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| Titel |
The Lateglacial to Holocene transition as recorded by glacier fluctuations |
| VerfasserIn |
I. Schindelwig, N. Akçar, P. W. Kubik, C. Schlüchter |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030867
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| Zusammenfassung |
| Examination of glacier associated records may contribute to a better understanding of
the ice-continent-ocean-atmosphere interactions, since glacial deposits related to
short-term temperature fluctuations, driven by climate change, might be preserved.
Surface exposure dating (SED) of such glacial deposits can improve the chronology
of climate records. The western Swiss Alps repeatedly hosted mountain glaciers
during the Pleistocene, and even during the Last Glacial-Interglacial transition, with
abundant stadial and interstadial transitions during the Lateglacial (e.g. Björck et al.
1998).
In this study, the adjacent valleys of Belalp and Great Aletsch (catchment area is
generally south facing) in the western Swiss Alps are investigated. The slow responding
Great Aletsch valley glacier shows only one confirmed moraine ridge related to the
Lateglacial (Egesen stadial) (Kelly et al. 2004). However, the rather fast responding
Unnerbäch cirque (recent) glacier at the Belalp (a similarly exposed - and tributary - valley to
the Great Aletsch valley), features 6 individual lateral-terminal moraine ridges
related to Lateglacial and early Holocene times. In the Belalp valley, 22 erratic
boulders from four out of six well-preserved moraines were sampled in order to
establish a detailed chronological framework. From the Great Aletsch valley four
samples (boulder and ice moulded bedrock) of the lateral moraine were collected for
SED.
Our 10Be exposure dates suggest a stabilization of the Great Aletsch moraine related to
the Egesen advance in the beginning of the Younger Dryas, assuming that the ages of the
oldest erratic boulders on a single moraine ridge are representative for the time of moraine
stabilization (Putkonen & Swanson, 2003). According to our investigations on the
right-lateral moraine and the dataset (recalculated from Kelly et al. 2004) for the
left-lateral moraine, the Egesen stadial is the first preserved re-advance after the last
deglaciation. In contrast, the glacier at the Belalp shows multiple advances during
the Lateglacial to early Holocene. 10Be exposure age data suggest that the outer
moraine ridge can be an advance older than the Egesen stadial and younger than the
LGM. This is in concert with other Younger Dryas related glacial landsystems in
Switzerland (reviewing the outer moraine ages e.g. Julier Pass, Ivy-Ochs et al. 1996,
2008).
A large number of Lateglacial moraines have been identified and relative correlations on
the basis of elevation, equilibrium line altitude (Gross et al. 1977; Maisch, 1987) and
morphological characteristics have been established. Nevertheless, it remains important to
refine the absolute chronology in order to put further temporal constraints on these
relative frameworks. This allows the allocation of such absolutely dated deposits to
distinguished cold phases (Preboreal oscillation, Younger Dryas, Aegelsee oscillation) thus
underlining their potential significance in the context of regional, as well as global
Lateglacial climate conditions. The 10Be exposure ages from an inner moraine
ridge are in a good agreement with the recalculated previously published 10Be
exposure ages from the Egesen moraines in the Alps. This suggests a synchronicity
of the Egesen stadial in the European Alps at the end of the Younger Dryas cold
phase.
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