The west-facing Great Escarpment of southern Africa is entirely denudational. It is preceded by a wide piedmont which, in apparent topographic uniformity, is composed of two distinct geomorphological units. The "Namib Unconformity Surface" is Precambrian rocks and covered by the clastic " Tsondab Sandstone Formation", while the "Tsondab Planation Surface" cuts basement and the arenites depending on the unevenness of the topography that these clastic deposits have buried. The piedmont was generated after the clastic beds were laid down. Although initially believed to be azoic, recently discovered have established that the formation is middle Miocene (10-15 Ma). Since this deposit was laid down, the development of exhibiting thick alluvial fans suggest mean scarp recession rates of 150 mm/ka in a context of sustained aridity. Keywords: planation surfaces, backwearing, denudation rates, Southern Africa, Namibia.