El control de la deformación cortical en la evolución de los relieves “tectónicos” del centro y suroeste del Macizo Ibérico.

Abstract

Stresses transmitted far from active plate boundaries deform the lithosphere in the intra-plate domains and build mountain ranges and sedimentary basins. A dramatic change of landscapes takes place, and former smooth topography, characterized by peneplain surfaces, is folded and faulted. This is true of the Iberian plate interior whose present-day morphostructure is dominated by mountain ranges and continental sedimentary basins formed during Alpine compressional events related to African and European plate convergence. To investigate regional patterns of relief and recognize its tectonic record we have performed a trend-surface analysis of topography in order to define surfaces capable of describing both the morphological features and structures that could reflect the relationship between crust relief and deformation. Bearing in mind that uplift is one of the main controlling mechanism of fluvial incision subenvelop maps of main drainage basins were produced. From subenvelop maps three zones can be recognize in Iberian intra-plate domain: a) Cordilleran areas, matching main mountainous relieves; b) Plateau, representing areas with almost a flat topography and hidric balance and c) Incised valleys, more conspicuous towards the west. Trend-surface analysis of topography revealed the existence of undulations transverse to the Alpine stress field. These undulations may be related to lithospheric folding that accommodate shortening. They are offset by N-S faults that clearly controlled recent sedimentation and river patterning. These surfaces have been compared with the existing landscape geomorphological ones in order to interpret their geological significance. The synthetic geomorphological surfaces map reveals a stepped mosaic of summit, pediment and plateau patches which configuration and tilting might be assimilated to the obtained spectral undulations. This fact allows correlating these trend-surfaces with the present geomorphologic surfaces, which correspond with the one that has been considered as a generalised Prepaleogenous surface and from which Tertiary sedimentary basins and mountain ranges were reshaped during the Alpine orogeny. This generalised surface, peneplain, developed over the Iberian Peninsula Western half is considered as an etchplain resulting from the washing away of the warm climate Mesozoic weathering mantle and locally further reshaped during Tertiary. In some places the former surface shows up in continuity with the summit surfaces, and can be even locally related to another pre-existent surface, the Pretriasic one, implying that once a planation surface has been reshaped, successive surfaces might develop from it lowering progressively from the original one, without obliterating its original planform.