Publication: Modelización gravimétrica en 2 1/2D Y 3D en la zona
nororiental de la Cuenca de Madrid
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Publication Date
1995
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Sociedad Geológica de España
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Abstract
El mapa de anomalías de Bouguer de la zona NE de la cuenca de Madrid está caracterizado por un mínimo relativo asociado a la cuenca terciaria y a la presencia de rocas de baja densidad en el basamento. Con objeto de conocer las fuentes de este mínimo se ha realizado la modelización gravimétrica en 2 1/2 D de tres perfiles. Este procedimiento ha permitido establecer las relaciones entre los mínimos relativos y los mayores espesores de sedimentos terciarios, salvo en la zona septentrional en dónde ha sido necesario introducir un cuerpo de baja densidad. A partir de los resultados
de la modelización se ha ensayado la posible forma tridimensional de este cuerpo y se ha calculado
su efecto gravitatorio. Esta anomalía ha sido sustraída del mapa observado de anomalías de Bouguer, obteniendose un mapa de anomalías residuales, dónde el mínimo relativo, coincidente con el área de máximo espesor del relleno de la cuenca queda bien delimitado por gradientes alineados
según las direcciones de las estructuras alpinas. Comparando ambos mapas se observa la mejor definición del gradiente que se extiende desde Sigüenza hasta Guadalajara y que corresponde a un cabalgamiento de dirección NE-SW, paralelo a las extructuras del borde sur del Sistema Central. Los
gradientes orientales están relacionados con fallas inversas y cabalgamientos de orientaciones NWSE y N-S que constituyen el borde de la Cordillera Ibérica y Sierra de Altomira. En el área occidental aparece un máximo relativo asociado a la zona de menor profundidad de la cuenca. Estas estructuras
condicionan la existencia de un depocentro en la zona NE de la cuenca de Madrid, individualizando la que podemos denominar subcuenca de Brihuega
The Bouguer gravity anomaly map of the NE zone of the Madrid Basin shows a relative gravity low related to basin tertiary infill and to low density rocks in the basement. A 2 I/2D gravity modelling of three profiles has been carried out to know the gravity sources. The relationship bewteen relative gravity lows and thicker tertiary sediments has been establish in the southern zone. However, in the northern area it has been necessary to introduce a low density body. Modelling results have been used to derive the three dimensional body formo The gravity effect of this body has been computed and it has been removed from the measured Bouguer anomaly map, obtaining a residual Bouguer anomaly map. The main relative gravity low, related to thicker basin infill, is enclosed by gradients oriented according to the the strike of alpine structures. A NE-SW gradient, better shown in the residual map, spands from Sigüenza to Guadalajara, and it is related to a thrust trending parallel to the structures of the southern border of the Spanish Central System. Eastern gradients are associated with thrusts and reverse faults of the Iberian and Altomira Ranges borders. A relative gravity high is located in the western boundary, where the basin is shallower. These structures bound a depocentre in the Madrid Basin, located in the Brihuega area
The Bouguer gravity anomaly map of the NE zone of the Madrid Basin shows a relative gravity low related to basin tertiary infill and to low density rocks in the basement. A 2 I/2D gravity modelling of three profiles has been carried out to know the gravity sources. The relationship bewteen relative gravity lows and thicker tertiary sediments has been establish in the southern zone. However, in the northern area it has been necessary to introduce a low density body. Modelling results have been used to derive the three dimensional body formo The gravity effect of this body has been computed and it has been removed from the measured Bouguer anomaly map, obtaining a residual Bouguer anomaly map. The main relative gravity low, related to thicker basin infill, is enclosed by gradients oriented according to the the strike of alpine structures. A NE-SW gradient, better shown in the residual map, spands from Sigüenza to Guadalajara, and it is related to a thrust trending parallel to the structures of the southern border of the Spanish Central System. Eastern gradients are associated with thrusts and reverse faults of the Iberian and Altomira Ranges borders. A relative gravity high is located in the western boundary, where the basin is shallower. These structures bound a depocentre in the Madrid Basin, located in the Brihuega area