Combined luminescence dating and ice-flow modelling to track Holocene sediment transport through Mer de Glace, French Alps

Many mountain glaciers have experienced an increase in supraglacial debris cover due to climate change. Understanding sediment transport processes in glacier systems is important because the accumulation of supraglacial debris affects glacier evolution and response to climate change. Tracking debris and sediment transport through glacial catchments is difficult and thus, the pathway and time scale of englacially transported debris are relatively poorly understood. We quantify the englacial transport time of debris within a glacier using a novel method combining luminescence rock surface burial dating and ice-flow modelling (Margirier et al., 2025). Our study focuses on the Mer de Glace catchment, French Alps, where supraglacial debris cover has expanded over the past half-century.

We collected granitic rock debris clasts (4–22 cm in diameter) that were embedded in ice in the ablation area of Mer de Glace, which we expected to have undergone varying durations of englacial transport. The clasts were assumed to originate from headwalls (paraglacial areas), where they were exposed to daylight before falling onto the glacier and being transported englacially. Cores were extracted from the unexposed rock surfaces and sliced into ~0.9 mm thick discs for luminescence dating. We measured the luminescence signal using a single-aliquot regenerative dose protocol comprising infra-red stimulation, followed by blue stimulation to explore the signals of different minerals with different luminescence properties. Of the 29 samples investigated, 19 were well bleached prior to burial, exhibiting a clear plateau in luminescence signals with depth, and 15 samples have been successfully dated giving burial ages between 0.58 ± 0.13 ka and 6.73 ± 0.72 ka. Except for two samples that are significantly older, luminescence ages are consistent across the glacier, which suggest that the rate of sediment transport is broadly consistent across the ice. Future work will contrast the englacial burial time obtained with luminescence dating with those predicted by an ice-flow model of particle transport trajectories within the Mer de Glace. This will allow particle sources to be better identified and to understand the ice dynamics of the glacier.

 

Reference:

Margirier A., J. Brondex, A.V. Rowan, C. Schmidt, V.K. Pedersen, B. Lehmann, L.S. Anderson, R. Veness, C.S. Watson, D. Swift, G.E. King (2025), Tracking sediment transport through Miage Glacier, Italy, using a Lagrangian approach with luminescence rock surface burial dating of englacial clasts, JGR: Earth Surface.