The role of the Miocene-to-Pliocene transition in the Eastern Mediterranean extrusion tectonics: constraints from numerical modelling

In the Eastern Mediterranean, extension in the Aegean Sea and lateral Anatolian extrusion are contrasting and seemingly unrelated examples of continental tectonics developed during Tethys closure. We use numerical modelling to investigate the relation of the tectonic regimes to the underlying subduction dynamics, during subduction land-locking and slab break-off. We find that the tectonics has a two-phase evolution: 1) an incipient phase, with back arc spreading and transcurrent shear zone formation and lateral escape of a block in the upper plate interiors, and 2) a reorganisation phase, during which the transcurrent shear zone propagates and the extruding block internally stretches, progressively separating from the opening back arc domain, while the collisional margin reactivates into a transform plate boundary. The regimes are explained by two concurring plate margin processes: 1) mantle tractions following the subduction and retreat of a land-locked oceanic slab, and 2) stresses propagated through rigid indentation upon slab break-off. These have different spatial and temporal fingerprints: long-term trench retreat and convergence slow-down follow continental subduction, while stresses localise atop the newly formed slab edge upon slab break-off, fastening up margin reorganisation, driving faulting and extrusion, yet fading rapidly, forcing local tectonics rearrangement. A comparison with the Eastern Mediterranean allows an explanation for the time evolution of the tectonics here, and emphasises the role of the Miocene-to-Pliocene tectonics transition, previously not considered. This offers a novel key to the dynamics of the enigmatic evolution of this area.