The rapid surface uplift of the Eastern Alps. Evidence from cosmogenic nuclides and mapping of elevated low relief surfaces

Surface uplift of the Eastern Alps is generally considered to have occurred more or less continuously over the last 30 Ma. During this period, the interplay of many kilometres of rock uplift and erosion has resulted in surface uplift of some 2-3 kilometres. However, reference frames that allow rock uplift and surface uplift to be distinguished are often hard to identify. Surface uplift rates can be determined in regions where erosion did not occur. That is classically done by the identification and dating of relicts of ancient base levels. In the Eastern Alps a suite of discrete elevated low relief landscapes (ELRLs) are present up to 3000 m surface elevation that have been identified as relicts of base levels.

 

In this contribution we present a map of these ELRL landforms for much of the Eastern Alps and report cosmogenic ¹⁰Be, ²¹Ne and ²⁶Al nuclide data from fluvial sediments sampled from 50 caves that are interpreted to have formed at the same time as the ELRL paleosurfaces. The samples that are interpreted to have been deposited during cave formation at the vadose-phreatic transition. As such, they form markers for base level and the time of their deposition in the cave may be interpreted as the time the cave was at base level. Our data indicate that the uplift rate of the Eastern Alps may be in the order of 200 – 500 m per million years for much of the Pliocene. This is significantly faster than previously thought and implies that much of the surface uplift of the Eastern Alps may have occurred since the late Miocene.