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Migrating deformation in the Central Andes from enhanced orographic rainfall
Kevin Norton1, Fritz Schlunegger
1School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
Nature Communications
|December 14, 2011
Summary
Andes mountain shortening migrated eastward due to changing erosion patterns. Orographic rainfall shifts altered erosion rates, steepening the western margin and driving deformation eastward, shaping the mountain belt.
Area of Science:
- Geosciences
- Tectonics
- Climatology
Background:
- Active shortening in the Central Andes migrated from the western to the eastern margin between 10-7 million years ago.
- This tectonic shift is hypothesized to be influenced by evolving erosion patterns.
Purpose of the Study:
- To investigate the primary controls on the eastward migration of active shortening in the Central Andes.
- To elucidate the role of erosion patterns and orographic rainfall in shaping the orogen-scale development of mountain belts.
Main Methods:
- Analysis of river channel profiles on western and eastern margins.
- Application of critical wedge theory.
- Local-scale fault friction calculations.
Main Results:
- Andean uplift altered wind patterns, increasing orographic rainfall on the eastern margin and reducing it on the western margin.
- Arid conditions on the western margin led to lower erosion rates, steepening the margin and inhibiting internal deformation.
- Deformation migrated to the eastern margin, where it is currently active, reflecting coupled climatic-tectonic feedback.
Conclusions:
- Changes in erosion patterns, driven by orographic rainfall, were the primary control on the eastward shift of active shortening in the Central Andes.
- Orographic rainfall and erosion significantly influence the long-term, orogen-scale evolution of mountain belts.
- River channel profiles provide evidence of past tectonic events and ongoing coupled climatic-tectonic processes.
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