Interplay between erosion and tectonics in the western Alps.

Bedrock fission-track analysis, high-resolution petrography and heavy mineral analyses of sediments are used to investigate the relationships between erosion and tectonics in the Western Alps. Along the Aosta Valley cross-section, exhumation rates based on fission-track data are higher in the fault-bounded western block than in the eastern block (0.4–1.5 vs. 0.1–0.3 mm yr-1). Erosion rates based on the analysis of bed-load in the Dora Baltea drainage display the same pattern and have similar magnitudes in the relative sub-basins (0.4–0.7 vs. 0.04–0.08 mm yr-1). Results highlight that climate, relief and lithology are not the controlling factors of erosion in the Western Alps. The main driving force behind erosion is instead tectonics that causes the differential upward motion of crustal blocks.