Surface uplift of the Eastern Alps. Much faster than we thought?

We present cosmogenic nucleide data that help to understand the ill-constrained  uplift history of the Eastern Aps. Well accepted, but indirect evidence  for this uplift history includes: (a) the onset of flexural subsidence of the foreland basins, or (b) the formation of the Periadriatic line (recording the onset of continent-continent collision in the Alps). Both are often used to suggest about 30 Ma as the starting date for the surface uplift of the range. Since this time the fine interplay of many kilometres of upwards rock uplift and downwards erosion resulted in net surface uplift of some 2-3 kilometres but reference frames that allow to discern between rock uplift and surface uplift are often hard to identify. One way of measuring surface uplift rates is through the study of areas where erosion did not occur. That is, dating and identifying relicts of ancient base levels for example in caves, sediments or paleosurfaces.

In this contribution we present ¹⁰Be, ²¹Ne, ²⁶Al cosmogenic nucleide data of fluvial sediments sampled in some 50 caves across the Eastern Alps from elevations between 300 and 2500 m surface elevation. We collected samples that were interpreted to have been deposited during cave formation at the vadose-phreatic transition. As such, they form markers for base level and  the age of their burial into the cave may be interpreted as the time the cave was at base level some few hundreds of meters above sea level. Interpretation of our data indicates that the uplift rate of the Eastern Alps may be in the order of 200 m – 500 m per Million years for much of the Pliocene. As such, much of the observed surface uplift of the Eastern Alps may have occurred since the late Miocene and surface uplift is thus much faster than previously thought.