Abstract Dronning Maud Land contains a fragment of an Archaean craton covered by sedimentary and magmatic rocks of Mesoproterozoic age, surrounded by a Late Mesoproterozoic metamorphic belt. Tectonothermal events at the end of the Mesoproterozoic and in Late Neoproterozoic–Cambrian times (Pan-African) have been proved within the metamorphic belt. In western Dronning Maud Land a juvenile Mesoproterozoic basement was accreted to the craton at c. 1.1 Ga. Mesoproterozoic rocks were also detected by zircon SHRIMP dating of gneisses in central Dronning Maud Land, followed by a long hiatus for which geochronological data are lacking, an amphibolite to granulite facies metamorphism and syntectonic granitoid emplacement of Pan-African age have been dated. During this orogeny older structures were completely overprinted in a sinistral tranpressive deformation regime, leading to the mainly coast-parallel tectonic structures of the East Antarctic Orogen. Putting Antarctica back in its Gondwana position, the East Antarctic Orogen continues northward in East Africa as the East African Orogen, whereas a connection to the marginal Ross Orogen at the Pacific margin of East Antarctica is suggested along the Shackleton Range. The East Antarctic-East African Orogen resulted from closure of the Mozambique Ocean and collision of West and East Gondwana, i.e. western Dronning Maud Land was part of West Gondwana. During this collision the lithospheric mantle probably delaminated, allowing the asthenosphere to underplate the continental crust and producing heat for the voluminous, typically anhydrous, Pan-African granitoids of central Dronning Maud Land.

Abstract The Variscan Orogen was formed during the closure of the Rheic Ocean and the final collision between the North American and West African cratons in the Late Paleozoic. This collision led to the multistage building of the Mauritanide Belt to the east of the Variscan suture and to the building of the well-known Appalachian Belt to the west. Both led to opposite vergences in this part of the Variscan belt. The earliest records of the main collision episode begin at ∼360 Ma and end about 250 myr ago, while a late extensional phase lasted until ∼190 Ma. Three distinct stages are recognized in West Africa. The first stage (c. 350–300 Ma) records the indentation of the Reguibat Shield into the central Appalachian margin of Laurentia. This indentation led to thrusting of the Souttoufide and Akjoujt ‘nappes’ onto the Reguibat Shield, to southward motion of the Senegalese block (SB), and to strike-slip motion in the Appalachians. The motion of the SB to the south is coeval with: (1) folding of the northern part of the Bové Basin, (2) north–south sinistral strike-slip motions in the central Mauritanides, and (3) the end of sedimentation in the Bové and Taoudeni Basins by the Late Devonian. The second stage (c. 300–250 Ma) involves the eastward motion of the Western Thrust Block (WTB) against the SB and, likely, some of the westward thrusts in the Appalachians. This second ‘Variscan’ event includes: (1) closure of parts of the lower Diourbel Carboniferous basin, which is now concealed beneath the Senegalo-Mauritanian Basin, (2) thrusting to the east of the Simenti Group over the Koulountou Group in the Bassaride Belt, (3) thrusting to the east of the Wa-Wa Group, (4) thrusting of the Mauritanide Belt onto the Taoudeni Basin in the central Mauritanide Belt, and finally (5) thrusting of the Agualilet Group over the Akjoujt nappes and eastward motion of the western units over the Dhloat Ensour (Late Ordovician to early Devonian) autochthonous unit in the Souttoufides. West of the supposed ‘Variscan’ suture, Appalachian thrusting affected parts of Appalachian Belt. The third stage (c. 250 to 190 Ma) began with the opening of Triassic rift basins in the Senegalo-Mauritanian basin and also in the north of Florida. As numerous previous correlations across the Variscan system do not include the West African part, our sythesis is intended to enhance these correlations.

Abstract A review of 60 isotopic age measurements on southern African rocks indicates that many of these data have a bearing on important Precambrian stratigraphic problems. In 1948 Arthur Holmes first used age measurements in deciphering the structural history of this region. His study emphasized dated pegmatite bodies in metamorphic terrains as indicating ancient orogenic belts of different ages. Recent work has focused on dating the relatively flat-lying and unmetamorphosed Precambrian systems, and a revised stratigraphic time scale for the Transvaal Province is proposed here. Certain relatively flat-lying systems in southern Africa have ages greater than 2000 millio n years, exceeding the ages determined in the high-grade metamorphic terrains. These old systems include the Ventersdorp, Witwatersrand, and Dominion Reef. The Transvaal System may be ˜2000 m.y. old. The “ancient orogenic belt” theory implies near-contemporaneous stablep l atformdeposition and possible formation of post-orogenic arkose troughs. Reliable times of deposition for the adjacent undeformed systems can thus supply critical evidence concerning this theory. The region paralleling the Orange River in northernCape Province provides an example: there are many age measurements on pegmatites and metamorphic rock of ˜950m.y., and Holmes postulated the existence of a 1000 m.y.-old orogenic belt; this implies the existence of ˜1000 m.y.-old stratigraphic systems, both as a geosynclinal sequence and as the “stable-platform” equivalent. However, the accepted geologic column for this region does not reveal stratigraphic systems that can be clearly linked to the history of the hypothetical ˜ 1000 m.y.-old orogen. Either the accepted geologic column is in error and part of the Kheis System is much younger than hitherto supposed, or a widespread regional metamorphism and pegmatization affected the Kheis rocks some 2000 m.y. after their deposition. There are many determinations close to 500 m.y. in a belt extending through South-West Africa, the Central African Federation, and Mozambique. Widespread metamorphism, with emplacement of granitic rocks, took place in parts of southern Africa at the close of the Precambrian and during the Cambrian Period. Arcuate synclinal belts of low-grade metavolcanic rock w ith an age > 2500 m.y. are characterized by the “Steinmann” geosynclinal association of rock types; rocks and related mineral deposits of this association were evidently not formed i n the subsequent history of southern Africa. Younger Precambrian metamorphic terrains have a different tectonic style, showing frequent alternation of metasedimentary units with massive and gneissose granites, and occasional highgrade regional metamorphism. The characteristic differences i n structure may be related to thermal history o f the crust. Many of the age measurements impose restraints on stratigraphic correlations between the various isolated Precambrian areas.