A deep geoelectrical survey in the Southern Central Alps

A deep geoelectrical survey was carried out on the Southern Central AIps, to the north of Bergamo, by means of the “continuous polar dipole-dipole” electrode array. Among the 6 profiles executed, 4 revealed the existence of a substratum with very high resistivity values (15 000-40 000 ohm.m) and a flat not very deep upper boundary; its thickness exceeds the maximum expIoration depths of the soundings (1 to 6 km). On the grounds of general considerations and resistivity field data set, it is possible to infer that the high values should be ascribed to endogenous rather than to sedimentary rocks. A problem arises since these geophysical results are not in agreement with some geological models.