Estructura de la mitad septentrional de la Zona de Ossa-Morena: deformación en el bloque inferior de un cabalgamiento cortical de evolución compleja

Résumé

The structure of the Ossa-Morena Zone (OMZ) is geometrically and kinematically complex, showing different types of structures superimposed along the Variscan Orogeny. Structures in the OMZ and its boundary with the Central Iberian Zone (CIZ) attest the existence of a Devonian-Carboniferous convergence between these zones, the OMZ being the footwall of a crustal-scale continental thrust. The first Variscan structures are of Devonian age and consist of Km-scale SW vergent recumbent folds followed by south-directed thrusts. The tectonic regime changed to regional transtension in Lower Carboniferous, as shown by the development of low-angle normal faults, basins and volcanism. In the Upper Visean compression restarted, giving way mainly to non-cylindrical upright folds. The new folds superimposed on the previous structures originating complex interference patterns depicted on the geological map. The characteristic structures of the late-collisional stage are strike-slip faults, mainly concentrated in two regional bands at the northern and southern borders of the OMZ. Strike-slip faults in northern OMZ obliterate the more important and older thrust contact of the CIZ onto the OMZ. Although severa1 evidences point to an oblique continental convergence between both zones, it seems that deformation was partitioned between areas dominated by left-lateral shearing (the CIZ 1 OMZ contact itself) and areas dominated by transversal shortening or extension (the OMZ).