Search

The Spanish Central System is the most relevant topographic feature in central Iberia. Along with the surrounding Duero and Tajo basins it presents an anomalous high elevation. This high topography is, most probably, the result of a combination of deep and surface processes. The crustal thickness, geometry of the Moho discontinuity and the crustal architecture are the main targets of current research efforts developed in the area. As part of a multi-seismic project limited controlled source data has been acquired, jointly with ambient noise seismic records. The preliminary results provide relatively strong constraints on the deep structure of the Spanish Central System. The ambient seismic noise records were acquired by a set of 24 short period (2 Hz) seismic stations deployed along a 120 km long NW-SE-trending profile with a 4.8 km average spacing. The transect crossed the southern branch of the mountain range. The stations recorded the ambient seismic field continuously for a month. Processing consisted on: phase autocorrelation of the seismic noise to retrieve the zero-offset reflection response at the receivers and, time-frequency domain phase weighted stack used to stack the auto correlations. For calibration and, along the same transect, over 500 TEXANS were deployed to record a wide-angle shot gather. The recording units with an approximate station spacing of 400 m recorded relatively high amplitude crustal and Moho events. The lower crust and the crust-mantle transition are constrained by both data sets. Further more small crustal discontinuities and structures are interpreted and correlated with surface geology features. The results of the processing are compared to synthetic models to certify the validity of our interpretations, Research support, Ref: CGL2016-81964-REDE, , EU grant 730900

Trabajo presentado en la EGU General Assembly 2016 (European Geosciences Union), celebrada en Viena del 17 al 22 de abril de 2016., The Galicia continental margin is a magma-poor rifted margin with an extremely complex structure. Its formation involves several rifting episodes during the Mesozoic in the vicinity of a ridge triple junction, which produces a change in the orientation of the main structures. In addition, there is an overimposed Cenozoic partial tectonic inversion along its northern border. Although this continental margin has been widely studied since the 70’s, most studies have focused on its western part in the transition to the Iberia Abyssal Plain, and there is a significant lack of information on the north and northwestern flanks of this margin. This fact, along with its great structural complexity, has resulted in the absence of a previous comprehensive regional geodynamic model integrating all the processes observed. In the present study we integrate a large volume of new geophysical data (gravity, swath bathymetry and 2D multichannel reflection seismic). Data come from the systematic mapping of the Spanish EEZ project which provides a dense grid of gravity data and full seafloor coverage with swath bathymetry, and from the ERGAP project which provides serially-arranged 2D seismic reflection profiles across the NW Iberia margin. The combined interpretation and modelling of this new information has arisen significant constraints on the origin, the deep crustal structure and the physiographic complexity of the margin, as well as on the characterization of the along- and across-strike variation of the ocean-continent transition along NW Iberia margin. The analysis of this information leads us to propose a conceptual model for the initiation of the tectonic inversion of a magma-poor rifted margin. Finally, a framework for the geodynamic evolution of the Galicia margin has been constructed, involving three main stages: A) an early stage from the end of rifting and oceanic drift in the Bay of Biscay (Santonian); B) an intermediate stage with the beginning of tectonic inversion in the north and northwestern Iberia margin (Campanian-Paleocene) mainly concentrated along the exhumed mantle zone; and C) a final stage of compressive deformation (Eocene-Oligocene) affecting both the continental and the oceanic crust, evidenced by large dip-slip thrusting

0

0

Sí