Geomorphology of the Western Bushmanland Plateau, Namaqualand, South Africa

Abstract

Abstract Results of a geomorphic investigation at and around a proposed low and intermediate level radioactive waste disposal site on the western portion of the Bushmanland Plateau are reported. This plateau reflects a more intricate geomorphic history than simple erosion surface development. A complex sequence of erosional and aggradational phases, which is evident in the geomorphic record, has been established through analysis of surficial deposits, and consideration of evidence provided by palaeontological and palynological work, by radiometric dating of intrusives, and by interpretation of palaeodrainage patterns. Following planation in late Cretaceous and early Tertiary times, marginal uplift of the continent in the Oligocene promoted fan accumulation on the planed surface. Fan sediments were subsequently regraded contemporaneously with Miocene incision into the plateau surface following redirection of drainage in the Orange River system. The area has been covered by extensive dune fields since the Miocene, but the dunes are at present in an advanced state of degradation.