Orogenward Migration of the Flexural Forebulge: A Response to Increased (Sub)surface Loading in the Orogenic Core?

The flexural profile of a foreland basin is controlled by lower plate strength and the magnitude of (sub)surface loads. Assuming that lower plate strength remains largely constant during flexure, changes in the flexural profile hint at reorganisations of (sub)surface loading. During the early Miocene, the forebulge in the Eastern Northern Alpine Foreland Basin migrated 80 km towards the orogenic front. This change in basin architecture occurred concurrently with intensified folding in the Tauern Window whilst the Eastern Alpine orogenic front ceased to propagate cratonward. Here, we construct 2D flexural models to test whether the resultant focusing of topographic loading into the hinterland, exerted by Tauern Window exhumation, forced orogenward migration of the forebulge. However, our results suggest that solely the focusing of the topographic load cannot explain the observed orogenward propagation of the forebulge. Likely, this requires a contribution of visco-elastic relaxation, supported by changes in subsurface loads during the necking of the European slab.