Folded Variscan thrusts in the Herrera Unit of the Iberian Range (NE Spain)
Pablo Calvín-Ballester, Antonio Casas, 2014. "Folded Variscan thrusts in the Herrera Unit of the Iberian Range (NE Spain)", Deformation Structures and Processes within the Continental Crust, S. Llana-Fúnez, A. Marcos, F. Bastida
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The Variscan structure of the Herrera unit (Iberian Chain, NE Spain) is characterized by a system of NNW–SSE-striking, east-verging, foreland-dipping thrusts, generated in a thin-skinned context, whose formation was favoured by the presence of two main detachment levels (Precambrian and Silurian shales). During the formation of the thrust system (first phase of deformation, D1), the thrust sheets were deformed internally, mainly by asymmetrical folds with axial surface cleavage and east-verging thrusts; the normal evolution of the thrust system and the emplacement of an underlying thrust sheet resulted in progressive tilting and stacking, thus generating a foreland-dipping thrust system. These structures were folded and tilted by the emplacement of the Datos thrust (second phase of deformation, D2), generating an associated deformation characterized by subvertical folds with axial surface cleavage, with slight east vergence. These structures can obliterate the previous D1 structures in the sector near the Datos thrust. D1 and D2 structures have not been observed in the same outcrops, but the relationship between bedding and cleavage as well as cleavage relationship with other structures allows discrimination between the two cleavage sets. Based on the features of Palaeozoic rocks of the Iberian Range and the Iberian Massif, we support the idea that the Herrera unit belongs to the Cantabrian Zone.
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Deformation Structures and Processes within the Continental Crust
This volume presents a selection of papers showing the current focus of studies of deformation structures and processes within the continental crust. The selected contributions use a large range of analytical techniques suited to the full range of structure sizes and fine-tuned to the physical process that controls the deformation, from the grain boundary at the micro-scale, the lithological contact at the meso-scale to the plate boundary at the global scale.
The papers in the volume are grouped into three sections relating to specific lines of research within the analysis of rock deformation structures and processes, in particular in respect to the continental crust: structures within shear zones and faults; magmatic structures, and microstructures and rheology. These sections include papers describing field studies, experimental rock deformation and numerical modelling of deformation processes.