GEOLQUEA

The present-day velocity field of the Earth’s surface holds valuable information about the spatial patterns and rates of tectonic activity. However, in the European Alps, which are uplifting at rates of up to ~2 mm/yr, no consensus exists on which processes drive the observed uplift. The processes suggested to account for uplift include isostatic response to tectonic shortening, the last deglaciation, long-term erosion, detachment of the Western Alpine slab, as well as lithospheric and surface deflection due to mantle convection. In this project, we want to test the hypothesis that spatiotemporal transients in glaciation and erosion have a significant influence on isostatic adjustments and that their quantification allows us to isolate the uplift related to tectonic and/or geodynamic processes. Field observations suggest rapid expansion and shrinkage of the Alpine ice cap during the last glacial cycle, and cast doubt on the validity of previously assumed isostatic equilibrium. Furthermore, trapping of sediments in overdeepened valleys of the Alps and in peripheral lake basins induces transients in the isostatic response to erosion. We will therefore employ transient numerical ice flow modeling during the last glacial cycle that includes erosion processes, calibrated to field observations, to estimate surface loading and unloading. We will use the model results in conjunction with new lithospheric models, derived from AlpArray data, to predict rock uplift rates due to surface processes. Comparison of modeled with observed rock uplift will clarify the role of glaciation and erosion in the present-day uplift of the Alps, and allow residual uplift to be linked to tectonic and/or geodynamic processes. Furthermore, we will upscale our results to longer periods, e.g., since the mid-Pleistocene transition, to estimate the integrated effect of Quaternary glacial erosion on rock uplift and exhumation in the Alps. Our modeling approach builds on results from the first phase of the SPP and will provide key constraints for linking spatial patterns of present-day to Quaternary rock uplift to deep-seated processes.