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| Titel |
Reconstruction of glacier fluctuations in the Western Alps since the LGM using OSL surface exposure dating |
| VerfasserIn |
Benjamin Lehmann, Georgina King, Pierre Valla, Frederic Herman |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129545
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| Publikation (Nr.) |
 EGU/EGU2016-9675.pdf |
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| Zusammenfassung |
| Providing tight spatial/temporal constraints on late-Pleistocene glacier fluctuations remains an important challenge for understanding glacier response to climate change. In most mountainous settings, paleo-glacier reconstructions are limited because they lack precise temporal constraint, which would enable their use as a paleoclimate proxy. OSL-surface exposure dating has been recently proposed [Sohbati et al., 2011] and offers the potential to improve paleo-glacier reconstruction. Because the OSL signal is sensitive to light, OSL-signal bleaching within a rock sample depends on its exposure time and environmental conditions, and can therefore be used to date the exposure time of glacially-polished bedrock or erratic boulders. However, successful application of this technique first requires calibration and validation.
Here, we focus on the Mer de Glace glacier (Mont Blanc massif, France) where the post-LGM glacier dynamics remain poorly constrained with numerous short glacier re-advances occuring during the mid-Pleistocene and Holocene [LeRoy et al., 2015]. First, the different parameters involved in OSL surface exposure dating were calibrated. Vertical transect of polished bedrock surfaces with known exposure ages (from 10 to 165 years) from the Montenvers train station (1913 m a.sl.) to the present-day position of the Mer de Glace (1600 m a.s.l.) was sampled.
Secondly, we sampled the Trelaporte transect where exposed bedrock surfaces are of uniform lithology. Here, we will apply similar approach on a much longer timescale, from the Last Glacial Maximum (LGM, ~24 ka, Coutterand et al., 2006) to the present day.
OSL data from rock slices show increasing exposure age with elevation which is consitent with glacier thinning since the Little Ice Age. Moreover, our results confirmed the possibility to first calibrate the model parameters on known-age surface and use it to constrain the exposure time for nearby bedrock surfaces. In summary, OSL-surface exposure dating applied to periglacial environments appears to be a promising method to high-resolution reconstruction (both spatial and temporal) of ice-extent fluctuations over the LGM.
REFERENCES
Sohbati, R., Murray A., Jain M., Buylaert J.-P., and Thomsen K. (2011), Investigating the resetting of OSL signals in rock surfaces, Geochronometria, 38 (3), 249_258, doi:10.2478/s13386-011-0029-2.
Le Roy, M., Nicolussi, K., Deline, P.,Astrade, L., Edouard, J-L., Miramont, C., Arnaud, F. (2015), Calendar dated glacier variations in the western European Alps during the Neoglacial: the Mer de Glace record, Mont Blanc massif, Quaternary Science Review 108 (2015) 1-22, doi:10.1016.
Coutterand S., Buoncristani J-.‐F. (2006), Pal.og.ographie du dernier maximum glaciaire du Pléistocene récent de la région du Massif du Mont Blanc, France, Quaternaire, 17, (1), 2006, p. 35-.‐4. |
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