Constraining plateau uplift in southern Africa by combining
thermochronology, sediment flux, topography, and landscape evolution
modeling
Abstract
The uplift of the southern African Plateau is often attributed to mantle
processes, but there are conflicting theories for the specific timing
and drivers of topographic development. Evidence for most proposed
plateau development histories is derived from continental erosion
histories, marine stratigraphic architecture, or landscape morphology.
Here we use a landscape evolution model to integrate these three types
of data for southern Africa, including a large dataset of low
temperature thermochronology, sediment flux rates to surrounding marine
basins. We explore three main hypotheses for surface uplift: 1) southern
Africa was already elevated at the time of Gondwana breakup, 2) uplift
and continental tilting occurred in the mid-Cretaceous, or 3) uplift
occurred in the mid to late Cenozoic. We test which of these three
intervals of plateau development are plausible by using an inversion
method to constrain the range in erosional and uplift model parameters
that can best reproduce the observed data. Results indicate two families
of uplift histories are most compatible with the data. Both have limited
initial topography with some topographic uplift and continental tilting
starting in the east at ~95 Ma. In one acceptable
scenario, nearly all of the topography, ~1400 m, is
created at this time with little Cenozoic uplift. In the other
acceptable scenario, only ~500 m of uplift occurs in the
mid-Cretaceous with another ~850 m of uplift in the
mid-Cenozoic. The two model scenarios have different geodynamic
implications, which in the future could be evaluated by direct
comparison between geodynamic and landscape model predictions.