Rock uplift rates in South Africa from isochron burial dating of fluvial and marine terraces

The high plateau of southern Africa is considered to be either uplifting due to mantle-driven dynamic topography, or to have been stable since Mesozoic rifting. To address this debate, we determined rock uplift in South Africa from the long-term incision rate of the Sundays River, near Port Elizabeth, and from an uplifted marine terrace near Durban. We dated the terraces with cosmogenic Al-26 and Be-10, using both isochron and simple burial dating methods. We find that the Sundays River has incised at 16.1 +/- 1.3 m/m.y. for the past similar to 4 m.y., and the marine terrace yields a rock uplift rate of 9.4 +/- 2.2 m/m.y. These results are inconsistent with rapid Neogene uplift.