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| Titel |
Deglaciation chronology of the Ecrins-Pelvoux massif (French Western Alps) revealed from new 10Be and 26Al Cosmic Ray Exposure ages. |
| VerfasserIn |
Romain Delunel, Peter van der Beek, Julien Carcaillet, Didier Bourlès |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039828
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| Zusammenfassung |
| We report new Cosmic Ray Exposure ages pertaining to the deglaciation chronology of the
Ecrins-Pelvoux massif (French Western Alps). 25 samples have been collected from various
glacial morphologic features (e.g., glacially scoured bedrock, erratic boulders, nunataks).
Most of the data presented in this study has been collected along 4 altitudinal profiles; the
initial goal was to quantify spatial variations in glacial erosion during the last glacial cycle
using coupled 10Be and 26Al measurements in order to identify complex surface exposure
histories. 10Be exposure ages vary from 4.7 ± 0.4 ka to 45.5 ± 3.0 ka, while those inferred
from 26Al concentrations vary from 5.2 ± 0.5 ka to 17.1 ± 1.2 ka. Generally, samples
collected from the highest parts of the relief, above the glacial trimline, present young
ages reflecting intense periglacial erosion processes. In addition, although some
of the samples could be interpreted as recording glacier retreat shortly after the
Last Glacial Maximum, most ages fall within the late-glacial period and appear
to record the Younger Dryas glacial advance in this part of the European Alps.
10Be/26Al concentration ratios suggest a simple exposure history for most samples, with
similar inferred exposure ages are for both isotopes. These results provide evidence
that glacial erosion has reset the cosmogenic signal in most studied areas of the
Ecrins-Pelvoux massif (i.e., glacier erosion has been at least ~3 m during the last
glaciation). However, 3 samples collected at a single locality have 10Be exposure ages
varying from 30.0 ± 2.0 ka to 45.5 ± 3.0 ka, while 26Al exposure ages confirm the
late-glacial deglaciation chronology obtained elsewhere within the Ecrins-Pelvoux
massif. In order to explain this apparent complex exposure history, we used the
climatic signal from SPECMAP to test different exposure scenarios that would lead to
such different 10Be and 26Al CRE ages. We thus propose that glacial erosion has
been limited in this specific area of the massif due to cold-based glacier dynamics. |
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