Mantle-driven, climatically modulated landscape evolution in Southern Patagonia

Victoria Milanez Fernandes , Andreas Ruby, Fergus McNab , Hella Wittmann, Andrew David Wickert, Lennart Grimm, Taylor Schildgen

We explore the relative importance of tectonic, geodynamic and surface processes in driving landscape evolution in Argentine Patagonia using 64 new 10Be exposure ages of fluvial terraces preserved over >250 km along the Shehuén and Santa Cruz rivers (50ºS). Terrace ages range from 33 ka to 1.5 Ma, and coincide with Patagonian glaciations. We demonstrate that landscapes can respond directly to changes in climate forcing driven by the Mid-Pleistocene Transition: our results reveal a transition to 100-ky terrace periodicity, and a transient phase of accelerated incision starting at ~1 Ma. A regionally uniform incision rate of 130–180 m Ma⁻¹ since 1 Ma suggests uplift linked to asthenospheric heating in the Patagonian slab window, while transient accelerated incision suggests convective instabilities in a low-viscosity mantle. We establish a temporal link between climate oscillations, fluvial incision, and mantle-driven epeirogenic uplift.