POSTGLACIAL PERMIAN STRATIGRAPHY AND GEOGRAPHY OF SOUTHERN AND CENTRAL-AFRICA - BOUNDARY-CONDITIONS FOR CLIMATIC MODELING

The post-glacial stratigraphy of southern and central Africa comprises mudrocks with subordinate sandstones and coal measures belonging to t he Ecca Group overlain by fossiliferous mudstones and sandstones of th e Beaufort Group (Madumabisa Mudstone of south-central Africa), preser ved in the Karoo, Congo and extreme western margin of the Parana basin s, the Kalahari-Zambezi and East Africa-Malagasy basin complexes, and the Nyasa basin and range complex. The palaeogeography of the region w as controlled by the stable, elevated Kalahari and Congo cratons, a NE -trending weak zone between the cratons (site of the Kalahari-Zambezi- Malagasy basin complexes), a NNW-trending weak zone between the craton s and the Mozambique mobile belt (site of the Nyasa basin and range co mplex) and an E-W mobile belt along the southern margin of the contine nt (site of the foreland Karoo Basin). The postglacial Artinskian land scape which was inherited from the Permo-Carboniferous glaciation, con sisted of a rugged interior plateau and shallow seas and seaways in th e south and west. The Early-Late Permian landscape was still dominated by an uneven coastline in the south and freshwater lakes in the Congo Basin and along the Kalahari-Zambezi-Malagasy drainage systems. A mar ine incursion occurred in the Malagasy Basin. Relief on the interior p lateau was steadily denuded. By Kazanian times large lakes covered the Karoo and Parana basins whereas along the coastal region all shallow seas were destroyed by an orogen. Freshwater lakes in the interior had reached their maximum extent. The Permo-Triassic landscape shows an i ncrease in the interior relief due to renewed graben formation with la kes becoming smaller and more desiccated. The surface area of southwes tern Gondwana covered by water reached a maximum of 34% during the Ear ly-Late Permian and decreased to about 6% at the Permo-Triassic bounda ry. Climatic zones shifted southeastwards as southwestern Gondwana dri fted into lower latitudes during the Permian. The ice margin started t o retreat in central Africa during the Sakmarian, but the marine ice s heet in the Karoo Basin collapsed only in the Artinskian. Deglaciation was followed by a cool wet climate suitable for the formation of peat lands. In central and south-central Africa this climate was followed b y temperate to warm, seasonal conditions which became progressively we tter with less seasonal fluctuation towards the east (Malagasy Basin) and drier towards the west. These conditions lasted until the end of t he Kazanian. In the Karoo Basin the cool wet climate of the Artinskian became more temperate and also lasted until the end of the Kazanian w hen warm, semi-arid conditions expanded over the entire southern and c entral Africa. The geographic controlling factors for Permian climatic change were the interplay of latitudinal setting and continental evol ution (formation of orographic barriers and loss of coastal seas).