Magnetotelluric signature of the western Cantabrian Mountains

The magnetotelluric signature of the Alpine part of the Cantabrian Mountain s was investigated in a N-S magnetotelluric profile, from the Duero basin t o the Cantabrian shoreline. A two-dimensional conductivity model was obtain ed from the joint inversion of TM, TE modes and the geomagnetic transfer fu nctions. A shallow conductor associated with the sediments of the Duero bas in, and three north-dipping conductors in the upper and middle crust were d etected. Of the latter, one is interpreted as the sole detachment of the Ca ntabrian Mountains, whereas the others correlate with the Cabuerniga and Sa n Vicente de la Barquera faults. This geometry suggests that the Cantabrian Mountains comprise uplifted Variscan basement. A comparison with a seismic reflection profile shows a good correlation between these conductors and s eismic features. The lower crust is characterised by high conductivities.