Dating bedrock gorge incision in the French Western Alps (Ecrins-Pelvoux massif) using cosmogenic 10Be |
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| Authors: | Pierre G Valla Peter A van der Beek Julien Carcaillet |
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| Institution: | Laboratoire de Géodynamique des Chaînes Alpines, UniversitéJoseph Fourier, BP 53, 38041 Grenoble, France |
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| Abstract: | We report in-situ produced 10Be data from the Gorge du Diable (French Western Alps) to date and quantify bedrock gorge incision into a glacial hanging valley. We sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka) at rates ranging from 6.5 to 13 mm yr?1. Present-day incision rates are significantly lower and vary from 0.5 to 3 mm yr?1 within the gorge. Our data imply either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Our results suggest that fluvial incision rates >1 cm yr?1 into crystalline bedrock may be encountered in transient landscape features induced by glacial-interglacial transitions. |
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