Kinematics of foreland-vergent crustal accretion : inferences from the Dinarides evolution

Abstract

One of the most common observation in Mediterranean areas is the migration of contractional deformation and associated slabs through time towards external orogenic areas, associated with lower plate crustal accretion. The Dinarides orogen of Central Europe is an optimal place to study such a sequence of contractional deformation. Compared with other areas, contraction in the Dinarides was less overprinted by subsequent extension, while a remnant of the subducted slab is observed in a far external orogenic position. Understanding the deformational evolution of the Dinarides is hampered by the reduced availability of kinematic studies. Therefore, we have performed a surface kinematic study in the external parts of the Dinarides. By correlating with available geophysical and evolutionary constraints, we constructed two large-scale, kinematically controlled regional transects. The results demonstrate a long-lived evolution of shortening that affected the Dinarides lower orogenic plate. While the Late Jurassic?earliest Cretaceous deformation was associated with an earlier obduction moment, the latest Cretaceous onset of continental collision has gradually focused deformation at inherited rheological weakness zones. We show that shortening was interrupted by a period of Miocene extension that affected all orogenic areas and created the Dinarides Lake System. The extension was followed by renewed shortening, that started during the latest Miocene and remains presently active, whose kinematics in the central and SE part of the Dinarides is revealed for the first time by our study. These results indicate a lower plate crustal accretion mechanism that was spatially and temporally connected with gradual slab-retreat in the Dinarides.