10Be-derived catchment-wide erosion rates from the Nock Mountains (Gurktal Alps, Austria): comparison with thermochronological data and implications for landscape evolution

In contrast to the mountainous topography and high relief of the eastern Tauern window, the adjacent Nock Mountains (Gurktal Alps, Austria) are characterized by hilly topography, lower relief and rounded summits with elevations of ca. 2000 m. Although the unusual landforms in the Nock Mountains have long been recognized (Hejl, 1997; Frisch et al., 2000, and references therein), little is known about rates of landscape evolution in this area, which was deglaciated ~15 ka ago (Wölfler et al., 2022). Here we present a new set of 16 catchment-wide erosion rates from the Nock Mountains derived from cosmogenic ¹⁰Be concentrations in stream-sediment samples. Samples from 10 major streams that drain the Nock Mountains toward the Mur-Mürz valley, the Katschberg-Lieser valley and the Drau valley range between ~130 and ~300 mm/ka. Smaller subcatchments with low relief located in the upper part of the larger catchments erode at lower rates between ~80 and ~160 mm/ka. A comparison between ¹⁰Be-derived erosion rates and exhumation rates obtained from low-temperature thermochronology and thermokinematic modelling reveals that short-term and long-term erosion rates are remarkably similar. In the central Nock Mountains, ¹⁰Be-derived erosion rates of 110-160 mm/ka are similar to the long-term exhumation rate of ~160 m/Ma since ~34 Ma (Wölfler et al., 2023). The southern Nock Mountains (Millstatt Complex) show higher short-term erosion rates of 170-300 mm/ka and also a higher long-term exhumation rate of ~270 m/Ma since 18 Ma (Wölfler et al., 2023). The similarity between short-term and long-term erosion rates suggests that the pace of erosion in the Nock Mountains did not change significantly during the late Cenozoic. A comparison of our data with ¹⁰Be erosion rates from the eastern Tauern Window (>500 m/Ma) and the Lavanttal Alps (<125 m/Ma) (Dixon et al., 2016; Delunel et al., 2021), which are located west and east of the Nock Mountains, respectively, reveals that erosion rates in the Eastern Alps decrease from west to east.

• References
• Delunel R, Schlunegger F, Valla PG, Dixon J, Glotzbach C et al. (2020) Earth-Sci. Rev. 211:103407.
• Dixon JL, von Blanckenburg F, Stüwe K, Christl M (2016) Earth Surf. Dyn. 4:895–909.
• Frisch W, Székely B, Kuhlemann J, Dunkl I (2000) Zeitschr. f. Geomorph. 44:103–138.
• Hejl E (1997) Tectonophysics 272:159–173.
• Wölfler A, Hampel A, Dielforder A, Hetzel R, Glotzbach C (2022) J. Quat. Sci. 37:677-687.
• Wölfler A, Wolff R, Hampel A, Hetzel R, Dunkl I (2023) Tectonics 42:e2022TC007698.