Slab rollback orogeny in the Alps and evolution of the Swiss Molasse basin.

Fritz Schlunegger,Edi Kissling

doi:10.1038/ncomms9605

Abstract

The stratigraphies of foreland basins have been related to orogeny, where continent–continent collision causes the construction of topography and the downwarping of the foreland plate. These mechanisms have been inferred for the Molasse basin, stretching along the northern margin of the European Alps. Continuous flexural bending of the subducting European lithosphere as a consequence of topographic loads alone would imply that the Alpine topography would have increased at least between 30 Ma and ca. 5–10 Ma when the basin accumulated the erosional detritus. This, however, is neither consistent with observations nor with isostatic mass balancing models because paleoaltimetry estimates suggest that the topography has not increased since 20 Ma. Here we show that a rollback mechanism for the European plate is capable of explaining the construction of thick sedimentary successions in the Molasse foreland basin where the extra slab load has maintained the Alpine surface at low, but constant, elevations.

Highlights

The stratigraphies of foreland basins have been related to orogeny, where continent– continent collision causes the construction of topography and the downwarping of the foreland plate
We suggest that a slab rollback orogeny scenario for the Alps and the Molasse Basin is capable of reconciling previously conflicting stratigraphic, palaeoaltimetry and tectonic observations
Extensive geophysical surveys and deep crustal mapping revealed that the material of the crustal root has been derived from the subducting European plate[18,21]

Summary

Introduction

The stratigraphies of foreland basins have been related to orogeny, where continent– continent collision causes the construction of topography and the downwarping of the foreland plate. The stratigraphic evolution is closely linked to the plate convergence rates and the related crustal thickening in the adjacent mountain belt[3,4,5,6] that resides on the upper plate These mechanisms drive the subsidence of the foreland basin through subduction slab load and topographic load forces, which downwarp the foreland plate and create a sedimentary trough[3]. These data sets have provided the basis to disclose the causal relationships between the construction of orogenic loads in the Alps, and the flexural response of the basin[9,10,12,13] These processes, in turn, have been linked to the convergence and the subsequent collision between the Adriatic and European continental plates, leading to the formation of the Alps through thrusting, crustal stacking and erosional recycling[14,15]. We suggest that a slab rollback orogeny scenario for the Alps and the Molasse Basin is capable of reconciling previously conflicting stratigraphic, palaeoaltimetry and tectonic observations

Methods

Results

Conclusion