Lateglacial glaciers dynamics in the Mont Blanc foreland (Northern French Alps): new chronological and geomorphological constraints, with model-data coupling in the Arve Valley

Despite several studies (Coutterand, 2010 and references theirin) over the past decades, the chronology of glaciers advance and expansion at the Last Glacial Maximum (LGM) and subsequent retreat during the Lateglacial period in the northern French Alps remains poorly constraint, as data are still too scarce and sometimes contradictory. In this area, the interactions between major glaciers, such as the Rhône and Arve glaciers in the north and Isère glacier in the south, represent major challenges for reconstructing post-LGM glacial dynamics. Here, we present a new framework for understanding Lateglacial glacial dynamics in the Arve Valley, integrating 18 new ¹⁰Be exposure ages from glacially-transported boulders, with revised geomorphological mapping based on LiDAR-derived DEMs.

Our results indicate that the deglaciation of the Arve Valley initiated with a phase of glacial thinning around 17.6 ka BP. The Arve glacier subsequently thinned progressively but persisted in the downstream sector of the valley until the end of a readvance phase at 15.9 ka BP. Then, the glacier retreated by over 30 km within 300 years, before withdrawing toward the Mont-Blanc massif ahead of the Younger Dryas readvance.

These findings are integrated with previous studies (Wirsig et al., 2016; Roattino et al., 2022; Serra et al., 2022) conducted in the Northwestern Alps, including the Lyon piedmont lobe and the Mont-Blanc massif area, to propose a regionally consistent deglaciation scenario. To further refine our understanding, we confront ¹⁰Be exposure ages with numerical simulations using the Instructed Glacier Model (IGM, Leger et al., 2025). A dual approach enables a critically assessment of both methods: calibration of exposure ages corrections (e.g., erosion rates, snow shielding) using a model run, and inversely, using calculated exposure ages to constrain the resulting model. This will enable us to analyse possible deglaciation rates and spatial patterns in the Northwestern Alps, as well as the influence of key parameters such as geography, topography, and climate.

Coutterand, S. 2010: Etude géomorphologique des flux glaciaires dans les Alpes nord-occidentales au Pléistocène récent : du maximum de la dernière glaciation aux premières étapes de la déglaciation. PhD thesis. Université Savoie Mont-Blanc.

Leger, T. P. M., Jouvet, G., Kamleitner, S., Mey, J., Herman, F., Finley, B. D., Ivy-Ochs, S., Vieli, A., Henz, A. & Nussbaumer, S. U. 2025: A data-consistent model of the last glaciation in the Alps achieved with physics-driven AI. Nature Communications 16, 848. https://doi.org/10.1038/s41467-025-56168-3.

Roattino, T., Crouzet, C., Vassallo, R., Buoncristiani, J.-F., Carcaillet, J., Gribenski, N. & Valla, P. G. 2022: Paleogeographical reconstruction of the western French Alps foreland during the last glacial maximum using cosmogenic exposure dating. Quaternary Research 111, 68–83. https://doi.org/10.1017/qua.2022.25.

Serra, E., Valla, P. G., Gribenski, N., Carcaillet, J. & Deline, P. 2022: Post-LGM glacial and geomorphic evolution of the Dora Baltea valley (western Italian Alps). Quaternary Science Reviews 282, 107446. https://doi.org/10.1016/j.quascirev.2022.107446.

Wirsig, C., Zasadni, J., Christl, M., Akçar, N. & Ivy-Ochs, S. 2016: Dating the onset of LGM ice surface lowering in the High Alps. Quaternary Science Reviews 143, 37–50. https://doi.org/10.1016/j.quascirev.2016.05.001.