Geodinámica del margen continental de Galicia: estructura profunda y morfotectónica

La presente Tesis Doctoral lleva por t tulo Geodin amica del margen continental de Galicia: Estructura profunda y morfotect onica. Este estudio se aborda a partir de la integraci on de un gran volumen de nuevos datos geof sicos (gravim etricos, batim etricos y s smica de re exi on multicanal 2D y de ultra-alta resoluci on), procedentes de los proyectos ZEEE, ERGAP y BURATO4242. La nueva informaci on ha aportado constricciones muy relevantes sobre el origen, la estructura profunda y la complejidad siogr a ca del margen, as como sobre la caracterizaci on de la variaci on lateral de la transici on oc eano-continente. El margen continental de Galicia se clasi ca como un margen de rift pobre en magma. Este tipo de m argenes tienen dos rasgos comunes, que son: 1) Los pares de m argenes conjugados son asim etricos, teniendo uno de ellos una zona m as ancha de corteza extremadamente adelgazada, subrayada por un re ector s smico subhorizontal; 2) Entre la corteza continental adelgazada y la corteza oce anica normal, hay una zona de basamento compuesto por manto serpentinizado. La estructura del margen continental gallego es extremadamente compleja, re ejando la superposici on de varias etapas sucesivas de rift, y una etapa compresiva posterior que da como resultado la inversi on parcial del margen. Adem as, la proximidad de un punto triple de dorsal produce un cambio de orientaci on de las estructuras principales. Este margen continental ha sido ampliamente estudiado desde la d ecada de los '70. Sin embargo, la mayor parte de los estudios se han centrado en la parte occidental, existiendo una importante carencia de informaci on en los ancos norte y noroeste. Este hecho, junto con su gran complejidad estructural, ha provocado que no exista un modelo geodin amico previo que integre todos los procesos observados. Algunos aspectos, como son la transici on entre el margen oeste (extensivo) y el margen norte (compresivo), y la forma en que se produce su inversi on tect onica, apen
This PhD Thesis is entitled Geodynamics of the continental margin of Galicia: Deep structure and morphotectonics. This study is approached from the integration of a large volume of new geophysical data (gravimetric, bathymetric, 2D multichannel seismic re ection and ultra-high resolution seismic imaging), from the ZEEE, ERGAP and BURATO4242 projects. The new information has brought signi cant constraints on the origin, the deep structure and the physiographic complexity of the margin, as well as on the characterization of the lateral variation of the oceancontinent transition. The Galicia continental margin is classi ed as a magma-poor rift margin. Margins of this type have two common features, namely: 1) The conjugate margin pairs are asymmetric, one of them showing a wider zone of extreme crustal thinning, as underlined by sub-horizontal seismic re ections; (2) Between the thinned continental crust and the normal oceanic crust, there is an area whose basement is composed of serpentinized mantle. The structure of the Galicia continental margin is extremely complex, since its formation involves several rifting episodes, and a later partial tectonic inversion. In addition, the vicinity of a ridge triple junction produces a change in the orientation of the main structures. This continental margin has been widely studied since the 70's. However, most studies have focused on the western part, and there is a signi cant lack of information on the north and northwestern anks. This fact, along with its great structural complexity, has resulted in the absence of a previous geodynamic model integrating all the processes observed. Some aspects, such as the transition between the western margin (extensive) and the northern margin (compressive), and the way the tectonic inversion develops, have barely been addressed previously by the scientific community...