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| Titel |
Initiation age and incision rates of inner gorges: Do they record multiple glacial-interglacial cycles? |
| VerfasserIn |
Romain Delunel, Jan Casagrande, Fritz Schlunegger, Naki Akçar, Peter W. Kubik |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106244
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| Publikation (Nr.) |
 EGU/EGU2015-5904.pdf |
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| Zusammenfassung |
| Inner gorges represent some of the most conspicuous landforms in the European Alps. They
form narrow and deep active-channel incisions that link hanging tributaries with trunk valleys
in glacially-conditioned environments. Despite abundant research carried out on these
objects, both their origin and evolution have remained unclear. In particular, the age of
initiation, the rate of incision, and the respective contribution of fluvial and subglacial
processes in the evolution of inner gorges have still been a matter of scientific debate. Indeed,
answering these questions has been complicated by the lack of appropriate quantitative
methods and/or suitable sampling strategies for studying inner gorges. Here, we report 10Be
concentrations measured in alluvial sediments that have been collected along the
main stream of a ~20-km2-catchment in the Swiss foreland (Central European
Alps). This catchment hosts a ca. 100-m-deep and 2-km-long inner gorge that has
been cut mainly in glacial till. Catchment wide denudation rates inferred from 10Be
analyses (n = 15) vary from ~120 to 650 mm/ka and show a general downstream
increasing trend. Additional field observations and GIS analyses reveal that the
denudation rates within the catchment increase from the headwaters, characterized
by relict glacial/periglacial landscapes, to the downstream end of the basin where
the inner gorge has been formed. Using a 10Be-based sediment budget approach
and the delineation of topographic domains from a 2-m-resolution LIDAR, we
provide an estimate of erosion rates within the gorge that are higher than 2.5 m/ka
and can reach up to ~ 7 m/ka. Combining these estimated erosion rates with the
reconstruction of eroded volumes within the gorge, we obtain a rough initiation
age in the early Holocene, in general agreement with previous studies reporting a
postglacial origin for the inner gorges. Our results therefore appear contradictory
with recent findings arguing for a gradual formation of inner gorges over multiple
interglacial cycles and a relative preservation of Alpine landscapes during glacial periods. |
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