Geokolloquium: Montag 09.12.2019

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 Kinematics of extrusion and back-arc extension in the Aegean (Greece)



 Vortragender: Prof. Bernhard Grasemann

Universität Wien


 In Alpine geodynamic evolution of the Aegean is characterized by a syn-orogenic Eocene subduction channel, which is overprinted by a post-orogenic Oligocene–Miocene back-arc extension. The exact geometry and kinematics of the syn-orogenic high-pressure channel is still controversial because it is masked by several low-angle major detachment systems, which did not reactivate, but cross-cut earlier thrusts and normal faults related with the exhumation of the high-pressure rocks. Comparing new geochronological, petrological and structural data with published data from the Cycladic islands suggest that the Eocene subduction channel had a complex internal geometry consisting of at least two different high-pressure units, which experienced roughly 10 and 20 kbar respectively. These two units were juxtaposed during S-directed extrusion above a thrust and below a normal fault. After significant block rotation and associated distortion of the exhumed channel, the high-pressure rocks were strongly overprinted by a top-N and top-S bivergent low-angle detachment system in the Middle to Late Miocene.