Publication: Estructura de la corteza en el centro peninsular mediante el análisis espectral de datos gravimétricos y modelización en 2+1/2D
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2003
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Sociedad Geológica de España
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Abstract
El análisis espectral de las anomalías de Bouguer del centro peninsular ha puesto de manifiesto la existencia de dos discontinuidades corticales situadas a unas profundidades medias de 29,2±1,7 y 8,2±0,4 km. De acuerdo con los datos sísmicos, la discontinuidad más profunda representa el Moho y la más superficial está situada dentro de la corteza superior. Mediante la inversión en el dominio de las frecuencias de la anomalía regional, se ha elaborado un modelo tridimensional del Moho. Su geometría está caracterizada por una depresión con las mayores profundidades dispuestas según una orientación NO-SE, alcanzando valores próximos a 30 km. Por tanto, la corteza en esta zona se encuentra ligeramente engrosada, descendiendo el Moho bajo las áreas centrales del Sistema
Central y sus márgenes con las Cuencas del Duero y del Tajo. Hacia los extremos de la cadena el espesor de la corteza disminuye. En los modelos gravimétricos transversales al Sistema Central realizados, la estructura de la cadena aparece definida como un bloque cortical elevado en el que el límite corteza superior-corteza media asciende en sentido transversal a la cadena, adquiriendo una forma arqueada. El límite con las Cuencas del Duero y del Tajo corresponde a dos fallas inversas de buzamientos próximos a 50°, asociados a gradientes gravimétricos de dirección NE-SO bien marcados.
El modelo gravimétrico longitudinal muestra el carácter heterogéneo de la corteza superior en el Sistema Central. Estas heterogeneidades están relacionadas con dominios establecidos en el basamento hercínico de forma que la densidad de los materiales disminuye hacia la zona occidental. Aunque tanto el análisis espectral de los datos gravimétricos como la modelización sugieren la existencia de
un engrosamiento bajo el Sistema Central, éste se encuentra circunscrito a la zona central y es menor que el propuesto por los modelos sísmicos
The spectral analysis of gravity anomalies in Central Spain has providedthe occurrence of two crustal discontinuities located at a mean depth of29,2±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 thejnverse modelling of regional gravity anomalies in Fourier domain. Moho geometry' is characterised bY,!l NW -SE trending depressed zone, where maximum depths reach values up to 30 km. As a result;pf 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 westenr: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 50° 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 decreases to the west related to an increase of granite outcrops. Gravity profile fitting requires a 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
The spectral analysis of gravity anomalies in Central Spain has providedthe occurrence of two crustal discontinuities located at a mean depth of29,2±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 thejnverse modelling of regional gravity anomalies in Fourier domain. Moho geometry' is characterised bY,!l NW -SE trending depressed zone, where maximum depths reach values up to 30 km. As a result;pf 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 westenr: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 50° 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 decreases to the west related to an increase of granite outcrops. Gravity profile fitting requires a 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