Timing of rockfalls in the Mont Blanc massif (Western Alps) : evidence from surface exposure dating with cosmogenic 10Be.

Xavi Gallach 1, 2 Markus Egli 3 Dagmar Brandova 3 Michael Schaepman 3 Marcus Christl 4 Stefan Gruber 5 Philip Deline 1 Julien Carcaillet 2 François Pallandre 6
1 EDYTEM - Environnements, Dynamiques et Territoires de la Montagne
2 ISTerre - Institut des Sciences de la Terre
3 Department of Geography [Zürich]
4 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich]
5 Department of Geography and Environmental Studies
6 Ecole nationale de ski et d'alpinisme
Abstract : Rockfalls and rock avalanches are a recurrent process in high mountain areas like the Mont Blanc massif. These processes are surveyed due to the hazard they present for infrastructure and alpinists. While rockfalls and rock avalanches have been documented for the last 150 years, we know very little about their frequency since the Last Glacial Maximum (LGM). In order to improve our understanding, it is imperative to date them on a longer timescale. A pilot campaign using Terrestrial Cosmogenic Nuclide (TCN) dating of five samples was carried out in 2006 at the Aiguille du Midi (3842 m a.s.l.). In 2011, a larger scale study (20 samples) was carried out in five other test sites in the Mont Blanc massif. This paper presents the exposure ages of the 2011 TCN study as well as the updated exposure ages of the 2006 study using newer TCN dating parameters. Most of these exposure ages lie within the Holocene but three ages are Pleistocene (59.87 ± 6.10 ka for the oldest). A comparison of these ages with air temperature and glacier cover proxies explored the possible relationship between the most active rockfall periods and the warmest periods of the Holocene: two clusters of exposure ages have been detected, corresponding to the Middle Holocene (8.2–4.2 ka) and the Roman Warm Period (c. 2 ka) climate periods. Some recent rockfalls have also been dated (< 0.56 ka).
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Submitted on : Tuesday, May 22, 2018 - 5:01:02 PM
Last modification on : Thursday, June 6, 2019 - 4:48:01 PM

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OSUG | UGA | IFSTTAR | EDYTEM-THEME-CHANGEMENTS-ENVIRONNEMENTAUX-SOCIETES | EDYTEM-GROUPE-MORPHODYNAMIQUE-VERSANTS | INSU | UNIV-SAVOIE | ISTERRE | EDYTEM

Citation

Xavi Gallach, Markus Egli, Dagmar Brandova, Michael Schaepman, Marcus Christl, et al.. Timing of rockfalls in the Mont Blanc massif (Western Alps) : evidence from surface exposure dating with cosmogenic 10Be.. Landslides, Springer Verlag, 2018, https://link.springer.com/article/10.1007/s10346-018-0999-8. ⟨hal-01797572⟩

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