Putting rates on the buzz-saw? Constraining the timing and rate of cirque valley incision, Rhône valley, Switzerland.

The observation that topography trends with snowline altitude despite large differences in tectonic uplift in various locations provides the foundation of the glacial buzz-saw hypothesis. However, despite numerous modelling studies, very few quantitative data are available that document the timing or rate of glacial topography formation. Consequently, challenges remain to explain why some localities (e.g. Alaska, southern Andes) seem to escape the glacial buzz-saw. This data gap is driven by the difficulty in constraining rates of glacial erosion over kyr-Myr timescales.

Here, we use a novel thermochronometry technique, based on the Electron Spin Resonance (ESR) of quartz minerals, to constrain the timing of cirque basin formation adjacent to the Rhône valley, Switzerland. The Fully basin, near the town of Sion, sits above the ~1.5 km deep glacial Rhône valley, and is thought to have been incised by ~400 m during the Quaternary. Samples were collected in a transect across the basin, and complement samples previously investigated using ESR-thermochronometry from the Rhône valley (Wen et al., 2024).

Forward modelling using a modified version of Pecube together with the kinetic parameters of existing ESR samples from the area (Wen et al., 2024) shows that ESR-thermochronometry data should be able to constrain the timing of cirque basin incision. This will provide the first dates and rates of glacial buzz-saw activity and will be contrasted with the timing of Rhône valley incision.