Deep electromagnetic studies of the Baltic Shield

The first systematic collection of magnetotelluric, magnetovariational and frequency sounding results for the Baltic Shield is presented. The great variations in data processing and interpretation methodology make it difficult to present any unified summary of the existing results. Conductive regions in the crust occur in all parts of the shield; sometimes in connection with schist zones, variations in bedrock structure and composition, and sometimes as apparent conductive layering in the depth range 15-25 km. The extent of this layer, as well as the conductive layer at asthenospheric depths in the northern parts of the shield, cannot yet be established. The usefulness of combining electromagnetic and other geophysical data is indicated by the example from central Finland, where deep seismic sounding results seem to be able to explain long-period anisotropies of magnetotelluric sounding curves.           ARK: https://n2t.net/ark:/88439/y024024 Permalink: https://geophysicsjournal.com/article/295 &nbsp