Much of the Norwegian upper crust was shaped by Caledonian thrusting and post-orogenic extension. We investigate the electrical conductivity structure of the crust and associated thrusts and detachments using magnetotellurics to obtain a better understanding Paleozoic tectonics. New magnetotelluric data were collected over an area of c. 60 × 70 km that includes the Gudbrandsdalen Antiform and Atnsjø tectonic window in central Norway.The final 3D electrical conductivity model reveals a highly resistive crustal block, extending E–W along the Gudbrandsdalen Antiform and from the surface to several tens of kilometres depths, imaging the parautochthonous Precambrian basement. No major thrust or detachment has been mapped under the Atnsjø tectonic window, which is therefore considered to most likely represent autochthonous or parautochthonous Baltica basement. Several conductors are imaged along the edge of the magnetotelluric survey, which can be correlated with a major Caledonian thrust and structures in the Precambrian basement.