Estructura de la corteza en el centro peninsular mediante el análisis espectral de datos gravimétricos y modelización en 2+1/2D

Abstract

The spectral analysis of gravity anomalies in Central Spain has provided the occurrence of two crustal discontinuities located at a mean depth of 29,2±1,7 and 8,2±0,4 km respectively. According to seismic data, the deeper discontinuity represents the Moho and the shallower one is located within the upper crust. A 3D-depth model for the Moho has been obtained by means of the inverse modelling of regional gravity anomalies in Fourier domain. Moho geometry is characterised by a NW-SE trending depressed zone, where maximum depths reach values up to 30 km. As a result of it, the crust in Central Spain is thickened below the central zone of the Spanish Central System and Duero and Tajo tertiary basin margins. This thickening vanishes towards the eastern and western boundaries of the mountainous chain. Transverse gravity models show that the Spanish Central System structure consists in an uplifted crustal block. Upper-middle crust boundary appears arched in the chain. Two main reverse faults limit the Central System and the Duero and Tajo basins. Faults dip around 50º and they are related to two main gravity gradients NE-SO trending. These gradients are well marked in Bouguer anomaly map and residual anomaly map. Chain parallel gravity model shows upper crust density heterogeneity. Rock density increase at the base of the upper crust in the western zone. Here, Bouguer anomaly presents a relative maximum to the central zone. Spectral analysis, as well as gravity modelling, suggests a crustal thickening under central part of the Spanish Central System. This thickening is lower than seismic modelling results.