Simplon fault zone in the western and central Alps: Mechanism of Neogene faulting and folding revisited

The Neogene Simplon fault zone is commonly either considered as a transfer zone for dextral strike-slip movements during oblique convergence or as a core complex-type normal fault leading to orogen-parallel extension in the Alps. There is, however, evidence that the Simplon fault zone lacks a southeastward continuation. On the basis of new structural and fission-track data, we propose a model of oblique indentation of a bent Adriatic indenter leading to the formation of a curved continuous wedge of backfolds in the south, not including a southern continuation of the Simplon fault zone. Updoming related to backfolding, followed by erosion, assisted exhumation of amphibolite facies rocks. In the north, indentation led to differential shortening in the footwall and hanging wall. Keywords: Simplon fault zone, indentation tectonics, backfolding, metamorphic domes.