Constraining plateau uplift in southern Africa by combining thermochronology, sediment flux, topography, and landscape evolution modeling
Résumé
The uplift of the southern African Plateau with its average elevations of ~1000 m is often attributed to mantle processes, but there are conflicting theories for the 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 a large dataset of low-temperature thermochronometry, sediment flux rates to surrounding marine basins, and current topography for southern Africa. We explore three main hypotheses for surface uplift: 1) southern Africa was already elevated by the Early Cretaceous before Gondwana breakup, 2) uplift and continental tilting occurred during the mid-Cretaceous, or 3) uplift occurred during 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 four regions of parameter space that fall into two families of uplift histories are most compatible with the data. Both uplift families have limited initial topography with some topographic uplift and continental tilting starting at ~90-100 Ma. In one acceptable scenario, nearly all of the topography, >1300 m, is created at this time with little Cenozoic uplift. In the other acceptable scenario, ~400-800 m of uplift occurs in the mid-Cretaceous with another ~500-1000 m of uplift in the mid-Cenozoic. The two model scenarios have different geodynamic implications, which we compare to geodynamic models.
Origine : Fichiers produits par l'(les) auteur(s)