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Journal of the Geological Society
doi: 10.1144/gsjgs.148.6.11151991, v.148; p1115-1123.Journal of the Geological Society
P. B. GROENEWALD, G. H. GRANTHAM and M. K. WATKEYS
southeastern Africa and Dronning Maud Land, AntarcticaGeological evidence for a Proterozoic to Mesozoic link between
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Notes
The Geological Society of London 2014
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Journal ofth e Geological Sociely,
London, Vol. 148
1991, pp. 1115-1123, 1 fig, 2 tables. Printed in Northern Ireland
Geological evidence for a Proterozoic to Mesozoic link between southeastern
Africa and Dronning Maud Land, Antarctica
P . B . GROENEWALD,G . H . GRANTHAMlY3 M. K . WATKEYS
Departm ent of G eolog y, University of Natal, Box
375
Pietermaritzburg
3200
South Africa
Department of Geology and Applied Geology, University of Natal, Durban, South Africa
3 P r e ~ e n tddress: Department of Geology, University of Pretoria, Pretoria, South Africa
Abstmft: Comparison of crustal provinces in Southeastern Africa and Dronning Maud Land, Antar-
ctica, eveals onsiderable imilarity
in
their volution romheArchaeanuntilheMesozoic
separation. Archaean granites and mid-Proterozoic supracrustal successions
in
these regions are so
comparable hatcorrelation is uggested.
A
major mid- to lateProterozoicorogenic errain in
Dronning Maud Land, comprising he H . U . Sverdrupfjella and Heimefrontfjella subprovinces and
termed the Maudheim Province, is very similar in age, lithology, structural style and metamorphic
history to the Mozambique and Natal orogenic provinces of Kibaran age
l o o 0 Ma) in
southeastern
Africa. Deformed supracrustal sequences in
all
three provinces host syn-tectonic granites ntruded
during upper amphibolite- to granulite-facies metamorphism. Isoclinal folding was accompanied
by
thrusting owardsadjacentcratonicareas.Development of orogenicprovinces of Kibaranage in
southeastern Africa and Antarctica reflects accretion of marginal basin-volcanic arc sequences onto
older continents. The500Ma Pan African event was a widespread, predominantly thermal, overprint-
ingof parts of the older orogenic provinces. Faulting
and
rifting of the supercontinent preceded
break-up and influenced the stratigraphy of Phanerozoic sedimentary successions in SE Africa.
Recent reconstructions
of
Gondwana place Dronning Maud
Land, Antarctica and the Mozambique coast of Africa into
juxtaposition at
c.
145 Ma on the basis of marine geophysical
evidence (Martin Hartnady 1986; Lawver Scotese
1987). The geological similarities
of
these regions, remarked
on earlier by du Toit (1937), Grantham
et
al. (1988) and
many others, may benlarged onhe basis of new
information from Antarctica. A major problem in
reassembling Gondwana is the precise juxtapositioning of
Antarctica and Africa. This stems partly from masking of
the original contact areas, inMozambique by a thick
Cretaceous-Tertiary sequence,and in Antarctica by ice.
The new datarom Antarctica allow more detailed
comparison of the marginal regions and offer strong support
for the reassembly proposed by Martin Hartnady (1986).
Studies
of
Phanerozoic crustal evolution in SE Africa have
demonstrated that syn-depositional tectonism in the Karoo
basin was rela ted o earlystages
of
Gondwanabreak-up
(Cox
et
al. 1967; Flores 1970). Theseuthors also
recognized early rifting (220-145 ma) andranscurrent
faulting, which initiated partial separation of Antarctica and
Africa prior to drifting. Geological evidence for correlation
of events in Africa and Antarctica from early Proterozoic
(and possibly Archaean)o mid-Phanerozoic will be
synthesized here. Implications of the extent andevolution of
Proterozoic orogenic provinces will also be discussed.
Southeastern Africa and Dronning Maud Land may be
considered in terms of ancient, cratonic nuclei separated by
orogenic belts
of
various ages (Fig. 1). The Kaapvaal and
Zimbabwe ratonic terrains comprisegranite-greenstone
provinces overlain by supracrustal sequences ranging in age
from late Archaean to mid-Proterozoic. In Dronning Maud
Land,herchaeano mid-Proterozoic Grunehogna
Province shows similarities to these provinces in having
3.0Ga granites and.7Ga red-coloured tenigenous
sediments. Around the cratonic provinces are the accreted
mid- to ate Proterozoicorogenic provinces which have
been the focus of several recent studies. It isnow known
that the 1OOOMa Kibaranectonic vent xtended from
centralMozambique, hrough Malawi into Zambia in the
west, and orthwards into Tanzania and Kenya (Daly
1986a;hackleton 1986). The Mozambiquerovince,
important in the presentcontext,hasbeen described in
some detail by Sacchi et
al.
(1984). Their data are used here.
The Namaqua-Natal orogenic belt, situated some distance
tohe south
of
and geographically discreterom the
Mozambique Province, is of similar age andeneral
lithological character. The ast coast Natal Province is
particularly relevant to this discussion and haseen
described in general terms by Cain (1975), Matthews (1981)
andhomas (1989). More specific aspects of the
geochronology, give by Eglington et al. (1989), reveal that
deformation,metamorphismandgraniteemplacement n
this area occurred synchronously with the same processes in
Mozambique Province.
In DronningMaud Land, a high-grade structuraland
metamorphic errain lies to heeast, south and west
of
Grunehogna Province (Fig. 1). Two sectors of this orogenic
province have been investigated. The eastern sector, first
examined by Roots (1953), consists of
H . U . Sverdrupfjella
and Kirwanveggen, described by Grantham et al. (1988) and
Wolmarans Kent (1982) respectively. The Heimefront-
fjella sector, situated to the west, has been reported on by
Juckes (1972), Spaeth Fielitz (1987) and Weber
et
al.
(1987). The geology of these areas is sufficientlywell
constrained to allow their interpretation in terms
of
a single
orogenic belt, henceforth termed the Maudheim Province.
This name is proposed in view
of
the former existence of
Maudheim base, used by the Norwegian-British-Swedish
Antarctic Expedition from 1950 to 1953. In age, lithology,
1115
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1116
P. B .
G R O E N E W A L D
E T AL .
deformation and metamorphism, theastern sector of
Maudheim Province shows significant similarities to he
Mozambiquerovince. Inddition, correlation of the
Heimefrontfjellasector with the Natal Province hasbeen
proposed(Spaeth Fielitz 1987; Weber et
al.
1987). The
parallel tectonic evolution of the late Proterozoic provinces
in the Mozambique, Natal-Namaqua and Dronning Maud
Land regions allows more detailed interpretation of their
evolution and identification of their original tectonic
settings. Furthermore, some inferences made regarding the
extent of this loo0Maectonothermal province have
implications for the original assembly of Gondwana.
A tectonothermal overprinting, spanning the period
600
to 450 Ma, is widely recognized in Africa as the Pan African
and in Antarctica ashe RossOrogeny. It as been
sueprimposed on he Mozambique and Maudheim Prov-
inces, but has not been recognized in Natal Province. It is
characterized by folding, thermal resetting
of
some isotopic
systems and the generation and emplacement of granites.
Development of predominantly sedimentary successions
across the older terrains occurred in the Phanerozoic. The
widespread Karoo Sequence in southern Africa comprises a
thick succession
of
sedimentsccumulated in diverse
environments. Its deposition terminated with widespread
emplacement of doleritic ntrusions and tholeiitic volcanic
rocks. A similar, albeit much thinner, succession is present
in the Heimefrontfjella and Kirwanveggen areas
of
the
Maudheimrovince. Likewise, post-Karoolkaline
intrusions are presentboth n theJutulstraumenarea of
Dronning Maud Land and in the northeastern sector of the
Karoo basin in Africa (Fig. 1). The similarity between the
patterns
of
jointing and faulting post-dating these intrusions
in both settings has been recognized by Grantham Hunter
(1991).
Linked cratonic fragm ents
In Dronning Maud Land, relatively undeformed and
unmetamorphosed Archaean and Proterozoicrocks n the
Ahlmannryggen, Straumsnutanend Borgmassivet areas
constitute the Grunehogna Province. This
is
bounded to the
east and south by the Maudheim Province (Fig. 1).The
Archaean ocks,occurringonly in theAnnandagstoppane
area, are c. 3000 Ma granites (Barton et
al.
1987). These are
of the same age as some granitic intrusions in the eastern
Kaapvaal and ZimbabweProvinces, but he limited data
available suggest slightly different geochemical characteris-
tics and provenance (Barton
et al.
1987).
Proterozoicedimentary and volcanic rocks of the
Ritscherflya Supergroup occupy the remainder of Gruneh-
ogna Province and have been extensively intruded by mafic
and ultramafic bodies. Ferreira (1986) interpretedhe
sedimentary rocks as a sequence, from the base upwards, of
shallow marine, tidal flat, braided stream, and alluvial fan
deposits. Measured palaeocurrent directionswere highly
variablebut thedepocentre was probablysituated to he
northeast
of
Grunehogna. The sediments ar e characteristi-
cally immature and red in colour. A sequence of continental
tholeiitic basalts overlies the sedimentary rocks (Watters et
al. 1991). The geochronological dataare equivocal, with
reported ages ranging from 800 Ma to 1800 Ma (Moyes
Barton 1990). Watters et al. (1991) obtained Sm-Nd
zhur
model ages in the range 1300-1620Ma for the basalts and
interpreted these as representative of the crystallization age,
and ascribed an Rb-Sr age of 876 Ma to later ectonothermal
overprinting.
The sediments of the Ritscherflya Supergroup ave
several possible correlates in southeastern Africa such as the
Umkondo, Waterberg andSoutspanberg Groups (Fig. 1).
Farther afield, the Volop Group and theNtingwe Formation
are situated along the southern margin of the Kaapvaal
Province adjacent o he Namaqua and Natal Provinces
respectively. All thesemid-Proterozoic equencescontain
immature fluvial to shallow marine sediments with distinct
ferric pigmentation. However, tholeiitic volcanic rocks are
present only in the Soutpansberg andUmkondo Groups.
Tankard
et al.
(1982) reported predominantlysouthwards
palaeocurrent directions in the Soutpansberg Group, which
is opposite to those in the Grunehogna area. The sediments
were depositedn andy,braided alluvial plain settings,
within either an aulacogen or a yoked basin. The Umkondo
Group situated onhe astern flank of the Zimbabwe
Province, has close similarity to the Ritscherflya Supergroup
in terms of sedimentary characteristics, which led Ferriera
(1986) to suggest correlation. Themkondoroup
sediments, described by Button (1977), represent tidal
flat-lacustrine, progradationalan delta, andmeandering
river depositional nvironments.Palaeocurrentdirections
are to the SE,N and E in the lower, middle and upper parts
of the sequence respectively.
Despite the similarities of the sedimentary sequences in
theUmkondo,Waterberg nd Soutpansberg Groups o
those of the Ritscherflya Supergroup, it is impossible to
correlate them with any certainty. It is significant, however,
thatmid-Proterozoicsequences in this part of Gondwana
are of similar character and re situatedn easonable
proximity to one another in the reconstruction (Fig. 1). The
fact that Soutspanbergediments have been observed
overlying Waterberg Group sediments (Jansen 1976) points
tohe development of severalntracratonic basins
or
aulacogens in the mid-Proterozoic. Certainly, the in-
tracratonic basins on the Kaapvaal craton had a long history
as Jansen (1982) recognized a much more complex
stratigraphy in theWaterbergGroup than previously
reported. However, heir chronology is not unequivocal.
Allsopp
et
al. (1989) presenteda well constrainedage
of
1080Ma forhe UmkondoGroup. Ageserivedor
lowermost parts of theWaterbergGroup range from
1790Ma o1420Ma (Oosthuyzen Burger 1964), which
conflictswith its correlation with the Umkondo Group on
the basis of similar palaeomagnetic poles (Jones
McElhinny 1967). The proximity of all these sequences to
orogenic provinces, which developed subsequently in the
mid- to late Proterozoic, suggests that initial crustal buckling
and the development
of
intracratonic basins was a
consequence of widespread tectonic processes prior to the
onset of the Kibaranorogenesis, itself a widespread and
long-lived collisional tectonic regime.
Comparison of the
loo0
Ma terrains
The geological characteristics of the 1000 Ma orogenic
terrains in SE Africa andAntarctica arecomparable, as
summarized in Table 1and discussed in more detail below,
and broad correlation of these is almost certain.
The Natal Province may be considered in terms of four
zones (Matthews 1981; Tankard et
al.
1982) or terranes
(Thomas 1989). Thenorthern marginal zone
or
Tugela
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ANTARCTICA-AFRICA:ROTEROZOIC-MESOZOICINKAGE 1117
Fig 1. Simplified geological map of SE Africa and Dronning Maud Land, Antarctica.The continents are juxtaposed asn the reconstruction
of Martin Hartnady (1986). The continental outline projection is hat used by de Wit
et
al. (1988). Bathograds at
3000
m depth areshown
using short solid dashed line for Africa and longer dashed line for Antarctica.
Terrane, where the orogenicelt abutshe Kaapvaal
amphibolite facies. They host severalayered mafic-
Province, comprises a narrow, southward dipping thrust belt
ultramafic and interleavedraniticntrusions. ectonic
of low-grade metasediments along its northernextremity,
transport was towards theorth. Thisequence is
and a wider, westward plunging nappe complex farther
considered to beophiolitic n character (Matthews
1972).
south. These nappes consists of a supracrustal suite of basic
Thenorthern marginal zone is succeeded outhwards by
lavas and clastic and chemical sediments metamorphosed at
one in which synformal structures consisting of paragneiss
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1118 P. B . GROENEWALD E T A L .
sequences are separated by augen gneisses. This is followed
toheouth by anrea in which granulite facies
paragneisses,ranites and charnockites predominate.
Thomas (1989) hasargued hat NatalProvincecomprises
three
or
four sectors, consisting of calc-alkaline granitoid
rocks andsubordinate metasedimentary lithologies, which
represent different accreted sequences.
The lithostratigraphy
of
theeastern Mozambiquebelt
comprises a migmatitic gneiss basement and a
volcano-sedimentary cover sequence that includes carbonate
and quartzitic units, all having undergone amphibolite facies
metamorphism (Sacchi et
al.
1984). Much
of
the succession
was interpreteds calc-alkaline volcanic inrigin.
Interlayering
of
mafic, ultramafic and sedimentary protoliths
gives parts of the Mozambique rovince an ophiolitic
character.
A
nappe of granulite facies paragneisses, which
was thrust over the volcano-sedimentary succession, consists
of metamorphic rocks ranging from rhyolitic to ultramafic in
composition.everalraniteswere intrudednto this
sequence.
In eastern Maudheim Province, H.U. Sverdrupfjella and
Kirwanveggen are underlain by ortho- and paragneisses of
the Sverdrupfjella Group(Roots 1953, 1969; Hjelle 1974;
Wolmarans Kent 1982; Grantham
et al.
1988). In H.U.
Sverdrupfjella,orthogneisses predominateadjacent o he
Grunehogna cratonic province. They display layering on a
variety of scales but are generally of rather monotonous,
intermediate composition. These gneisses have calc-alkaline
geochemical characteristics andare nterpreted obe of
volcanic origin. Fartherastre paragneissic meta-
carbonates and pelites interlayered with grey orthogneisses.
These are followed eastwards by paragneisses which are
predominantlyquartzofeldspathic but containwidespread
metapelites, iron-rich amphibolites, uartzitic and semi-
pelitic gneisses. This part of the succession is characterized
by granulite facies mineral assemblages. Rocksn
Kirwanveggen haveeennterpreted asredominantly
volcanic in origin (Wolmarans Kent 1982). Heimefront-
fjella is still relatively unknown,but mphibolite facies
carbonates,para- and orthogneisses have been reported
(Juckes 1972). Pre- and syn-orogenic mafic intrusions,
represented by amphibolite and pyroxene-garnet boudins o r
lenses are also common throughout Maudheim Province.
Several generations
of
syn-tectonic intrusions have been
recognized in the Maudheim Province. Grantham et al.
(1988) described tabular syn-tectonic granitesn H.U.
Sverdrupfjella subprovince. Charnockites are present in the
Kirwanveggen, but the contact relations are ambiguous in
being gradational Wolmarans Kent 1982). Relatively
extensive,oarse-grained, gneissic granitesccurn
HeimefrontfjellaJuckes 1972). Similarly, therere
numerousgranites and charnockites nNatalProvince, in
tabular and batholitic forms of pre-, syn- and late-tectonic
character (Thomas 1989). In MozambiqueProvince, the
c. loo0 Ma granites are domical and migmatitic (Sacchi et al.
1984).
Table
1. Summary and compar i son
of
Kibaran and R oss lPan Afr i can l i thos t ratigraphy and t ec tonotherm al hi s tor i es
Maudheim Province
Mozambiquerovince
Sverdrupfjella/Kirwanveggen
Heimefrontfjella Natal Province
Lithostrat igraphy
Gneiss-migmatite basement. Meta-
sedimentary
meta-volcanic
cover
sequence. Minor carbonates, Fe-
quartzites, greywackes, dominantly
calcalkaline meta-volcanic rocks.
Overthrust granulitemetasedimentary
nappe.
Deformat ion
Intense early folding and thrusting.
Main thrusts to N W in western parts,
to
SE in southern zone. Wide thrust
belts
and
shear zones. Later more
gentle
folding,
possibly accompanied
by thrusting.
Metamorphism
Regional mid-amphibolite facies n
southern
zone
with klippen of gra-
nulites. InNW widespread granulites,
partly retrogressed.
Magmat i sm
Early deformed
and
relatively unde-
formed granites, later with migmatitic
aureoles. Late
porphyritic
granites
are Pan African.
Migmatitic volcano-sedimentary
succession. No
basement-cover
relations. Minor carbonate,
quartzite, greywacke pelites.
Orthogneisses
calcalkaline vol-
canic
rocks Overthrust granulite
sequence
in
the east.
Early coaxial
isoclinal
folding
events
accompanied by thrusting.
Main
thrusts towards N W. Later
open
to close
folding
with
minor
thrusts. Major shear zones (?).
Regional
amphibolite
facies met-
amorphism in west,
granulites
above main thrusts
to
northeast
and in
the south.
Widespread
retrogression
of
granulites.
Suitesof megacrystic, sheeted
highly deformedearly granites
(S-type and calcalkaline?). Char-
nockites
in south. Sheeted
grano-
toid suites
Pan African.
Metamorphosed volcano-
sedimentary sequence.
Basement cover relation
reported.
Metavolcanic
rocks
are
calcalkaline.
Abundant mafic dykes.
Early isoclinalfolding
with
thrust component
to
NE
(Kibaran age). Younger
folding, thrusting toNW
of
Pan African age. Major
shear zone
between
cover
and
basement.
Regional
mid-amphibolite
facies. Granulites in
NW.
Retrogressed and over-
printed
during Pan
African.
Numerous early granite
intrusions.
Metavolcanic-dominated north-
ern
zone, southwards various
metasediments with numerous
intrusive granitoids. Ophiolitic
affinity
of
amphibolites.
Intense
early
thrust and fold
nappe development. Abundant.
evidence for thrusting towards
and NW. Local backthrusts.
No
post-Kibaran
deformation.
Dominantly amphibolite facies in
north, granulite zonen south.
Local
granulites throughout.
No
evidence for post-Kilbaran
retrogression/rehydration.
Abundant graniteand charnock-
ite batholiths and sheets. S-type,
calcalkaline and A-type bodies.
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A N T A R C T I C A - A F R I C A :R O T E R O Z O I C - M E S O Z O I CINKAGE 1 1 1 9
Available geochronological data from the various prov-
inces reveal near contemporaneity of tectonothermal events
(Table
2).
In all the Kibaran provinces considered here, the
marginal basin-volcanic arc successions accumulated before
about200Ma, when metamorphism and deformation
began. The orogeny was particularly prolonged, as revealed
by the presence of granites with ages ranging from 1163 Ma
to 850 Ma.Althoughhesentrusionsange from syn-
orogenic to anorogenic alkaline character, all show evidence
of some metamorphic/deformational history. The ages
may, therefore, represent metamorphic resetting rather than
Table 2. G e o c h r o n o l o g y
of
he Kibaran orogenic provinces ( M S W D
values in brackets if k n own )
Mozambique Province
Basement :Rb-Sr1200 MaR,
=
0.7060 (3 point isochron)
Cover :Rb-Sr950
f
0 Ma R,
=
0.7091
Rb-Sr lo o0 Ma
R,
= 0.7013
Early grani te : Rb-Sr 1100 M u R, = 0.7027
Amphibo1ites :Rb-Sr whole rock 1391 f 8 Ma R,
=
0.707 (0.3)
Granulites : Rb-Sr wh ole rock 1073
f
5Ma
R,
= 0.707 (0.59)
Maudheim Province
Sverdrupj j e l la Group, Kirwanveggen
orth~gneisses(?)~
zirconb-Pbircon U-Pb:
1071
f
4 Ma 90) 112
f
2 Ma (9.5)
1075
f
0Ma (127)1107
f
27 Ma (2 60)
1061f 6 Ma (108 ) 1045
f
93 Ma (548)
Rb-Sr whole rock3 1015f 4 Ma R, = 0.704 (1.04)
1164
f
8 Ma
R, =
0.704 (11.2)
Rb-Sr whole rock-biotite ages 460-485 Ma
Sverdrupj j e l la Group, H .U . Sverdrupfjella
Amphibolite facies orthognei~ses~
Rb-Sr whole rock 1141 f 3 Ma R, = 0.708 (0.4)
Granulite facies paragneisses4
Rb-Sr whole rock 1170
f
6 Ma R, = 0.7040 (0.76)
Syn-orogenic granite4
Rb-Sr whole rock 1163
f
9Ma
R,
= 0.7036 (8.88)
Late syn-orogenic granitoids3
Rb-Sr whole rock 519
f
7 Ma
R , =
0.708 (1.7)
whole rock-biotite ages4 430-480 Ma
Heimefr~ntfjella~
Volcanism: 1100-1200 Ma
Metamorphism: 1OOO-1100 Ma
Natal
Province
All Rb-Sr whole rock6
Northern marginal area metavolcanic rocks
1240
f
3 Ma
R ,
=
0.704 (2.2)
Northern marginal area, granites
1194f83MaRO=0.7017 0.8); 0 6 7 f 2 0 M a R 0 = 0 . 7 0 6 ( 1 . 7 2 )
examples
of
granites further south
calc-alkalin e 981 f 1 Ma R, = 0.7032 (11.3)
A-type 1089
f
4 Ma
R, =
0.7038 (1.73);
1003 f 9 Ma R,
=
0.7054 (0.75)
transitional 1011 f 9 Ma R , = 0.7063 (2.36)
syn-orogenic metabasite 1024
f
2 Ma
R , =
0.7026 (2.21)
tonalitic basement Nd 7
=
1405 Ma
Data
source
references:
'
Sacchi etal. 1984; *Cahen etal. 1984; 3M oyes Barton1990;
4M oyes Groene wald, unpublished;Weber et
al.
1987;
1065
f
1 Ma
R ,
=
0.707 (0.21)
Eglington et al. 1989.
emplacement, especially as mostwere determined using
Rb-Sr isotopes. Nonetheless, the initial
87Sr/86Sr
atios ( R , )
may be particularly significant. Many
of
the isochrons
(Table 2) have
R ,
values between 0.703 and 0.705 indicative
of a relatively short crustal esidence ime of the source
rocks.
Metamorphic histories were similar in all the 1000 Ma
terrains. In NatalProvince,amphibolite facies conditions
predominatedn theorthern marginal zone with
P >4.5 kbar, T
=
550 600 C and at higher temperature but
lower pressure in the northern zone (Rhodes Leith 1971).
In the southern part
of
Natal conditions of
P
= 4.8-6.8 kbar
at T
=
650-850C persisted hrough much
of
the early
tectonic history (Talbot Grantham 1987). In outhern
Mozambique Province, amphibolite facies rocks predomin-
ate except in klippen consisting
of
granulite facies gneisses
(Sacchi et
al.
1984). Andreoli (1984) documented granulite
facies conditions
of P
= 7-9 kbar, T = 725-800C in
southern Malawi. Maudheim Province also underwent
predominantly high-grade metamorphism.uckes (1972)
found that Heimefrontfjella had undergonelmandine-
amphibolite facies metamorphism, and Weber et
al.
(1987)
identified a granulite facies basement underlying amphibol-
ite facies cover. Wallace (in Wolmarans Kent 1982) has
identified granulite and amphibolite facies assemblages in
Kirwanveggen. Groenewald Hunter (1991) have recog-
nized earlygranulite facies conditions of relatively high
pressure ( P = 8-10 kbar) and temperature T = 800 C),
followed by amphibolite-facies retrogressionand ehydra-
tion ( P = 6 kbar, T = 600C) in the main range of H.U.
Sverdrupfjella. Generally lower grade conditions applied in
the west, closer tohe adjacentGrunehognaratonic
province, where epidote-amphibolite facies conditions were
never exceeded.
The deformational histories of the reas were also
similar (Table1).Structuralevolution in the Mozambique
Province, as documented by Sacchi
et
al.
(1984), was
dominated by thrust-nappe tectonics at c. 1000Ma which
produced strongly linear frontal ramps and imbricate stacks
in areas of morentenseeformation.lsewhere,
recumbent folds are typical. The thrust system had a root
zone in southern Malawi, from which tectonic transport was
towards theSE. Outside his hrustsystem,NW-trending
folds predating the thrusting were superimposed on earlier
structures. In the southeast , widespread gentle deformation
with a WNW trend may represent a late tage of the
thrusting event. This folding is more intense locally where it
gave rise to new foliation.Kibaran tectonics inAfrica,
described in general terms by Daly (1986a, b 1988) and
Shackleton (1986), involved considerable crustal shortening
through NW- and SE-directed hrusting.This divergence
was related to a postulated regional pop-up ooted in a
mid-crustal shearor decoupling one. The NW-verging
structures are considered to represent the main thrust
system whereas those tohe SE are thought to be
backthrusts (Daly 19866).
A similar orogenic history haseen identified in
Maudheim Province. The granulite facies paragneisses in
H.U.' Sverdrupfjellawere eformed by almost co-axial
isoclinal folding events and ater thrustover the adjacent
amphibolite facies succession (Groenewald
Hunter 1991).
The sense of movement on thrustlanes, which are
subparallel to the general SE to E dip of layering, is towards
the northwest. The transgression of thrust planes across the
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1120 P. B . G R O E N E W A L D E T A L .
tectonic foliation indicates that the thrusting postdated much
of the folding. Open to close folding superimposed on the
earlier structures makes interpretation difficult. In Heimefr-
ontfjella older folds trend NW with N E vergence, nd
younger folds trend NE and verge NW Spaeth Fielitz
1987). An older granulite facies basement is separated from
the amphibolite terrain by a major hear zone.Several
flat-lying thrust faults are present in NE Heimefrontfjella.
The Natal orogenic province also underwent thrust and
nappe-dominatedectonism. The orthern arts
of
this
terrain are inferred to be obducted ophiolites in a series of
N-verging thrust nappes (Matthews 1981). The central part
is characterized by upright ynformal structures, whereas
thrust faulting and isoclinal folding occurred in thesouth
(Thomas 1989).
Summary of the
10o0
Mu provinces
The hree provinces describedabove appear o constitute
parts of a single, extensive orogenic province on the basis of
similarities in lithology, tectonic style (Table
1)
and age
(Table 2). Thrust faulting in Natal Province and Dronning
Maud Land involved tectonic transport towards the cratons,
whereas that in the Mozambique Province was bi-directional.
Thrusting in Mozambique and.U. Sverdrupfjella
emplaced granulite-facies successions aboveamphibolites.
The lithologies in all three provinces are interpreted tohave
been volcanic and sedimentary deposits typical of marginal
basins, with aense of polarity in that metavolcanics
predominate close to, nd metasediments further away
from, theadjacent cratonic areas. Geochronological data
suggest contemporaneity.Metamorphism shows the same
general pattern of initial granulite and amphibolite facies,
followed by amphibolite facies retrogression.irect
correlation of lithostratigraphicunits is not possible, and
variations in level of exposure may account for some
of
the
major differences. If the nterpretation
of
the lithological
sequences as marginal basin-volcanic arc deposits is correct,
the Kibaran orogeny was one of accretion of newly formed
crust onto an older continental nucleus.
It is therefore suggested thathe Kibaran Province
encompassessub-provinces neast Africa, Antarctica and
southAfrica, and was thus
of
considerable extent.t
represents major accretion at a relatively early stage in the
construction of Gondwana.Groenewald Hunter (1991)
reported the
P-T-t
path
of
H.U. Sverdrupfjella and argued
that the metamorphism was related to pla te collision. The
generally low PIT conditions, which applied in Natal, may
be at variance with collision orogeny, and Tankard et
al
(1982) argued for an ensialic rather than ensimatic marginal
basin,although more hanone accretionarysegment was
recognized by Thomas (1989). Isotopicvidence that
supports accretion
of
juvenile sialic crust was presented by
Eglington et
al.
(1989). The ophiolitesnNatal and
Mozambique Provinces are also evidence that accretion
occurred through collision of segments
of
continental crust
that were once separated by oceanic crust.
Pan African and
Row
orogenic events
A widespread tectonothermal event affected Gondwana in
the period 600-450Ma, resulting in several fold belts. The
Gariep,Damara nd Saldanian rogenic rovinces and
pervasive thermaloverprinting
of
larger racts
of
Africa
(Fig.
1
are ascribed to he PanAfricanevent, whilst the
extensive tectonothermal province in Antarctica is termed
the Ross Orogeny. In SE Africa evidence for tectonother-
mal overprinting is restricted to the Mozambique Province
where Sacchi
et
al. (1984) recognized that gentle refolding
was related to the emplacement of
500
Ma granites. Despite
the limited new fabrics and etrogression associated with
this event, widespread resetting
of
isotope systems occurred,
particularly Rb-Sr andK-Ar, which resultedn the
Mozambique Province being considered as entirely
of
Pan
African age in somearly publications (for example
Bloomfield 1981).
Orogenesis also occurred in the Maudheim Province at
this time. Many of the granitic intrusions in H.U.
Sverdrupfjella weremplaceduring D3, which was
characterized by open to close folding and minor reverse or
thrust faulting. These granites form subhorizontal to
subvertical tabular bodies highly variable in thickness and
associated with NW-directed thrust faulting. The Brattskar-
vet alkalic granitoidbody, the largest of these intrusions
(100km), has yielded a well constrained whole rock Rb-Sr
age of 519 17 Ma (MSWD = 1.7,
R,,
= 0.708) (Moyes
Barton 1990). Otherate granites,haracterized by
tourmaline or magnetite phenocrysts, are considered to be
younger because theyut monzonitic dykes of the
Brattskarvet uite. The atterpredates a poorly defined
tectonic foliation in which biotite crystallized. This biotite,
in conjunction with whole-rock data, has provided Rb-Sr
ages of 460-490 Ma in the Brattskarvet intrusion (Moyes
Groenewald, unpublished data), similar to biotite blocking
temperature ages of 475 Ma from Kirwanveggen (Elworthy,
in
Wolmarans Kent 1982). Most of the K-Ar age
determinations by Russian workers in the 1960s ranged from
400-500Ma throughout the region (Ravich Solovev
1966), suggesting that the thermal effect
of
this orogeny was
pervasive isotopic resetting, perhaps through retrogressive
rehydration.
In Heimefrontfjella,a rnafic dykedisturbed by one of
the thrust faults provided an age of 450 Ma (Juckes 1972).
Spaeth Fielitz (1987) and Weber et al. (1987) recognized
folding younger than the main 1000Ma deformation. These
folds, which trend NW and verge NE, are associated with
thrust faulting. Extensive etrogression ccompanied this
deformation. Weber et al. (1987) interpreted these events to
be of Pan African age. The vast extent
of
this thermal event
in Antarctica is revealed by the occurrence
of
gneisses
of
this age in the Shackleton Range, at he western limit of
Dronning Maud Land, and in the S c Rondane, to the east
(Fig. 1 as described by Rex (1972) and Picciotto et al
(1964), respectively, and the considerable extent of the Ross
Orogeny outlined by Craddock (1972). In the case of
S0r
Rondane, 1OOOMa ages havebeen suggested recently by
Shiraishi Kagami (1989), which reveal difficulties similar
to those experienced in earlier dating
of
the Mozambique
and Maudheim Provinces.
There is no evidence that the Pan African orogeny had
any effect on Natal Province as isotopic data reveal no ages
younger than 850 Ma. Nor is there any published evidence
foreformation
or
retrogression post-dating the main
orogeny, which was entirelyKibaran in age. Theres,
however, an orogenic province
of
Pan African age in the
southernmost part of Africa, termed the Saldanian, in which
thrust aulting, ntense folding and granite mplacement
have beenocumented (see Tankard et al. 1982, for
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ANTARCTICA-AFRICA:ROTEROZOIC-MESOZOICINKAGE
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references). It would therefore seem likely that he Pan
African swathe of tectonism passed from the Mozambique
Province through the MaudheimProvince, thenextended
southwest, but it did not reach westwards into Natal
Province.
Phanerozoic-Palaeozoic deposition, volcanism and
tectonism
Majorntracratonicepositional basins developed in
Gondwana after the Ross/Pan African orogeny. The Karoo
Sequence of southern Africa (Fig. 1 is of particular interest
because its accumulation spanned the critical period during
which initial stages of rifting began.Tectonic adjustments
which heralded the main phase of continental fragmentation
influenced depositional patterns hroughout he develop-
ment of theKaroo basin. These tectonic ontrols also
applied to the succeeding Karoo volcanism which has been
related, in theLebomboarea, o a failed triple unction
(Burke Dewey 1973). These volcanic rocks erupted
between 200-175 Ma (Erlank 1984) andare significantly
older than the earliest marine geophysical anomaly used in
the econstruction
of
Gondwana by Martin Hartnady
(1986).
The KarooSequence of centraland outhern Africa
represents a Carboniferous to Triassic sedimentary succes-
sion capped by late Triassic to Jurassic flood basalts
(Tankard et al. 1982; Dingle
et
al. 1983; Erlank 1984).
Karoo sedimentation proceeded after accumulation of the
Cape Sequence and, in the main basin in southern Africa,
was influenced by deformation in the Cape fold belt (Rust
1975). Termination
of
activity in the fold belt was followed
closely by eruption
of
theKaroo basalts, anvent
considered to be closely relatedohereak-up of
Gondwana (Cox 1970; Eales et al. 1984).
The stratigraphy
of
Karoo sediments in southern Africa
will be described in terms
of
lower and upper subdivisions
for the purposes
of
this paper (using Tankard et al. 1982
and references cited therein as sources). The lower sequence
has a basal succession
of
tillites, diamictites and associated
sediments which reaches its maximum thickness
of
750 m in
the southwestern Karoo basin, but which is absent n the
extreme northeast. This succession is overlain by lower
Permian basinal mudstonesdeposited in a large, possibly
marine, body of water. In the ortheast art of the
depository alluvial sandstones are present at this strat-
igraphic level and hostoaleposits. Overlying the
mudstones and sandstones is asequence of upward-fining
fluviatile cycles which may once have exceeded 5000111 in
thickness in the outhernKaroo basin,but which thins
considerably towards the northeast.
The upper Karoo sedimentary succession commences
with a middle to upper Triassic coarse sediment wedge, up
to 500m thick in the south-central part of the basin, which
is overlain by laterally persistent red mudstone up to 490 m
thick. Thisas low sandstone/mudstoneatios, lacks
carbonaceous shales, and marked the onset
of
aridity which
culminated in deposition of sandstones under aeolian
conditions during the upper Triassic. Although the aeolian
sandstones attain maximum thickness in the southwestern
Karoo basin, they do not become thinner to the northeast s
is characteristic of the other units. In contrast , they occupy a
NE-trending trough within which there are a variety of local
thickness variations. Outside the trough, an approximately
constant thickness of 150 m is present throughout almost the
entire region affected by Karoo sedimentation, making this
the most widely developed sedimentary unit of the Karoo
Sequence.
Deposition
of
theKaroo Sequenceoccurrednwo
broadly different tectonic settings (Rust 1975). South of the
Limpopo River, a marginal cratonic shelf to miogeosynclinal
trough environmentxisted,hereas toheorth
sedimentationook place in separate, fault-controlled
troughs. Although complicated by fault control which led to
considerable thickness variation and intra-strata1 unconfor-
mities, the stratigraphicsequences in the two terrains are
very similar. In the northeast there s, however, evidence for
a long-lived palaeo-high where the late Karoovolcanic rocks
rest directly upon basement. This is the Nuanetsi Igneous
Province, situated in the Limpopo region (Fig. 1). Nearby,
in the Lebombo region, there is a hin veneer
of
aeolian
arenitesbetween the basement and he volcanic rocks,a
feature particularly relevant in the presentontext of
correlatingetween theKaroo Sequence and Permian
sedimentary rocks of Maudheim Province. In Heimefrontj-
fella, the thin (
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1122
P . B . G R O E N E W A L D E T A L .
probably situated between Grunehogna Province and he
Kirwanveggen, but is not yet sufficiently well-constrained to
contribute precision to the Gondwana reconstruction.
Discussion
The reconstruction and geological parallelism of these parts
of Gondwana have implications for an understanding
of
its
crustal evolution from Mid-Proterozoic until Mesozoic time.
Much
of
the supercontinent, in particular the parts adjacent
to
SE
Africa, was almost certainly complete 1000Ma ago.
Subsequently, about hree Wilson cycles occurred n the
northernhemisphere,but he evidence from this part of
Gondwana indicatesredominantly ensialic orogenesis.
Repeated accretion of continentalrustragments and
intervening volcanic arc-marginal basin complexes onto
Africa requiresvaluations viable mechanism for
assembly, oronstruction, of the supercontinent.
continuous record of geological evolution after Gondwana
assembly provides insights into hebreakup mechanism.
This may have broader implications for the current cycle
of
plate tectonic activity from which almost all understanding
of the hypothesis stems.
Similarities between therunehogna supracrustal
succession andhat of the Kaapvaalrovince suggest
continuity between theseerrainsuringhe mid-
Proterozoic. This continuity could possibly have existed as
early as the Archaean if the Annandagstoppane granite is
equivalent to granites of the Swaziland region.his
correlation should perhaps be approached with caution, but
the proposedid-Proterozoicuxtaposition
of
these
terrains requireshat it be considered. If these crustal
segments were originally separate and only juxtaposed after
deposition of the Soutspanberg and Ritscherflya Super-
groups, then a sutureone of some kindhould be
recognizable. There is no direct evidence that such a zone
exists in theeastern Kaapvaalprovince,although Stettler
et al.
(1989) haveeconized variety of very early
discontinuities in the patterns defined by magnetic trends in
KaapvaalProvince. Thereason why the line ollowed by
subsequent breakup passed through this crustal fragment of
considerable longevity requires further investigation.
The similarities between the provinces of Kibaran age
have been detailed above. Clearly, their correlation would
provide evidence for one of the largest orogenic provinces
onarth, extendingouthward from Kenya through
Mozambique intoAntarctica, hen back into Africa in a
westerly direction, and across southern Africa intoSouth
America.
Of
significance in thisproposed correlation
is
evidence thatatere-breakup tectonics modified the
original construction, leading to non-linear fracturing across
the Gondwanaupercontinent and complicating the
present-day reassembly. Furthermore , the Muhlig Hofmann
mountains,extendingeastwards from heH.U. Sverdrup-
fjella tohebrondanerea (Fig. l) , have
lithostratigraphy, metamorphic history and age closely
similar to hose
of
the Maudheim Province (Ravich
Solov'ev 1966; Asami
et d .
1989; Shiraishi Kagami 1989),
which suggests an even greaterextent or thisorogenic
province. Kibaran orogenesis is also known in Madagascar
(Cahen et al. 1984), andBerhe (1990) argued hat he
Mozambique rovince and Arabian-Nubian Shield may
have been contiguous.
On a regional scale, the tectonic history
of
the Karoo
basin reflects jostling of crustal segments prior to and during
the break-up of Gondwana as different crustal blocks were
subjected to the vast stress field associated with this event.
Karooedimentation and magmatism in the Limpopo
region were ontrolled by faults which were, in part,
reactivated structures of Archaeanand earlyProterozoic
age. Flores (1970) recognized a transcurrent component to
some of these faults which suggests that they may have been
related toreak-upnd excision of theGrunehogna
segment from Kaapvaal Province.
Much of theAntarcticdatareported here were acquiredduring
work on the South African National Antarctic Research Program,
supportedby
the
Department
of
EnvironmentAffairs, owhom
P.B.G. and G.H.G. are grateful for sponsorship. D . Hunter s
thanked for his
help
andguidance.Wegratefully cknowledge
constructive analysis
of
the manuscript by
A.
B . Moyes and T.
S
Brewer.
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