Geochronological reconstruction of the Lateglacial deglaciation in the Arve Valley (Northern French Alps)

ABSTRACT

The timing and spatial patterns of glaciers retreat in the Northern French Alps during the Lateglacial (19.0–11.7 ka) remain debated, reflecting discrepancies among available chronological data sets. The complex interactions between major glaciers, such as the Rhône and Arve glaciers to the north and the Isère glacier to the south, represent a significant challenge for reconstructing post‐Last Glacial Maximum (LGM) glacial retreat. In this study, we present a new framework for understanding Lateglacial glacier history in the Arve Valley, integrating 18 new in situ ¹⁰ Be terrestrial cosmogenic nuclide (TCN) exposure ages obtained from erratic and morainic boulders together with refined geomorphological interpretations based on LiDAR‐derived Digital Elevation Models (DEMs). Results, expressed as minimum exposure ages, indicate that glacier recession began around 17.6 ka, with the Arve glacier remaining in the downstream sector of the valley until the end of a readvance phase around 15.9 ka. Following this readvance, the glacier receded by more than 30 km in a few hundred years at most, before continuing to withdraw towards the Mont‐Blanc massif prior to the Younger Dryas readvance. These findings provide new constraints on the timing of deglaciation in the Northwestern Alps and contribute toward a better understanding of post‐LGM glacier retreat in a complex confluence system.