The influence of tectonic boundaries on geomagnetic variations in the Scotia Sea

Geomagnetic variation fields recorded at a particular location can be analysed to provide information on the distribution of induced currents within the Earth. An analysis of the variation fields on South Georgia, in the Scotia Sea, has revealed some unusual features in the geomagnetic response characterizing the distribution of internal currents. Both vertical and horizontal components of the variation fields appear anomalous with respect to the behaviour expected for a deep ocean island such as South Georgia. It is suggested that the anomalous variations can be accounted for by lithospheric conductivity contrasts between the older South American and much younger Scotia plates.