Constraining the geodynamic evolution of the Alps with sedimentary provenance and detrital thermochronometer data

01.02.2021 bis 31.01.2024

This proposal disentangles sedimentary signals related to changes in the deep
lithosphere, the upper crust, and climate change in the Alps. The overarching hypothesis of this proposal is that if lithospheric reorganisation in the Alps (e.g. slab breakoff, tearing) occurred, then it led to spatial and temporal changes in buoyancy that relocated the focus of rock uplift and erosion. These changes are preserved in diverse sedimentary and geochemical records in the
Alpine foreland basins. To test this hypothesis, we apply a multi-proxy provenance approach at key stratigraphic time slices (28, 25, 20, 17, 15 and 12 Ma) preserved in circum-Alpine proximal fan deposits. Our approach overcomes the limitations of previous studies, by bridging methodological, temporal and integrational gaps through the combination of detrital geo-
thermochronology (apatite and zircon triple dating with U-Pb, fission track and (U-Th)/He) dating, and provenance tools (petrography, heavy mineral composition, garnet chemistry). From this, we will reconstruct the 4D exhumation and sedimentation history of the entire Alps by quantifying the
spatial (west to east) and temporal (28-12 Ma) evolution of lithologies exhumed across the Central and Eastern Alps. These observations will yield new insights into the complex crustal and Earth surface response to deeper lithospheric changes (theme 2 of phase II of the SPP 4D-MB). More specifically, we will sample modern river sediment as well as sandstone from proximal foreland basins in the northern Alpine foreland basin, Venetian basin and the Gonfolite Lombarda to compile an Alpine-wide detrital dataset of detrital cooling ages and provenance data. In order to test our hypothesis, the provenance and thermochronological signal of modern rivers will be compared to the present-day erosional pattern of the Alps and to seismological data and interpreted crustal and lithospheric structures from phase I. In a second step, this approach will be extended to Oligo- to Miocene sandstones in the foreland basin in order to reconstruct the paleo-geography, drainage patterns and exhumation hot spots. These orogen-wide reconstructions enable us to identify potential climate, tectonic or deep lithospheric drivers (based on the location, timing and magnitude of events/changes), and also to test proposed geodynamic models for the post-collisional evolution of the Alps. Our project will therefore significantly
contribute to a better understanding of the 4D evolution of the Alps.