Crustal uplift in the Alps: why the drainage pattern matters

The Alpine drainage system comprises two large orogen-parallel drainage basins in the core of the Alps (the Rhone and Rhine valleys), and smaller orogen-normal orientated systems. Discharge of the large rivers is approximate to5-10 higher than that of the small ones. In addition, the courses of the Rhone and Rhine Rivers are trapped by faults and thrusts that display lower erosional resistance than the neighbouiring lithologies. Enhanced discharge of these rivers and the low erosional resistance of their bedrocks potentially enhances surface erosion. indeed, present-day and glacial sediment yields are approximate to1.6-1.7 times higher in these valleys than in the orogen-normal systems. Interestingly, rates of crustal uplift are also enhanced in the Rhine and Rhone valleys, where current rates of approximate to1.4-1.6 mm yr(-1) are measured. The :spatial coincidence between the location of enhanced erosion and maximum crustal uplift rates are interpreted to reflect a positive feedback between surface erosion and tectonic forcing.