Constraining Plateau Uplift in Southern Africa by Combining Thermochronology, Sediment Flux, Topography, and Landscape Evolution Modeling

Abstract

The southern African Plateau is a dominant feature of African topography reaching heights of >3,000 m, with an average elevation of 1,000 m in the predominantly low relief plateau interior. The elevated margins of the plateau drop through higher relief regions to the coastal plain (Figure 1). However, extensive debate remains regarding when and how it formed. The long wavelength topographic high in absence of collisional tectonism combined with Cretaceous kimberlite activity and a large low shear velocity province (LLSVP) in the deep mantle below southern Africa have led many to suggest uplift related to mantle processes. Given that surface uplift may be related to LLSVP development (e.g., Lithgow-Bertelloni & Silver, 1998), better

Linking uplift, erosion, and sedimentation using landscape evolution models: Madagascar since the Late Cretaceous

“…Moreover, the optimized value of K f is most consistent with the results (log(K f ) ⇡ 5.5) of the "hybrid early scenario" model of Stanley et al (2021), which in addition to the Cretaceous uplift involves a phase of early Cenozoic uplift due to the mantle process; the similar, two phases of uplift history are also used in our models. Therefore, if the same erodibility can be assumed for the bedrocks from southern Africa and Madagascar (both predominantly Precambrian basement), our results support a consistency in the uplift and erosion scenarios between models of southern Africa and Madagascar.…”

“…This can be expected, as we impose the sediment yield and therefore the mean erosion rate of the landscape; thus, a higher threshold for the minimal erosion rate in the headwaters or low-relief regions requires to be balanced by higher efficiency in the fluvial incision rate in lower reaches or steep sections of rivers. The same correlation between the fluvial incision efficiency and erosion threshold was also observed in the inverse modeling presented in Stanley et al (2021), which were used to inspect the uplift and erosion history of southern Africa.…”

“…These are within the ranges of commonly estimated or assumed values (m/n, 0.35-0.6; n, 0-4; K d , 0.01-10). A recent study in southern Africa (Stanley et al, 2021) followed similar assumptions, and our adopted values were among those used to simulate the landscape evolution of passive margins (Braun, 2018). In addition, our initial experiments show that different values of m and n will affect the estimated values of K f , but have insignificant impacts on the sediment volumes predicted by the optimized models.…”

Large‐Scale Tectonic Forcing of the African Landscape

“…We recognize that these assumptions are significant ones and alternative schemes have also been thoroughly investigated (see Figures S6 and S7 of Supporting Information S1). Calculated landscapes and drainage patterns are robust to noisy initial topographies with amplitudes 𝐴𝐴 𝐴500 m. It is important to point out that the prior existence of an elevated plateau across southern Africa at 40 Ma is incompatible with our calibrated values of v and m (see e.g., Baby et al, 2019;Doucouré & de Wit, 2003;Guillocheau et al, 2012;Stanley et al, 2021;Tinker et al, 2008;Wildman et al, 2016). Our approximation of the initial state of the African and Arabian landscapes and coastlines is supported by geologic observations, which suggest that continental relief was subdued during Paleogene times (i.e., 60-30 Ma).…”

Exhumation of the passive margin of the DR Congo during pre- and post- Gondwana breakup: Evidence from low-temperature thermochronology, geology and geomorphology

“…Low-temperature thermochronology is sensitive to both upper crustal and large-scale surface processes and can as such be used to date and/ or link geodynamic processes to their upper crustal and surface manifestations (e.g. Stanley et al, 2021;Baughman and Flowers, 2020;Malusá and Fitzgerald, 2019;Wildman et al, 2017). In the Lower Congo region, such a quantitative approach has hitherto not been performed and is necessary to clarify the magnitude of CAAS uplift, and the evolution of the passive margin landscape.…”