Geoelectrical characterisation of Alpine orogenic belts in the Iberian Peninsula using the magnetotelluric method
[eng] The Iberian Peninsula is considered as a “micro-continent”, located between the Eurasian and the African plates. Several ranges formed during the Alpine orogeny, in the borders of the plate or intraplate. As part of this thesis the first magnetotelluric (MT) data was collected across the intra...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/107485 |
| Acceso en línea: | https://hdl.handle.net/2445/107485 http://hdl.handle.net/10803/400759 |
| Access Level: | acceso abierto |
| Palabra clave: | Tectònica de plaques Serralada Cantàbrica Serralada Ibèrica Plate tectonics Cantabrian Mountains Iberian Mountains |
| Sumario: | [eng] The Iberian Peninsula is considered as a “micro-continent”, located between the Eurasian and the African plates. Several ranges formed during the Alpine orogeny, in the borders of the plate or intraplate. As part of this thesis the first magnetotelluric (MT) data was collected across the intraplate Iberian fold and thrust belt and the first long-period magnetotelluric was collected across the Cantabrian Mountains, located in the northern boundary of the Iberian plate. This MT data was used to image the electrical conductivity distribution of the crust beneath these two orogens. The analysis of the MT data revealed the presence of three-dimensional structures in both studied areas and therefore 3-D inversion algorithms were used to obtain the final resistivity models. In the Cantabrian Mountains the correlation between the geoelectric image, the existing geophysical models and the surface geology provided a deeper understanding of the lithospherical processes. The final model shows excellent correlation with the superficial geology, depicting the main faults and lithologies at depth. The Duero Basin sediments are well delineated. A thickness of 2.5 to 3.5 km was deduced, and is in agreement with the seismic studies and well log data. Conductive zones in the Palaeozoic basement are related to enhanced permeability along the main Alpine faults. These conductive zones detected in the model do not reach more than 10 km in the southern part of the Cantabrian Mountains and 15 km in the northern part, and are therefore concentrated in the upper crust. The hydration/serpentinization of the upper mantle within the mantle wedge and beneath the Moho of the Cantabrian Margin is imaged as a zone of low resistivities. In the Iberian Chain the 3-D inversion model indicates that several Alpine thrusts are imaged as dipping conductors, which are limited to the upper crust. Two of them are the North Iberian Thrust and the Serranía de Cuenca Thrust, which bound to the north and to the south respectively the basement involved areas of the Iberian Chain. Both faults do not reach more than 15 km depth, suggesting that they are linked to the thrust system detachment at 10–15 km depth. This indicates that the Cenozoic thrust system causing the crustal thickening of the Iberian Chain is concentrated in the upper crust, which confirms the previous geological hypothesis proposed by Guimerà and Alvaro (1990). The 3-D inversion model is consistent with the collocated seismic image. A statistical analysis of the correlation between seismic velocity and electrical resistivity along a NE-SW profile is carried out for the upper crust and shows a clear correlation between both parameters. An increase in both seismic velocity and electrical resistivity is observed and is related to the depth at which the geological formations are located. |
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