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| Titel |
Tectonic interpretation of erosion rates at different spatial scales in an upliting block |
| VerfasserIn |
S. Carretier, B. Poisson, R. Vassallo, E. Pepin, M. Farias |
| 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 |
250023463
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| Zusammenfassung |
| A theoretical framework is still lacking to interpret erosion rate data at differing
spatial scales in active mountains in terms of erosion laws, climate or tectonics
for transient landscapes. We explore the extent to which it is possible to convert
erosion rate data into uplift rate or erosion laws, using a landscape evolution model.
Transient stages of topography and erosion rates of a block uplifting at a constant rate
are investigated at different spatial scales, for a constant climate, and for various
erosion laws and initial topographies. We identify three main model types for the
evolution of the mountain-scale mean erosion rate: “linear”-type, “sigmoid”-type and
“exponential”-type. Linear-type models are obtained for topographies without drainage
system reorganization, in which river incision rates never exceed the uplift rate and stepped
river terraces converge upstream. In sigmoid-type and exponential-type models (typically
detachment-limited or transport-limited models with a significant transport threshold),
drainage growth lasts a long time, and correspond to more-than-linear transport laws in water
discharge and slope. In exponential-type models, the mean erosion rate passes through a
maximum that is higher than the rock uplift rate. This happens when the time taken to
connect the drainage network exceeds half the total response time to reach dynamic
equilibrium. River incision rates can be much greater than the uplift rate in both
cases. In the exponential-type model, river terraces converge downstream. Thus,
documenting erosion rates and the geometry of river terraces together should allow us to
better constrain the limiting erosion processes. Observations of a mountain in the
Gobi-Altay range in Mongolia support the exponential-type model. This suggests that the
erosion of this mountain is either detachment-limited or transport-limited with a
significant transport threshold. This study shows that drainage growth could explain
differences in erosion rate measurements on different spatial scales in a catchment. |
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