Surface uplift of the Eastern Alps. Was it much faster than we thought?

Constraining the surface uplift history of mountain belts is difficult because – due to erosion – the surface is made of ever-changing rock levels and changes in surface elevation over time can only be indirectly inferred. Here we present 26 Al/ 10 Be burial ages of siliceous fluvial sediments that were deposited into karst caves as a proxy for surface uplift of the Eastern Alps. We present a consistent and homogenized dataset for the Eastern Alps that includes 31 new burial ages, together with 36 previously published burial ages that have been recalculated. Most of the sampled caves are now inactive and are located at between 600 and 2400 m a.s.l.. The cave sediments were deposited when they formed at the phreatic-vadose transition at base level, which we assume has remained at constant elevation through time. The samples are from regions that were variably affected by Pleistocene glaciation. Cosmogenic 21 Ne concentrations in samples from 20 caves record prolonged and complicated Neogene exposure. Generally 21 Ne/ 10 Be burial ages cannot be used to determine cave level ages, but the 21 Ne data preserve a record of denudation and burial since the Oligocene. The homogenized dataset of 67 of 26 Al/ 10 Be burial ages allows us to infer 1200–1500 m of surface uplift for the Northern Calcareous Alps and ~ 500 m in the transition zone towards the Pannonian Basin in the east during the last 3–5 Ma. The fastest surface uplift rate is estimated for the ranges around the Salzach valley (407 ± 34 m/Ma), followed by the Gesäuse region (357 ± 19 m/Ma). For the Dachstein Massif, the Hochschwab and the Schneealm regions we interpret post-Miocene surface uplift rates of 224 ± 21 m/Ma, 272 ± 12 m/Ma and 283 ± 13 m/Ma, respectively. Uplift rates decrease to the east: the Mur valley and the Semmering uplifted at 137 ± 11 m/Ma and 125 ± 3 m/Ma, respectively. The data support the notion that much of the topography of the Eastern Alps was created in the last 5 Ma rather than the 30 Ma timescale that previous studies have suggested. The long wavelength nature of the uplift over formerly glaciated and unglaciated regions implies that the surface uplift was caused by sub-lithospheric processes and that climatic factors played only a minor role.