10Be-derived catchment-wide erosion rates from a high-elevation, low-relief landscape in the Gurktal Alps (Austria): comparison with thermochronological data and implications for landscape evolution

Abstract

In contrast to the mountainous topography and high relief of the Hohe Tauern, the adjacent Nock Mountains (Gurktal Alps) are characterized by hilly topography, lower relief and rounded summits. Although the peculiar landforms in the Nock Mountains have long been recognized, little is known about the rates of landscape evolution in this area. Here we present the first set of 16 10Be-based catchment-wide erosion rates from the Nock Mountains. Our results show that the 10 main catchments erode at rates between ~ 120 and ~ 280 mm/ka. Sub-catchments comprising a high percentage of low-relief surfaces erode at lower rates than the steeper lower parts of the main catchments, which indicates active river incision and relief growth. A comparison between 10Be erosion rates and exhumation rates derived from thermochronology and thermokinematic modelling reveals that short-term and long-term erosion rates are remarkably similar. In the central Nock Mountains, the average 10Be erosion rate (166 ± 35 mm/ka) is almost identical to the average exhumation rate (160 ± 20 m/Ma since ~ 34 Ma). The southern Nock Mountains show a higher 10Be rate (202 ± 58 mm/ka) and a higher long-term exhumation rate (270 ± 30 m/Ma since ~ 18 Ma). The agreement between short-term and long-term erosion rates suggests that average erosion rates in the Nock Mountains did not change significantly during the late Cenozoic. Comparing our data to surrounding regions shows that erosion rates from the Nock Mountains fit to the general W–E decrease in catchment-wide erosion rates observed in the Eastern Alps. Graphical abstract