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Abstract:
The Cenozoic continental collision of Europe and Africa that raised the European Alps, led to the formation of the adjacent Alpine foreland basins (Molasse and Po). Though the amount of geological and geophysical observations in this region has steadily increased over the past few decades, different hypotheses have been put forward relating to the crustal and lithospheric structure, the deep collisional geometry, and the evolution of the system, making integration of these observations challenging. Progress can be made in deriving a description of the present-day physical state of the orogenic system through the creation of a gravity constrained, 3D, density differentiated, structural model of the Alps and their forelands that integrates the numerous available geoscientific datasets. These include: regional scale models of the Transalp study area, the Molasse basin and the Upper Rhine Graben; regional scale models of the Po Basin; plate scale seismologically constrained models; reflector tops, velocities and interpretations from seismic sections across the region; and the observed gravity anomaly. The generated model differentiates vertically between sedimentary layers (unconsolidated and consolidated), crystalline crustal layers (upper and lower) and mantle layers (lithospheric and asthenosphere). We find that the European crystalline crust is less dense and thicker (~2820 kg/m3, ~27.5 km) than the Adriatic crust (~2920 kg/m3, ~22.5 km). Strong lateral density contrasts within the crust of the two plates were found necessary to resolve the gravity response. Some of these correspond to features expressed at the surface, such as faults but also boundaries between domains of different deformation intensity.
