Stratigraphie der Karoosedimente der Huabregion (NW-Namibia) und deren Korrelation mit zeitäquivalenten Sedimenten des Paranàbeckens (Südamerika) und des Großen Karoobeckens (Südafrika) unter besonderer Berücksichtigung der überregionalen geodynamischen und klimatischen Entwicklung Westgondwanas

Abstract

Abstract provided by author in published version of thesis:

In the Paleozoic and Mesozoic the Huab Basin (Namibia), the Parana Basin (South America) and the Great Karoo Basin (South Africa) were parts of a large sedimentary basin in Western Gondwana. Consequently the sedimentary sequences corresponding to each basin show good correlations of stratigraphy and facies. The stratigraphy of the Huab Basin is based on numerous newly found fossils and on the changes of facies within the Huab Basin

From the Dwyka Formation an ichnocoenosis of five genera/species is reported with the introduction of the new species Punctichnium namibiense. This ichnocoenosis is of stratigraphic and environmental significance for Western and Central Gondwana. With respect to radiometric ages of the Cape Fold Belt in South Africa, this indicates a Lower Permian age at the Sakmarian-Artinskian boundary at the end of the Dwyka Formation and Itararé Formation in Brazil

The Verbrande Berg Formation and the Tsarabis Formation are characterized by fossil plants, remains of vertebrates and bivalves. The fossil plants within the carbonaceous Verbrande Berg sequence are important in order to reconstruct the paleoclimate and its melioration, whereas the bone bed of the Tsarabis Formation is also of stratigraphic importance. These two formations were sedimentated during the Artinskian. The remains of Labyrinthodonts, Actinopterygians and Elasmobranchs and the internal moulds of Palaeomutela tanganyikensis Cox 1936 in this bone bed are all found in the Huab area for the first time and represent the oldest vertebrate and mollusk fauna in the Huab Basin

Mesosaurus tenuidens, an aquatic reptile, occurs in all the three basins and therefore it is a strong tool for the correlation of the sedimentary sequences of the Huab, Parana and Great Karoo Basin. The distribution of Mesosaurus tenuidens in the Huab Basin could be widened by discovering a basinwide bone bed. Because of the chronostratigraphic character of the Mesosaurus-bearing sediments within the Huab Formation, the Irati Formation (Parana Basin) and the Whitehill Formation (Great Karoo Basin) these three formations are regarded as time equivalents with an estimated age around 270 m. y. (i. e. the Artinskian-Kungurian boundary). Beyond this the environmental similarities in these formations are significant

Some bivalves of the species Terraia altissima (Holdhaus) 1918 which are found for the first time in the Huab area belong to an "endemic" Permian bivalve fauna of the Parana Basin. This indicates the correspondence of facies as well as the stratigraphic equivalence of the Gai-As Formation (Huab Basin) and the Lower Rio do Rasto Formation (Parana Basin)

Because of geodynamic and environmental relations between both the Huab Basin and the Great Karoo Basin, the dating of the 2nd folding of the Cape Fold Belt gives a minimum age of 258+2 m. y. (Lowermost Kazanian resp. Kungurian-Kazanian boundary) for the termination of the Gai-As Formation. Therefore the Permian age of the Gai-As Formation is confirmed and the stratigraphic correlation of the Gai-As Formation with the Triassic Omingonde Formation is demonstrably false

Based on biostratigraphic and radiometric ages from Namibia and South Africa, a timespan from 210±5 m. y. to 149+1 m. y. (Rhaetian to Oxfordian) can be deduced for the sedimentation of the Triassic Etjo Sandstone Formation

A Palynostratigraphy for the Karoo sediments of the Huab Basin could not be established due to the lack of pollen and spores in statistically relevant amounts. The prevailing stratigraphies of South America and South Africa lead to different ages of comparable formations of both, the Parana Basin and the Great Karoo Basin. The connection of both stratigraphies with respect to the new results of the Huab Basin shows that the slightly higher ages of South Africa, deduced from radiometric datings, reflect the chronological conditions in the best way

In addition the geodynamic and climatic development of Western Gondwana is described. In detail the reconnaissence of the diachronous development of climate for the Parana-Huab area and the Great Karoo area explains the different facies developments of the three basins. The climatic differences directly resulted from different distances of the basins from the paleo-southpole. Fundamentally all basins show a continuous climate-melioration. This development started with glacial conditions of an ice age (Dwyka, Harare), passed cool- and warm-temperate climates and terminated with a subtropical-aride desert environment

The whole sedimentation in the Huab Basin was accompanied by magmatism. Basaltic volcanism appeares locally in. the Lower Permian Verbrande Berg Formation and, after the Mesozoic sedimentation, basinwide in the Upper Jurassic. Doleritic intrusions with ages of Upper Jurassic-Lower Cretaceous are very common in all the Karoo sediments of the Huab Basin