Geoelectrical recognition of paleo-valleys in Ciudad Rodrigo Tertiary depression

The V.E.S. (vertical electrical sounding) study undertaken in the Ciudad Rodrigo Craben unravels the structure and the lithology of the graben infill. The basement resistivity values (200-350 Qm) indicate the presence of NW-SE oriented paleovalleys which were responsible for the tertiary drainage. The resistivity values of the tertiary rocks show the presence of sandstones and conglomerates (40-70 Qm), sand and clay (20-30 ?m) and claystone (10-18 ?m). Each of these groups can be correlated to Paleogene and Neogene rocks according to surface observation