Electrical conductivity and tectonics of Scotland

Abstract

A REGION of anomalously high electrical conductivity in southern Scotland, known as the Eskdalemuir anomaly, has been discovered and mapped, in terms of related anomalies in time-varying geomagnetic disturbance fields1,2. Magnetotelluric soundings3 have indicated the depth of the conductor as 12 km, at which depth Jacob4 has reported an anomaly in seismic wave velocities. Bamford and Prodehl5 have also found anomalous seismic wave velocities in this region. In 1973 the University of Edinburgh operated two magnetometer arrays which together covered nearly all of Scotland. In each array 20 three-component recording magnetometers of Gough–Reitzel type6 were operated for 6–8 weeks. These arrays, together with extended magnetotelluric study of the Eskdalemuir anomaly7, now make possible a fuller description and interpretation of conductive structures. Data from stations north of the Midland Valley, where only limited geomagnetic variation studies 8,9 had preceded ours, indicate further regions of anomalously high conductivity in Scotland. Full discussion and analysis of these data will be presented elsewhere. This note gives some preliminary indications of these conductivity anomalies and suggests possible tectonic implications.