From field data to lithospheric-scale models going through analogue experimentsthe Gibraltar Arc System revisited in the light of the external zones structural evolution

Zusammenfassung

We present the most relevant results of our research group concerning the structural and kinematic evolution of the Gibraltar Arc System external zones. Field data permitted us to evidence that the main shortening deformation took place during the Early and Middle Miocene. This main shortening is followed by a Late Miocene to Holocene tectonic event which tightened the Western Gibraltar Arc (NNW-SSE directed compression). In the westernmost part of the arc, strain partitioning took place during both events of deformation as shortening with radial transport direction is coetaneous with arc-parallel extension accommodated by arc-perpendicular normal faults and arcoblique strike-slip faults. The Late Miocene to Holocene arc tightening is associated with vertical axis rotations of blocks whose dimensions reach a few hundreds of kilometers, clockwise in the Betics and counterclockwise in the Rif. These data permit us to infer that the deformation mechanism of the external zones situated in the Western Gibraltar Arc is that of a progressive arc that we were able to simulate in analogue model laboratory. They also allow us to determine that the most probable lithospheric-scale model for the Gibraltar Arc System tectonic evolution is that of a retreating subduction slab, with progressive increasing of the arc curvature and coeval lengthening and extension of the upper plate.