The demise of the Northern Alpine Foreland Basin: what caused its erosion?

The Northern Alpine Foreland Basin (NAFB), also called Molasse basin, records the geological evolution of the Alpine orogenic belt. The basin accumulated sediments almost continuously for over 25 Myr, beginning in the Eocene. However, sedimentation ceased approximately at 5 Ma, accompanied by the erosion of up to several kilometres of sediments. The cause of this drastic shift in basin dynamics remains elusive.

Data suggests that the erosion pattern of the NAFB vary spatially and temporally and are unlikely to be explained by a single mechanism. Preliminary findings suggest that internal (i.e. Alpine) tectonics might play a primary role. Significant erosion in the western part of the basin correlates with pronounced vertical tectonic activity, including uplift associated with the thrusting of the Jura Mountains and subsidence due to the bending of the upper plate. In contrast, areas of lower erosion in the central basin correspond to more limited thrusting of the Alpine front and moderate subsidence of the basin. Meanwhile, the eastern basin likely experienced erosion earlier in its history, possibly driven by tectonic reorganisation and the cessation of convergence.

These interpretations are, however, based on correlations, and the quantitative impact of these tectonic movements on sedimentation dynamics has yet to be tested. Similarly, other external factors — such as tectonic activity in the European Cenozoic Rift System, filling of the Pannonian basin, climatic changes, and base-level shifts related to the Messinian Salinity Crisis — and their compounding effects must be tested.

Here, landscape evolution numerical modelling is used to better understand the basin dynamics. The goSPL code allows to model landscape evolution at continental scale accounting for different tectonic, climatic, and sea-level forcing conditions. This code is used to test the relative contributions of both internal and external mechanisms mentioned above and their interactions. The anticipated results will provide a quantitative assessment of the relative contributions of these factors on the dynamics of the Northern Alpine Foreland Basin since the Miocene.