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Evolution géomorphologique du massif des Ecrins-Pelvoux depuis le Dernier Maximum Glaciaire – Apports des nucléides cosmogéniques produits in-situ

Abstract : Since the early 90's, the coupling and interaction between tectonics, climate and surface processes have been a key question in the Geosciences community. Here, the recent relief evolution of the Ecrins-Pelvoux massif (French Western Alps) induced by Pleistocene / Holocene climate change is studied using in-situ produced Terrestrial Cosmogenic Nuclide (TCN) measurements that have been performed on more than 60 samples consisting of both bedrock and detrital material. 10Be and 26Al measurements performed on samples collected from glacial features (glacially polished bedrock, roches moutonnées, nunataks) allow constraining both the chronology and pattern of ice retreat within the massif. Cosmic-ray exposure dating shows a contrasting response of glacial drainage basins on the eastern and western flanks of the massif, evidence by asynchronous ice retreat following the Last Glacial Maximum, and highlights the progressive retreat of glaciers towards their present-day positions during the Late Glacial (~20 and 11 ka). Measurements of 10Be concentrations in stream sediments collected in several rivers draining the massif show that the post-glacial denudation at the massif scale is controlled by frost shattering processes, which mostly affect rock crests. Mean catchment denudation rates vary from 0.27 to 1.07 mm yr-1, in agreement with post-glacial denudation rates obtained throughout the Alps. Therefore, these results highlight that frost-induced processes play an important role in the present-day relief evolution of mid-latitude mountains. Finally, results obtained at a smaller scale within the Vallon des Etages catchment (Upper Vénéon) indicate that 10Be concentrations carried by stream sediments are strongly controlled by glacial detrital materials exported from present-day and/or Little Ice Age (XVII-XIXth centuries) ice margins. However, glacial materials that currently supply the stream sediment system probably represent a mixture between glacially scoured sediments and periglacial products that fed the glacier tongue due to frost-shattering activity on headwater rock cliffs.
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https://tel.archives-ouvertes.fr/tel-00511048
Contributor : Romain Delunel <>
Submitted on : Monday, August 23, 2010 - 3:41:49 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Wednesday, November 24, 2010 - 3:01:19 AM

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Romain Delunel. Evolution géomorphologique du massif des Ecrins-Pelvoux depuis le Dernier Maximum Glaciaire – Apports des nucléides cosmogéniques produits in-situ. Géomorphologie. Université Joseph-Fourier - Grenoble I, 2010. Français. ⟨tel-00511048⟩

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