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Linking erosion history and mantle processes in southern Africa

Abstract : The large, low relief, high elevation plateau of southern Africa has been the focus of many studies, but there is still considerable debate about how it formed. Lack of tectonic convergence and crustal thickening suggests mantle dynamics play an important role in the evolution of topography there, but the time and specific mechanisms of topographic development are still contested. Many mantle mechanisms of topographic support have been suggested including dynamic topography associated with either deep or shallow mantle thermal anomalies, thermochemical modification of the lithosphere, and plume tails related to Mesozoic magmatic activity. These mechanisms predict different timing and patterns of surface uplift such that better constraints on the uplift history have the potential to constrain the nature of the source of topographic support. Here we test several of these geodynamic hypotheses using a landscape evolution model that is used to predict the erosional response to surface uplift. Several recent studies have provided a clearer picture of the erosion history of the plateau surface and margins using low temperature thermochronology and the geometries of the surrounding offshore depositional systems. Model results are directly compared with these data. We use an inversion method (the Neighborhood Algorithm) to constrain the range in erosional and uplift parameters that can best reproduce the observed data. The combination of different types of geologic information including sedimentary flux, landscape shape, and thermochronolology is valuable for constraining many of these parameters. We show that both the characteristics of the geodynamic forcing as well as the physical characteristics of the eroding plateau have significant control on the plateau erosion patterns. Models that match the erosion history data well suggest uplift of the eastern margin in the Cretaceous (~100 Ma) followed by uplift of the western margin ~20 Myr later. The amplitude of this uplift is on the order of 1000 m. The data cannot resolve whether there was smaller amplitude phase of uplift in the Cenozoic. These results suggest that the scenario proposed by Braun et al. (2014) of uplift caused by the continent moving over the African superswell is viable. We are currently investigating the compatibility of other uplift geometries.
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Conference papers
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https://hal-insu.archives-ouvertes.fr/insu-01734869
Contributor : Isabelle Dubigeon <>
Submitted on : Thursday, March 15, 2018 - 10:38:47 AM
Last modification on : Friday, July 26, 2019 - 1:44:05 PM

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  • HAL Id : insu-01734869, version 1

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Jessica Stanley, Jean Braun, Rebecca Flowers, Guillaume Baby, Mark Wildman, et al.. Linking erosion history and mantle processes in southern Africa. American Geophysical Union Fall Meeting 2017, Dec 2017, New Orleans, United States. pp.DI13B-05. ⟨insu-01734869⟩

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