Constraints on the geomorphological evolution of Namibia from the offshore stratigraphic record

Abstract

This paper addresses aspects of the geomorphological evolution of Namibia in the light of recent results of seismic surveying and drilling in the offshore basins. As suggested by Henno Martin in 1976, this offshore data holds important clues for interpreting epeirogenic events onshore Namibia. The main aim in this paper is to correlate significant stratigraphic events offshore with important landscape elements on¬shore. Major depositional systems offshore have been delineated and categorized with respect to terrestrial feeder systems. Major deltaic inputs in the north into the Walvis Basin have also been noted and the inference has been made that supply for these muddominated systems was from the erosion of the Etendeka Group basalts. The major stratigraphic surfaces along the marginal basins from South Africa as far north as the Namibe Basin have been correlated and from this, significant along strike variations in depocentres and in sediment calibre in the post-rift have been identified. Recognition of distinct changes in the timing and magnitude of post-rift uplift of the onshore has led to the conclusion that King’s early view of a Great Escarpment composed of distinct geomorphic elements with different tectonic and erosional histories is substantially correct. Little evidence was found to support more recent proposals that the Escarpment has its roots in rift flank uplift and fault scarp retreat.