| Título: | Cainozoic deformation of Iberia: a model for intraplate mountain building and basin development based on analogue modelling |
| Autores: | Fernández Lozano, Javier |
| Tipo de documento: | texto impreso |
| Editorial: | El autor, 2012 |
| Dimensiones: | application/pdf |
| Nota general: | info:eu-repo/semantics/openAccess |
| Idiomas: | |
| Palabras clave: | Estado = Publicado , Materia = Ciencias: Geología: Geodinámica , Tipo = Tesis |
| Resumen: |
Long-term topography in Europe results from the interaction between Alpine continental collision and anomalously raising mantle material. The Alpine belt runs from southern Europe all the way to the Himalayas along thousands of kilometres. It resulted from the closure of oceanic realms and subsequent continental subduction and collision (Pyrenees, Alps, Carpathians, Dinarides, and Himalayas). However, far from the suture zone, little is known about the mountain building processes within plate interiors. For this reason, new research projects such as Topo-Europe (see Cloetingh et al., 2011b, in Topo-Europe Tectonophysics volume) and Topo-Iberia have recently arisen under international cooperation. The aim of these multi-scale investigations is to add new insights into deep Earth and surface processes. Following this line of research, this thesis builds on analogue modelling and spectral analysis of topography and gravity data, aiming to portray and discuss the mechanisms of mountain building in intra-plate settings. More specifically the research focuses on the evolving topography and formation of related basins in Iberia, although the results can be extrapolated to other intra-plate areas where geophysical and geological data are scarce. As is evident from aerial pictures, western Iberia is characterised by a regular pattern of topography from the Cantabrian Mountains in the north to the Sierra Morena Mountains in the south, following E-W to NE-SW trends. This periodic pattern has been linked to large-scale folds affecting the entire lithosphere. In contrast, in the Eastern part of the Peninsula topography relief follows E-W, NW-SE and NE-SW trends without any observable regularity. Although many theories have been formulated to explain these differences, none of them reconcile Surface topography with deep earth processes. Among the questions that have not been answered yet by previous studies in Iberia the following stand out: what is the nature of the lithosphere in terms of possible strength variations inherited from different episodes of mountain building (Variscan) or rifting (Mesozoic); what are the process of intra-plate mountain development and the high elevation of the Duero Basin, or the Cainozoic influence of pre-existent late-Variscan tectonic structures over present-day topography. The models presented in this thesis are based on geological and geophysical data available from Spain. The first series of models aims to understand the mechanism behind intraplate mountain building and basin development in Iberia by testing two different lithosphere set-ups. I describe favourable conditions for the evolution of lithosphere folds that led to presentday topography. A de-coupled lithosphere where strength resides in the upper crust and mantle seems to be the key for the evolution of large-scale folds. However, the Iberian lithosphere is far from being homogenous in terms of lithospheric strength. Inherited structures stemming from Variscan phases of deformation as well as the weakening of the lithosphere related to Mesozoic extension possibly affected deformation during Cainozoic times. Therefore, a new set of experiments was carried out in order to study the mode of deformation under different thermomechanical conditions prior to the onset of Alpine shortening. Since analogue experiments allow the direct observation of the lithosphere after deformation, I established a new approach in order to reconcile surface and deep earth architecture through the study of gravity and topography. Digital elevation models obtained from the model surface, together with the theoretical gravity data calculated from digitized model cross-sections, were analysed in terms of spectral analysis and compared with the Moho depth maps. This analysis allowed differentiating between periodic and non-periodic signals, which may explain the mechanism of mountain building (folding versus crustal thickening, respectively). Finally, models with heterogeneous lithosphere were implemented with the addition of pre-existent late-Variscan faults which may have influenced the position of the lithosphere folds and in turn the final configuration of topography. In order to study the influence of these tectonic structures, surface particle displacement field techniques were performed (Particle Image Velocimetry or PIV). PIV, therefore, aimed to discriminate between re-activation of old structures and neo-formed tectonic structures. The results of analogue models were compared with fieldwork carried out along the boundary between the Spanish Central System and the Iberian Range, where interfering structures (E-W to NE-SW oriented) are coeval with NE-SW, NW-SE and E-W striking structures in Central Spain. Interestingly, field data and analogue modelling concluded that different topographic trends can be caused by folding of the lithosphere with laterally different thermo-mechanical conditions under a single N-S stress field during the Pyrenean stage of the Alpine Orogeny. |
| En línea: | https://eprints.ucm.es/id/eprint/15793/1/thesis.pdf |
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