Dynamic topography controls on source-to-sink systems: Example of the last 40 Ma in South Africa.

Abstract

<p>Over deep time, mantle flow-induced dynamic topography drives deposition moderated by higher-frequency fluctuations in climate and sea level. The effects of deep mantle convection impact all the segment of the source to sink systems at different wavelengths and over various scales which remains poorly quantified. Field observations and numerical investigations suggest that the long-term stratigraphic record along continental margins contains essential clues on the interactions between dynamic topography and surface processes. However, it remains challenging to isolate the fingerprints of dynamic topography in the geological record.</p><p>We use the open-source surface evolution code Badlands (badlands.readthedocs.io), to quantify the impact of different timings and wavelengths of dynamic topography migration on the South African landscape responses.</p><p>We test three different dynamic topography scenarios obtained by both backwards advection and forwards modelling of mantle flow. We investigate their influence on landscape dynamics, stratal geometries and depositional patterns of South Africa over the past 40 Ma. We compare the evolution of the drainage organization, sediments flux, and stratigraphy obtained with the models with seismic, geochronological, and thermochronological data. We demonstrate that inland incision, spatial sediment accumulation, and depocenter migration strongly depend on the direction of sediment transport relative to the direction of dynamic topography propagation. It allows to identify realistic evolutions of mantle flow associated with the South African uplift history. Our results suggest that our source-to-sink numerical workflow can be used to explore, in a systematic way, the interplay between dynamic topography and surface processes and can provide insights into recognizing the geomorphic and stratigraphic signals of dynamic topography in the geological record.</p>