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Summary Heat flow values have been determined for three areas in western Canada by a combination of temperature gradient measurements in abandoned oil wells, and thermal conductivity determinations on core samples. The heat flux ranges from 1.46 × 10‐6cal cm‐2 s‐1 in central Alberta to 2.00 × 10‐6 cal cm‐2 s‐1 for a well near the Arctic Circle. Possible disturbances in the temperature gradients tesulting from oil production and from surface temperature inequalities are considered.

This paper presents a generalized cross-section of the electrical conductivity structure in eastern Canada, based on magnetotelluric interpretation at 16 stations. Observations of the electric and magnetic fields at periods between 15 and 10 000 s were fitted to two-dimensional models of the crust and upper mantle. Although the results at some stations were influenced by local surface geology and the effect of conductive salt water in the St Lawrence River and Gulf, the models show a marked contrast between the Precambrian Shield and the northern Appalachians. Beneath the Shield, the lower crust is relatively conductive, while the uppermost mantle is resistive, while to the south-east in the Appalachians the situation is reversed. The change in pattern does not occur at the Shield boundary, but further to the south-east, and it is proposed that the boundary may be related to the site of a proto-Atlantic Ocean.