Sixteen heat flow measurements have been obtained on the continental rise and slope off Nova Scotia and off the southern Grand Banks of Newfoundland. The mean of the 14 most reliable values is 48 ± 4 mW m−2 (1.15 ± 0.09 μcal cm−2 s−1), which is in agreement with the mean for previous measurements on ocean floor of age greater than 100 m.y. However, the heat flux from the crust indicated by the new values is significantly lower because of the heat produced in the some 5 km of terrigenous sediments underlying the stations. The low values could represent an edge effect between continent and ocean. Two lines of stations across the Nova Scotia rise show large heat flow variations. Numerical models indicate that the variations could arise from thermal refraction by high thermal conductivity salt, which probably constitutes the 'sedimentary ridge complex' outlined by deep seismic reflection profiles. The salt or evaporites formed in the restricted basin that was parallel to this rifted margin during the first phase of opening of the Atlantic Ocean. The heat flow variations measured on a profile perpendicular to the southern edge of the Grand Banks are smaller. This margin was a transform fault between Newfoundland and northwest Africa during the early ocean opening, so that the seafloor in the region of the profile was produced after the restricted basin phase of evaporite formation.