a zone of deep crustal
in
the
defining
a positive
in the recent
1 km,
with
and ring structures
coincides
Africa.
Gona-re-Zhou
Syncline’
Lebombo,
position
Jurassic
associated
data
of the stratigraphic
GEOLOGICAL SETTING In the far northeastern corner of South
late
of more than
succession
in reconstructing palaeo-drainage during the post-Gondwana period
STUDY
sheets
coeval with continental
The
regional
New
and correlation of the Malonga Formation region. This data can be integrated with advances evolution
‘Nuanetsi
landsurface
overlying
extension
subsidence
of the mafic
sediments
succession,
zone
et a/. , 1984;
was to provide
to the age of this sedimentary a re-evaluation
the
this distinction.
of the calcified
this post-Gondwanan
associated
pertaining
describing
units used in Zimbabwe
after
uplift
of up to 8000 m of Karoo lavas and intrusion
of acid igneous
areas.
the stratigraphic
crustal
extrusion
ICJ
occurred permanent
Africa,
Zimbabwe,
the
a possible failed third arm manifested as a dyke swarm in northern Botswana (Reeves, 1978;
and
Gwavava
et al., 1992).
Journal of African Earth Sciences 165
G. A. BOTHA and M. C. J. DE WIT
A. Gona-re-Zhou
C. Massingir Dam study area
cy=-
BosbokpOOrt
. >
*Pafuri
2
Pf”G Maria .
B. Pafuri
.
study area N
‘.‘k.. .-_ _ _
vvvvvvvv~\ . .fvvvvvvvv\
1.1.
LEGEND Salamanga
Eocene ,
Formation
Malonga Fm.’ (South Africa) Gona-re-Zhou Plateau Beds (Zimbabwe) FormaGao de Sena (Mozambique) Formaqao de SinguBdeze/Elefantes
igneous
rocks
sedimentary
ArchaeozoicProterozoic
Pre-Karoo
rocks
basement
Pos t-Gondwanan
Wilson
(I 970)
described
poorly
con tinen tal sedimentation,
sorted
red and
white sandstone and conglomerate in the Kadzi area of the Zambezi River valley and in the Cabora Bassa basin
in northern
Karoo
age sedimentary
Zimbabwe,
thick, the Dande sandstone to be of latest (Oesterlen
an equivalent
succession Formation,
Jurassic
to mid
and Millsteed,
1994).
River valley of northwestern
m
is considered
Cretaceous
age
In the mid Zambezi
Mozambique,
the Lupata
Group comprises
two
vulcanicity
occurred
from the Late Jurassic to
(Flares,
1964).
which
Late Cretaceous period,
cycles
post-
up to 1700
red argillaceous
sediments,
initial
Basin were accumulating Money,
area of northern Miller,
During
and subordinate
representing
Formation,
of sedimentation
Namibia
the same arenaceous
infill of the Kalahari
in western
1972)
and
Zambia
Limpopo
The geophysical
region,
Schutte
dipping
at 5-10” to the east.
(Ombalantu
which
transport
Schutte,
description
exposed
and Masisi
and marls
SACS,
1983).
The
dictate
for the sedimentary Pafuri
observation
occurring
Kop
f-50
m)
pebbly
m thick composite
coded
using capital
letters
altered
sediment
in the context
and seismic
in the further
refraction
surveys
and hence considerable pedofeatures
Pafuri area:- lithofacies
Outcrop
the Silahlandonga
and and
three stacked
the
Mozambique
reported
border.
in the eastern
and Chefu thickness
Rivers.
Finer
sediments
areas between
The geophysically
increases
of Sango
on
were
northeast penetrated basalt
This was proved
15 km northeast 1100
(Barber,
m of sediments 1987).
A gravity
areas.
2. Geological
context
sedimentary is a change
planar-bedded,
cycles
stretch
more than
in this area.
of the Limpopo
in the rocks
unsorted
pebbly
from
River thin,
sandstone
conglomerate
with
thin matrix-supported,
pebble
conglomerate
(Gms) beds near Masisi,
to thicker,
by a borehole
fining-upward
which
red palaeosol
overlying
Karoo
grained
low,
probably
of the post-Gondwanan
continental
sedimentary
units comprising
channel-
bound, clast-supported, rounded cobble- and boulder conglomerate and sandstone with well developed
of Sango,
coincident with an acid igneous intrusion, underlies the deepest part of the basin (Sutton, 1968).
Figure
expose
(I 972) recognised
interpreted
from 265 m near Tswiza to 887
of Sango.
about
there
seldom Keyser
the Guluene
m at Sango and increases to 1356 m, about 21.2 km drilled
valley,
into an
conglomerate, stream
description
of the basin north
of calcareous
siltstone
the eastward the centre
description
valley
In the Masisi-Pafuri
to calcareous
is presented.
red, mottled
illustrates
which
previously succession
along the Malonga
a detailed
of the succession
to the
can be sub-divided
with intercalated
sandstone.
relating
The pedogenically
detail pertaining
and microfabric
20 m of the succession.
thickening
case letter
has not been described
by Muirhead (I 967) and Sutton (I 967, 1968) provided of basin morphology,
by are
C, S, and P representing
of this post-Gondwanan
sandstone
exposed
River valley
suite of
The l,ithofacies-
conglomerate, sandstones and pedogenically-altered sediment, respectively. Each sub-type is indicated
is thinner
m section
bed
codes used here are based on those described Miall (I 977, 1978). The main sediment types
sequence
Cliffs area of the Lundi
and
and
of a limited
lithofacies.
structures.
stream
fabrics
has led to the definition
aggradational
towards
areas,
sedimentary
textural
Formation
Gravimetric
exposed
DESCRIPTION
lower
(reddened)
the-91
structures,
The Malonga
north.
succession
of grain-sizes,
main sedimentary
succession
rubified
than the -190
and
a separate
respectively.
section exposed in the Mwenezi valley, between the river and the top of the Ntabambomvu escarpment, Chilojo
lithologies
and Massingir
by the appropriate
where the Silahlandonga
sandstone is exposed. In southern Zimbabwe,
by up to
km. Significant
associations
is the 80 m +
In the west near Mathaphela
deeply
200
of outcrop,
south of
Fountain,
section
(Fig. 2) a thinner
comprising
are the main areas separated
of about
in the Gona-re-Zhou,
commonly
and reddish brown,
1974;
Pafuri and the most complete succession
as
points along the palaeoslopel
LITHOLOGICAL
Formation
sandstones
occur near Malonga
enters Mozambique.
the sediments
in the nature
lithofacies
Formation,
River, the Malonga
conglomerates, 1972;
are spatially
direction
differences
Detailed
up to 120 m of white
(Keyser,
(I 974) described
150 km, and represent
contacts
type sections
a regional
(Lueti
BASIN MORPHOLOGY AND SEDIMENTARY SUCCESSION comprises
revealed
The three study areas described of outcrop
authigenic
calcareous
investigation
dip of the succession in the Gona-re-Zhou area of 2”-4” to the south-southwest or south. In the Pafuri
and the Owamboland
1992).
South of the Limpopo
region
profiles
sandstone
in the upper, in the
Pafuri
locally within the eastern-most Pafuri are red or grey calcareous hardpan calcrete horizons.
deposits
in the Gona-re-Zhou,
Pafuri
silty area.
and fineExposed
outcrops south of marls and massive
and Massingir
study
G. A. BOTHA
and M.
C. J. DE WIT
clasts
is reduced
within
3 m from the Gm/Ps contact.
to medium-
Intraformational, dominate
calcareous
the pebble
Ps lithofacies elsewhere
to small
sandstone
assemblage
contact,
being
the
composed
pebble
size
clasts
close to the Gmi clast
assemblage
predominantly
of red
quartzite (Soutpansberg Group), agate amygdales and basalt (Letaba Formation), vein quartz, granitoid, dolomite,
jasper,
banded
very rare silicified decomposed
wood.
basalt
are often
reduced
resistate
clasts
sphericity,
iron formation The deeply
and basement
to saprolite
granitoid
‘ghosts’.
are well-rounded
with the exception
appear fresh and have retained surface
percussion
Very
few
and some
Measurements palaeoflow
direction
but generally indicate cemented
imbricated
the
display
of well rounded clasts
clasts.
suggest
a
which varies from south to east,
to the southeast.
that
their original,
of the red quartzite
from
low
amygdales
clasts
scars, with the exception
vein quartz
Most of the
of agate
which
and clasts
but display
pitted
features.
(BIF) and
weathered
sandy
by micritic
Thin section
clay
calcite
matrix which
analyses
is patchily has displaced
and etched the siliceous grains and pebbles severely, completely
replacing
Horizontally
stratified,
Most exposures coloured,
Figure
3. Basal,
bedrock. common
Gm facies,
calcified
gravel
overlying
basalt
Angular to sub-rounded basalt clasts are only in the basal beds, with exotic clasts dominating in
the gravel
beds above.
Silahlandonga,
Pafuri.
parts of some quartz white sandstones
are dominated
well-cemented,
grains.
(Sh)
by massive,
very
coarse
cream-
sandstone
comprising beds up to 80 cm thick. The upper part of the section depicted in Fig. 4 is almost 7 m thick and comprises
a stacked
sequence
of Sh sandstone
beds with isolated, interbedded Gm lithofacies conglomerate lenses. The lower contact of depositional
units is erosional
with
channels,
10 m
wide and 2 m deep, incised locally into the underlying Horizontally-stratified, conglomerate
clast-supported
pebbly
Gml
Many
conglomerates
Clast-supported, pebbly conglomerates occur as thin lenses at the base of upward-fining beds. The clasts range from
sediments.
boulder-size
to granule-size,
but
The sandstone contain granules but concentrated
are between
discontinuous,
0.8 m and 2.0 m thick.
These
pebbly
followed
laterally they
conglomerate
lenses
over distances thicken
can
be
of 15 m to 20 m,
and infill
channels,
they
increase to between 2 m and 3 m thick (Fig. 3). Most of these shallow channels are symmetrical but in cases where the cohesive Ps lithofacies has been undercut, or where there is bedrock structural control, asymmetrical erosion channels occur. The erosive bases are clearly illustrated in the exposure depicted in Fig. 4, where many Gm beds contain rafts of intraformationally rubified and calcified, Ps sandstone, channel
up to 2 m in diameter
close to the irregular
base. The size of the intraformational
168 Journal of African Earfh Suences
Ps
the
clasts-supported
vertically
into these
units, suggesting are intimately related.
clasts in the medium to very large pebble range are most common. The units have erosional bases and
and where
down
sandstone lithofacies
of
grade
that
these
beds are very coarse-grained
white two, and
and pebbles scattered throughout, at the base of sandy units are single-clast
layers. The basal coarser
lithologies rapidly fine-upwards and grade into medium- to coarse-grained sandstone. Although sandstone
beds appear
massive,
stratification is locally evident. Sh lithofacies sandstones
vague
horizontal
Some channel-infill, also contain
intraformational rafts (up to 50 cm diameter) of pedogenically-altered Ps sediment. Whereas these extraformational clasts occur as basal channel lags, many Ps clasts occur as floating blocks within the sand suggesting derivation from channel bank collapse during infill. In some sections the altered coloured
sandstone
tops of the cream-
units grade into pink Ps facies
Post-Gondwanan
continental
sedimentation,
Limpopo
region
Journal of African Earfh Sciences 169
G. A. BOTHA
and M.
C. J. DE WIT
massive
sandstone
erosive
and
channels
the cross-bedded
underlain foreset
units.
where
Basal contacts
the
by a single
planar
beds
sandstones
are noninfill
clast layer of pebbles.
beds grade laterally
scour
are generally Planar
into Gm conglomerates
and are incised by overlying Gm units. Reactivation surfaces are characterised by single pebble horizons. Trough cross-bedded
sandstone
(St)
Trough
cross-bedded
sandstones
textures
to those of the Sp and Sm facies can be up
to 40 cm thick and can be followed 8 m (Fig. 4). The sands grained
and contain,
and small
similar
laterally for about
are medium-
to coarse-
dark red (2.5 YR 3/6), granular
pebble-sized
mudstone
with
mudstone
clasts are composed
clasts.
of quartz,
and smectite,
with traces of plagioclase,
and gypsum.
Palaeoflow
direction
palygorskite
obtained
unit indicates that flow in the channel towards the east-southeast.
These
microcline from this
was directed
Pedogenically
rubified and calcretized siltstone (Ps)
Poorly sorted,
laminated
grained,
mottled
containing overlie
silt and fine- to very coarse-
sandstone
scattered
small
the planar and trough
units up to 3 m thick, pebbles
or cobbles,
cross-bedded,
pebbly
sandstone (Sp, St) and calcified cobble and boulder gravels (Gm). The colour of these mottled units varies from homogeneous yellow Figure 5. Termitarium comprising network Sh facies, calcified
structure
(Termitichnus
of sinuous, sand.
sand-in filled
ichnofacies) channels
within
analyses
of the matrix
silt indicate dolomite, quartz,
sandstone domed
above.
The
depicted structure
cross-bedded, structure
vertical, diameter,
about
sandstone
70 cm high,
small pebble
is underlain
zone extending comprising
pink
about
gravels
2 m below network
cylindrical structures which are infilled with
draped
by a with
and sand. This
by an intensely
an intertwined
bioturbated
smectite plagioclase
by displacive
structure
is interpreted
micritic as a
termitarium. Microscopic analysis indicated that cementation of the Ps, Sp and St facies are similar to that of the Gm sediments. Planar cross-bedded
sandstone
(Spl
Isolated planar cross-bedded sandstone lithofacies units occur as laterally extensive beds up to 20 m in length and 1 m thick (Fig. 6). The texture of these lithofacies
Yellowish elongate,
cemented
is similar to the horizontally
bedded
and
with
elastic
also present.
secondary
calcareous
and Mozambique.
of predominantly
carbonate.
groundmass,
and
of the basin, so aspects of the detailed description below also apply to this lithofacies in Gona-re-Zhou
sandstone
up to 0.75 cm in poorly sorted sand
and palygorskite and microcline
sands
by authigenic
features and clastic/authigenic phase textural relationships of this lithofacies are similar over much
the dome (Fig. 5),
and preferentially This
at the
in Fig. 5 and 6, is disturbed
of red coloured
that these are dominated
The rubified
exposure
red (2,5YR 4/6,1 OR 4/6), reddish
(5YR 6/6) or pink (5YR 7/3). X-ray diffraction
red (5YR 5/6) are
mainly
branching,
colours
within
associated
with
subvertical
the red white,
and subordinate
subhorizontal, calcareous cylindrical structures and mottles. Maximum calcification occurs near the top of the individual
mottled
sandstone
units and tends
to decrease towards the base. The cylindrical calcareous features are generally between 30 and 40 cm in length, but examples over 1 m long have also been noted (Fig. 7). Some vertical carbonate structures up to 15 cm in diameter, containing blocks of calcified red sandstone, penetrate the sandstone and are apparently integrated with thin, horizontal, massive calcrete bands in some outcrops. Round calcareous nodules (0.5 - 3 cm) within the red mottled sandstone, comprising micritic dolomite, are surrounded by irregular, radial cracks infilled with
Figure
5m
6. Schematic
section
through
showing
relationship
of termitarium
clast-supported pebbly conglomerate (Gm)
outcrop
Horizontally-stratified,
Planar cross-bedded sandstone (Sp)
Horizontally stratified, white sandstones (Sh)
Mottled sand and laminated silt (Ps)
LITHOFACIES
:$$ vertical/horizontal .:::.:.: :::;:j,.: (02/02) sample position
.::::;:$$;:<:>;. ::;;.:.;.;.y:...I:.’
rhizocretions
G. A. BOTHA and n/l. C. J. DE WIT
I72 Journal of African Earth Sciences
Post-Gondwanan
equant, filled
sparry
cracks
pattern
calcite
define
nodular
sedimentation,
(Fig. 8). The thin carbonatea cubic
(2-4 cm) within
where
continental
carbonate
cementation
granostriated
or strial
fabric.
hematitic
in areas
opaque
is of limited
laterally
bands
within
the
IO - 15 cm thick
9). XRD analysis
coalesce
Runiquartz
top
of a
cracks
unit in one exposure
(Fig.
heavily
red sandstone
calcretised
has shown
almost entirely
of micritic
are convoluted,
defining hummocky
low
amplitude
Slickensided sparry
and
surfaces
calcite
interface
veins
The calcitic
+30
suggest
cm
calcified
bands
stains
the
fine
void
grains. of
(or
infill.
oxides penetrate
of the rubified groundmass
zones
replacing
bands and
micritic
comprises
dolomite
displacing)
dolomite
crystals
along
the
Whereas
rubified
the
red
porphyric
relationship
sandstone
is
and
rubified
and
of ferro-
ferruginous
the
apparently
argillaceous
fine
groundmass. The carbonate and clay groundmass between accumulations of rhombohedral limpid
wavelength.
movement
The laminated,
bands
surrounds
forming
forms where ferruginous
in quartz
diffuse
‘tepee’ structures
of the convoluted
between
sandstone.
calcite.
(micromass)
ferruginisation
minerals,
Calcification
these to be composed
birefringence
mineral clasts or ore pseudomorphs
hypocoatings, calcified
bioturbated
of
Strong
magnesian
extent. White
region
blocky
or subangular
the red sandstone
Limpopo
components,
is replaced zones
by pervasive
commonly
between
the micritic
calcite.
have
a close (c.f. 1
coarse/fine
zones
display
a more
intensively bioturbated with abundant vertical to subvertical, backfilled burrows. Downward concave,
open porphyric c.f. relationship suggestive of volume increase during crystallisation of the
lunate backfill units, generally 1 mm to 3 mm thick occur within the rounded (1 cm - 1.5 cm diameter),
authigenic
sinuous
grey
plagioclase
and sparry calcite
suggesting
burrows
mudstone
(Fig.
IO).
with a dolomite
Homogeneous,
cement
veins occurs at the top of upward
Fountain
stage Micromorphological
The
description
relationship
groundmass
between
sandstone
very fine
calcretised calcite
sesquioxides
poorly
poorly
displaying
undulose
sand grains are commonly coatings of well-oriented
Captions Figure
for
7. Reddish
blocky pattern Figure
11.
plate
brown,
defined
8. Spherical
later generation Figure
colour
The Chilojo
Gona-re-Zhou
Plateau
Cliffs,
The 178 m type section Figure
13. Poorly sorted,
weathering represented River valley, Zimbabwe.
palaeosols calcite
of dolomicrite calcite.
Beds,
siltstone
Large
carbonate
the latter
replacing
Dolomite
in the
sandstone towards
and
units
gravels
smectite
is
heavily with
the base.
the stratified
palygorskite
hematite,
mineral
present
clasts within
abundant
gypsum
fine sand show
smectite.
top of mottled
generally
are a late
Red
contain
and
some
gypsum.
opposite:Ps facies
nodules
extinction.
surrounded by thin red clay, defining a
by late stage
of sparry
sorted,
oriented,
calcite lenticular
comprises
and dioctahedral
dominant
the
cleavage planes. mineralogy of red, calcretised
commonly
palygorskite
massive
with
and
Rare
with late stage calcite,
reaction
the gypsum along The groundmass
sand grains are infilled silt
of sparry
and
margins
components.
the red, calcified
cement
and grain zones
between
elastic
within
rubified high used
reaction
crystals
the
and
veins
infills
embayed
and
phenomenon.
to describe the authigenically altered sandstone and siltstone is after Bullock et al. (1985). Voids between sand
a chemical
mottled,
is best observed in thin section under magnification. Micromorphological terminology
Void
the micritic
display
groundmass
calcareous
the
and the authigenic
grains
Cross-cutting
area.
phase.
are rare within
micritic
fining sedimentary
unit at two sites in the Malonga
mineral
coatings
was measured Gms facies,
along white,
within
and horizontal
rhizoliths,
round
dolomitic
nodules
and
south of Pafuri.
red palaeosol.
Cracks
radiating
from
the nodules
are filled with a
the southern
poorly
sorted
rim of the Lundi River conglomerate
overlain
valley,
expose
by calcareous,
a repetitive
sequence
pink or reddish
of
sandstone.
on the right of the field of view.
matrix
by rubification Scale = 10 cm.
vertical Fountain,
south of Pa furi.
Fountain,
escarpment
with
Malonga
developed
Malonga
comprising
profile
veins.
supportedpebble
of matrix
conglomerate
and sinuous,
calcareous
with poorly sorted rhizocretions.
sandy matrix.
Swimuwini/Buffalo
Figure 14. Network of long, calcareous rhizoliths developed within red palaeosol profile, Chilojo Cliffs set tion, Lundi River valle v, Zimbabwe. Cliff is approximately I3 m high.
Gona-re-Zhou
Palaeopedogenic Bed,
Plateau
Mwenezi
Beds at the
Figure 15. A dense pattern of sinuous, calcitic vermicular mottles, rhizoliths, root moulds and nodules occuring below massive, hardpan calcre te in 4 m calcareous palaeosol pro file. Hello w rhombic pits, in filled with red sand in fresh outcrop, may represent
gypsum
casts.
Formacao
de Singuedeze/Ele
fan tees, Mahosi,
western
Mozambique.
Journal of African Earrh Sciences 173
and M.
C. J. DE WIT
calcrete
horizons
G. A. BOTHA
Figure 9. ‘Tepee’structure on calcrete
horizons
in massive,
suggest
micritic
movement
Figure
10. Downward
within
red, Ps lithofacies
concave,
calcite,
due to volume
lunate backfilled
palaeosol
horizon.
and
red upper
sediments,
with
no
disl :inctive intraformational markers. River bank ,osures in the Swimuwini/Buffalo Bend and exp Wri ght’s Tower/Makonde Pool areas, and the esc arpment
section
near NtabambomvuAronwood
I74 Journal of African Earth Sciences
Taenidium
Malonga
GOI la-re-Zhou area:- lithofacies description Ligl itfoot (I 938) and Cox (I 963) noted that the Mw lenezi Valley succession is characterised by a wh1ite base
increase.
within bioturbated
Malonga
Fountain,
ichnofacies
Fountain,
Viewpoint,
south
Slickensides
of Pafuri.
(Mason
pers.
comm.)
of Pafuri.
provided
the succession south
burrows
red siltstone.
south
a composite
in the Mwenezi
section
thrc ugh inI the
River valley
(Fig. 2).
The escarpment along the southern rim of the L.undi River valley, particularly the Chilojo Cliffs, expa se a repetitive sequence of sedimentary units compri sing white, poorly sorted conglomerate overlair 1 by calcareous, pink or reddish sandstone. The 17‘8 m
Pos t-Gondwanan
type section opposite
measured
from the river to the cliff-top
Chilojo camp (Fig. 11) reveals a succession
of numerous calcareous pebbly
con tinen tal sedimentation,
sedimentary
units
conglomerate
sandstone
Outcrops
comprising
overlain
by reddish
Limpopo
shallow
channel
modified
top of a depositional
white
supported,
brown
a rarity
incised
Gm lithfacies,
are more
widely
spaced
Horizon tally-stratified The poorly sorted,
succession
Makonde
of units
comprising
similar
are conformable
lithofacies
or display
minor
of white,
Gms lithofacies
in the cliff sections
are characteristically
basal
gravelly
and unsorted,
and cobble
conglomerate
lithologies
exposed
Pool comprises
clasts
were
noted.
quartz,
At least two
valley
locally. (0.5-2
of
the massive, characterised
and conglomerate
at
Wright’s Tower. The rock is cemented by white calcite micrite and microsparite with a later phase of fine-textured,
pink,
micritic
calcite
sinuous zones up to 1 m wide within within
these zones are lined with
Approximately
is exposed
below Swimuwini white,
basal
reddish
sandstone.
lithofacies
units
supported, beds,
reddish brown
upward
into Sh
interbedded
Gms
poorly-sorted,
are only
a few
on the sedimentary matrix coloration
matrix-
clasts
bedding
cliffs
comprises
which commonly
upward
fining
have white,
unit is
calcareous
(Spl at all of the sites
and one set of planar beds
up to
indicating
a southward
observed
at the Wright’s
1 m thick, transport Tower
cross with
bedded foresets
direction,
were
and the Chilojo Cliffs
exposures. Pedogenically rubified and calcretked sandstone (psi The
upper
part
characterised
of
each
by a reddish
elongated features
of
diameter, and some through the sediment colour
units
poorly sorted,
of larger, angular
investigated
horizontal,
cobble conglomerate. The conglomerate beds are commonly only a few clasts thick and contain accumulations
nodules
the basal part,
thin tubular
Planar cross-bedded sandstone This lithofacies is uncommon
carbonate
coarse-grained pebbly sandstone with interbedded, angular, matrix-supported, granule, pebble and
lenticular
calcareous
structures.
thick.
at the Chilojo
sedimentary
calcified,
basal
are present
sedimentary brown
unit
colour,
is
variable
density of carbonate nodules (0.5-5 cm diameter), and sinuous or branching, vertical and subordinate
and white carbonate
measured
Thin,
pebbles
part of each sandstone
are the
nodules and sinuous rhizoliths and pedotubes, palaeopedogenic origin (Fig. 13). The 178 m succession
units,
to coarse-grained,
characterise
by sparse,
the
The repetitive
Calcified,
pebble and cobble conglomerate
of which
Superimposed
Bend’ in the
coarse-grained,
Thin,
comprise
granule,
many
grades
calcareous,
cliffs
the upper above
sandstone.
authigenic,
upper
sandstone
sandstone
of Mabalaute.
conglomerate
brown,
lithofacies
calcite.
in the riverbank
camp, on the ‘Buffalo
River, downstream
in
the rock. Voids
30 m of poorly-sorted,
and conglomerate Mwenezi
occurring
sparry
Whereas
rim of the
lithological
medium-
calcareous
cm diameter)
of
The basal part of each
beds of rounded
the
phases
sorted,
conglomerate
to the depth
exposes
sandy
1-3 m thick.
brown,
brown
in each unit.
stratigraphically
comprises
reddish
BIF and
occur within
is related
Bend outcrop.
from
in the
or reddish
is cut into the northern
Swimuwini/Buffalo
unit is poorly
in the upper part
units exposed white
rubification
part of the succession,
commonly
to
Tower/
and reddish banded,
valley at Ntabambomvu
sequence
cementation
sandstone
of the sandstone
palaeopedogenic
with
Mwenezi
The variable
The pass which
the range of Karoo-age the
colour
Mwenezi
pebble
white
is common
Cliffs.
thinly
The angular
above the basal
at Wright’s
depositional
Chilojo
comprise
rare pegmatoid
carbonate
coarse-grained
is
calcareous, pebbly coarse-grained sandstone with weak horizontal bedding defined by coarser grained
sandstone
beds. in
although
authigenic
Tower,
and unsorted,
matrix supported,
clasts represent
provenance
Wright’s
bedded
conglomerate m)
unimbricated
granite
below
locally-derived rhyolite clasts up The finer textured sediments
(0.5-I
subrounded
units up to 3 m thick,
poorly
containing angular, to 2 m in diameter. the
conglomerate,
sands tone (Sh)
conglomerate
of upward-fining
strongly-calcified,
pebble to boulder conglomerate
above
matrix-supported
(Gms)
The basal sequence
bedded
pedogenically
succession.
pebbly sandstone
beds. Similar sandstone Massive or horizon tally-stratified,
exposed
the
unit, infilled with clast pebble
in this lithological
and display different lithofacies associations requiring site specific description of each facies. The stacked
conglomerate
into
(Fig. 12).
in this region
associations incision.
region
clasts. A
and
sandstone to those detail
textural and white
from
calcareous
structures.
are commonly
These
5-30
cm
in
can be traced downwards for up to 5 m (Fig. 14). The characteristics carbonate
the Pafuri
of
features
outcrops,
the
red
are similar
described
in
above.
Mozambique
area:-
lithofacies
description
The poor outcrop of the Formacao de Sena near Pafuri in the Limpopo River valley and points north on the interfluves adjacent to the Mwenezi River
Journalof African
Earth Sciences 7 75
G. A. BOTHA
and M.
C. J. DE WIT
unconsolidated
red sand
thm derived gravel horizor
GONA-RE-ZHOU
PLATEAU
‘African’ landsurface Silcrete
BEDS
Chilojo Cliffs section LlTHOFAClES
Reddish brown palaeosol K horizons with white calcrete nodules and vertical rhizocretions Calcified, poorly sorted, matnx supported, weakly stratified pebble conglomerate (Gms), granule-stone and coarse grained sandstone (Sh)
section above
heights in metres river bed datum
terrace /eve/ with sparse pebble cover
Ol-
Figure
Lundi River bed
12. Section
Gona-re-Zhou,
through
Zimbabwe.
176 Journal of Afr;can Earth Soences
Gona-re-Zhou
Plateau
Beds
at
the
Chilojo
Cliffs
section,
Lundi
River
valley,
Pos t-Gondwanan
system
prohibits
associations
a detailed
although
description
the lithologies
the range of rocks described of South
Africa
Formacao
and Zimbabwe.
Massingir
near Mahosi
of lithofacies
these
are similar
weathered
from the adjacent
of the
in the Olifants
on the northern
Dam, provide
to
areas
Exposures
de Singuedeze/Elefantes
River valley
con tinen tal sedimentation,
good sections
shores
facies
sands.
were
the
upper part of this unit. The sections here, although restricted, are dominated by the fine grained Ps lithofacies.
The
main
lags of gravel
rubified and calcre tised silts tone lPs)
directions
The Mahosi
outcrops
of the Singuedeze/Elefantes
bedload
of pedogenically
clasts
supporting the north.
that
but small
the palaeoflow
to southwest,
flow
direction
COX’S (1963)
findings
but a
was measured, in Zimbabwe
in
8 (Gm, Stt)
bedded,
sandstone
sand,
locally.
indicate
southward
floodplain
was
varied from southeast
general
Thinly
banks
developed
Facies Association
Pedogenically
eroding
and carbonate-cemented
lmbricated
of
through
Limpopo region
horizontally
stratified
and interbedded,
thinly
pebbly
bedded
pebble
succession expose rubified siltstone with authigenic carbonate structures. A massive, calcified profile (up
conglomerate are interpreted as sheetflow deposits derived from the areas of steep bedrock relief. These
to 4 m thick)
are particularly
siltstone,
developed
within
up to 12 m thick.
A dense
calcitic
mottles,
vermicular
cylindrical calcified parent
exposed
is
pattern
of sinuous, and elongate
also includes with
infilled
represent
gypsum
features
are
casts
and
represent
lithofacies
which
sediment
Gona-re-Zhou
north
of the Limpopo
is similar
described
from
rubification
precipitation
to the Pafuri
Ps and
A (Gm, Sh, St, Sp/
An intimate association exists between the massive conglomerates, the horizontally stratified sandstones
of many
by upward:fining related,
association
(Facies Association
sandy
units
conglomerate
and conglomerate
genetically
interpretation
as palaeosol
forming
red coloration
of palaeosol
above,
features
can
brown
sandstone
units are regarded
with downward
of pervasive
decreasing
intensity
which is superimposed on depositional bedding lamination. The presence of surface-related
pedogenic
lithofacies
part
of one
is
sandstones
are interpreted
classified
as buried
the Stage
are
and honeycomb
A). This lithofacies
and the presence
or
siltstone
and sand bars suggests that the main environment was one of channel upward
fining
represent bar formation their association with
conglomerates
bars
were
migrating
downstream direction. The presence Ps facies indicates that the channels
Bk or K palaeosol
in a
of blocks of infilled with
morphology
calcrete
of Netterberg
calcareous
modified
rhizoliths
calcareous
representing (rhizocretions)
(Klappa, features
postred
rubified profiles, horizons similar
to
or nodular (1980).
cylindrical
units, include features
structures
sandstone
and
grouped
in the family
1980).
The majority
are interpreted
as
carbonate precipitation around roots although some root moulds and
carbonate-lined,
in a fluvial channel and trough cross-bedding
pedogenic
II and III of Gile et al (1966)
The composite,
1980;
to subaerial The calcareous
as representing
feature
present in the pedogenically
of
(Netterberg,
calcretised
carbonate
and facies
calcretes
Klappa, 1980) also point depositional modification.
of theses
bedforms
these
to
the sandy
of the red calcareous
profiles due to the presence
of calcareous
that
within
in all areas.
absence
indicates
carbonate be related
units in the three areas described
association, according to Rust (19791, is typical of a sand-dominant braided stream deposit. The
The
to
Due to the similarity
showing
(Fig. 4). The base
braiding.
authigenic
considered
sediment.
other
small gravel depositional
sandstone/
sandstone
and subsequently
of major
calcretised
profile-development
and the trough and low angle, planar cross-bedded pebbly sandstones which grade laterally into each
the sandstone
in the from the
pedogenic
recent
Pafuri area
characterised
derived
bioturbation structures attributed to plant roots and calcareous structures similar to those described from
interpretation
facies Association
and
and are
The reddish
and
above.
Lithofacies
The
be applied
rubified
rubified
the following
component.
coarse-grained,
sandstone
in the
and plagioclase
elastic
the exposures
comprise
may
authigenic
occurring
microcline
the dominant
In contrast,
with
smectite
Quartz,
Pedogenically
of
which
in exposures
with sediment
silts tone IPs)
(Fig. 15). The carbonate
dolomite-rich
palygorskite groundmass.
accumulations
red sand,
well developed
Masisi escarpment, east.
structures occurs below the massive horizon. The homogeneous siltstone pits
calcified
brown which
nodules
sediment
rhombic
River,
the reddish
caps the succession
hollow
root
tubules
also occur
(Klappa, 1980). In general the morphology of rhizoliths and calcrete nodules are broadly similar to the calcrete profiles described from the Old Red Sandstone
of southern
carbonate
pedofeatures
Britain
(Allen,
described
19861,
the
by Purvis
and
G. A. BOTHA
and M. C. J. DE WIT
Figure 16. Wea thering profile developed within Malonga Formation rocks is a zone of decalcification, charac terised by circular s true tures up to 2 m in diameter and irregular fissures, tapering down ward (up to 6 m deep), decalcified
Wright
in filled with red, strongly
parent
sandstone.
(I 991) from Triassic
and rhizoliths Formation Cohen,
braided
1984).
1982;
Mount
within
The mottled,
a substrate within
rubified
Limpopo
and
structures
to be the result of displacive
occur
rubified
Koobi Fora
The ‘tepee’ or antiformal
are interpreted of carbonate
(Cohen,
area,
river deposits
from the Plio-Pleistocene of Kenya
commonly
Masisi
(Watts,
growth
1977),
sand, rounded River
clasts and fragments
succession
exposed
lithofacies
association
and
intensely bioturbated by calcified rhizoliths, backfilled Taenidium ichnofacies burrows (Smith et a/., 1993;
interpreted
as sheetflood flow
fan surfaces proximal
the succession
structures
and the colour mottling
that these subaerially
fluvial channel exposed and
strongly
sediments pedogenically
‘tepee’
suggests have been altered.
Calcrete profiles with dolomite and palygorskite the matrix suggests that the palaeoenvironment during
sediment
incision
and
deposition
migration,
and periodic was
arid
probably
within
the 400-600
(Goudie,
1983;
Botha and Hughes,
to
in
channel semi-arid,
mm per annum
range
deposits
(Wright
Zarza eta/.,
clast-supported confined
by
steep alluvial 1994).
Very
associated
with
in the Chilojo
and Alonzo
1992).
conglomerate
within
shallow
at the base of the succession represent
incised
it is
into the
sandstone. The rare point to a southerly bouldery
deposits
in the Wright’sTower
high density
of the Gonakudzingwa
areas of high bedrock
1990;
is exposed
channels
sediment transport direction. The unsorted nature of angular, area probably
Zarza
Where rare, interbedded,
underlying, horizontally-bedded planar foresets observed,
generated
1992).
on relatively
colluvial
are
produced
Cliffs section studied and the pebbly conglomerate and sandstone, with associated palaeosol profiles points to a medial fan environment of deposition for Alonso
calcrete
deposits
action
transport
and the deposits
fan areas are not exposed
presence
root structures,
water
region. This
sediment
(Blair and McPherson,,
angular
Masonpers. comm.) and at one locality a termitarium (Termitichnus ichnofacies; Smith et al., 1993). The of calcified
suggests
unconfined
coarse,
sands near Pafuri are locally,
in the Gona-re-Zhou
by shallow, catastrophic
calcretes.
of yellowish,
valley.
relief towards
flows,
possibly
and Mateke
hills,
the west.
Gona-re-Zhou Facies
Association
A (Gms,
Shl
The common lithofacies association of basal, poorlysorted, matrix supported pebble conglomerate fining upward into massive or weakly horizontally stratified pebbly sandstone extensive conglomerate
with interbedded,
matrix-supported, beds,
is typical
thin, yet laterally
pebble
and cobble
of much
of the
Mozambique The Mahosi
area outcrop
of
Singuedeze/Elefantes
Formation siltstone, with similar palaeopedogenic features to the Pafuri deposits further north, is regarded as being the finer-textured distal part of the fluvial Lebombo
system foothills
flowing
southward
from the Limpopo
along
the
valley area. The
Pos t-Gondwanan
dominance coarser
of floodplain
component
facies over the channelized closer
to the provenance
probably due to a greater degree confinement in the distal reaches.
WEATHERING
PRODUCTS
the calcareous
is a ‘lateritic (1972)
sedimentary described
sediments
River
Formacao
rim,
Mwenezi
and the
and Limpopo
profile
Formation along
the
of the
in the Olifants
Formacao
de Sena
River valleys.
and sand cover
gravel
widespread
gravels.
below
the
but is generally
Muirhead
by Lightfoot
(1938),
(I 967) and Sutton
only the
describe the relevance
Along the rim of the Malonga of Pafuri, porous, decalcified sandstone horizontal white,
1968)
The generalised
hollow,
Formation
rocks
stream valley south and ferruginised
silica precipitation
channels.
containing
in the
do not
of the thick silcrete
is characterised locally by a strong structural component defined by milky
opaline
around
Cox (1963),
(1967,
profile developed within the Malonga in parts of the region.
capping the Zimbabwe.
outcrop
de Singuedeze/Elefantes
valley
derived
adequately
described
locations
above
is apparently
The descriptions
by Keyser
Malonga
out at many valley
in the derived
The ferricrete
Silcrete
profile
that a weathering
the calcareous
crops
Limpopo River
revealed
within
FROM
succession
a similar ferruginous conglomerate sedimentary succession in southeast developed
region
exposed near drainage lines and pans where sandy overburden has been thinned.
in the Pafuri area, and Cox (1963)
This investigation
channel
weathering
conglomerate’
Limpopo
similar to those concentrated is
ROCKS
and ferruginised
Overlying
of
DERIVED
THE POST-GONDWANAN Decalcified
con tinen tal sedimentation,
Bands
a latticework
sinuous
occur
white
of hematite-filled
channels
within
along planes
of milky
and
silcrete, cracks and
lined with quartz crystals,
this
weathering
profile.
sequence is variably decalcified parent material, with silcrete or a ferruginised zone and hard ferricrete
Micromorphological investigation revealed that the silcretised sandstone in many exposures is
developed
characterised
patchily,
unconsolidated yellow
by
clasts
a layer
of
and surficial
red/
characterised
by
sand cover up to 6 m thick.
The zone
of decalcification,
circular structures
up to 2 m in diameter
fissures, tapering with
overlain
rounded
downward
red, strongly
sandstone Pafuri
(up to 6 m deep), infilled
rubified
and fragments
sand and rounded
of yellowish,
clasts
decalcified
region.
These
represent
infilled
karstic
‘pothole’
solution
with terra rossa pedogenic weathering rubified sediment is highly porous abundant
sinuous,
pedotubules.
clay
Brink (1967)
defined
by
comprising
an
irregular
manganiferous
material
brecciated
infilling
structure. In places
along
valley
and
around
occur where
have
and
commonly
as pedogenic overlies
and contains
plinthite
the decalcified,
an assemblage
of rounded
rock
of fibrous,
material
with
in
material
of some
in some
silcrete
similar
The thickest,
outcrops
Mwenezi steep
Nyamtongwe within
defining hill expose
the underlying
(1968)
the
silcrete
also reported
in Zimbabwe.
a silcrete
silcrete
profile
is
the rim of the
escarpment
calcareous
that
synchronously
defining
and Lundi River valleys cliffs
of red
The purple
suggests
best developed
in the escarpments
to the
pedorelicts silcretes.
ferruginisation preceded or occurred with the silcretisation processes. exposed
slow
of depositional
and pebble-sized
palaeosol
length
appears
preservation
from grey to purple,
the top of the silcrete
within
etching
the is
pans,
or ferricrete, ferruginised
parent
within
deposits comprising unsorted clasts cemented by a hard, ferruginous matrix are exposed beneath thin sand cover. The massive, hematitic deposit, interpreted
grains ‘floating’
The
around
profile
formed
sandstone.
Sutton
from the Chefu
River
area in the south. The colour of the silcrete is variable,
a nodular
around
elastic
growths
Black
‘potholes’
residua rims
Vaal
margin
cracks
and lamellae
the rubified
and
rounded, terra are commonly
material
material
decalcified,
late Neogene
sediment.
nodules
weathered
have a similar
brecciated
decalcified
and
by Partridge
Zones surrounding solution hollows
rubified
yellowish
possibly
described
from the calcified,
River gravels. rossa-infilled
infilled
channels
botryoidal
chalcedony. The silcretized
colour
features
products. The and contains
lined
These features
origin to the ‘makondos’
in the
cavities
with
stratification
parent
(Figs 16 and 17) is well exposed
probably
deeply
and irregular
by skeletal
a mass of micro- and cryptocrystalline quartz (F-fabric; Summer-field, 1983). Sinuous vugs are partially infilled
zone clasts
the
and the knobbly
of a network
Malonga
vesicular
profile
of sinuous,
Formation
rhizocretions
carbonate
biogenic
protolith. are centres
precipitation
in the
silcretjzation process apparently textural inversion with preferential the sandy
matrix
and dissolution
within silcrete
the rhizoliths (Fig. 18). profile is relatively weakly
opaline
silica infilling
ferruginous lining
appearance
coating
tubes
Whereas
in the
of authigenic protolith,
the
leads to a silicification of of carbonate The top of the cemented with
some intergranular
sequioxides
of
is due to the solution
pores and
sand grains
and
pores.
Journal of African Earrh Sciences 179
G. A. BOTHA
Figure
17.
Base
decalcified
of solution
Malonga
represents
the
Silahlandonga
coarse, valley,
pothole
Formation resistant Pafuri
developed
rocks.
C. J. DE WIT
within
Figure
18. Basal part
infill
within
Gona-re-Zhou
Rubified
fraction
and M.
of the protolith.
area.
Previously tubes.
calcareous
The matrix
massive
of ‘African’ Plateau features
is weakly
accumulations
silcrete
profile
Beds at Chilojo
developed
Cliffs
are represented silicified
occur irregularly
section.
by sinuous
by opaline
silica
throughout
and
the basal
part of the profile.
The silcrete
horizon
dips towards
the Chilojo
Cliff
Drakensberg
escarpment
exposure to the ESE at about 0” 21’, although the silcrete surface is not smooth and local undulations
western Mozambique thick accumulations
with a wavelength
overlie
of up to 50 m and amplitude
of
the
-6 m are evident.
widespread
Derived
conceals derived
gravels
The top and base of the Malonga
exposed
post-Gondwanan sand
cover
calcareous,
Kalahari
Group
Botswana
this derived
gravel
by ‘veil’ of up to 12 m of rounded
pebbles
Letlhakane
stoneline
Formation
and cobbles
weathered
from the calcareous
rocks
(Lightfoot, 1938; Cox, 1963; Keyser, 1972). This ‘derived gravel’ layer of unconsolidated, rounded clasts is well exposed by the escarpment south of Pafuri. About
185 km to the south of the Pafuri area
on the crest of the Lebombo
mountain
range, there
‘sealing’
effect
of the resistant
lithology Transvaal
o,.4,ncan
_~
&wr,,
soences
In the
by Du Plessis and
the predominantly sandy nature of the upper part of the underlying Malonga Formation rocks, or to the
underlies the cover and is interpreted
180 .Jo”r”al
lithologies.
Le Roux (1995). The ‘derived gravel’, is very thin and impersistent in the Gona-re-Zhou region. Whether this is due to
are similar unconsolidated gravels and sand (Venter and Bristow, 19861, although the different clastpoints to a provenance of lithologies exposed in the
The Desert
has been termed
the surface, is debateable. The unconsolidated ‘derived
assemblage Sequence
Kalahari
a variable layer of unconsolidated gravel from weathering of the underlying
is often
isolated
In
foothills gravels’
lithologies.
in the
hill and cliff exposures
in valley-side, obscured
Formation
110 km to the west.
along the Lebombo of similar ‘derived
silcrete
layer near
gravel’
sand over much as representing
probably
of the area material
Post-Gondwanan
released
from
weathering
the
ferruginous
profile
through
landscape associated erosion.
continental
or siliceous
lowering
that
this thick,
and
relatively
Redistribution of the derived gravel weathered from protolith
commonly
region
of the maximum
age. The
Lupata Group in the Zambezi River valley comprises two cycles of sedimentation
and vulcanicity
which
occurred from the Late Jurassic to Late Cretaceous.
evenly distributed pebble and cobble gravel deposit was deposited by fluvial systems flowing across the low gradient land surface. the calcareous
Limpopo
valley for an indication
of the
with ongoing weathering
It is unlikely
sedimentation,
accumulates
Whereas
sedimentation
began in this area during
the Jurassic, on lithological Formation is correlated sandstone
deposited
grounds the Malonga with conglomeratic
on an unconformity
surface
above rhyolite dated at 166 +- 10 My (Flares, 1964)
through colluvial and alluvial action at the base of
and light grey, red and light reddish brown, unsorted,
hills and
calcareous,
escarpments
Gondwanan
incised
into
the
post-
rocks. In some areas ongoing incision
of these landsurfaces
by tributaries
of major rivers
has created raised gravel covered terraces which contain rounded clasts of strongly calcified, reddish sandstone,
typical
of Ps lithofacies
palaeosol
Formation
sedimentary
rocks of the upper Sena
which were deposited
Middle Cretaceous (Flares, 1964).
above Lower to
(I 15 + IO My) alkaline
In the Limpopo valley continental sedimentation
lavas
region of Mozambique, dominated on the margin
material derived from the Malonga Formation protolith.
of the emergent African continent during the Lower
Moderate
to Middle Cretaceous, with marine conditions being established in the west only in the Senonian (Flares,
calcification
conglomerate
of this sediment
which
is sometimes
differentiate from the weathered
results in difficult
to
Malonga Formation
protolith.
1973;
Forster, 1975).
eastwards,
The Sena Formation
was probably diachronous Unconsolidated
sand
cover
grades
and upwards into marine sediments, and along strike across the
basin. The earliest Sena Formation
deposits south
The Nwambia sandveld plateau area, the eastern Lebombo foothills in Mozambique and the Gona-re-
of the Zambezi graben are of Cenomanian or Turonian age (palynological evidence) and grade into marine
Zhou
deposits dating from the initiation of the Mozambique
region
are blanketed
unconsolidated
by a thick
layer
red or yellow sand (Keyser,
of
1972;
Venter, 1986) previously regarded as being of aeolian
Channel during the Lower Cretaceous the Senonian (Flares, 1973).
origin (Schutte, 1974; Keyser, 1972). Red, yellow or grey, well- to moderately-well drained, eutrophic soil
and parts of the intracontinental
profiles are developed clay-rich smectitic lines.
The thick
within the coarse sand with
soils formed in shallow drainage sand
numerous ephemeral
blanket
thins
around
the
pans, drainage lines and along
the valley escarpments incised into the underlying calcareous sediment. The mechanism which led to effective separation of the sediment
comprising
the thick surficial sand
cover from the unconsolidated
gravel layer below,
of the calcareous
Malonga
not well defined.
It is possible that biogenic activity
led to concentration
is
of the gravel clasts although
in the proto-Zambezi
lavas
(165
Namaacha eta/.,
My)
intercalated have
been
with late Jurassic described
from the
area on the Lebombo mountains
1983).
In northern KwaZulu-Natal,
(Dingle localised
Msunduze Formation alluvial fan sedimentation occurred in association with the emplacement of acid extrusive and intrusive igneous rocks of the Bumbeni Complex around 140 Ma (Wolmarans and 19881,
with subsequent
widespread,
coarse, elastic sedimentation
(Makatini
during the Early Cretaceous. Critical evidence regarding
the minimum
the effect of periodic winnowing by wind action cannot
the Sena sediments
be discounted, despite the fact that no dune features
of the diachronous
are associated with the Nwambia
transgressive
sand cover in this
River valley
Kalahari Basin have
been described above. South of the Limpopo valley region, sediments
Saggerson,
both of which were probably derived by weathering Formation sediments,
Sedimentation
period until
Formation)
is based on borehole relationship
age of records
with the overlying,
marine Grudja Formation of Senonian
to Palaeocene age (Flares, 1973). It is possible that deposition on the MalongaSena alluvial fans
region.
DISCUSSION Age of the Malonga
Formation
The initiation of Malonga
and correlatives
Formation
sedimentation
in the Limpopo River valley and Gona-re-Zhou region is poorly constrained, and one must look to continental/marine stratigraphic relationships below the Mozambique coastal plain and the postGondwanan sedimentary history of the Zambezi
decreased
during the period of rising base-level
associated
with the Senonian marine transgression
which
inundated
much of the southern
basin of
Mozambique. The ‘African landsurface’ and silcrete profile developed within the Malonga/Sena Formation, which also occurs seaward of the ‘Great Escarpment’ along the south and west coast of southern Africa, brackets the period during which active sedimentation ceased.
Journal of African Earth Sciences 18 7
G. A. BOTHA and M. C. J. DE WIT
This thick,
pedogenic
silcrete
profile
is regarded
as
rates
during
the
period
representing the long period of geomorphic stability associated with the ‘African landsurface’ which was
Gondwana. In the Gona-re-Zhou
in existence
Limpopo
from
the
Late
Palaeocene
(Partridge,
this silcrete
‘landsurface’
(1987)
classification
between
the
landsurface
1993).
until
Lundi
militates
and
Lister’s
planar-bedded, conglomerate
plateau
depositional
against
Mwenezi
Rivers
age. Formation
between
as the Chefu represent
Nyamtongwe
and Guluene
of the -35
Pliocene/early
of the
and Chilojo, as well
Rivers,
is more likely to
Pleistocene
Cox (1963) regarded succession in Zimbabwe
of
as a
along the Lundi River and incision
tributaries
the
The preservation
of the Gona-re-Zhou
of Pliocene
m terrace
Cretaceous
valley
1994).
processes.
bottom
marginal
Formation
correlate
Palaeogene,
in the Olifants
Mozambique,
the Malonga
is overlain
Salamanga
sandstone
by fossiliferous
Formation
and conglomerate.
Early descriptions
poorly-sorted
by
of the protoflow
Limpopo
in the valley-
basin
hills,
the
rudaceous
relief,
proximal
and pebbly, perspective,
was dominated
transport
basin.
southward
Cox
direction
(1963)
component
Zimbabwe
sediments
sand. Seen in a regional
or southeasterly broad
marine
probably
indicate high energy and high-density, transport with sediment deposited as
the alluvial environment
near Massingir
and fan
of coalesced
areas. Close to areas of high bedrock as the
Pafuri. Further
south,
surface
channelized
matrix-supported,
of western
extensive,
transport
a Piedmont
and Keyser (I 972) reports finding only indeterminable fragments of bone in outcrops in the area south of River valley
of
(Blair and McPherson,
sediment
fans on the margins
sediments sheetflood
the Malonga Formation as being unfossiliferous
the laterally
environments
Basin with localized, such
breakup
poorly-sorted, pebbly sandstone is characteristic of alluvial
across
alluvial
the
area and the westernmost
exposures,
Sheetflood
occurred
after
by a southerly
over much of the
described
a strong
in the northern
with derivation
outcrops
in
from the west in the Pafuri
Rennie (I 944) and Borges (I 944) actually equated the fossiliferous marine rocks exposed at Mabosi
area, invoking the proto-Limpopo River as a possible source. In the Pafuri area, channel bound, fining-
(Mahosi near Massingir), nearly 160 km southsoutheast of the Pafuri area in Mozambique, with
upward gravel and sand units and bioturbated silty sediments, probably
the Malonga
this
correlated 1972;
Formation.
Subsequent
these deposits
SACS,
1983).
lamellibranchs of Upper
These
rocks
and gastropod
Senonian
also
Keyser,
and
contain
marine
apparently
(36 Ma to 55 Ma)
a decidedly
by the authors
system,
1969;
species characteristic
to Eocene
strata, giving the deposits aspect (Rennie, 1944). Recent fieldwork
references
(Haughton,
Palaeogene
on
were
Cainozoic
boundary
data derived from derived palygorskite age (below).
western Mozambique, showed fossiliferous, Salamanga
environments
Formation
rocks.
associated
with
gravels confirms overlying
that these gravelly, Formation rocks
the red Shingwedzi/Olifants
Identification the basal
of silicified
Salamanga
Formation
correlated
A piece of silicified wood associated Malonga
Formation
outcrop
sedimentary valleys changes
with the upper
Upper Cretaceousl pers. comm. 1.
taphrogenesis related the development
wedges
in the Zambezi
to uplift
in the
in the
regional
rocks.
south of Pafuri is typical
of Podocarpus from the Palaeocene period (Bamford, Post-Gondwanan Nairn et a/. (1991)
wood
Formation
the Eocene age of the marine rocks
the Malonga
interior stress
across
the
as is suggested
Mesozoic/ by the proxy
the analysis of terrestriallyin oceanic sediments of this
and Limpopo
associated field
with
due to the
conditions reconstruction
on the
of the alluvial
post-Karoo
age Piedmont
surface is facilitated by the relationships between sedimentary units and palaeosol profiles, whose thickness, factors
maturity such
episodic,
and lateral
as minor
high
channel
sedimentation
continuity
sedimentary suggests
rate,
units and associated
major, episodic,
reflect
entrenchment,
conditions and possible tectonic sedimentation. The lateral persistence
arid climatic control on of individual
palaeosol
sedimentary
profiles
events.
The
sequence of thick, coarser-textured, sedimentary units and associated calcic palaeosol profiles, represents
of thick
development of the Agulhas fracture zone during the breakup of Gondwana. The thick sediment pile confirms the general view of vigorous river incision in the interior with high erosion and sediment transport
782 .fo”rnal of African Earth Sciences
channels
Sedimentation
and staff from the Palaeoenvironmental Palaeoenvironmental
overlie
in fluvial
surfaces.
continued
Direccao National de Geologia (DNG) on the shores of Massingir Dam in the Olifants River valley of
unconformably
deposited
floodplain
overlying, related to
repetitive
events
comprising
episodic
sedimentary pulses followed by geomorphic stability, which were relatively consistent during the long period of sediment
accretion
in this area. Where
sedimentation rate was high, surfaces aggraded and little or no soil development occurred, contrasting with areas starved of sediment where thick, mature pedogenic profiles developed (Wright and Alonzo Zarza, 1990).
Post-Gondwanan
There is a sharp contrast
between
upper parts of the Mwenezi
valley
continental sedimentation,
the basal and succession.
The
poorly-defined relationship between calcareous palaeosol development and the sedimentary units comprising higher
the -30
m basal succession,
sedimentation
rate with
dating accumulation
pedogenesis
of a number
nodular lower
units and intimately
calcic energy
palaeosols,
periods of pedogenic events
(Wright
be contrasted
stability
Zarza, further
coarser-textured,
sedimentary profiles.
palaeosol
comprising
episodic
longer-lived
features
and calcite
conditions
were
smectite,
in calcareous
during
the
succession
relatively
palygorskite,
palaeosol
should be seen in the context
Cainozoic
in this region.
continent,
regional
In the south
deep kaolinisation
the
Early
of the subresulted
from
a long period of intense weathering experienced by the post-Gondwanan, African land surface, followed by the formation
of ferruginous
and siliceous duricrust
profiles over wide areas of southern 1993).
Africa (Partridge,
During the Mid Cretaceous,
was forested
and experienced
and wet climate
(Rayner
central Botswana
a temperate,
et al., 1991).
seasonal The Upper
Cretaceous in southern Africa was characterised by a humid, tropical climate with deep weathering and high
runoff
which
sedimentation
is reflected rates
(Partridge,
Cretaceous/Palaeogene with
by rapid
boundary prolonged
marked
change
stepwise
cooling during the early Cainozoic
and Maud, 1989). The Upper Cretaceous
offshore
1993).
climatic
The a global
desiccation
suggested
of the Sena/Gona-re-Zhou/Malonga
rocks
this
places of initial
succession
However, lithostratigraphic
broadly
sedimentation
Kalahari Group sediments direct
and
(Partridge
accumulation period
In the extreme no evidence influence
of
basalt
correlation
units related
for
within
the
of the widespread
in central
southern of
humid
in the
of South
joint
palaeoenvironmental
weathering sediments
along
best
conditions
there is under the
Formation
The
and
Instead, the fresh
calcretization
pattern.
episodic
Africa
tropical above.
Malonga
is the
Namib
weathering
and
as described
‘boxwork’
region
(I 993) stressing
aridity
northeast
underlying
displays
African
(1990) favouring
of deep kaolinitic
environments
a closely
interpretation
of
during accumulation
of the Malonga Formation sediments is provided by the authigenic mineral assemblage associated with intraformational kaolinite and
palaeosols.
is absent
the
calcareous minerals,
occurrence
duricrusts
crystals,
point
or authigenic
of
including
palygorskite
inferred
Detrital
in all of the sequences
common
studied
interbedded
Mg2+-enriched
and dolomite
and rare gypsum
to more arid conditions
during the Upper Cretaceous
nodules,
Africa.
specific
to arid events
across
southern Africa is difficult as the east-west climatic gradient which characterises the subcontinent could have been established during the early Cainozoic (Partridge, 1993). The chronology defining establishment of post-Late Cretaceous aridity in the
profiles
and horizontal the palaeosols and Wright where
with
subvertical,
than those in this region.
tat conditions dolomicrite
branching,
sheet
(1991).
interpreted
and calcite
calcitic rhizocretions
calcretes
described
are very similar
by Allen (1986)
The reddened
most of the calcrete as truncated
sandstone
features palaeosol
to
and Purvis units
are located
are
sola developed
within stable areas adjacent to fluvial channels or on alluvial fan surface. The red coloration reflects authigenic
iron oxide formation
in geomorphic
settings
and oxidising Mount
which
conditions
penetration
of vertical
and Cohen
(Pye,
(1984)
(I 991) was attributed
overbank
which promote
is enhanced free drainage
1983).
rhizocretions
The deep
described
and Purvis
deposits.
fringe above the phreatic channel sediments and
A series of horizontal
layers following sedimentary bedding attributed to carbonate preciptiation A close dolomite, Formation
calcrete was also above a
water table. palaeoenvironmental smectite calcrete
of palygorskite comprising
by
and Wright
to the tap roots of phreatophytic
plants utilising the capilliary water table zone in fluvial
fluctuating age
Partridge
Miocene interior.
The calcrete
of the Malonga during
Eocene whereas post-Upper continental
Pedogenic palaeoenvironmen
palaeoenvironmental
aridification
of the southern
Ward and Corbett
profiles
conditions.
accumulation
of the progressive
by
period of sediment clay minerals and
to arid climatic of
events
pulses followed
stability,
comprise
Interpretation
of thicker,
repetitive
sedimentary
formed
under semi-arid
This can
units and associated
during the long The authigenic
Formation
1990).
parts
controversial,
spaced
north in the basin,
Here,
geomorphic
consistent accretion.
short
depositional
by the Chilojo Cliffs sequence
calcic
carbonate
with
between
and Alonzo
fine
an episodic,
environment
with events
represented
of numerous,
associated,
suggest
sedimentary
post-
of the depositional
units. In the upper part, the sequence thin sandstone
points to a
western
Limpopo region
analogy
and palygorskite-rich profiles is the extensive
and associated
pedogenic
pedogenic
profiles formed
Cainozoic,
Zuurverdiend
Formation)
sediments
Member in the upper
of the Malonga deposits dolocrete
within undated (Rooibokkraal Limpopo
River
basin and the Springbok Flats areas to the west (Botha and Hughes, 1992). Palygorskite in terrestrial environments is often associated with dolomite and represents semi-arid or seasonally arid conditions which were generally not as extreme as those of
Journal of African Earth Sciences 183
G. A. BOTHA and M. C. J. DE WIT
desert dune or evaporite
mineral
formation
(Callen,
1984). The crystallization of fibrous palygorskite clay from soil water occurred in poorly drained, waterlogged
areas where
evaporation
groundwater
solutes
concentrated Norrish,
1974;
elevated
Botha
(Singer
and Hughes,
1992).
groundwater
through
cation
extraction processes
(Watts, 1980; Nickel, 1985; De Deckker 1989; Botha and Hughes, 1992).
The
the periodicity
the fluvial
system,
Callen (I 984) described the Upper Cretaceous Early Eocene period as one of the major periods palygorskite
formation
and Robert accumulation
to of
with Vernier and Froget (I 984)
and Charnley
(1991)
of pedogenic
describing
palygorskite
similar
the
eroded from
periods
to draw
in a
sedimentary
as the
bracketing
conclusions stability studied
are
is no absolute
the Malonga
required
in
by Allen (I 986) for
sections
and there
of stability
any
of geomorphic
as calculated
calcrete
discontinuous framework
and Last,
profiles
fluvial
units implies episodic sediment accretion separated by long periods of geomorphic stability in the fluvial It is difficult
profiles
calcrete
of similar
regarding
in calcrete
in soil
of similar
succession
system.
of Ca2+ ions from
calcite precipitation
exchange
presence
and
Mg/Ca ratio of vadose water was interpreted
as the result of selective and
effectively
The stacked
dating
Formation.
for the formation
The of the
calcrete profiles described was possibly of the order of 1 O4 years or 3x1 O4 years, regarded as necessary for formation
of similar
Stage
II and III calcretes
Leeder (1975) and Allen (I 9861, respectively. nodules up to 1 cm in diameter year
period
in buried
formed
within
palaeosols
by
Calcrete a 1000
within
Late
the southern African continent within oceanic sediments of this age beneath the Atlantic and Indian
Pleistocene colluvium (Botha et al., 1994). However, reliable estimation of time required for formation of
Oceans.
smectite
calcrete
to
in rainfall,
These
derived
authors
from
the
attributed
adjacent
conditions
with
Increased
palygorskite
during
Palaeocene/Eocene
the
alternating
reflects enhanced contrast. Rubified
coloration
profiles
and seasonal
formed
in low-lying,
minerals
above the vadose The per
calcrete
rhizocretionary
features
a phreatic cementing
mode
groundwater
source
613C from currently
profile.
the
calcareous
being
environment of calcareous
features
undertaken,
of carbonate aeolian
analysis will
precipitation.
dust is difficult
Formation sediments deposition
of diffuse
in pedogenic implies
calcareous
profiles
relative
in levees/alluvial
within
stability ridge
derived
incision away
of
more
mature
in stable,
distal floodplain
to the channel
to incision
of 6180 and and cement,
probably
a distinct
the in
and
of
sediments probably climatic conditions.
fluvial
river valleys
to changed the
and Kraus, within
the
deposits
prior
in the region,
climatic
conditions, or drainage
decalcification
underlying
and
calcareous
occurred under more humid The formation of a hematite-
dominated, terra rossa weathering profile suggests deep leaching under a climatic regime with strong seasonality through
the overbank
developed
Deep weathering,
ferruginisation
conditions
change in pedogenic
in response
conditions.
The influence
mottles
of the major
represents
environments
or levees (Bown
carbonate
Formation
and
pedofacies
depositional
profile
below
migration
palaeosol
calcareous
to establish
supply
are interpreted
channel
Malonga
and
elucidate
variation
Ca”
in the red sandy
lithologies
during
from the more active
adjacent
this environment but is a likely contributor given the arid palaeoenvironmental conditions inferred. nodules
These clay-rich
as being
profiles and
and sandstone
Isotopic
to that found
1987). The weathering
nodule
of
and
blocks of red clay, with a similar
assemblage
occurring
carbonate
of pedogenic for
in the palaeosol
the conglomerate
the pedogenic
of ferro-magnesian
is favoured
mineral
profiles.
zone of the groundwater
descensum
formation
by regional
palaeosols, occur as clasts in the cross-bedded gravel infilling channels incised into the palaeosol
point to a the red
of authigenic
is hindered
evapotranspiration
Small pebble-sized
period
aridity
due to in situ oxidation
structures
(Wright, 1990).
deposited
River floodplain sediments pedogenic environment,
with crystallization
warm
and dry seasons. boundary
terrestrial
minerals, table.
wet
in sediments
palaeosol
proto-Limpopo well-drained
the
continent
and
lowering
periodic
desiccation,
probably
of the water-table.
as high rates of areas
close
to
Tectonism
channels would inhibit pedogenesis and calcrete formation (Bown and Kraus, 1987; Wright, 1990). The precipitation of sparry calcite rims around clasts and within the coarse, sandy interstitial matrix in
The accumulation of the Malonga Formation occurred after the differential uplift, crustal extension and continental rifting associated with the extrusion of a thick pile of Karoo lavas and intrusion of acid igneous
the underlying gravels probably occurred phreatic groundwater flowing through these
sheets
permeable
sediments.
from more
Nuanetsi Jurassic.
and ring structures
within
Syncline (Broderick, In northern Botswana,
the axis of the
1991) during the Du Plessis and Le
Pos t-Gondwanan
Roux (I 995) describe which
influenced
Late Cretaceous
deposition
block faulting
of the basal Kalahari
Group rocks. Flores (I 973) described and faulting
associated
the tectonism
with the development
Urema Graben to the east as occurring after,
accumulation
region,
of the east-west and
trending
a northerly
succession (1995)
Sengwe
fracture
Formation
the
Bosbokpoort fault described
the vertical, Malonga
fault
north trending
Formation
Brand1 of
River valley,
is related
It is unclear
fracture
outcrop
south of Pafuri, is related Whether
1991).
by the east-west
which
above.
in this
displacement
west of the Kruger Park boundary, Sengwe
Gona-re-
occurs
rocks in the Limpopo
trending
In the
to the south
(Broderick,
described
and
Fault near Dumisa
trend
near Malapati
recently
Malonga
the post-Karoo,
has been downthrown
to the
zone cutting
the
fountain,
the depositional
cyclicity
the Malonga Formation tectonism in the Limpopo
preserved
represents region,
within
episodic or climatic
and
sequence
flowing
controlled
channel
from
within
The periodic
successive of
a structurally-
the
of the
relationships
sedimentary
units
palaeosol
and the
material derived
underlying
sediments
Pafuri
area
can be contrasted
continuous,
thinly-bedded,
with
the laterally
sheetflood
sediments
to areas of high relief. The wide occurrence
of this system
along the margins
of the tectonically
active Limpopo and Zambezi valleys, suggests the existence of a Piedmont land surface comprising alluvial
fans along the continental
margin
during the Late Jurassic to Early Cainozoic era. The age of the succession remains enigmatic. The maximum
age is inferred
from
the lithologically
similar sediments overlying the 1 15 Ma lava in the Zambezi River valley. The minimum Late Cretaceous
of individual
age is based on the overlying
transgressive
associated
palaeosol
profiles
suggests
major,
Grudja
Formation
in the Zambezi
sedimentary
events.
Palaeosol
profiles
valley.
It is suggested
with
alluvial
fan depositions
channel-infill/floodplain
deposits
lateral
units
and
units and
comprise
the
succession in different parts of the basin, showing similar development. Interpreted in terms of periods of geomorphic interpreted
stability, as
perturbation
a rhythmic,
of the
environmental
this phenomenon
drainage
conditions
can be
possibly system.
and
long
to episodic
tectonic
succession
silcrete
formed
palaeoenvironmental
of
uplift.
the Malonga
sedimentary
Formation
Gona-re-Zhou Formation)
Plateau
Beds
Dande Formation Correlative
in western
de Sena of the Zambezi and the ‘Formacao
continental,
Cainozoic
the eastern margin of the emergent after
the breakup
of Gondwana.
succession
and provides
described
a valuable
link between
sedimentary
River valley. are
and Limpopo These deposits
sedimentation African
The investigation support
provided
B. Pretorius
Malvernia
de Singuedezel
River valley.
taphrogenic
as
with the
Mozambique
River valleys
Elefantes’ in the Olifants
during
the
is locally
lithological
and
the eastern margin
succession
is poorly
exposed.
and the similar
the Formacao
represent
known
(formerly
Zimbabwe
rocks of the Zambezi
sequences
was deposited
ACKNOWLEDGEMENTS
succession
can be correlated
in southeastern
River
of the Malonga
of the emergent African continent and development of the intracontinental Kalahari basin, where the early
CONCLUSIONS The post-Karoo,
much
in this region.
The sedimentary
The
arid
that
marine
period of aridification prior to the Late Cretaceous or Early Palaeogene when the ‘African’ land surface
well exposed
geomorphic stability throughout the accretionary period suggest that individual depositional events may have been related
Formation
sediments
regional periods
as
intraformational clasts in younger sediments. The fluvial depositional environments active in the
remains
sedimentary
an
fluvial
migration
by erosional
of calcretised
erosion
in the
represents
of a mixed-load
is defined
incorporation
area
southward
river valley.
between
The succession
Pafuri
persistence
associated
The
system fluvial
valley.
valley
influence,
episodic,
speculative.
Limpopo
coalesced
to this faulting.
region
the proto-Limpopo
adjacent
whether
near Malonga
Limpopo
aggradational
of the
during,
of the Sena deposits.
Limpopo-Mwenezi Zhou succession
con tinen tal sedimentation,
on
continent
Sedimentation
followed the long period of eustatic uplift associated with Karoo vulcanicity and the extensional tectonics and rifting along the continental margin and within
benefitted
greatly
to the authors
from the field
by Dr F. J. Venter,
(Punda Maria) and S. Ronaldson
of the National We are indebted
to Prof. T. Mason
Natal,
for
Durban)
(Pafuri)
Parks Board in Kruger National identifying
Park.
(University the
of
Taenidium
ichnofacies and MS M. Bamford who identified the silicified wood samples. The Malonga Formation succession
in the Pafuri area could
be described
in
a regional context due to the support of the Executive Officer and Directors of the Council for Geoscience and the assistance of Mr J. Marques, Director of the Direccao National de Geologia in Maputo, Mozambique and the Acting Director, Zimbabwe Geological Survey, who facilitated field investigations
G. A. BOTHA
in their respective unpublished
countries
information.
Mr P. Fey, formerly Survey,
who
access to
are grateful
of the Zimbabwe
arranged
Gona-re-Zhou
and provided
The authors
to
in the
with measurement
American
Survey
Research
image processing
of South
Africa.
Laboratories
made
and CAD facilities
satellite
1984.
(Edited
by Singer,
is based
on a paper
at the XII biennial
conference
during
A. S., 1982. Fora
Petrology Commission
African
for
Society
Cox,
K. G.,
1963.
their
REFERENCES Sandstone
facies
Anglo-Welsh 58-86.
(Late
area,
recognition Alonro
Pedogenic
calcretes
Silurian-Early
southern
Blackwell Zarza,
Cura, M. A., 1992. in the middle
Publ.,
Red
of the
Paleosols:
by Wright,
their
V. P.) pp.
J. P. and Garcia
and climatic
of the Madrid
del
Boyd,
and
Save-Limpopo
Zimbabwe
Basins
distinction
processes, Journalof Borges,
Tectonics
A., 1944.
Marques
6. 5-l 2.
139-l Botha,
in a late
do Alto Limpopo.
Pedogenrc
Lorenco
G.,
Geoderma
A. G. and Vogel,
palaeogully
Africa. G. A.,
erosion
Catena
J. C., 1994.
rn northern
53,
De Wit,
1993.
Transactions
De Deckker,
P. and Last,
dolomrte
in evaporitic
Sedimentary
setting.
(Malvernia)
Formation
Park, South
Africa.
Pafuri
relations
suites, of
paleosols.
P., Fedoroff, U.,
description.
152~.
Sengwe Survey
Warne,
and
faults
of the
Society
Mwenerr
A., S?oops,
England.
lateral
for soil
Land.
thin
of
valley Annals
G., Turcina,
of
tectonics
pp 21 I-235,
the
Penod of (Edrted
Olrver
and
plumes
in the development
Nature
342,
of the Royal
W. M., 64,
T.
section
lake
Botswana.
20.
7-l 5. H. V.,
Marsh,
Igneous
Province:
volcanic
873-877.
1989.
underplating.
Society
Modern,
of western
of London nonmarIne
Vrctona,
Australra
223-238. A. R., 1983.
Africa.
Mesozorc
375~~.
rocks
J. P., 1995.
complexes
Late
of the
Balkema,
J. S. and Cox,
of the Karoo
1984.
Province,
Special
Lupata
The Cretaceous
Mozambrque
of theAfrican
Coasts.
Forster,
the
Mozambrque.
L. H.,
Printer,
Peterson,
Morphological
and some
aspects
accumulation Goudle. A. S.,
envrronment
pp 93-I
31. Academrc
Gwavava,
0..
genetic
Swain,
Evidence
S. H., 1969.
and
residua
by Goudre,
Press,
in the
mlnerais,
escala
Republica
Podmore,
F. and
thinning
beneath
of crustal
K),
Farrhead.
J.
the Llmpopo
of southern Africa based on and rmpllcatlons for the Tectonophysics 212, I-20.
Geologicalhistory
7: 1 000 Popular
nears
A. S and Pye,
of southern
pp 427. Geological Society of South Africa. Instrtuto Nacinnal de Geologia.. 1987. Carta Mozambique,
1966.
carbonate
London.
Belt and Lebombo monoclrne regional gravity studies reconstructlon of Gondwana. Haughton,
R. B., of
Soil Science 101, 347-360. and In: Chemrcal sedrments
(Edited C. J.,
Grossman, sequences
Precipitates
surface
Geological
Pretona.
in desert soils. 1983. Calcrete.
geomorphology:
of the
Palaeogeography,
Channel.
F. F. and
and
Pans.
of the sedimentary
Palaeoclrmatology, Palaeoecology 17, 267-287. Geological Survey., 1981. 2230 Messina, 1:250000 Goverment
Basins
G.), pp 88-
Surveys,
history
Lower
sedimentary
by Blant,
Geological
Mozambique
rocks,
of
of the Geologrcal
In: Sedimentary
(Edited
The geological
of southern of
2ndpart
of African
R., 1975.
Society
and Tertiary
and Zululand.
Karoo of the
Publrcatron
Geologrcal
River, Mozambique. Transactions Society of South Africa LXVII, 11 l-l 20. 1973.
The
In: Petrogenesis
Zambezr
G.,
Group
Earth Sciences,
K. G.,
and introduction.
Cretaceous
Kalahari
JournalofAfrican
13 (Edited by Erlank, A. J.) pp l-26. South Africa. Flores, G., 1964. On the age of the
D., 1992.
Geocongress
Communal XV, 53-58.
Handbook
and
rn the Llmpopo
Geological
000.
341-344.
magmatic
P. I. and Le Roux,
Eales,
Gale,
Council
of Sedimentary
Centennial
N., Jongerius, 1985.
I.G.)
geology of Southern
and slaine
Series,
Nattonal
of channel
sequence Journal
of certarn
Quaternary.
Malapati, Geological
and Babel,
and
Malonga
Kruger
lntegratlon
Extended Abstracts 1, 442-444. South Africa, Johannesburg. Brodenck, T. J., 1991. The geology south of Zimbabwe
the
1995-0046,
I. Developmental
alluvial
the
The
Pretoria.
Petrology 57, 587-601. Brandl, G.. 1995. Fieactrvatron during
area,
ReportNo.
1995.
successron of
T. M. and Kraus, M. J., 1987.
floodplarn
F. J.,
lithologrcal
in the
33pp.
Transactions 66.
magmatismand
playas
Geology
and Tertiary
basin
Kwa ZuluNatal,
M. C. J. and Venter,
1986.
000
fragmentation
Continental
66.
155-l
orlgln
palaeoenvironments
for Geoscience,
Episodrc late
23, 327-340.
geologlcal
1:5
of the Karoo
patterns.
A, 342,
basinsof
succession,
Africa.
World.,
postulated
The role of mantle drainage
Philosophical
Flores,
palygorskrte
sedimentary
South
of the
and vulcanism
and Gass,
11 1. Association
depositional
Bullock,
hydraulic
54.
regronal
Belt
the
fans and their
e Geologia,
J. C., 1992. Neogene
Transvaal,
G. A., Wintle,
South
Bown.
conglomeraticos de lndtistria
G. A. and Hughes,
Cluaternary Botha,
of
processes, and facres assemblages. Research A64. 450-489.
Depositos
northwestern
Alluvial
from nvers based on morphology,
dos Services
and dolomrte
Annals
from the
of Sedimentary
Africa,
of beds.
onthe
In: African T.N.
in northern
Xl, 41-55.
J. G., 1994.
sedimentary Sedimentary
Boletim Botha,
K.
Du Plessis.
of the Mid-Zambezl
in Zimbabwe.
GeologicalSurvey
Blair, T. C. and McPherson, natural
potential
Developments
Edrnburgh.
alkaline The hydrocarbon
uses
Rotterdam.
relationships
Sedimenfology
Basin.
39, I’-35. Barber, B., 1987.
Map
Map
Dingle, R. V., Sresser, W. G. and Newton,
Oxford.
V. P., Calve,
Soil-landscape
Miocene
In:
(Edited
Scientific
A. M., Wright,
Old
Carboniferous)
Britain.
andinterpretation
in the
Journal
of South Africa
bearing
by Clifford,
995.
Cox, R. L. 1986.
In:
and
of root casts
Kenya.
Malvernia
Society
of continental
J.
genesis
Paleoenvironments
Geological
Cox, K. G., 1989.
Allen,
group:
distribution.
E.) pp l-37.
52,401.414. for the Geological
Gondwanaland.
Research
from 30/4-6/5/l
and
Elsevrer.
Formation,
International
and
Southern
Quaternary
held in Cape Town
age occurrences,
37,
Cox, K. G., 1970.
presented
of the
of the palygorskite-sepiolite
A. and Galan,
in Sedimentology
Geological
This manuscript
Clays
environment,
UNESCO.
the investigation.
(SASQUA)
R. A.,
depositional
Koobi
Anglo
available
Callen,
Cohen,
of the Chilojo Cliffs section. XRD and XRF analyses and micromorphological thin sections were provided by the Geological
C. J. DE WIT
Palygorskite-sepiolite:
Geological
the visit to outcrops
area and assisted
and M.
000,
Minrsterro
de Mozambrque,
Africa.
Geologrca dos recursos
Maputo.
Pos t-Gondwanan
Keyser,
A. W.,
van
die
1972.
Jong gesteentes
Nasionale
C. F.,
classification,
Rhizoliths
lithofacies.
genesis
Geological
Rhodesia.
Transactions 193-l
Lister, L., 1987.
The erosion surfaces
A. D., 1977.
braided
Lithofacies
river
Money,
7992, 42-51.
N. J.,
1972.
12,
Mount,
Geological
J.
Cohen,
J. D. G.,
Rhodesia.
S.,
1984.
east
Petrology
1967.
potential
of
Petrology
Lake
and
fluvial and
Turkana,
Preliminary
of the
Zimbabwe
Geological
Survey
Files.
Nairn, A. E. M., Lerche, I. and Iliffe, J. E., 1991. Geology, basin analysis, and hydrocarbon potential of Mozambique and the Mozambique
Channel.
Netterberg,
F.,
calcretes,
Earth-Science
1980.
1. Terminology,
of
classification.
Transactions 83,
24.
of the
Geological
and
Society
P. M. and Millsteed.
and
B. II.,
1994.
Partridge,
T. C. and
terraces
of
Journal
the
49,
Partridge,
Geology
Brink,
lower
event:
Vaal
Journalof
Lithostratigraphy,
River
Gravels
basin.
and
Geographical
Africa.
K. and
&rat.
lnt. 17, 105-l V.
P.,
1991
environment
Rayner, Shaw,
R. J., Waters, A. L., 1991.
(Edited
Academic
by Goudie, Press,
S. B., McKay,
A. S and
Pye,
London. I. J., Dobbs,
The mid-Cretaceous
P. N. and
palaeoenvironment
of central Southern Africa (Orapa, Botswana). Palaeogeograph y, Palaeoclima tolog y and Palaeoecolog 88, 147-l
56.
Bristow,
J. W.,
K),
geophysical Zimbabwe Tswiza-Vila Lowveld
Geological
1986.
of the
1984.
du
bassin
Sud
Ouest
supepieur
(sites
Dynamique
of
Survey
de
D.S.D.P. et
de
An
account
Kruger
Park.
argileuse
Somalre
240
of the
National
Sedimentation
depuis
et 241).
Geographic
y
Monograph
N. L., 1977.
le
Revue
Physique
de 25,
7. 17-26.
Pseudo-anticlines
of Botswana
and other
and South
Africa.
Quaternary
(southern
valley,
pedogenic
Africa):
Sedimentology
A. H., 1970.
Sipolilo
calcretes
Mineralogy, 27,
Notes
rn
L. G. and Saggerson,
Detritus
of the Kadzr area,
E. P.. 1988.
Geology
of the
rocks of the southern Lebombo Excursion A, Geocongress ‘88.
in ancient
Magazine 127(3), 273-276. Wright, V. P. and Alonso Pedostratigraphic
the and
5, 26-28.
Geological Society of South Africa, 37pp. Wright, V. P., 1990. Estimating rates of calcrete accretion
from
genesrs
661.686.
on the geology
District.
volcanic and intrusive Mountains. Guidebook:
sedrment
structures
Earth Surface
2, 63-74.
N. L., 1980.
Wolmarans, to
Pye, K., 1983. Red beds. In: Chemical sediments and geomorphology: Precipitates and residua in the nearK), pp 227-263.
in the near-
A. S and Pye,
survey,
Zimbabwe
C.,
Zambezi
aridification related
In: Chemicalsediments
south-eastern
E. and Froget,
diagenesis.
South
10. Calcretes
Geology
Files.
le
Kalahari
phreatophytic vegetatron from the Middle Triassic Qtter Sandstone of South West England. Sedimentology 38, 539551.
surface
F. J. and
some calcretes
Wilson,
for Cainozoic
Pleistocene
Sedimentary
seismic
geomorphology and drainage Koedoe 29, 1 17-l 24.
Processes
85, 428-430.
The evidence
Wright,
hemisphere.
Flash-
Late
Unpublished
border,
Files.
J. D., 1993.
and residua
Technical
Technical
59,
on a reconnaissance
Refraction
TransvaalMuseum
The end-Cretaceous
from the southern
Namibia.
palygorskite
Venter, F. J., 1986. Soil patterns associated with the major geologrcal units of the Kruger National Park. Koedoe 29, 125-l 38.
Watts,
205-224. 1967.
R. R., 1989.
Science
T. C., 1993.
in southern
B. A.,
Survey
Anna/s
Mineralogist
of the
Lowveld.
Unpublished
Watts,
New evidence
Partridge,
A.
97(2),
Pedogenic
Silcrete.
Report east
die Formasie
339-348. Ward, J. D. and Corbett, I., 1990. Towards an age for the Namib ecology: 25 years of Namib research. Namib.
2 l-38.
T. C. and Maud,
African
Purvrs,
Journalof
In,
9, 83-84.
American
River,
Rhodesia.
Geologic
diagenesis.
1974.
T. R. and Ward,
Mozambique
C&ace
in alluvial fan systems. An approach
K.,
1983.
E. R., 1968.
dans
palaeontology, and sedimentary environments of the western Cabora Bassa Basin, Lower Zambezi Valley, Zimbabwe. South African
Sutton,
Vernier,
255-283.
Carbonates
Kurseb
van
of South Africa
and ichnofacies
- south
Venter,
African
macrofeatures
sedimentology to physiography, Sedimentary Geology 42. 83-l 04. Oesterlen,
30, 81-l
southern
description,
of South Africa Nickel, E., 1985.
Reviews
Geology
Survey
E. R., 1967.
alluvium.
Krugerwildtuin.
(Edited by Goudie, Press, London.
Salazar,
rocks, S. E. Lowveld,
foorkoms
Nasionale
surface environment pp 59-91. Academic Sutton,
mineral
and Planetary
for braided
Precipitates
Geological
investigations
y (Global
and geomorphology:
survey
Kenya.
54, 263-275.
of the Cretaceous
Unpublished
Technical
Republic
‘n Nuwe
85, 579-599. Summerfield, M. A.,
of western
Survey,
of early
clay
Palaeogeography,
models
in Australia.
Silts,
from
e
(Edited by Miall, A.D.), pp 605-625. Society for Petroleum Geologists 5.
508-5 17. Smith, R. M. H., Mason, Homeb
6, 27-35. 1991. Development
Depositional
sediments
de
de lndustria
315-331.
A. and Norrish,
flood
Namibia,
from Plio-Pleistocene
deposits,
Sedimentary
petroleum
A.
of rhizoliths
lacustrine
Muirhead,
of
of the geology
of the Geological
and
geochemistry Journalof
of the
103-123.
F.
marginal
sediments
89,
In
Conglomerados
sediments.
suid van Pafuri,
occurrences
Canadian
Kalahariiymposium, Society
An outline
Records
Zambia
volume,
B. R., 1979.
Singer,
Fluvial
in,
Mabosi,
axis
222-223.
dos Services
tolog y, palaeoecolog
Section)
spreading 19781,
as inferred
oceanic
of the Geological
models
5.
The Etjo and Kalahari
in
Malvernia,
a summary.
climates,
Calgary, Canada. Schutte, I. C., 1974.
l-62.
Geo!ogis ts, Memoir
Basin. Abstracts
Zambia.
Zimbabwe
profile
(18 May,
Boletim
Fluvial Sedimentology, Memoirs Canadian
depositional
and vertical
deposits,
R. G., 1992.
November Windhoek.
Rust,
of South
(Edited by Miall, A. D), pp, 597-604.
of Petroleum
Owambo
types
13,
warm
Change
pp. 163
Reviews
Gondwana
273
Fossils from
Marques.
palaeoclima
of Zimbabwe.
A failed
Nature,
J. V. L., 1944.
variations
part of Southern
of the braided-river
Earth Science
sedimentology Miller,
90,
A review
Miall, A. D., 1978.
Society
Bulletin
1978.
Africa.
Eocene
257-270.
of the GeologicalSociety
region
Geologia, Lorenco Marques Robert, C. and Charnley, H.,
significance.
98.
Survey
environment. in
112,
C. V.,
Lourenco
carbonates and flood sediment model for alluvial arid-zone
Magazine
Reeves, Rennie,
8p.
and
Limpopo
southern
carbonates:
Notes on the south-eastern
Africa 41,,
Miall,
deel report
27, 613-629.
B., 1938.
Geological
1972-0053,
in terrestrial
recognition,
Leeder, M. Ft., 1975. Pedogenic accretion rates: a quantitative Lightfoot,
Unpublished
South Africa,,
1980.
Sedimentology,
in die noordelike
Kruger-wildtuin.
GeologicalSurveyof Klappa,
con tinen tal sedimentation,
models
formation
alluvial deposits. Zarza,
for alluvtal
A.
and
Geological M..
1990.
fan deposrts:
for interpreting ancrent sequences. Journal Geological Society of London 147, 8-l 0. Zimbabwe Geologrcal Survey., 1991. Zimbabwe
a tool of
the
geology
7: 7 ODD DOD, 7th edition.
Journal
of Afman
Earth
Soences
187
of African
Vol.
Earth Sciences,
Pergamon
23, No. 2, PP. 163.187,
PII: SO899-5362(96)00060-7
0899-5362196
Post-Gondwanan continental sedimentation, Limpopo region, southeastern Africa
G. A. BOTHA’ and M. C. J. DE WIT2 ‘Council for Geoscience, 2Anglo-American
P.O. Box 900, Pietermaritzburg, 3200, South Africa Research Laboratories IPty) Ltd, PO Box 106,
Crown
Abstract-The
post-Karoo
Formation,
is currently
Singuedeze/Elefantes’ Africa,
breakup
and within
systems
active
followed
the extensional
tectonics valleys.
an eastward
sandstones
and conglomerates,
units comprising
succession
alluvial
exposed possibly
developed
within
plain.
comprising
coarse-grained off areas
in the
Olifants
sandstone,
River
units
for an indication accumulation Late
relationships
landsurface
sediments
Resume-Sit&e se partagent Formatron
formation, vastes
I’exrstence
en bordure
coalescents
La sedimentation ainsi qu’a
suggere
du continent
la tectonique
in
palaeosols on the broad
depositional
interbedded
units
with very generated
d’une
surface
des vallees proto-Limpopo
autrefois
Beds’.
majeurs
formee
associes
La Formation
de
de Sena’,
resultent
d’une
en voie de
jalonnant
a tectonique
sur de
active
du
a Cenozo’ique
precoce,
par des cones
alluviaux
d’inondation.
associee au volcanisme
la bordure
de Malonga
Ltd.
et le Zimbabwe
a des plames
eustatique
affectant
of littoral and
africain
Ce type de sedimentation,
de Piedmont
‘African’
The Eocene
sous le nom
Ces roches
tardif
during the
the
‘Formacao
du continent
dans les vallees
valley
period of
Elsevier Science
connue
de Malonga,
orientale
et au rifting
et Zambeze.
and deposition
du Sud, le Mozambique
a la longue periode de remontee d’extension
ceased with
Copyright D 1996
du Mesozo’ique
fluviatiles
apparently assocrated
Formation
Plateau
septentrional
accepted
prior to the Palaeocene.
Formation
du Gondwana.
a chenaux
layer
post-Karoo
en bordure
plain and in the Zambezi
Deposition
oti I’Afrique
au courant
and one must look to continental/
The most commonly
silcrete
et ‘Gona-re-Zhou
du Lebombo
est posterieure
stability
continuous
coastal
mountains.
appelee
taphrogenique
et des systemes
mountains
on an alluvial fan complex
stability
sedimentaire
au terme de la fragmentation les collines
planar
The homogeneous,
Calcareous
conglomerate,
of the Malonga
est maintenant
et du Zambeze,
I’interieur
ages.
of the thick
in truncation
la serie
continentale
Btendues
Limpopo
Karoo,
and minimum
de Singuedeze/Elefantes’
sedimentation
of fining-upward
Lebombo
geomorphic
is poorly constrained,
dans le bassin du Limpopo, la front&e,
of the
laterally
with deposition
high against the Lebombo
de Malvernia
Formacao
periodic
below the Mozambique
the formation
resulted
east
thinly-bedded
and overlyrng
of this system.
Zimbabwe,
during this long period of geomorphic
marine transgression estuarine
to a sequence
conglomerate
valley,
NW of South
poorly-sorted,
action,
grade
is during the Middle to Late Cretaceous. with
and
topography.
of the maximum
Cretaceous
era.
margin and within the proto-Limpopo
matrix-supported
is consistent
bedrock
of a
with Karoo vulcanicity
near Pafuri in the extreme
reaches
suggest
The Initiation of this period of sedimentation marine stratigraphic
exposed
the
channel/floodplain
to Early Cainozorc
from homogeneous,
the distal
poorly-sorted,
after
mountains
the existence
and major fluvial
uplift assocrated
to boulder
north in southeastern
of high relief
suggests
de
South
continental,
continent
in fluvial channel and floodplarn environments.
represents
thinly-bedded,
African
valleys,
fans
by sheetflood
pebble
the sedimentary
Further
alluvial
change
deposited
clast-supported
bedded silt and sand, deposited
Mozambique,
and Zambezi
Formation
lithological
Malvernia
‘Formacao
rocks represent
margin during the Late Mesozoic
The Malonga
as the
de Sena’,
of this system along the northern Lebombo
and rifting along the continental
Africa
These
of the emergent
the long period of eustatic
and Zambezi shows
borders.
margin
coalesced
close to the continental
formerly
‘Formacao
Beds in the Limpopo Basin region where
have common
Limpopo
comprising
known
Formation,
Plateau
on the eastern
the tectonically
South Africa
succession
Malonga
The wide occurrence
landsurface
Sedimentation
silty
the
and Zimbabwe
sedimentation
of Gondwana.
Piedmont
sedimentary
termed
and Gona-re-Zhou
Mozambique
taphrogenic
age
Mines 2025,
1996
Copvght o 1996 Elsever Scence Ltd Prmted m Great Bmam. All rights reserved
du continent
affleurant
et
au voisinage
S15.00
+ 0.00
G. A. BOTHA and M. C. J. DE WIT
de Pafuri
dans
I’extrbme
nord-ouest
de I’Afrique
lithologique montrant des gres homogenes, deposes
sous I’action du rurssellement
decroissante sables
comprenant
lit&s planaires,
d’inondation.
Des paleosols
sud-orientale
du Zimbabwe,
de conglomerats
tres grossiers,
Le debut de cette
pourrait correspondre
aux termes
Davantage
distaux
et de plame
d’un tel systeme.
suggerent
une stabilrte
vers le nord, dans la partie
laterale
dissemines
en intercalation
avec des depots d’un systeme
par des silts et
River, 5 I’est des
a continuite
et a elements
a granulometne
fluviatiles
sedimentaires
plaine alluviale.
periode de sedimentation
et minimal
tardif
‘Africarne’,
developpee
avec
comprenant
de minces
avec des gres
de cone alluvial forme en contrebas
les relations
et dans la vallee du Zambeze.
au Cretace
la formation
et pour en obtenir une indicatron des
stratigraphiques
continentalesimarrnes
La periode
moyen a tardif. La sedimentation
d’une
epaisse
couche
de silcrete
de depot la plus
prit fin apparemment
associee
a la peneplaine
au tours de cette longue penode de stabilite geomorphologique
La transgression
et le depot de sediments Elsevier Science
est mal contraint
il y a lieu d’etudier
du Mozambique
au C&ace
1996
de chenaux
dans la vallee de la Olifants
des unites sedimentaires
admise correspond
le Paleocene.
d’unites
galets et blocs, coiffes
au sein des unites
mal classes
par une variation
a relief prononce.
sous la plaine cot&e generalement
affleurant
de la vaste
sont compatibles
d’un soubassement
ages maximal
silteuse
developpes
periodique
a abondants
un environnement
au Mozambique,
calcaires
geomorphologique
pas&es
dans
La serie homogene
collines de Lebombo
en nappe, passant a une sequence
des conglomerats deposes
du Sud est caracterisee
mal calibres et frnement lit&s ainsi que des conglomerats,
marine Eocene engendra
littoraux
et estuariens
la troncature
surplombant
de la Formation
precedant de Malonga
les collrnes de Lebombo.
Copyright ’
Ltd.
(Received
31 January
1996:
revised
version received
6 May
19961
INTRODUCTION Research
into
the
geomorphological emphasised
post-Gondwanan
evolution
long-term
of southern
erosional
Mid-Cretaceous
Africa
processes
has
rather
than the characteristics of post-Jurassic rock suites. This is due to the limited exposure of Cretaceous terrestrial dating
deposits
and the difficulty
involved
with
the lithologies.
supposedly Elefantes’ lnstituto
the
(1 :I
National
Previous 1938;
Schutte, lithological
further
palaeoenvironments
these
rocks,
changes,
understanding The
complicated has also
of this lithological
post-Karoo
southeastern
hindered
regional in
the Plateau
Beds by Lightfoot (I 938), and subsequently the Malvernia Formation by Cox (1963). The Zimbabwean nomenclature was utilized in naming this
lithostratigraphic
context, (SACS,
in order 1983).
unit to avoid
Recently,
in the
South
proliferation however,
African of names
Barber
SACS,
(I 987)
suggested that the lithostratigraphic naming ‘Malvernia Formation’ be altered to the ‘Gona-reZhou Plateau Beds’ as the name of the town of Malvernia in Mozambique, from where the Malvernia Formation name was derived, has been changed.
1967;
of the three of Pafuri National
1983)
succession
calcareous (Lightfoot,
Sutton,
1967;
countries
de Geologia, 1991)
whose 1987; the
cover
borders
Survey,
with
emphasis
the calcareous
sand and gravel
rocks in each
meet
1981;
Zimbabwe result
north
lnstituto Geological
that
three,
incompatible representations of the geology been compiled on the International Geological of Africa
(Commission
the
depositional
in any detail. Different
(Geological
Survey,
did not describe
nor interpret
on mapping
and unconsolidated
succession
was named
1974;
has been placed
succession.
sedimentary
Zimbabwe
by several the
the
Zimbabwe
1968; Barber, 1987), western Mozambique (Barges, 1944; Rennie, 1944) and South Africa (Keyser, 1972;
names associated
name
Geologica;
1987).
of
Muirhead,
the
‘Formacao
Carta
de Geologia,
Cox, 1963;
Sena’,
de Singuedeze/
Neogene 000
rocks in southern
The proliferation with
000
descriptions
sediments in this region is due to the isolation of investigations with respect to political boundaries. of stratigraphic
de
‘Formacao
and the overlying
de Mazamba’
sedimentary
Much of the misunderstanding surrounding relationship between the post-Gondwanan
‘Formacao younger
for the Geological
have Map
Map of
the World, 1986). In order to distinguish the calcareous sedimentary succession from its decalcified weathering products
In adjacent Mozambique the same succession was initially described as the ‘Conglomerados de Lorenco Marques’ (Borges, 1944; Rennie, 1944) and
unconsolidated sediment cover, Botha deemed it necessary to redefine this lithostratigraphic unit in South Africa as the Malonga Formation. The criteria used by Botha et al. (1995) for differentiation of the lithostratigraphic unit from its weathering products
more
are
recently
was subdivided
~_____ 164 Journal of African Earth Sciences
into the Lower
to
and derived
et a/. (1995)
utilised
throughout,
even
though
the
Post-Gondwanan
continental
sedimentation,
along
Limpopo
region
the Lebombo
central
mountain
foothills
flat,
sand covered
Mozambique,
in western plateau
areas stand in stark contrast to areas with high drainage density defined by tributaries of the Limpopo, I).
Luvuvhu,
Mwenezi
The escarpment
topography calcareous plateaus
is dominated
by these
sedimentary
rocks.
covered
at elevations
Unconsolidated
Sand
400 m and 528 m
by poorly-defined streams
sand
these wide plateau Late
between
blind ephemeral
drainage
with
and spherical
and gravel
pans.
deposits
areas, concealing
Mesozoic/Early
sedimentary
plateau
in this region
asl are characterised linear,
and Lundi Rivers (Fig.
and sand-covered
cover
the underlying
Cainozoic
calcareous
rocks,
Proterozoic
and the Archaeozoic, and Palaeozoic bedrock (Fig. 2). The
high density
dendritic
tributary
low escarpments below into the post-Gondwanan the underlying
bedrock.
major rivers define
The calcareous
The wide floodplains
of the 200 m
terraces
at the northern
occur
post-Gondwanan
and Limpopo
up to 40 m
succession
in
River valleys accumulated
extremity
in close proximity
the
are incised rocks and
local base levels at about
asl and a flight of alluvial above current river level. the Luvuvhu
basins defining
flat plateaus sedimentary
of the Lebombo
to a Karoo-age
mountains
depositional
trough
controlled by extensional tectonics and basement structure along the line of the current Limpopo valley. Figure
1. Locality
map
showing
extent of post-Gondwanan correlated with the Malonga/ Formations
in
represent
IA)
Massingir
study
(in black)
Sedimentation
the
continental deposits Gona-re-Zhou /Sena
southeastern
Gona-re-Zhou,
Africa. fB1 Pafuri;
differential, followed
insets and
terminology
successions
and mapping
and Mozambique
may not draw
The objective a detailed
of this investigation
description
comprising
weathering
sediments,
and
depositional enables
an
profile
and
interpretation
of
palaeoenvironments.
southern
the
within of the
(Cox, 1970,
and felsic
volcanic
localised
defined
1989,
possibly of a hilly
sediments were deposited.
by the
Nuanetsi-Sabi
volcanic
anomaly
which
continental
and
successions fractures
could
and
represent
and thinned-
continental or oceanic crust related to the separation of east Antarctica from Africa during the breakup of Gondwana during the Late Jurassic to Cretaceous (Nairn et a/., 1991; Gwavava
et al., 1992; Cox, 1993).
The linear zones of crustal thinning in southern
Zimbabwe,
close
intersect
to the Pafuri
at 120” study
area. The geometry of these gravity highs has been described as representing a rift triple-junction with
AREA AND REGIONAL
region of southeastern
rocks,
gravity
between
Eales
erosion
areas of high relief upon
Karoo-age
the boundary
1993;
rifting, led to creation
which the post-Gondwanan area
axis
199 1). Differential
Broderick,
with
the
with a zone of deep crustal
in
the
defining
a positive
in the recent
1 km,
with
and ring structures
coincides
Africa.
Gona-re-Zhou
Syncline’
Lebombo,
position
Jurassic
associated
data
of the stratigraphic
GEOLOGICAL SETTING In the far northeastern corner of South
late
of more than
succession
in reconstructing palaeo-drainage during the post-Gondwana period
STUDY
sheets
coeval with continental
The
regional
New
and correlation of the Malonga Formation region. This data can be integrated with advances evolution
‘Nuanetsi
landsurface
overlying
extension
subsidence
of the mafic
sediments
succession,
zone
et a/. , 1984;
was to provide
to the age of this sedimentary a re-evaluation
the
this distinction.
of the calcified
this post-Gondwanan
associated
pertaining
describing
units used in Zimbabwe
after
uplift
of up to 8000 m of Karoo lavas and intrusion
of acid igneous
areas.
the stratigraphic
crustal
extrusion
ICJ
occurred permanent
Africa,
Zimbabwe,
the
a possible failed third arm manifested as a dyke swarm in northern Botswana (Reeves, 1978;
and
Gwavava
et al., 1992).
Journal of African Earth Sciences 165
G. A. BOTHA and M. C. J. DE WIT
A. Gona-re-Zhou
C. Massingir Dam study area
cy=-
BosbokpOOrt
. >
*Pafuri
2
Pf”G Maria .
B. Pafuri
.
study area N
‘.‘k.. .-_ _ _
vvvvvvvv~\ . .fvvvvvvvv\
1.1.
LEGEND Salamanga
Eocene ,
Formation
Malonga Fm.’ (South Africa) Gona-re-Zhou Plateau Beds (Zimbabwe) FormaGao de Sena (Mozambique) Formaqao de SinguBdeze/Elefantes
igneous
rocks
sedimentary
ArchaeozoicProterozoic
Pre-Karoo
rocks
basement
Pos t-Gondwanan
Wilson
(I 970)
described
poorly
con tinen tal sedimentation,
sorted
red and
white sandstone and conglomerate in the Kadzi area of the Zambezi River valley and in the Cabora Bassa basin
in northern
Karoo
age sedimentary
Zimbabwe,
thick, the Dande sandstone to be of latest (Oesterlen
an equivalent
succession Formation,
Jurassic
to mid
and Millsteed,
1994).
River valley of northwestern
m
is considered
Cretaceous
age
In the mid Zambezi
Mozambique,
the Lupata
Group comprises
two
vulcanicity
occurred
from the Late Jurassic to
(Flares,
1964).
which
Late Cretaceous period,
cycles
post-
up to 1700
red argillaceous
sediments,
initial
Basin were accumulating Money,
area of northern Miller,
During
and subordinate
representing
Formation,
of sedimentation
Namibia
the same arenaceous
infill of the Kalahari
in western
1972)
and
Zambia
Limpopo
The geophysical
region,
Schutte
dipping
at 5-10” to the east.
(Ombalantu
which
transport
Schutte,
description
exposed
and Masisi
and marls
SACS,
1983).
The
dictate
for the sedimentary Pafuri
observation
occurring
Kop
f-50
m)
pebbly
m thick composite
coded
using capital
letters
altered
sediment
in the context
and seismic
in the further
refraction
surveys
and hence considerable pedofeatures
Pafuri area:- lithofacies
Outcrop
the Silahlandonga
and and
three stacked
the
Mozambique
reported
border.
in the eastern
and Chefu thickness
Rivers.
Finer
sediments
areas between
The geophysically
increases
of Sango
on
were
northeast penetrated basalt
This was proved
15 km northeast 1100
(Barber,
m of sediments 1987).
A gravity
areas.
2. Geological
context
sedimentary is a change
planar-bedded,
cycles
stretch
more than
in this area.
of the Limpopo
in the rocks
unsorted
pebbly
from
River thin,
sandstone
conglomerate
with
thin matrix-supported,
pebble
conglomerate
(Gms) beds near Masisi,
to thicker,
by a borehole
fining-upward
which
red palaeosol
overlying
Karoo
grained
low,
probably
of the post-Gondwanan
continental
sedimentary
units comprising
channel-
bound, clast-supported, rounded cobble- and boulder conglomerate and sandstone with well developed
of Sango,
coincident with an acid igneous intrusion, underlies the deepest part of the basin (Sutton, 1968).
Figure
expose
(I 972) recognised
interpreted
from 265 m near Tswiza to 887
of Sango.
about
there
seldom Keyser
the Guluene
m at Sango and increases to 1356 m, about 21.2 km drilled
valley,
into an
conglomerate, stream
description
of the basin north
of calcareous
siltstone
the eastward the centre
description
valley
In the Masisi-Pafuri
to calcareous
is presented.
red, mottled
illustrates
which
previously succession
along the Malonga
a detailed
of the succession
to the
can be sub-divided
with intercalated
sandstone.
relating
The pedogenically
detail pertaining
and microfabric
20 m of the succession.
thickening
case letter
has not been described
by Muirhead (I 967) and Sutton (I 967, 1968) provided of basin morphology,
by are
C, S, and P representing
of this post-Gondwanan
sandstone
exposed
River valley
suite of
The l,ithofacies-
conglomerate, sandstones and pedogenically-altered sediment, respectively. Each sub-type is indicated
is thinner
m section
bed
codes used here are based on those described Miall (I 977, 1978). The main sediment types
sequence
Cliffs area of the Lundi
and
and
of a limited
lithofacies.
structures.
stream
fabrics
has led to the definition
aggradational
towards
areas,
sedimentary
textural
Formation
Gravimetric
exposed
DESCRIPTION
lower
(reddened)
the-91
structures,
The Malonga
north.
succession
of grain-sizes,
main sedimentary
succession
rubified
than the -190
and
a separate
respectively.
section exposed in the Mwenezi valley, between the river and the top of the Ntabambomvu escarpment, Chilojo
lithologies
and Massingir
by the appropriate
where the Silahlandonga
sandstone is exposed. In southern Zimbabwe,
by up to
km. Significant
associations
is the 80 m +
In the west near Mathaphela
deeply
200
of outcrop,
south of
Fountain,
section
(Fig. 2) a thinner
comprising
are the main areas separated
of about
in the Gona-re-Zhou,
commonly
and reddish brown,
1974;
Pafuri and the most complete succession
as
points along the palaeoslopel
LITHOLOGICAL
Formation
sandstones
occur near Malonga
enters Mozambique.
the sediments
in the nature
lithofacies
Formation,
River, the Malonga
conglomerates, 1972;
are spatially
direction
differences
Detailed
up to 120 m of white
(Keyser,
(I 974) described
150 km, and represent
contacts
type sections
a regional
(Lueti
BASIN MORPHOLOGY AND SEDIMENTARY SUCCESSION comprises
revealed
The three study areas described of outcrop
authigenic
calcareous
investigation
dip of the succession in the Gona-re-Zhou area of 2”-4” to the south-southwest or south. In the Pafuri
and the Owamboland
1992).
South of the Limpopo
region
profiles
sandstone
in the upper, in the
Pafuri
locally within the eastern-most Pafuri are red or grey calcareous hardpan calcrete horizons.
deposits
in the Gona-re-Zhou,
Pafuri
silty area.
and fineExposed
outcrops south of marls and massive
and Massingir
study
G. A. BOTHA
and M.
C. J. DE WIT
clasts
is reduced
within
3 m from the Gm/Ps contact.
to medium-
Intraformational, dominate
calcareous
the pebble
Ps lithofacies elsewhere
to small
sandstone
assemblage
contact,
being
the
composed
pebble
size
clasts
close to the Gmi clast
assemblage
predominantly
of red
quartzite (Soutpansberg Group), agate amygdales and basalt (Letaba Formation), vein quartz, granitoid, dolomite,
jasper,
banded
very rare silicified decomposed
wood.
basalt
are often
reduced
resistate
clasts
sphericity,
iron formation The deeply
and basement
to saprolite
granitoid
‘ghosts’.
are well-rounded
with the exception
appear fresh and have retained surface
percussion
Very
few
and some
Measurements palaeoflow
direction
but generally indicate cemented
imbricated
the
display
of well rounded clasts
clasts.
suggest
a
which varies from south to east,
to the southeast.
that
their original,
of the red quartzite
from
low
amygdales
clasts
scars, with the exception
vein quartz
Most of the
of agate
which
and clasts
but display
pitted
features.
(BIF) and
weathered
sandy
by micritic
Thin section
clay
calcite
matrix which
analyses
is patchily has displaced
and etched the siliceous grains and pebbles severely, completely
replacing
Horizontally
stratified,
Most exposures coloured,
Figure
3. Basal,
bedrock. common
Gm facies,
calcified
gravel
overlying
basalt
Angular to sub-rounded basalt clasts are only in the basal beds, with exotic clasts dominating in
the gravel
beds above.
Silahlandonga,
Pafuri.
parts of some quartz white sandstones
are dominated
well-cemented,
grains.
(Sh)
by massive,
very
coarse
cream-
sandstone
comprising beds up to 80 cm thick. The upper part of the section depicted in Fig. 4 is almost 7 m thick and comprises
a stacked
sequence
of Sh sandstone
beds with isolated, interbedded Gm lithofacies conglomerate lenses. The lower contact of depositional
units is erosional
with
channels,
10 m
wide and 2 m deep, incised locally into the underlying Horizontally-stratified, conglomerate
clast-supported
pebbly
Gml
Many
conglomerates
Clast-supported, pebbly conglomerates occur as thin lenses at the base of upward-fining beds. The clasts range from
sediments.
boulder-size
to granule-size,
but
The sandstone contain granules but concentrated
are between
discontinuous,
0.8 m and 2.0 m thick.
These
pebbly
followed
laterally they
conglomerate
lenses
over distances thicken
can
be
of 15 m to 20 m,
and infill
channels,
they
increase to between 2 m and 3 m thick (Fig. 3). Most of these shallow channels are symmetrical but in cases where the cohesive Ps lithofacies has been undercut, or where there is bedrock structural control, asymmetrical erosion channels occur. The erosive bases are clearly illustrated in the exposure depicted in Fig. 4, where many Gm beds contain rafts of intraformationally rubified and calcified, Ps sandstone, channel
up to 2 m in diameter
close to the irregular
base. The size of the intraformational
168 Journal of African Earfh Suences
Ps
the
clasts-supported
vertically
into these
units, suggesting are intimately related.
clasts in the medium to very large pebble range are most common. The units have erosional bases and
and where
down
sandstone lithofacies
of
grade
that
these
beds are very coarse-grained
white two, and
and pebbles scattered throughout, at the base of sandy units are single-clast
layers. The basal coarser
lithologies rapidly fine-upwards and grade into medium- to coarse-grained sandstone. Although sandstone
beds appear
massive,
stratification is locally evident. Sh lithofacies sandstones
vague
horizontal
Some channel-infill, also contain
intraformational rafts (up to 50 cm diameter) of pedogenically-altered Ps sediment. Whereas these extraformational clasts occur as basal channel lags, many Ps clasts occur as floating blocks within the sand suggesting derivation from channel bank collapse during infill. In some sections the altered coloured
sandstone
tops of the cream-
units grade into pink Ps facies
Post-Gondwanan
continental
sedimentation,
Limpopo
region
Journal of African Earfh Sciences 169
G. A. BOTHA
and M.
C. J. DE WIT
massive
sandstone
erosive
and
channels
the cross-bedded
underlain foreset
units.
where
Basal contacts
the
by a single
planar
beds
sandstones
are noninfill
clast layer of pebbles.
beds grade laterally
scour
are generally Planar
into Gm conglomerates
and are incised by overlying Gm units. Reactivation surfaces are characterised by single pebble horizons. Trough cross-bedded
sandstone
(St)
Trough
cross-bedded
sandstones
textures
to those of the Sp and Sm facies can be up
to 40 cm thick and can be followed 8 m (Fig. 4). The sands grained
and contain,
and small
similar
laterally for about
are medium-
to coarse-
dark red (2.5 YR 3/6), granular
pebble-sized
mudstone
with
mudstone
clasts are composed
clasts.
of quartz,
and smectite,
with traces of plagioclase,
and gypsum.
Palaeoflow
direction
palygorskite
obtained
unit indicates that flow in the channel towards the east-southeast.
These
microcline from this
was directed
Pedogenically
rubified and calcretized siltstone (Ps)
Poorly sorted,
laminated
grained,
mottled
containing overlie
silt and fine- to very coarse-
sandstone
scattered
small
the planar and trough
units up to 3 m thick, pebbles
or cobbles,
cross-bedded,
pebbly
sandstone (Sp, St) and calcified cobble and boulder gravels (Gm). The colour of these mottled units varies from homogeneous yellow Figure 5. Termitarium comprising network Sh facies, calcified
structure
(Termitichnus
of sinuous, sand.
sand-in filled
ichnofacies) channels
within
analyses
of the matrix
silt indicate dolomite, quartz,
sandstone domed
above.
The
depicted structure
cross-bedded, structure
vertical, diameter,
about
sandstone
70 cm high,
small pebble
is underlain
zone extending comprising
pink
about
gravels
2 m below network
cylindrical structures which are infilled with
draped
by a with
and sand. This
by an intensely
an intertwined
bioturbated
smectite plagioclase
by displacive
structure
is interpreted
micritic as a
termitarium. Microscopic analysis indicated that cementation of the Ps, Sp and St facies are similar to that of the Gm sediments. Planar cross-bedded
sandstone
(Spl
Isolated planar cross-bedded sandstone lithofacies units occur as laterally extensive beds up to 20 m in length and 1 m thick (Fig. 6). The texture of these lithofacies
Yellowish elongate,
cemented
is similar to the horizontally
bedded
and
with
elastic
also present.
secondary
calcareous
and Mozambique.
of predominantly
carbonate.
groundmass,
and
of the basin, so aspects of the detailed description below also apply to this lithofacies in Gona-re-Zhou
sandstone
up to 0.75 cm in poorly sorted sand
and palygorskite and microcline
sands
by authigenic
features and clastic/authigenic phase textural relationships of this lithofacies are similar over much
the dome (Fig. 5),
and preferentially This
at the
in Fig. 5 and 6, is disturbed
of red coloured
that these are dominated
The rubified
exposure
red (2,5YR 4/6,1 OR 4/6), reddish
(5YR 6/6) or pink (5YR 7/3). X-ray diffraction
red (5YR 5/6) are
mainly
branching,
colours
within
associated
with
subvertical
the red white,
and subordinate
subhorizontal, calcareous cylindrical structures and mottles. Maximum calcification occurs near the top of the individual
mottled
sandstone
units and tends
to decrease towards the base. The cylindrical calcareous features are generally between 30 and 40 cm in length, but examples over 1 m long have also been noted (Fig. 7). Some vertical carbonate structures up to 15 cm in diameter, containing blocks of calcified red sandstone, penetrate the sandstone and are apparently integrated with thin, horizontal, massive calcrete bands in some outcrops. Round calcareous nodules (0.5 - 3 cm) within the red mottled sandstone, comprising micritic dolomite, are surrounded by irregular, radial cracks infilled with
Figure
5m
6. Schematic
section
through
showing
relationship
of termitarium
clast-supported pebbly conglomerate (Gm)
outcrop
Horizontally-stratified,
Planar cross-bedded sandstone (Sp)
Horizontally stratified, white sandstones (Sh)
Mottled sand and laminated silt (Ps)
LITHOFACIES
:$$ vertical/horizontal .:::.:.: :::;:j,.: (02/02) sample position
.::::;:$$;:<:>;. ::;;.:.;.;.y:...I:.’
rhizocretions
G. A. BOTHA and n/l. C. J. DE WIT
I72 Journal of African Earth Sciences
Post-Gondwanan
equant, filled
sparry
cracks
pattern
calcite
define
nodular
sedimentation,
(Fig. 8). The thin carbonatea cubic
(2-4 cm) within
where
continental
carbonate
cementation
granostriated
or strial
fabric.
hematitic
in areas
opaque
is of limited
laterally
bands
within
the
IO - 15 cm thick
9). XRD analysis
coalesce
Runiquartz
top
of a
cracks
unit in one exposure
(Fig.
heavily
red sandstone
calcretised
has shown
almost entirely
of micritic
are convoluted,
defining hummocky
low
amplitude
Slickensided sparry
and
surfaces
calcite
interface
veins
The calcitic
+30
suggest
cm
calcified
bands
stains
the
fine
void
grains. of
(or
infill.
oxides penetrate
of the rubified groundmass
zones
replacing
bands and
micritic
comprises
dolomite
displacing)
dolomite
crystals
along
the
Whereas
rubified
the
red
porphyric
relationship
sandstone
is
and
rubified
and
of ferro-
ferruginous
the
apparently
argillaceous
fine
groundmass. The carbonate and clay groundmass between accumulations of rhombohedral limpid
wavelength.
movement
The laminated,
bands
surrounds
forming
forms where ferruginous
in quartz
diffuse
‘tepee’ structures
of the convoluted
between
sandstone.
calcite.
(micromass)
ferruginisation
minerals,
Calcification
these to be composed
birefringence
mineral clasts or ore pseudomorphs
hypocoatings, calcified
bioturbated
of
Strong
magnesian
extent. White
region
blocky
or subangular
the red sandstone
Limpopo
components,
is replaced zones
by pervasive
commonly
between
the micritic
calcite.
have
a close (c.f. 1
coarse/fine
zones
display
a more
intensively bioturbated with abundant vertical to subvertical, backfilled burrows. Downward concave,
open porphyric c.f. relationship suggestive of volume increase during crystallisation of the
lunate backfill units, generally 1 mm to 3 mm thick occur within the rounded (1 cm - 1.5 cm diameter),
authigenic
sinuous
grey
plagioclase
and sparry calcite
suggesting
burrows
mudstone
(Fig.
IO).
with a dolomite
Homogeneous,
cement
veins occurs at the top of upward
Fountain
stage Micromorphological
The
description
relationship
groundmass
between
sandstone
very fine
calcretised calcite
sesquioxides
poorly
poorly
displaying
undulose
sand grains are commonly coatings of well-oriented
Captions Figure
for
7. Reddish
blocky pattern Figure
11.
plate
brown,
defined
8. Spherical
later generation Figure
colour
The Chilojo
Gona-re-Zhou
Plateau
Cliffs,
The 178 m type section Figure
13. Poorly sorted,
weathering represented River valley, Zimbabwe.
palaeosols calcite
of dolomicrite calcite.
Beds,
siltstone
Large
carbonate
the latter
replacing
Dolomite
in the
sandstone towards
and
units
gravels
smectite
is
heavily with
the base.
the stratified
palygorskite
hematite,
mineral
present
clasts within
abundant
gypsum
fine sand show
smectite.
top of mottled
generally
are a late
Red
contain
and
some
gypsum.
opposite:Ps facies
nodules
extinction.
surrounded by thin red clay, defining a
by late stage
of sparry
sorted,
oriented,
calcite lenticular
comprises
and dioctahedral
dominant
the
cleavage planes. mineralogy of red, calcretised
commonly
palygorskite
massive
with
and
Rare
with late stage calcite,
reaction
the gypsum along The groundmass
sand grains are infilled silt
of sparry
and
margins
components.
the red, calcified
cement
and grain zones
between
elastic
within
rubified high used
reaction
crystals
the
and
veins
infills
embayed
and
phenomenon.
to describe the authigenically altered sandstone and siltstone is after Bullock et al. (1985). Voids between sand
a chemical
mottled,
is best observed in thin section under magnification. Micromorphological terminology
Void
the micritic
display
groundmass
calcareous
the
and the authigenic
grains
Cross-cutting
area.
phase.
are rare within
micritic
fining sedimentary
unit at two sites in the Malonga
mineral
coatings
was measured Gms facies,
along white,
within
and horizontal
rhizoliths,
round
dolomitic
nodules
and
south of Pafuri.
red palaeosol.
Cracks
radiating
from
the nodules
are filled with a
the southern
poorly
sorted
rim of the Lundi River conglomerate
overlain
valley,
expose
by calcareous,
a repetitive
sequence
pink or reddish
of
sandstone.
on the right of the field of view.
matrix
by rubification Scale = 10 cm.
vertical Fountain,
south of Pa furi.
Fountain,
escarpment
with
Malonga
developed
Malonga
comprising
profile
veins.
supportedpebble
of matrix
conglomerate
and sinuous,
calcareous
with poorly sorted rhizocretions.
sandy matrix.
Swimuwini/Buffalo
Figure 14. Network of long, calcareous rhizoliths developed within red palaeosol profile, Chilojo Cliffs set tion, Lundi River valle v, Zimbabwe. Cliff is approximately I3 m high.
Gona-re-Zhou
Palaeopedogenic Bed,
Plateau
Mwenezi
Beds at the
Figure 15. A dense pattern of sinuous, calcitic vermicular mottles, rhizoliths, root moulds and nodules occuring below massive, hardpan calcre te in 4 m calcareous palaeosol pro file. Hello w rhombic pits, in filled with red sand in fresh outcrop, may represent
gypsum
casts.
Formacao
de Singuedeze/Ele
fan tees, Mahosi,
western
Mozambique.
Journal of African Earrh Sciences 173
and M.
C. J. DE WIT
calcrete
horizons
G. A. BOTHA
Figure 9. ‘Tepee’structure on calcrete
horizons
in massive,
suggest
micritic
movement
Figure
10. Downward
within
red, Ps lithofacies
concave,
calcite,
due to volume
lunate backfilled
palaeosol
horizon.
and
red upper
sediments,
with
no
disl :inctive intraformational markers. River bank ,osures in the Swimuwini/Buffalo Bend and exp Wri ght’s Tower/Makonde Pool areas, and the esc arpment
section
near NtabambomvuAronwood
I74 Journal of African Earth Sciences
Taenidium
Malonga
GOI la-re-Zhou area:- lithofacies description Ligl itfoot (I 938) and Cox (I 963) noted that the Mw lenezi Valley succession is characterised by a wh1ite base
increase.
within bioturbated
Malonga
Fountain,
ichnofacies
Fountain,
Viewpoint,
south
Slickensides
of Pafuri.
(Mason
pers.
comm.)
of Pafuri.
provided
the succession south
burrows
red siltstone.
south
a composite
in the Mwenezi
section
thrc ugh inI the
River valley
(Fig. 2).
The escarpment along the southern rim of the L.undi River valley, particularly the Chilojo Cliffs, expa se a repetitive sequence of sedimentary units compri sing white, poorly sorted conglomerate overlair 1 by calcareous, pink or reddish sandstone. The 17‘8 m
Pos t-Gondwanan
type section opposite
measured
from the river to the cliff-top
Chilojo camp (Fig. 11) reveals a succession
of numerous calcareous pebbly
con tinen tal sedimentation,
sedimentary
units
conglomerate
sandstone
Outcrops
comprising
overlain
by reddish
Limpopo
shallow
channel
modified
top of a depositional
white
supported,
brown
a rarity
incised
Gm lithfacies,
are more
widely
spaced
Horizon tally-stratified The poorly sorted,
succession
Makonde
of units
comprising
similar
are conformable
lithofacies
or display
minor
of white,
Gms lithofacies
in the cliff sections
are characteristically
basal
gravelly
and unsorted,
and cobble
conglomerate
lithologies
exposed
Pool comprises
clasts
were
noted.
quartz,
At least two
valley
locally. (0.5-2
of
the massive, characterised
and conglomerate
at
Wright’s Tower. The rock is cemented by white calcite micrite and microsparite with a later phase of fine-textured,
pink,
micritic
calcite
sinuous zones up to 1 m wide within within
these zones are lined with
Approximately
is exposed
below Swimuwini white,
basal
reddish
sandstone.
lithofacies
units
supported, beds,
reddish brown
upward
into Sh
interbedded
Gms
poorly-sorted,
are only
a few
on the sedimentary matrix coloration
matrix-
clasts
bedding
cliffs
comprises
which commonly
upward
fining
have white,
unit is
calcareous
(Spl at all of the sites
and one set of planar beds
up to
indicating
a southward
observed
at the Wright’s
1 m thick, transport Tower
cross with
bedded foresets
direction,
were
and the Chilojo Cliffs
exposures. Pedogenically rubified and calcretked sandstone (psi The
upper
part
characterised
of
each
by a reddish
elongated features
of
diameter, and some through the sediment colour
units
poorly sorted,
of larger, angular
investigated
horizontal,
cobble conglomerate. The conglomerate beds are commonly only a few clasts thick and contain accumulations
nodules
the basal part,
thin tubular
Planar cross-bedded sandstone This lithofacies is uncommon
carbonate
coarse-grained pebbly sandstone with interbedded, angular, matrix-supported, granule, pebble and
lenticular
calcareous
structures.
thick.
at the Chilojo
sedimentary
calcified,
basal
are present
sedimentary brown
unit
colour,
is
variable
density of carbonate nodules (0.5-5 cm diameter), and sinuous or branching, vertical and subordinate
and white carbonate
measured
Thin,
pebbles
part of each sandstone
are the
nodules and sinuous rhizoliths and pedotubes, palaeopedogenic origin (Fig. 13). The 178 m succession
units,
to coarse-grained,
characterise
by sparse,
the
The repetitive
Calcified,
pebble and cobble conglomerate
of which
Superimposed
Bend’ in the
coarse-grained,
Thin,
comprise
granule,
many
grades
calcareous,
cliffs
the upper above
sandstone.
authigenic,
upper
sandstone
sandstone
of Mabalaute.
conglomerate
brown,
lithofacies
calcite.
in the riverbank
camp, on the ‘Buffalo
River, downstream
in
the rock. Voids
30 m of poorly-sorted,
and conglomerate Mwenezi
occurring
sparry
Whereas
rim of the
lithological
medium-
calcareous
cm diameter)
of
The basal part of each
beds of rounded
the
phases
sorted,
conglomerate
to the depth
exposes
sandy
1-3 m thick.
brown,
brown
in each unit.
stratigraphically
comprises
reddish
BIF and
occur within
is related
Bend outcrop.
from
in the
or reddish
is cut into the northern
Swimuwini/Buffalo
unit is poorly
in the upper part
units exposed white
rubification
part of the succession,
commonly
to
Tower/
and reddish banded,
valley at Ntabambomvu
sequence
cementation
sandstone
of the sandstone
palaeopedogenic
with
Mwenezi
The variable
The pass which
the range of Karoo-age the
colour
Mwenezi
pebble
white
is common
Cliffs.
thinly
The angular
above the basal
at Wright’s
depositional
Chilojo
comprise
rare pegmatoid
carbonate
coarse-grained
is
calcareous, pebbly coarse-grained sandstone with weak horizontal bedding defined by coarser grained
sandstone
beds. in
although
authigenic
Tower,
and unsorted,
matrix supported,
clasts represent
provenance
Wright’s
bedded
conglomerate m)
unimbricated
granite
below
locally-derived rhyolite clasts up The finer textured sediments
(0.5-I
subrounded
units up to 3 m thick,
poorly
containing angular, to 2 m in diameter. the
conglomerate,
sands tone (Sh)
conglomerate
of upward-fining
strongly-calcified,
pebble to boulder conglomerate
above
matrix-supported
(Gms)
The basal sequence
bedded
pedogenically
succession.
pebbly sandstone
beds. Similar sandstone Massive or horizon tally-stratified,
exposed
the
unit, infilled with clast pebble
in this lithological
and display different lithofacies associations requiring site specific description of each facies. The stacked
conglomerate
into
(Fig. 12).
in this region
associations incision.
region
clasts. A
and
sandstone to those detail
textural and white
from
calcareous
structures.
are commonly
These
5-30
cm
in
can be traced downwards for up to 5 m (Fig. 14). The characteristics carbonate
the Pafuri
of
features
outcrops,
the
red
are similar
described
in
above.
Mozambique
area:-
lithofacies
description
The poor outcrop of the Formacao de Sena near Pafuri in the Limpopo River valley and points north on the interfluves adjacent to the Mwenezi River
Journalof African
Earth Sciences 7 75
G. A. BOTHA
and M.
C. J. DE WIT
unconsolidated
red sand
thm derived gravel horizor
GONA-RE-ZHOU
PLATEAU
‘African’ landsurface Silcrete
BEDS
Chilojo Cliffs section LlTHOFAClES
Reddish brown palaeosol K horizons with white calcrete nodules and vertical rhizocretions Calcified, poorly sorted, matnx supported, weakly stratified pebble conglomerate (Gms), granule-stone and coarse grained sandstone (Sh)
section above
heights in metres river bed datum
terrace /eve/ with sparse pebble cover
Ol-
Figure
Lundi River bed
12. Section
Gona-re-Zhou,
through
Zimbabwe.
176 Journal of Afr;can Earth Soences
Gona-re-Zhou
Plateau
Beds
at
the
Chilojo
Cliffs
section,
Lundi
River
valley,
Pos t-Gondwanan
system
prohibits
associations
a detailed
although
description
the lithologies
the range of rocks described of South
Africa
Formacao
and Zimbabwe.
Massingir
near Mahosi
of lithofacies
these
are similar
weathered
from the adjacent
of the
in the Olifants
on the northern
Dam, provide
to
areas
Exposures
de Singuedeze/Elefantes
River valley
con tinen tal sedimentation,
good sections
shores
facies
sands.
were
the
upper part of this unit. The sections here, although restricted, are dominated by the fine grained Ps lithofacies.
The
main
lags of gravel
rubified and calcre tised silts tone lPs)
directions
The Mahosi
outcrops
of the Singuedeze/Elefantes
bedload
of pedogenically
clasts
supporting the north.
that
but small
the palaeoflow
to southwest,
flow
direction
COX’S (1963)
findings
but a
was measured, in Zimbabwe
in
8 (Gm, Stt)
bedded,
sandstone
sand,
locally.
indicate
southward
floodplain
was
varied from southeast
general
Thinly
banks
developed
Facies Association
Pedogenically
eroding
and carbonate-cemented
lmbricated
of
through
Limpopo region
horizontally
stratified
and interbedded,
thinly
pebbly
bedded
pebble
succession expose rubified siltstone with authigenic carbonate structures. A massive, calcified profile (up
conglomerate are interpreted as sheetflow deposits derived from the areas of steep bedrock relief. These
to 4 m thick)
are particularly
siltstone,
developed
within
up to 12 m thick.
A dense
calcitic
mottles,
vermicular
cylindrical calcified parent
exposed
is
pattern
of sinuous, and elongate
also includes with
infilled
represent
gypsum
features
are
casts
and
represent
lithofacies
which
sediment
Gona-re-Zhou
north
of the Limpopo
is similar
described
from
rubification
precipitation
to the Pafuri
Ps and
A (Gm, Sh, St, Sp/
An intimate association exists between the massive conglomerates, the horizontally stratified sandstones
of many
by upward:fining related,
association
(Facies Association
sandy
units
conglomerate
and conglomerate
genetically
interpretation
as palaeosol
forming
red coloration
of palaeosol
above,
features
can
brown
sandstone
units are regarded
with downward
of pervasive
decreasing
intensity
which is superimposed on depositional bedding lamination. The presence of surface-related
pedogenic
lithofacies
part
of one
is
sandstones
are interpreted
classified
as buried
the Stage
are
and honeycomb
A). This lithofacies
and the presence
or
siltstone
and sand bars suggests that the main environment was one of channel upward
fining
represent bar formation their association with
conglomerates
bars
were
migrating
downstream direction. The presence Ps facies indicates that the channels
Bk or K palaeosol
in a
of blocks of infilled with
morphology
calcrete
of Netterberg
calcareous
modified
rhizoliths
calcareous
representing (rhizocretions)
(Klappa, features
postred
rubified profiles, horizons similar
to
or nodular (1980).
cylindrical
units, include features
structures
sandstone
and
grouped
in the family
1980).
The majority
are interpreted
as
carbonate precipitation around roots although some root moulds and
carbonate-lined,
in a fluvial channel and trough cross-bedding
pedogenic
II and III of Gile et al (1966)
The composite,
1980;
to subaerial The calcareous
as representing
feature
present in the pedogenically
of
(Netterberg,
calcretised
carbonate
and facies
calcretes
Klappa, 1980) also point depositional modification.
of theses
bedforms
these
to
the sandy
of the red calcareous
profiles due to the presence
of calcareous
that
within
in all areas.
absence
indicates
carbonate be related
units in the three areas described
association, according to Rust (19791, is typical of a sand-dominant braided stream deposit. The
The
to
Due to the similarity
showing
(Fig. 4). The base
braiding.
authigenic
considered
sediment.
other
small gravel depositional
sandstone/
sandstone
and subsequently
of major
calcretised
profile-development
and the trough and low angle, planar cross-bedded pebbly sandstones which grade laterally into each
the sandstone
in the from the
pedogenic
recent
Pafuri area
characterised
derived
bioturbation structures attributed to plant roots and calcareous structures similar to those described from
interpretation
facies Association
and
and are
The reddish
and
above.
Lithofacies
The
be applied
rubified
rubified
the following
component.
coarse-grained,
sandstone
in the
and plagioclase
elastic
the exposures
comprise
may
authigenic
occurring
microcline
the dominant
In contrast,
with
smectite
Quartz,
Pedogenically
of
which
in exposures
with sediment
silts tone IPs)
(Fig. 15). The carbonate
dolomite-rich
palygorskite groundmass.
accumulations
red sand,
well developed
Masisi escarpment, east.
structures occurs below the massive horizon. The homogeneous siltstone pits
calcified
brown which
nodules
sediment
rhombic
River,
the reddish
caps the succession
hollow
root
tubules
also occur
(Klappa, 1980). In general the morphology of rhizoliths and calcrete nodules are broadly similar to the calcrete profiles described from the Old Red Sandstone
of southern
carbonate
pedofeatures
Britain
(Allen,
described
19861,
the
by Purvis
and
G. A. BOTHA
and M. C. J. DE WIT
Figure 16. Wea thering profile developed within Malonga Formation rocks is a zone of decalcification, charac terised by circular s true tures up to 2 m in diameter and irregular fissures, tapering down ward (up to 6 m deep), decalcified
Wright
in filled with red, strongly
parent
sandstone.
(I 991) from Triassic
and rhizoliths Formation Cohen,
braided
1984).
1982;
Mount
within
The mottled,
a substrate within
rubified
Limpopo
and
structures
to be the result of displacive
occur
rubified
Koobi Fora
The ‘tepee’ or antiformal
are interpreted of carbonate
(Cohen,
area,
river deposits
from the Plio-Pleistocene of Kenya
commonly
Masisi
(Watts,
growth
1977),
sand, rounded River
clasts and fragments
succession
exposed
lithofacies
association
and
intensely bioturbated by calcified rhizoliths, backfilled Taenidium ichnofacies burrows (Smith et a/., 1993;
interpreted
as sheetflood flow
fan surfaces proximal
the succession
structures
and the colour mottling
that these subaerially
fluvial channel exposed and
strongly
sediments pedogenically
‘tepee’
suggests have been altered.
Calcrete profiles with dolomite and palygorskite the matrix suggests that the palaeoenvironment during
sediment
incision
and
deposition
migration,
and periodic was
arid
probably
within
the 400-600
(Goudie,
1983;
Botha and Hughes,
to
in
channel semi-arid,
mm per annum
range
deposits
(Wright
Zarza eta/.,
clast-supported confined
by
steep alluvial 1994).
Very
associated
with
in the Chilojo
and Alonzo
1992).
conglomerate
within
shallow
at the base of the succession represent
incised
it is
into the
sandstone. The rare point to a southerly bouldery
deposits
in the Wright’sTower
high density
of the Gonakudzingwa
areas of high bedrock
1990;
is exposed
channels
sediment transport direction. The unsorted nature of angular, area probably
Zarza
Where rare, interbedded,
underlying, horizontally-bedded planar foresets observed,
generated
1992).
on relatively
colluvial
are
produced
Cliffs section studied and the pebbly conglomerate and sandstone, with associated palaeosol profiles points to a medial fan environment of deposition for Alonso
calcrete
deposits
action
transport
and the deposits
fan areas are not exposed
presence
root structures,
water
region. This
sediment
(Blair and McPherson,,
angular
Masonpers. comm.) and at one locality a termitarium (Termitichnus ichnofacies; Smith et al., 1993). The of calcified
suggests
unconfined
coarse,
sands near Pafuri are locally,
in the Gona-re-Zhou
by shallow, catastrophic
calcretes.
of yellowish,
valley.
relief towards
flows,
possibly
and Mateke
hills,
the west.
Gona-re-Zhou Facies
Association
A (Gms,
Shl
The common lithofacies association of basal, poorlysorted, matrix supported pebble conglomerate fining upward into massive or weakly horizontally stratified pebbly sandstone extensive conglomerate
with interbedded,
matrix-supported, beds,
is typical
thin, yet laterally
pebble
and cobble
of much
of the
Mozambique The Mahosi
area outcrop
of
Singuedeze/Elefantes
Formation siltstone, with similar palaeopedogenic features to the Pafuri deposits further north, is regarded as being the finer-textured distal part of the fluvial Lebombo
system foothills
flowing
southward
from the Limpopo
along
the
valley area. The
Pos t-Gondwanan
dominance coarser
of floodplain
component
facies over the channelized closer
to the provenance
probably due to a greater degree confinement in the distal reaches.
WEATHERING
PRODUCTS
the calcareous
is a ‘lateritic (1972)
sedimentary described
sediments
River
Formacao
rim,
Mwenezi
and the
and Limpopo
profile
Formation along
the
of the
in the Olifants
Formacao
de Sena
River valleys.
and sand cover
gravel
widespread
gravels.
below
the
but is generally
Muirhead
by Lightfoot
(1938),
(I 967) and Sutton
only the
describe the relevance
Along the rim of the Malonga of Pafuri, porous, decalcified sandstone horizontal white,
1968)
The generalised
hollow,
Formation
rocks
stream valley south and ferruginised
silica precipitation
channels.
containing
in the
do not
of the thick silcrete
is characterised locally by a strong structural component defined by milky
opaline
around
Cox (1963),
(1967,
profile developed within the Malonga in parts of the region.
capping the Zimbabwe.
outcrop
de Singuedeze/Elefantes
valley
derived
adequately
described
locations
above
is apparently
The descriptions
by Keyser
Malonga
out at many valley
in the derived
The ferricrete
Silcrete
profile
that a weathering
the calcareous
crops
Limpopo River
revealed
within
FROM
succession
a similar ferruginous conglomerate sedimentary succession in southeast developed
region
exposed near drainage lines and pans where sandy overburden has been thinned.
in the Pafuri area, and Cox (1963)
This investigation
channel
weathering
conglomerate’
Limpopo
similar to those concentrated is
ROCKS
and ferruginised
Overlying
of
DERIVED
THE POST-GONDWANAN Decalcified
con tinen tal sedimentation,
Bands
a latticework
sinuous
occur
white
of hematite-filled
channels
within
along planes
of milky
and
silcrete, cracks and
lined with quartz crystals,
this
weathering
profile.
sequence is variably decalcified parent material, with silcrete or a ferruginised zone and hard ferricrete
Micromorphological investigation revealed that the silcretised sandstone in many exposures is
developed
characterised
patchily,
unconsolidated yellow
by
clasts
a layer
of
and surficial
red/
characterised
by
sand cover up to 6 m thick.
The zone
of decalcification,
circular structures
up to 2 m in diameter
fissures, tapering with
overlain
rounded
downward
red, strongly
sandstone Pafuri
(up to 6 m deep), infilled
rubified
and fragments
sand and rounded
of yellowish,
clasts
decalcified
region.
These
represent
infilled
karstic
‘pothole’
solution
with terra rossa pedogenic weathering rubified sediment is highly porous abundant
sinuous,
pedotubules.
clay
Brink (1967)
defined
by
comprising
an
irregular
manganiferous
material
brecciated
infilling
structure. In places
along
valley
and
around
occur where
have
and
commonly
as pedogenic overlies
and contains
plinthite
the decalcified,
an assemblage
of rounded
rock
of fibrous,
material
with
in
material
of some
in some
silcrete
similar
The thickest,
outcrops
Mwenezi steep
Nyamtongwe within
defining hill expose
the underlying
(1968)
the
silcrete
also reported
in Zimbabwe.
a silcrete
silcrete
profile
is
the rim of the
escarpment
calcareous
that
synchronously
defining
and Lundi River valleys cliffs
of red
The purple
suggests
best developed
in the escarpments
to the
pedorelicts silcretes.
ferruginisation preceded or occurred with the silcretisation processes. exposed
slow
of depositional
and pebble-sized
palaeosol
length
appears
preservation
from grey to purple,
the top of the silcrete
within
etching
the is
pans,
or ferricrete, ferruginised
parent
within
deposits comprising unsorted clasts cemented by a hard, ferruginous matrix are exposed beneath thin sand cover. The massive, hematitic deposit, interpreted
grains ‘floating’
The
around
profile
formed
sandstone.
Sutton
from the Chefu
River
area in the south. The colour of the silcrete is variable,
a nodular
around
elastic
growths
Black
‘potholes’
residua rims
Vaal
margin
cracks
and lamellae
the rubified
and
rounded, terra are commonly
material
material
decalcified,
late Neogene
sediment.
nodules
weathered
have a similar
brecciated
decalcified
and
by Partridge
Zones surrounding solution hollows
rubified
yellowish
possibly
described
from the calcified,
River gravels. rossa-infilled
infilled
channels
botryoidal
chalcedony. The silcretized
colour
features
products. The and contains
lined
These features
origin to the ‘makondos’
in the
cavities
with
stratification
parent
(Figs 16 and 17) is well exposed
probably
deeply
and irregular
by skeletal
a mass of micro- and cryptocrystalline quartz (F-fabric; Summer-field, 1983). Sinuous vugs are partially infilled
zone clasts
the
and the knobbly
of a network
Malonga
vesicular
profile
of sinuous,
Formation
rhizocretions
carbonate
biogenic
protolith. are centres
precipitation
in the
silcretjzation process apparently textural inversion with preferential the sandy
matrix
and dissolution
within silcrete
the rhizoliths (Fig. 18). profile is relatively weakly
opaline
silica infilling
ferruginous lining
appearance
coating
tubes
Whereas
in the
of authigenic protolith,
the
leads to a silicification of of carbonate The top of the cemented with
some intergranular
sequioxides
of
is due to the solution
pores and
sand grains
and
pores.
Journal of African Earrh Sciences 179
G. A. BOTHA
Figure
17.
Base
decalcified
of solution
Malonga
represents
the
Silahlandonga
coarse, valley,
pothole
Formation resistant Pafuri
developed
rocks.
C. J. DE WIT
within
Figure
18. Basal part
infill
within
Gona-re-Zhou
Rubified
fraction
and M.
of the protolith.
area.
Previously tubes.
calcareous
The matrix
massive
of ‘African’ Plateau features
is weakly
accumulations
silcrete
profile
Beds at Chilojo
developed
Cliffs
are represented silicified
occur irregularly
section.
by sinuous
by opaline
silica
throughout
and
the basal
part of the profile.
The silcrete
horizon
dips towards
the Chilojo
Cliff
Drakensberg
escarpment
exposure to the ESE at about 0” 21’, although the silcrete surface is not smooth and local undulations
western Mozambique thick accumulations
with a wavelength
overlie
of up to 50 m and amplitude
of
the
-6 m are evident.
widespread
Derived
conceals derived
gravels
The top and base of the Malonga
exposed
post-Gondwanan sand
cover
calcareous,
Kalahari
Group
Botswana
this derived
gravel
by ‘veil’ of up to 12 m of rounded
pebbles
Letlhakane
stoneline
Formation
and cobbles
weathered
from the calcareous
rocks
(Lightfoot, 1938; Cox, 1963; Keyser, 1972). This ‘derived gravel’ layer of unconsolidated, rounded clasts is well exposed by the escarpment south of Pafuri. About
185 km to the south of the Pafuri area
on the crest of the Lebombo
mountain
range, there
‘sealing’
effect
of the resistant
lithology Transvaal
o,.4,ncan
_~
&wr,,
soences
In the
by Du Plessis and
the predominantly sandy nature of the upper part of the underlying Malonga Formation rocks, or to the
underlies the cover and is interpreted
180 .Jo”r”al
lithologies.
Le Roux (1995). The ‘derived gravel’, is very thin and impersistent in the Gona-re-Zhou region. Whether this is due to
are similar unconsolidated gravels and sand (Venter and Bristow, 19861, although the different clastpoints to a provenance of lithologies exposed in the
The Desert
has been termed
the surface, is debateable. The unconsolidated ‘derived
assemblage Sequence
Kalahari
a variable layer of unconsolidated gravel from weathering of the underlying
is often
isolated
In
foothills gravels’
lithologies.
in the
hill and cliff exposures
in valley-side, obscured
Formation
110 km to the west.
along the Lebombo of similar ‘derived
silcrete
layer near
gravel’
sand over much as representing
probably
of the area material
Post-Gondwanan
released
from
weathering
the
ferruginous
profile
through
landscape associated erosion.
continental
or siliceous
lowering
that
this thick,
and
relatively
Redistribution of the derived gravel weathered from protolith
commonly
region
of the maximum
age. The
Lupata Group in the Zambezi River valley comprises two cycles of sedimentation
and vulcanicity
which
occurred from the Late Jurassic to Late Cretaceous.
evenly distributed pebble and cobble gravel deposit was deposited by fluvial systems flowing across the low gradient land surface. the calcareous
Limpopo
valley for an indication
of the
with ongoing weathering
It is unlikely
sedimentation,
accumulates
Whereas
sedimentation
began in this area during
the Jurassic, on lithological Formation is correlated sandstone
deposited
grounds the Malonga with conglomeratic
on an unconformity
surface
above rhyolite dated at 166 +- 10 My (Flares, 1964)
through colluvial and alluvial action at the base of
and light grey, red and light reddish brown, unsorted,
hills and
calcareous,
escarpments
Gondwanan
incised
into
the
post-
rocks. In some areas ongoing incision
of these landsurfaces
by tributaries
of major rivers
has created raised gravel covered terraces which contain rounded clasts of strongly calcified, reddish sandstone,
typical
of Ps lithofacies
palaeosol
Formation
sedimentary
rocks of the upper Sena
which were deposited
Middle Cretaceous (Flares, 1964).
above Lower to
(I 15 + IO My) alkaline
In the Limpopo valley continental sedimentation
lavas
region of Mozambique, dominated on the margin
material derived from the Malonga Formation protolith.
of the emergent African continent during the Lower
Moderate
to Middle Cretaceous, with marine conditions being established in the west only in the Senonian (Flares,
calcification
conglomerate
of this sediment
which
is sometimes
differentiate from the weathered
results in difficult
to
Malonga Formation
protolith.
1973;
Forster, 1975).
eastwards,
The Sena Formation
was probably diachronous Unconsolidated
sand
cover
grades
and upwards into marine sediments, and along strike across the
basin. The earliest Sena Formation
deposits south
The Nwambia sandveld plateau area, the eastern Lebombo foothills in Mozambique and the Gona-re-
of the Zambezi graben are of Cenomanian or Turonian age (palynological evidence) and grade into marine
Zhou
deposits dating from the initiation of the Mozambique
region
are blanketed
unconsolidated
by a thick
layer
red or yellow sand (Keyser,
of
1972;
Venter, 1986) previously regarded as being of aeolian
Channel during the Lower Cretaceous the Senonian (Flares, 1973).
origin (Schutte, 1974; Keyser, 1972). Red, yellow or grey, well- to moderately-well drained, eutrophic soil
and parts of the intracontinental
profiles are developed clay-rich smectitic lines.
The thick
within the coarse sand with
soils formed in shallow drainage sand
numerous ephemeral
blanket
thins
around
the
pans, drainage lines and along
the valley escarpments incised into the underlying calcareous sediment. The mechanism which led to effective separation of the sediment
comprising
the thick surficial sand
cover from the unconsolidated
gravel layer below,
of the calcareous
Malonga
not well defined.
It is possible that biogenic activity
led to concentration
is
of the gravel clasts although
in the proto-Zambezi
lavas
(165
Namaacha eta/.,
My)
intercalated have
been
with late Jurassic described
from the
area on the Lebombo mountains
1983).
In northern KwaZulu-Natal,
(Dingle localised
Msunduze Formation alluvial fan sedimentation occurred in association with the emplacement of acid extrusive and intrusive igneous rocks of the Bumbeni Complex around 140 Ma (Wolmarans and 19881,
with subsequent
widespread,
coarse, elastic sedimentation
(Makatini
during the Early Cretaceous. Critical evidence regarding
the minimum
the effect of periodic winnowing by wind action cannot
the Sena sediments
be discounted, despite the fact that no dune features
of the diachronous
are associated with the Nwambia
transgressive
sand cover in this
River valley
Kalahari Basin have
been described above. South of the Limpopo valley region, sediments
Saggerson,
both of which were probably derived by weathering Formation sediments,
Sedimentation
period until
Formation)
is based on borehole relationship
age of records
with the overlying,
marine Grudja Formation of Senonian
to Palaeocene age (Flares, 1973). It is possible that deposition on the MalongaSena alluvial fans
region.
DISCUSSION Age of the Malonga
Formation
The initiation of Malonga
and correlatives
Formation
sedimentation
in the Limpopo River valley and Gona-re-Zhou region is poorly constrained, and one must look to continental/marine stratigraphic relationships below the Mozambique coastal plain and the postGondwanan sedimentary history of the Zambezi
decreased
during the period of rising base-level
associated
with the Senonian marine transgression
which
inundated
much of the southern
basin of
Mozambique. The ‘African landsurface’ and silcrete profile developed within the Malonga/Sena Formation, which also occurs seaward of the ‘Great Escarpment’ along the south and west coast of southern Africa, brackets the period during which active sedimentation ceased.
Journal of African Earth Sciences 18 7
G. A. BOTHA and M. C. J. DE WIT
This thick,
pedogenic
silcrete
profile
is regarded
as
rates
during
the
period
representing the long period of geomorphic stability associated with the ‘African landsurface’ which was
Gondwana. In the Gona-re-Zhou
in existence
Limpopo
from
the
Late
Palaeocene
(Partridge,
this silcrete
‘landsurface’
(1987)
classification
between
the
landsurface
1993).
until
Lundi
militates
and
Lister’s
planar-bedded, conglomerate
plateau
depositional
against
Mwenezi
Rivers
age. Formation
between
as the Chefu represent
Nyamtongwe
and Guluene
of the -35
Pliocene/early
of the
and Chilojo, as well
Rivers,
is more likely to
Pleistocene
Cox (1963) regarded succession in Zimbabwe
of
as a
along the Lundi River and incision
tributaries
the
The preservation
of the Gona-re-Zhou
of Pliocene
m terrace
Cretaceous
valley
1994).
processes.
bottom
marginal
Formation
correlate
Palaeogene,
in the Olifants
Mozambique,
the Malonga
is overlain
Salamanga
sandstone
by fossiliferous
Formation
and conglomerate.
Early descriptions
poorly-sorted
by
of the protoflow
Limpopo
in the valley-
basin
hills,
the
rudaceous
relief,
proximal
and pebbly, perspective,
was dominated
transport
basin.
southward
Cox
direction
(1963)
component
Zimbabwe
sediments
sand. Seen in a regional
or southeasterly broad
marine
probably
indicate high energy and high-density, transport with sediment deposited as
the alluvial environment
near Massingir
and fan
of coalesced
areas. Close to areas of high bedrock as the
Pafuri. Further
south,
surface
channelized
matrix-supported,
of western
extensive,
transport
a Piedmont
and Keyser (I 972) reports finding only indeterminable fragments of bone in outcrops in the area south of River valley
of
(Blair and McPherson,
sediment
fans on the margins
sediments sheetflood
the Malonga Formation as being unfossiliferous
the laterally
environments
Basin with localized, such
breakup
poorly-sorted, pebbly sandstone is characteristic of alluvial
across
alluvial
the
area and the westernmost
exposures,
Sheetflood
occurred
after
by a southerly
over much of the
described
a strong
in the northern
with derivation
outcrops
in
from the west in the Pafuri
Rennie (I 944) and Borges (I 944) actually equated the fossiliferous marine rocks exposed at Mabosi
area, invoking the proto-Limpopo River as a possible source. In the Pafuri area, channel bound, fining-
(Mahosi near Massingir), nearly 160 km southsoutheast of the Pafuri area in Mozambique, with
upward gravel and sand units and bioturbated silty sediments, probably
the Malonga
this
correlated 1972;
Formation.
Subsequent
these deposits
SACS,
1983).
lamellibranchs of Upper
These
rocks
and gastropod
Senonian
also
Keyser,
and
contain
marine
apparently
(36 Ma to 55 Ma)
a decidedly
by the authors
system,
1969;
species characteristic
to Eocene
strata, giving the deposits aspect (Rennie, 1944). Recent fieldwork
references
(Haughton,
Palaeogene
on
were
Cainozoic
boundary
data derived from derived palygorskite age (below).
western Mozambique, showed fossiliferous, Salamanga
environments
Formation
rocks.
associated
with
gravels confirms overlying
that these gravelly, Formation rocks
the red Shingwedzi/Olifants
Identification the basal
of silicified
Salamanga
Formation
correlated
A piece of silicified wood associated Malonga
Formation
outcrop
sedimentary valleys changes
with the upper
Upper Cretaceousl pers. comm. 1.
taphrogenesis related the development
wedges
in the Zambezi
to uplift
in the
in the
regional
rocks.
south of Pafuri is typical
of Podocarpus from the Palaeocene period (Bamford, Post-Gondwanan Nairn et a/. (1991)
wood
Formation
the Eocene age of the marine rocks
the Malonga
interior stress
across
the
as is suggested
Mesozoic/ by the proxy
the analysis of terrestriallyin oceanic sediments of this
and Limpopo
associated field
with
due to the
conditions reconstruction
on the
of the alluvial
post-Karoo
age Piedmont
surface is facilitated by the relationships between sedimentary units and palaeosol profiles, whose thickness, factors
maturity such
episodic,
and lateral
as minor
high
channel
sedimentation
continuity
sedimentary suggests
rate,
units and associated
major, episodic,
reflect
entrenchment,
conditions and possible tectonic sedimentation. The lateral persistence
arid climatic control on of individual
palaeosol
sedimentary
profiles
events.
The
sequence of thick, coarser-textured, sedimentary units and associated calcic palaeosol profiles, represents
of thick
development of the Agulhas fracture zone during the breakup of Gondwana. The thick sediment pile confirms the general view of vigorous river incision in the interior with high erosion and sediment transport
782 .fo”rnal of African Earth Sciences
channels
Sedimentation
and staff from the Palaeoenvironmental Palaeoenvironmental
overlie
in fluvial
surfaces.
continued
Direccao National de Geologia (DNG) on the shores of Massingir Dam in the Olifants River valley of
unconformably
deposited
floodplain
overlying, related to
repetitive
events
comprising
episodic
sedimentary pulses followed by geomorphic stability, which were relatively consistent during the long period of sediment
accretion
in this area. Where
sedimentation rate was high, surfaces aggraded and little or no soil development occurred, contrasting with areas starved of sediment where thick, mature pedogenic profiles developed (Wright and Alonzo Zarza, 1990).
Post-Gondwanan
There is a sharp contrast
between
upper parts of the Mwenezi
valley
continental sedimentation,
the basal and succession.
The
poorly-defined relationship between calcareous palaeosol development and the sedimentary units comprising higher
the -30
m basal succession,
sedimentation
rate with
dating accumulation
pedogenesis
of a number
nodular lower
units and intimately
calcic energy
palaeosols,
periods of pedogenic events
(Wright
be contrasted
stability
Zarza, further
coarser-textured,
sedimentary profiles.
palaeosol
comprising
episodic
longer-lived
features
and calcite
conditions
were
smectite,
in calcareous
during
the
succession
relatively
palygorskite,
palaeosol
should be seen in the context
Cainozoic
in this region.
continent,
regional
In the south
deep kaolinisation
the
Early
of the subresulted
from
a long period of intense weathering experienced by the post-Gondwanan, African land surface, followed by the formation
of ferruginous
and siliceous duricrust
profiles over wide areas of southern 1993).
Africa (Partridge,
During the Mid Cretaceous,
was forested
and experienced
and wet climate
(Rayner
central Botswana
a temperate,
et al., 1991).
seasonal The Upper
Cretaceous in southern Africa was characterised by a humid, tropical climate with deep weathering and high
runoff
which
sedimentation
is reflected rates
(Partridge,
Cretaceous/Palaeogene with
by rapid
boundary prolonged
marked
change
stepwise
cooling during the early Cainozoic
and Maud, 1989). The Upper Cretaceous
offshore
1993).
climatic
The a global
desiccation
suggested
of the Sena/Gona-re-Zhou/Malonga
rocks
this
places of initial
succession
However, lithostratigraphic
broadly
sedimentation
Kalahari Group sediments direct
and
(Partridge
accumulation period
In the extreme no evidence influence
of
basalt
correlation
units related
for
within
the
of the widespread
in central
southern of
humid
in the
of South
joint
palaeoenvironmental
weathering sediments
along
best
conditions
there is under the
Formation
The
and
Instead, the fresh
calcretization
pattern.
episodic
Africa
tropical above.
Malonga
is the
Namib
weathering
and
as described
‘boxwork’
region
(I 993) stressing
aridity
northeast
underlying
displays
African
(1990) favouring
of deep kaolinitic
environments
a closely
interpretation
of
during accumulation
of the Malonga Formation sediments is provided by the authigenic mineral assemblage associated with intraformational kaolinite and
palaeosols.
is absent
the
calcareous minerals,
occurrence
duricrusts
crystals,
point
or authigenic
of
including
palygorskite
inferred
Detrital
in all of the sequences
common
studied
interbedded
Mg2+-enriched
and dolomite
and rare gypsum
to more arid conditions
during the Upper Cretaceous
nodules,
Africa.
specific
to arid events
across
southern Africa is difficult as the east-west climatic gradient which characterises the subcontinent could have been established during the early Cainozoic (Partridge, 1993). The chronology defining establishment of post-Late Cretaceous aridity in the
profiles
and horizontal the palaeosols and Wright where
with
subvertical,
than those in this region.
tat conditions dolomicrite
branching,
sheet
(1991).
interpreted
and calcite
calcitic rhizocretions
calcretes
described
are very similar
by Allen (1986)
The reddened
most of the calcrete as truncated
sandstone
features palaeosol
to
and Purvis units
are located
are
sola developed
within stable areas adjacent to fluvial channels or on alluvial fan surface. The red coloration reflects authigenic
iron oxide formation
in geomorphic
settings
and oxidising Mount
which
conditions
penetration
of vertical
and Cohen
(Pye,
(1984)
(I 991) was attributed
overbank
which promote
is enhanced free drainage
1983).
rhizocretions
The deep
described
and Purvis
deposits.
fringe above the phreatic channel sediments and
A series of horizontal
layers following sedimentary bedding attributed to carbonate preciptiation A close dolomite, Formation
calcrete was also above a
water table. palaeoenvironmental smectite calcrete
of palygorskite comprising
by
and Wright
to the tap roots of phreatophytic
plants utilising the capilliary water table zone in fluvial
fluctuating age
Partridge
Miocene interior.
The calcrete
of the Malonga during
Eocene whereas post-Upper continental
Pedogenic palaeoenvironmen
palaeoenvironmental
aridification
of the southern
Ward and Corbett
profiles
conditions.
accumulation
of the progressive
by
period of sediment clay minerals and
to arid climatic of
events
pulses followed
stability,
comprise
Interpretation
of thicker,
repetitive
sedimentary
formed
under semi-arid
This can
units and associated
during the long The authigenic
Formation
1990).
parts
controversial,
spaced
north in the basin,
Here,
geomorphic
consistent accretion.
short
depositional
by the Chilojo Cliffs sequence
calcic
carbonate
with
between
and Alonzo
fine
an episodic,
environment
with events
represented
of numerous,
associated,
suggest
sedimentary
post-
of the depositional
units. In the upper part, the sequence thin sandstone
points to a
western
Limpopo region
analogy
and palygorskite-rich profiles is the extensive
and associated
pedogenic
pedogenic
profiles formed
Cainozoic,
Zuurverdiend
Formation)
sediments
Member in the upper
of the Malonga deposits dolocrete
within undated (Rooibokkraal Limpopo
River
basin and the Springbok Flats areas to the west (Botha and Hughes, 1992). Palygorskite in terrestrial environments is often associated with dolomite and represents semi-arid or seasonally arid conditions which were generally not as extreme as those of
Journal of African Earth Sciences 183
G. A. BOTHA and M. C. J. DE WIT
desert dune or evaporite
mineral
formation
(Callen,
1984). The crystallization of fibrous palygorskite clay from soil water occurred in poorly drained, waterlogged
areas where
evaporation
groundwater
solutes
concentrated Norrish,
1974;
elevated
Botha
(Singer
and Hughes,
1992).
groundwater
through
cation
extraction processes
(Watts, 1980; Nickel, 1985; De Deckker 1989; Botha and Hughes, 1992).
The
the periodicity
the fluvial
system,
Callen (I 984) described the Upper Cretaceous Early Eocene period as one of the major periods palygorskite
formation
and Robert accumulation
to of
with Vernier and Froget (I 984)
and Charnley
(1991)
of pedogenic
describing
palygorskite
similar
the
eroded from
periods
to draw
in a
sedimentary
as the
bracketing
conclusions stability studied
are
is no absolute
the Malonga
required
in
by Allen (I 986) for
sections
and there
of stability
any
of geomorphic
as calculated
calcrete
discontinuous framework
and Last,
profiles
fluvial
units implies episodic sediment accretion separated by long periods of geomorphic stability in the fluvial It is difficult
profiles
calcrete
of similar
regarding
in calcrete
in soil
of similar
succession
system.
of Ca2+ ions from
calcite precipitation
exchange
presence
and
Mg/Ca ratio of vadose water was interpreted
as the result of selective and
effectively
The stacked
dating
Formation.
for the formation
The of the
calcrete profiles described was possibly of the order of 1 O4 years or 3x1 O4 years, regarded as necessary for formation
of similar
Stage
II and III calcretes
Leeder (1975) and Allen (I 9861, respectively. nodules up to 1 cm in diameter year
period
in buried
formed
within
palaeosols
by
Calcrete a 1000
within
Late
the southern African continent within oceanic sediments of this age beneath the Atlantic and Indian
Pleistocene colluvium (Botha et al., 1994). However, reliable estimation of time required for formation of
Oceans.
smectite
calcrete
to
in rainfall,
These
derived
authors
from
the
attributed
adjacent
conditions
with
Increased
palygorskite
during
Palaeocene/Eocene
the
alternating
reflects enhanced contrast. Rubified
coloration
profiles
and seasonal
formed
in low-lying,
minerals
above the vadose The per
calcrete
rhizocretionary
features
a phreatic cementing
mode
groundwater
source
613C from currently
profile.
the
calcareous
being
environment of calcareous
features
undertaken,
of carbonate aeolian
analysis will
precipitation.
dust is difficult
Formation sediments deposition
of diffuse
in pedogenic implies
calcareous
profiles
relative
in levees/alluvial
within
stability ridge
derived
incision away
of
more
mature
in stable,
distal floodplain
to the channel
to incision
of 6180 and and cement,
probably
a distinct
the in
and
of
sediments probably climatic conditions.
fluvial
river valleys
to changed the
and Kraus, within
the
deposits
prior
in the region,
climatic
conditions, or drainage
decalcification
underlying
and
calcareous
occurred under more humid The formation of a hematite-
dominated, terra rossa weathering profile suggests deep leaching under a climatic regime with strong seasonality through
the overbank
developed
Deep weathering,
ferruginisation
conditions
change in pedogenic
in response
conditions.
The influence
mottles
of the major
represents
environments
or levees (Bown
carbonate
Formation
and
pedofacies
depositional
profile
below
migration
palaeosol
calcareous
to establish
supply
are interpreted
channel
Malonga
and
elucidate
variation
Ca”
in the red sandy
lithologies
during
from the more active
adjacent
this environment but is a likely contributor given the arid palaeoenvironmental conditions inferred. nodules
These clay-rich
as being
profiles and
and sandstone
Isotopic
to that found
1987). The weathering
nodule
of
and
blocks of red clay, with a similar
assemblage
occurring
carbonate
of pedogenic for
in the palaeosol
the conglomerate
the pedogenic
of ferro-magnesian
is favoured
mineral
profiles.
zone of the groundwater
descensum
formation
by regional
palaeosols, occur as clasts in the cross-bedded gravel infilling channels incised into the palaeosol
point to a the red
of authigenic
is hindered
evapotranspiration
Small pebble-sized
period
aridity
due to in situ oxidation
structures
(Wright, 1990).
deposited
River floodplain sediments pedogenic environment,
with crystallization
warm
and dry seasons. boundary
terrestrial
minerals, table.
wet
in sediments
palaeosol
proto-Limpopo well-drained
the
continent
and
lowering
periodic
desiccation,
probably
of the water-table.
as high rates of areas
close
to
Tectonism
channels would inhibit pedogenesis and calcrete formation (Bown and Kraus, 1987; Wright, 1990). The precipitation of sparry calcite rims around clasts and within the coarse, sandy interstitial matrix in
The accumulation of the Malonga Formation occurred after the differential uplift, crustal extension and continental rifting associated with the extrusion of a thick pile of Karoo lavas and intrusion of acid igneous
the underlying gravels probably occurred phreatic groundwater flowing through these
sheets
permeable
sediments.
from more
Nuanetsi Jurassic.
and ring structures
within
Syncline (Broderick, In northern Botswana,
the axis of the
1991) during the Du Plessis and Le
Pos t-Gondwanan
Roux (I 995) describe which
influenced
Late Cretaceous
deposition
block faulting
of the basal Kalahari
Group rocks. Flores (I 973) described and faulting
associated
the tectonism
with the development
Urema Graben to the east as occurring after,
accumulation
region,
of the east-west and
trending
a northerly
succession (1995)
Sengwe
fracture
Formation
the
Bosbokpoort fault described
the vertical, Malonga
fault
north trending
Formation
Brand1 of
River valley,
is related
It is unclear
fracture
outcrop
south of Pafuri, is related Whether
1991).
by the east-west
which
above.
in this
displacement
west of the Kruger Park boundary, Sengwe
Gona-re-
occurs
rocks in the Limpopo
trending
In the
to the south
(Broderick,
described
and
Fault near Dumisa
trend
near Malapati
recently
Malonga
the post-Karoo,
has been downthrown
to the
zone cutting
the
fountain,
the depositional
cyclicity
the Malonga Formation tectonism in the Limpopo
preserved
represents region,
within
episodic or climatic
and
sequence
flowing
controlled
channel
from
within
The periodic
successive of
a structurally-
the
of the
relationships
sedimentary
units
palaeosol
and the
material derived
underlying
sediments
Pafuri
area
can be contrasted
continuous,
thinly-bedded,
with
the laterally
sheetflood
sediments
to areas of high relief. The wide occurrence
of this system
along the margins
of the tectonically
active Limpopo and Zambezi valleys, suggests the existence of a Piedmont land surface comprising alluvial
fans along the continental
margin
during the Late Jurassic to Early Cainozoic era. The age of the succession remains enigmatic. The maximum
age is inferred
from
the lithologically
similar sediments overlying the 1 15 Ma lava in the Zambezi River valley. The minimum Late Cretaceous
of individual
age is based on the overlying
transgressive
associated
palaeosol
profiles
suggests
major,
Grudja
Formation
in the Zambezi
sedimentary
events.
Palaeosol
profiles
valley.
It is suggested
with
alluvial
fan depositions
channel-infill/floodplain
deposits
lateral
units
and
units and
comprise
the
succession in different parts of the basin, showing similar development. Interpreted in terms of periods of geomorphic interpreted
stability, as
perturbation
a rhythmic,
of the
environmental
this phenomenon
drainage
conditions
can be
possibly system.
and
long
to episodic
tectonic
succession
silcrete
formed
palaeoenvironmental
of
uplift.
the Malonga
sedimentary
Formation
Gona-re-Zhou Formation)
Plateau
Beds
Dande Formation Correlative
in western
de Sena of the Zambezi and the ‘Formacao
continental,
Cainozoic
the eastern margin of the emergent after
the breakup
of Gondwana.
succession
and provides
described
a valuable
link between
sedimentary
River valley. are
and Limpopo These deposits
sedimentation African
The investigation support
provided
B. Pretorius
Malvernia
de Singuedezel
River valley.
taphrogenic
as
with the
Mozambique
River valleys
Elefantes’ in the Olifants
during
the
is locally
lithological
and
the eastern margin
succession
is poorly
exposed.
and the similar
the Formacao
represent
known
(formerly
Zimbabwe
rocks of the Zambezi
sequences
was deposited
ACKNOWLEDGEMENTS
succession
can be correlated
in southeastern
River
of the Malonga
of the emergent African continent and development of the intracontinental Kalahari basin, where the early
CONCLUSIONS The post-Karoo,
much
in this region.
The sedimentary
The
arid
that
marine
period of aridification prior to the Late Cretaceous or Early Palaeogene when the ‘African’ land surface
well exposed
geomorphic stability throughout the accretionary period suggest that individual depositional events may have been related
Formation
sediments
regional periods
as
intraformational clasts in younger sediments. The fluvial depositional environments active in the
remains
sedimentary
an
fluvial
migration
by erosional
of calcretised
erosion
in the
represents
of a mixed-load
is defined
incorporation
area
southward
river valley.
between
The succession
Pafuri
persistence
associated
The
system fluvial
valley.
valley
influence,
episodic,
speculative.
Limpopo
coalesced
to this faulting.
region
the proto-Limpopo
adjacent
whether
near Malonga
Limpopo
aggradational
of the
during,
of the Sena deposits.
Limpopo-Mwenezi Zhou succession
con tinen tal sedimentation,
on
continent
Sedimentation
followed the long period of eustatic uplift associated with Karoo vulcanicity and the extensional tectonics and rifting along the continental margin and within
benefitted
greatly
to the authors
from the field
by Dr F. J. Venter,
(Punda Maria) and S. Ronaldson
of the National We are indebted
to Prof. T. Mason
Natal,
for
Durban)
(Pafuri)
Parks Board in Kruger National identifying
Park.
(University the
of
Taenidium
ichnofacies and MS M. Bamford who identified the silicified wood samples. The Malonga Formation succession
in the Pafuri area could
be described
in
a regional context due to the support of the Executive Officer and Directors of the Council for Geoscience and the assistance of Mr J. Marques, Director of the Direccao National de Geologia in Maputo, Mozambique and the Acting Director, Zimbabwe Geological Survey, who facilitated field investigations
G. A. BOTHA
in their respective unpublished
countries
information.
Mr P. Fey, formerly Survey,
who
access to
are grateful
of the Zimbabwe
arranged
Gona-re-Zhou
and provided
The authors
to
in the
with measurement
American
Survey
Research
image processing
of South
Africa.
Laboratories
made
and CAD facilities
satellite
1984.
(Edited
by Singer,
is based
on a paper
at the XII biennial
conference
during
A. S., 1982. Fora
Petrology Commission
African
for
Society
Cox,
K. G.,
1963.
their
REFERENCES Sandstone
facies
Anglo-Welsh 58-86.
(Late
area,
recognition Alonro
Pedogenic
calcretes
Silurian-Early
southern
Blackwell Zarza,
Cura, M. A., 1992. in the middle
Publ.,
Red
of the
Paleosols:
by Wright,
their
V. P.) pp.
J. P. and Garcia
and climatic
of the Madrid
del
Boyd,
and
Save-Limpopo
Zimbabwe
Basins
distinction
processes, Journalof Borges,
Tectonics
A., 1944.
Marques
6. 5-l 2.
139-l Botha,
in a late
do Alto Limpopo.
Pedogenrc
Lorenco
G.,
Geoderma
A. G. and Vogel,
palaeogully
Africa. G. A.,
erosion
Catena
J. C., 1994.
rn northern
53,
De Wit,
1993.
Transactions
De Deckker,
P. and Last,
dolomrte
in evaporitic
Sedimentary
setting.
(Malvernia)
Formation
Park, South
Africa.
Pafuri
relations
suites, of
paleosols.
P., Fedoroff, U.,
description.
152~.
Sengwe Survey
Warne,
and
faults
of the
Society
Mwenerr
A., S?oops,
England.
lateral
for soil
Land.
thin
of
valley Annals
G., Turcina,
of
tectonics
pp 21 I-235,
the
Penod of (Edrted
Olrver
and
plumes
in the development
Nature
342,
of the Royal
W. M., 64,
T.
section
lake
Botswana.
20.
7-l 5. H. V.,
Marsh,
Igneous
Province:
volcanic
873-877.
1989.
underplating.
Society
Modern,
of western
of London nonmarIne
Vrctona,
Australra
223-238. A. R., 1983.
Africa.
Mesozorc
375~~.
rocks
J. P., 1995.
complexes
Late
of the
Balkema,
J. S. and Cox,
of the Karoo
1984.
Province,
Special
Lupata
The Cretaceous
Mozambrque
of theAfrican
Coasts.
Forster,
the
Mozambrque.
L. H.,
Printer,
Peterson,
Morphological
and some
aspects
accumulation Goudle. A. S.,
envrronment
pp 93-I
31. Academrc
Gwavava,
0..
genetic
Swain,
Evidence
S. H., 1969.
and
residua
by Goudre,
Press,
in the
mlnerais,
escala
Republica
Podmore,
F. and
thinning
beneath
of crustal
K),
Farrhead.
J.
the Llmpopo
of southern Africa based on and rmpllcatlons for the Tectonophysics 212, I-20.
Geologicalhistory
7: 1 000 Popular
nears
A. S and Pye,
of southern
pp 427. Geological Society of South Africa. Instrtuto Nacinnal de Geologia.. 1987. Carta Mozambique,
1966.
carbonate
London.
Belt and Lebombo monoclrne regional gravity studies reconstructlon of Gondwana. Haughton,
R. B., of
Soil Science 101, 347-360. and In: Chemrcal sedrments
(Edited C. J.,
Grossman, sequences
Precipitates
surface
Geological
Pretona.
in desert soils. 1983. Calcrete.
geomorphology:
of the
Palaeogeography,
Channel.
F. F. and
and
Pans.
of the sedimentary
Palaeoclrmatology, Palaeoecology 17, 267-287. Geological Survey., 1981. 2230 Messina, 1:250000 Goverment
Basins
G.), pp 88-
Surveys,
history
Lower
sedimentary
by Blant,
Geological
Mozambique
rocks,
of
of the Geologrcal
In: Sedimentary
(Edited
The geological
of southern of
2ndpart
of African
R., 1975.
Society
and Tertiary
and Zululand.
Karoo of the
Publrcatron
Geologrcal
River, Mozambique. Transactions Society of South Africa LXVII, 11 l-l 20. 1973.
The
In: Petrogenesis
Zambezr
G.,
Group
Earth Sciences,
K. G.,
and introduction.
Cretaceous
Kalahari
JournalofAfrican
13 (Edited by Erlank, A. J.) pp l-26. South Africa. Flores, G., 1964. On the age of the
D., 1992.
Geocongress
Communal XV, 53-58.
Handbook
and
rn the Llmpopo
Geological
000.
341-344.
magmatic
P. I. and Le Roux,
Eales,
Gale,
Council
of Sedimentary
Centennial
N., Jongerius, 1985.
I.G.)
geology of Southern
and slaine
Series,
Nattonal
of channel
sequence Journal
of certarn
Quaternary.
Malapati, Geological
and Babel,
and
Malonga
Kruger
lntegratlon
Extended Abstracts 1, 442-444. South Africa, Johannesburg. Brodenck, T. J., 1991. The geology south of Zimbabwe
the
1995-0046,
I. Developmental
alluvial
the
The
Pretoria.
Petrology 57, 587-601. Brandl, G.. 1995. Fieactrvatron during
area,
ReportNo.
1995.
successron of
T. M. and Kraus, M. J., 1987.
floodplarn
F. J.,
lithologrcal
in the
33pp.
Transactions 66.
magmatismand
playas
Geology
and Tertiary
basin
Kwa ZuluNatal,
M. C. J. and Venter,
1986.
000
fragmentation
Continental
66.
155-l
orlgln
palaeoenvironments
for Geoscience,
Episodrc late
23, 327-340.
geologlcal
1:5
of the Karoo
patterns.
A, 342,
basinsof
succession,
Africa.
World.,
postulated
The role of mantle drainage
Philosophical
Flores,
palygorskrte
sedimentary
South
of the
and vulcanism
and Gass,
11 1. Association
depositional
Bullock,
hydraulic
54.
regronal
Belt
the
fans and their
e Geologia,
J. C., 1992. Neogene
Transvaal,
G. A., Wintle,
South
Bown.
conglomeraticos de lndtistria
G. A. and Hughes,
Cluaternary Botha,
of
processes, and facres assemblages. Research A64. 450-489.
Depositos
northwestern
Alluvial
from nvers based on morphology,
dos Services
and dolomrte
Annals
from the
of Sedimentary
Africa,
of beds.
onthe
In: African T.N.
in northern
Xl, 41-55.
J. G., 1994.
sedimentary Sedimentary
Boletim Botha,
K.
Du Plessis.
of the Mid-Zambezl
in Zimbabwe.
GeologicalSurvey
Blair, T. C. and McPherson, natural
potential
Developments
Edrnburgh.
alkaline The hydrocarbon
uses
Rotterdam.
relationships
Sedimenfology
Basin.
39, I’-35. Barber, B., 1987.
Map
Map
Dingle, R. V., Sresser, W. G. and Newton,
Oxford.
V. P., Calve,
Soil-landscape
Miocene
In:
(Edited
Scientific
A. M., Wright,
Old
Carboniferous)
Britain.
andinterpretation
in the
Journal
of South Africa
bearing
by Clifford,
995.
Cox, R. L. 1986.
In:
and
of root casts
Kenya.
Malvernia
Society
of continental
J.
genesis
Paleoenvironments
Geological
Cox, K. G., 1989.
Allen,
group:
distribution.
E.) pp l-37.
52,401.414. for the Geological
Gondwanaland.
Research
from 30/4-6/5/l
and
Elsevrer.
Formation,
International
and
Southern
Quaternary
held in Cape Town
age occurrences,
37,
Cox, K. G., 1970.
presented
of the
of the palygorskite-sepiolite
A. and Galan,
in Sedimentology
Geological
This manuscript
Clays
environment,
UNESCO.
the investigation.
(SASQUA)
R. A.,
depositional
Koobi
Anglo
available
Callen,
Cohen,
of the Chilojo Cliffs section. XRD and XRF analyses and micromorphological thin sections were provided by the Geological
C. J. DE WIT
Palygorskite-sepiolite:
Geological
the visit to outcrops
area and assisted
and M.
000,
Minrsterro
de Mozambrque,
Africa.
Geologrca dos recursos
Maputo.
Pos t-Gondwanan
Keyser,
A. W.,
van
die
1972.
Jong gesteentes
Nasionale
C. F.,
classification,
Rhizoliths
lithofacies.
genesis
Geological
Rhodesia.
Transactions 193-l
Lister, L., 1987.
The erosion surfaces
A. D., 1977.
braided
Lithofacies
river
Money,
7992, 42-51.
N. J.,
1972.
12,
Mount,
Geological
J.
Cohen,
J. D. G.,
Rhodesia.
S.,
1984.
east
Petrology
1967.
potential
of
Petrology
Lake
and
fluvial and
Turkana,
Preliminary
of the
Zimbabwe
Geological
Survey
Files.
Nairn, A. E. M., Lerche, I. and Iliffe, J. E., 1991. Geology, basin analysis, and hydrocarbon potential of Mozambique and the Mozambique
Channel.
Netterberg,
F.,
calcretes,
Earth-Science
1980.
1. Terminology,
of
classification.
Transactions 83,
24.
of the
Geological
and
Society
P. M. and Millsteed.
and
B. II.,
1994.
Partridge,
T. C. and
terraces
of
Journal
the
49,
Partridge,
Geology
Brink,
lower
event:
Vaal
Journalof
Lithostratigraphy,
River
Gravels
basin.
and
Geographical
Africa.
K. and
&rat.
lnt. 17, 105-l V.
P.,
1991
environment
Rayner, Shaw,
R. J., Waters, A. L., 1991.
(Edited
Academic
by Goudie, Press,
S. B., McKay,
A. S and
Pye,
London. I. J., Dobbs,
The mid-Cretaceous
P. N. and
palaeoenvironment
of central Southern Africa (Orapa, Botswana). Palaeogeograph y, Palaeoclima tolog y and Palaeoecolog 88, 147-l
56.
Bristow,
J. W.,
K),
geophysical Zimbabwe Tswiza-Vila Lowveld
Geological
1986.
of the
1984.
du
bassin
Sud
Ouest
supepieur
(sites
Dynamique
of
Survey
de
D.S.D.P. et
de
An
account
Kruger
Park.
argileuse
Somalre
240
of the
National
Sedimentation
depuis
et 241).
Geographic
y
Monograph
N. L., 1977.
le
Revue
Physique
de 25,
7. 17-26.
Pseudo-anticlines
of Botswana
and other
and South
Africa.
Quaternary
(southern
valley,
pedogenic
Africa):
Sedimentology
A. H., 1970.
Sipolilo
calcretes
Mineralogy, 27,
Notes
rn
L. G. and Saggerson,
Detritus
of the Kadzr area,
E. P.. 1988.
Geology
of the
rocks of the southern Lebombo Excursion A, Geocongress ‘88.
in ancient
Magazine 127(3), 273-276. Wright, V. P. and Alonso Pedostratigraphic
the and
5, 26-28.
Geological Society of South Africa, 37pp. Wright, V. P., 1990. Estimating rates of calcrete accretion
from
genesrs
661.686.
on the geology
District.
volcanic and intrusive Mountains. Guidebook:
sedrment
structures
Earth Surface
2, 63-74.
N. L., 1980.
Wolmarans, to
Pye, K., 1983. Red beds. In: Chemical sediments and geomorphology: Precipitates and residua in the nearK), pp 227-263.
in the near-
A. S and Pye,
survey,
Zimbabwe
C.,
Zambezi
aridification related
In: Chemicalsediments
south-eastern
E. and Froget,
diagenesis.
South
10. Calcretes
Geology
Files.
le
Kalahari
phreatophytic vegetatron from the Middle Triassic Qtter Sandstone of South West England. Sedimentology 38, 539551.
surface
F. J. and
some calcretes
Wilson,
for Cainozoic
Pleistocene
Sedimentary
seismic
geomorphology and drainage Koedoe 29, 1 17-l 24.
Processes
85, 428-430.
The evidence
Wright,
hemisphere.
Flash-
Late
Unpublished
border,
Files.
J. D., 1993.
and residua
Technical
Technical
59,
on a reconnaissance
Refraction
TransvaalMuseum
The end-Cretaceous
from the southern
Namibia.
palygorskite
Venter, F. J., 1986. Soil patterns associated with the major geologrcal units of the Kruger National Park. Koedoe 29, 125-l 38.
Watts,
205-224. 1967.
R. R., 1989.
Science
T. C., 1993.
in southern
B. A.,
Survey
Anna/s
Mineralogist
of the
Lowveld.
Unpublished
Watts,
New evidence
Partridge,
A.
97(2),
Pedogenic
Silcrete.
Report east
die Formasie
339-348. Ward, J. D. and Corbett, I., 1990. Towards an age for the Namib ecology: 25 years of Namib research. Namib.
2 l-38.
T. C. and Maud,
African
Purvrs,
Journalof
In,
9, 83-84.
American
River,
Rhodesia.
Geologic
diagenesis.
1974.
T. R. and Ward,
Mozambique
C&ace
in alluvial fan systems. An approach
K.,
1983.
E. R., 1968.
dans
palaeontology, and sedimentary environments of the western Cabora Bassa Basin, Lower Zambezi Valley, Zimbabwe. South African
Sutton,
Vernier,
255-283.
Carbonates
Kurseb
van
of South Africa
and ichnofacies
- south
Venter,
African
macrofeatures
sedimentology to physiography, Sedimentary Geology 42. 83-l 04. Oesterlen,
30, 81-l
southern
description,
of South Africa Nickel, E., 1985.
Reviews
Geology
Survey
E. R., 1967.
alluvium.
Krugerwildtuin.
(Edited by Goudie, Press, London.
Salazar,
rocks, S. E. Lowveld,
foorkoms
Nasionale
surface environment pp 59-91. Academic Sutton,
mineral
and Planetary
for braided
Precipitates
Geological
investigations
y (Global
and geomorphology:
survey
Kenya.
54, 263-275.
of the Cretaceous
Unpublished
Technical
Republic
‘n Nuwe
85, 579-599. Summerfield, M. A.,
of western
Survey,
of early
clay
Palaeogeography,
models
in Australia.
Silts,
from
e
(Edited by Miall, A.D.), pp 605-625. Society for Petroleum Geologists 5.
508-5 17. Smith, R. M. H., Mason, Homeb
6, 27-35. 1991. Development
Depositional
sediments
de
de lndustria
315-331.
A. and Norrish,
flood
Namibia,
from Plio-Pleistocene
deposits,
Sedimentary
petroleum
A.
of rhizoliths
lacustrine
Muirhead,
of
of the geology
of the Geological
and
geochemistry Journalof
of the
103-123.
F.
marginal
sediments
89,
In
Conglomerados
sediments.
suid van Pafuri,
occurrences
Canadian
Kalahariiymposium, Society
An outline
Records
Zambia
volume,
B. R., 1979.
Singer,
Fluvial
in,
Mabosi,
axis
222-223.
dos Services
tolog y, palaeoecolog
Section)
spreading 19781,
as inferred
oceanic
of the Geological
models
5.
The Etjo and Kalahari
in
Malvernia,
a summary.
climates,
Calgary, Canada. Schutte, I. C., 1974.
l-62.
Geo!ogis ts, Memoir
Basin. Abstracts
Zambia.
Zimbabwe
profile
(18 May,
Boletim
Fluvial Sedimentology, Memoirs Canadian
depositional
and vertical
deposits,
R. G., 1992.
November Windhoek.
Rust,
of South
(Edited by Miall, A. D), pp, 597-604.
of Petroleum
Owambo
types
13,
warm
Change
pp. 163
Reviews
Gondwana
273
Fossils from
Marques.
palaeoclima
of Zimbabwe.
A failed
Nature,
J. V. L., 1944.
variations
part of Southern
of the braided-river
Earth Science
sedimentology Miller,
90,
A review
Miall, A. D., 1978.
Society
Bulletin
1978.
Africa.
Eocene
257-270.
of the GeologicalSociety
region
Geologia, Lorenco Marques Robert, C. and Charnley, H.,
significance.
98.
Survey
environment. in
112,
C. V.,
Lourenco
carbonates and flood sediment model for alluvial arid-zone
Magazine
Reeves, Rennie,
8p.
and
Limpopo
southern
carbonates:
Notes on the south-eastern
Africa 41,,
Miall,
deel report
27, 613-629.
B., 1938.
Geological
1972-0053,
in terrestrial
recognition,
Leeder, M. Ft., 1975. Pedogenic accretion rates: a quantitative Lightfoot,
Unpublished
South Africa,,
1980.
Sedimentology,
in die noordelike
Kruger-wildtuin.
GeologicalSurveyof Klappa,
con tinen tal sedimentation,
models
formation
alluvial deposits. Zarza,
for alluvtal
A.
and
Geological M..
1990.
fan deposrts:
for interpreting ancrent sequences. Journal Geological Society of London 147, 8-l 0. Zimbabwe Geologrcal Survey., 1991. Zimbabwe
a tool of
the
geology
7: 7 ODD DOD, 7th edition.
Journal
of Afman
Earth
Soences
187