| Cote: | 1206 |
| Auteur: | RECH Dilan |
| Année: | Janvier 2021 |
| Titre: | Investigating rock surface exposure dating on alpine rockfall scars using OSL: a case study on Nunataks at the Aiguille du Midi |
| Sous la direction de: | Prof. Georgina King et Prof. Frederic Herman et Dr Benjamin Lehmann |
| Type: | Mémoire de master en géographie |
| Pages: | 65 |
| Complément: | 23 pages d'annexes paginées (tableaux de données, codes, références) |
| Mots-clés: | Optically stimulated luminescence / surface exposure dating, permafrost degradation / rock falls / rock falls scars / Aiguille du Midi (Chamonix, France) / terrestrial cosmogenic nuclide dating |
| Résumé: | Assessing the impacts of rock falls in mountainous terrain requires an understanding of the evolution of alpine landscapes. It is necessary to quantify these events using different tools in order to better integrate the expected changes in the future. The understanding of the evolution of our alpine landscapes needs to be done on different time scales, both short and long term (e.g. decade to thousand years), in order to better understand the surface dynamics in these high altitude environments which are subject to global and local climatic variations. More fundamentally, it is also important to study the evolution of landforms on a relatively fine spatial scale. This report will present a relatively recent and promising approach to evaluate the bedrock surface exposure of rockfall scars at the Aiguille du Midi (Chamonix, France) by comparing data obtained using the terrestrial cosmogenic nuclide beryllium - 10 (TCN) and surface exposure dating using optically stimulated luminescence (OSL). Using a numerical approach, it will be shown how OSL signals can be inverted into quantitative estimates of post-collapse exposure time of the bedrock surface of faces studied on granite pillars. By exploiting the fact that the two methods are effective for different time scales, this approach can be used to cross-check the exposure time on a rockfall scar since its exposure to daylight. |