Linking Glacial Exhumation and Fluvial Incision During the Mid-Pleistocene Transition, Southern Patagonia, Argentina

The Mid-Pleistocene Transition (MPT; ~1.2–0.9 Ma) marked a shift in global climate cycles, amplifying glacial-interglacial oscillations and lengthening their periodicity. In the Patagonian Andes, intensified erosion due to late-Miocene glaciation is well documented, but geomorphic evidence also suggests accelerated exhumation after the MPT. The Southern Patagonian Icefield, draining into Argentino Lake and the Santa Cruz River, provides a direct link between glacial erosion and downstream fluvial systems. To quantify these impacts, we combine Apatite (U-Th)/He thermochronology and cosmogenic ¹⁰Be dating. Single-grain apatite (U-Th)/He ages from bedrock bordering Argentino Lake, and an 1175 m elevation profile, range from ~4–8 Ma, with apparent exhumation rates of ~0.28 km Ma⁻¹. Coupled thermal and landscape modeling suggests an acceleration of erosion post-4 Ma. Downstream, ¹⁰Be-dated fluvial terraces of the Santa Cruz River reveal incision rates of ~0.13–0.18 km Ma⁻¹ over the last 1 Ma, with transient acceleration (~0.66 km Ma⁻¹) between 1.03–0.93 Ma, coinciding with intensified glaciation after the MPT. Terrace ages also show a shift from shorter periodicities to 100-kyr cycles. Our results suggest the MPT triggered enhanced glacial erosion in the Andes, influencing sediment discharge and downstream channel-bed elevation. This study highlights the MPT’s measurable impact on both glacial source areas and downstream depositional systems.