Modelización gravimétrica en 2 1/2D y 3D en la zona nororiental de la Cuenca de Madrid

Résumé

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 l/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 form. 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.