Southern African topography and erosion history: plumes or plate tectonics?

Abstract

The physiography of southern Africa comprises a narrow coastal plain, separated from an inland plateau by a horseshoe‐shaped escarpment. The interior of the inland plateau is a sedimentary basin. The drainage network of southern Africa is characterized by three river divides, broadly parallel to the coastline. These features contrast strongly with the broad dome and radial drainage patterns predicted by models which ascribe the physiography of southern Africa to uplift over a deep mantle plume. The drainage divides are interpreted as axes of epeirogenic uplift. The ages of these axes, which young from the margin to the interior, correlate closely with major reorganizations of spreading regimes in the oceanic ridges surrounding southern Africa, suggesting an origin from stresses related to plate motion. Successive epeirogenic uplifts of southern Africa on the axes, forming the major river divides, initiated cyclic episodes of denudation, which are coeval with erosion surfaces recognized elsewhere across Africa.

Mantle superplumes induce geomagnetic superchrons

“…These geodynamical simulations predict that the African superplume collapsed some time between 120 and 90 Ma, contemporaneous with the CNS and the major fall in CMB heat flux shown in Figure 4, although somewhat earlier than what thermochronometry indicates. In contrast, Moore et al (2009) inferred that plate tectonic controls explain the South African topographic history. Nyblade and Sleep (2003) examined various uplift mechanisms for the older southern African Plateau and concluded that a long-lasting plume structure would be needed to maintain its anomalous elevation, assuming it formed in the Mesozoic.…”

The Great Escarpment of southern Africa: a new frontier for biodiversity exploration

“…The formation of the Escarpment has been a matter of debate for several decades (Birkenhauer 1991 provides a very detailed overview of Escarpment geomorphological theory and literature), but it is agreed that the Escarpment forms a (often dramatic) rim to the African plateau that dominates the interior of southern Africa (Van Zinderen Bakker 1983;White 1983;Birkenhauer 1991;Burke et al 1998;Moore et al 2009;McCarthy and Rubidge 2005;Burke and Gunnell 2008).…”

“…Following future research it may be reasonable to include the Muchinga Escarpment in Zambia, but further north than this the mountains are associated with the Rift Valley System and not with a passive continental margin. Several mountain ranges adjoin the Escarpment and are biogeographically related to it, but are excluded from this overview given their different orogenies (Schönhofer 2008;Moore et al 2009;McCarthy and Rubidge 2005). These are the Soutpansberg, Witwatersrand, Magaliesberg, Waterberg, KwaZulu-Natal (KZN) Midlands (South Africa), Otavi-Waterberge (Namibia) and the Mashonaland plateau (Zimbabwe).…”

Flood analysis of the Limpopo River basin through past evolution reconstruction and a geomorphological approach

“…Importantly, the three identified axes of flexure, namely the Escarpment Axis, the EGT Axis and the OKZ Axis, show a sequential uplifting according to a concentric pattern developing farther inland (Moore, 1999). This triggered successive river rejuvenation on the coastal side of each axis of flexure, and hence activated the previously mentioned cycles of erosion (Moore et al, 2009b).…”

“…These axes of uplifting, which define the divides of important river watersheds today, have much influenced the drainage evolution in the region by determining successive river cuts and river captures (Moore and Larkin, 2001). According to Moore (1999) and Moore et al (2009b), they appeared in the following chronological order:…”