Geophysical signatures of a basic-body rock placed in the upper crust of the External Zones of the Betic Cordillera (Southern Spain)

The combined use of different geophysical techniques (seismic tomography, gravity and magnetic research) carried out in the External Zones of the Betic Cordillera (Southern Spain) points to the existence of a controversial set of anomalies. The high resolution seismic tomography clearly indicates a fast anomaly of up to +7% P-wave velocity, and the surface magnetic and aeromagnetic measurements also show a positive anomaly. The negative anomaly of the dipole is very smooth. However, the estimated Bouguer anomaly values are clearly negative. This set of anomalies has been interpreted as due to a basic-body rock (gabbros) located in the upper crust. The existence of this body suggests that the Iberian Massif constitutes the basement of the External Zones of the Betic Cordilleras, up to near the boundary with the Internal Zones.