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| Titel |
Pre-glacial topography of the European Alps |
| VerfasserIn |
P. Sternai, F. Herman, J.-D. Champagnac, M. Fox, B. Salcher, S. D. Willett |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065117
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| Zusammenfassung |
| We present a reconstruction of the Alpine topography prior to Quaternary glaciation, based
on the assumption that the pre-glacial topography of the Alps was a fluvial landscape in
equilibrium with tectonic and isostatic rock uplift. Amongst the models that have been
proposed, the stream-power law has been profitably used for modeling the dynamics of
fluvial bedrock channel incision:
-z-= U - KAmSn
-t
(1)
where -z--t (m a-1) is the time rate of change of channel elevation, U(m a-1) is rock-uplift
rate, A(m) is upstream drainage area, S is local channel gradient, K is a dimensionless
coefficient of erosion and m and n are positive constants related to basin hydrology and
erosion process. Under steady-state conditions (-z--t = 0), equation (1) can be solved to
yield an expression for equilibrium channel gradient:
1
( U-)n - (m)
S = K A n
(2)
where the ratios U-K and m-n are generally referred to as the steepness and concavity
index, respectively. Particular focus is put on the spatial variability of the steepness index
over the Alpine mountain belt. Assuming a constant concavity index, the pre-glacial
topography of the Alps is obtained through an inversion technique that resolves local slopes
(as described in eq. 2) by minimizing the misfit between the elevations of the actual and
modeled channel heads. Comparing the present-day and reconstructed pre-glacial
topography, we infer patterns and magnitudes of exhumation and rock uplift produced by
Quaternary glaciation in the Alps. We find a correspondence between rock type
and pre-glacial channel steepness which may indicate that rock erodibility has a
significant importance in determining the pre-glacial fluvial network elevation. Our
results also provide insight into patterns of glacial erosion and associated isostatic
adjustment, and provide estimates of the increase of valley-scale topographic relief and
decrease of mean elevation that glaciation seems to have produced in the Alps. |
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