The Permo-Carboniferous glacial to marine Karoo record in Southern Namibia

Abstract

English abstract provided by author:

Interpretation of the studied succession using sequence stratigraphic techniques revealed four third-order sequences. Several of these cycles can be successfully correlated with published global changes of relative sea-level in this time interval

The stratigraphic position of the tuff beds also shows a distinct association with transgressive developments. Most of them concentrate between the upper part of the transgressive systems tracts and the lower part of the subsequent highstand systems tracts. This correlation may not only result from the enhanced preservation potential during transgressive development, but rather from a genetical coupling between magmatism, extensional tectonics and basin subsidence. This interaction is significant, not only for the recent discussion of potential controls on relative sea-level, but also for the understanding of the early geodynamic evolution of the south Atlantic continental margin

Associated mostly with sediments of the lower Dwyka Group acidic tuff beds with a wide lateral distribution were discovered. Also a small percentage of the glacial clasts consists of undeformed basalts, trachytes and rhyolithes. All pre-Karoo magmatic rocks in the source area are deformed and tuffs have been described only from significantly younger strata in southern Africa. Thus new evidence for the early onset of volcanic activity in southern Namibia is presented here. Contemporaneous tectonism is recorded by type-1 unconformities and systematic thickness changes across E-W trending normal faults. This period of volcanic and tectonic activity in the late Carboniferous to early Permian may mark initial extensional events along the Namibian continental margin