Erosion patterns in the European Alps from zircon fission-track tracer thermochronology

Applications of tracer thermochronology exploit a known or assumed surface thermochronometric age map (based on either interpolated observed or modelled bedrock ages) to determine the provenance of detrital grains within fluvial or glacial catchments. The goal is to interpret the erosion pattern and processes within the sampled catchment. So far, most studies focused on modern sediments and glacial deposits.

We extend this approach to several time slices (between 28 and 12 Ma) of well-dated stratigraphic sections of pro- and retro-foreland basins of the European Alps. Foreland basin deposits represent a rich archive of erosional processes that were controlled by tectonics, climate, and lithology. However, importantly, before we reconstruct and interpret past erosion patterns and exhumation from detrital zircon fission-track (ZFT) age distributions and modelled bedrock ZFT ages back in time, we produce a frame of reference of today's situation. We do this by investigating signals from modern river samples and the present-day erosion pattern and mineral fertility in the Alps.

Here, we focus on 26 modern river samples (21 previous samples from the Western and Central Alps, and 5 new samples from the Eastern Alps) and discuss observed and predicted (based on possible erosion scenarios) ZFT age distributions, as well as potential pitfalls of the method (such as poor bedrock control in some areas of the Alps). We also show preliminary results from stratigraphic sections.