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| Titel |
Extremely eroded or incredibly young - 10Be depth profile dating of moraines in the Swiss Midlands |
| VerfasserIn |
Lorenz Wüthrich, Roland Zech, Negar Haghipour, Christian Gnägi, Markus Christl, Susan Ivy-Ochs, Heinz Veit |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097589
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| Publikation (Nr.) |
 EGU/EGU2014-13188.pdf |
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| Zusammenfassung |
| During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extent and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Valais (Rhone) glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1].
In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on moraines at two locations. Steinhof has previously been dated to the global LGM based on exposure ages from four boulders [3], and Niederbuchsiten presumably lies outside the last glacial ice extent [1]. The 10Be concentrations at both sites decrease consistently with depth, but are very similar. Assuming only a few decimeters of erosion since moraine deposition, we obtain apparent exposure ages of ~20 ka. Niederbuchsiten would thus be unexpectedly young, implying a much more extensive extent of the LGM glacier than assumed so far. Alternatively, if the till at Niederbuchsiten was deposited during or before the penultimate glaciation (>130 ka), the surprisingly low 10Be concentrations indicate several meters of erosion during the last glacial cycle and/or the Holocene, which seems to be at odds with the deep and intensive soil formation.
References:
[1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108.
[2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084.
[3] Ivy- Ochs et al. (2004) Ecl. Geol. Helv. 97, 47-55. |
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