Investigation of the exhumation mechanisms of the axial core of a collisional orogen, by means of structural analysis of brittle deformation and of thermochronology in the Eastern Alps.

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Tertiary exhumation of the Eastern Alps remained localised within a restricted area (Tauern Window) from the early Tertiary to the Late Miocene. Based on previous and new thermo-chronological investigations the cooling patterns of this area will be constructed, with special attention to the relationship between the 3-D geometry of the isochrones, the 3-D geometry of the extensional fault planes, and the 3-D geometry of the large scale folds. These spatial relationships will be used to constrain the mechanisms of exhumation, i.e. the contribution of extensional unroofing vs. folding and erosion. The comparison of thermal models of endmember- types of exhumation by extensional unroofing and by folding and erosion, in addition to mixed-type models, will allow us to quantify the contribution of each mechanism to the bulk exhumation.Considering that brittle deformation generally starts after the rocks passed through the brittle-ductile transition, whose temperature is approximately defined by the annealing temperature of zircon fission tracks, we will define the maximum age of brittle structures by measuring zircon fission tracks. These ages combined with a structural analysis of brittle deformation will allow us to reconstruct the middle- to late Miocene kinematics and paleostress fields of the axial core of the Eastern Alps, and to constrain the late mechanisms of exhumation.