Gravity and magnetic investigations along the Alaska Highway

A gravity and magnetic survey was made along the Alaska Highway between Dawson Creek, Alberta, and Fairbanks, Alaska, and 296 gravimeter stations were occupied. Ties were made to 10 pendulum stations covering a gravity range of 1486 mgls., and a calibration factor of 0.246804 mg!., per scale division was derived for the gravimeters. A study of profiles of elevation, Bouguer anomaly, magnetic intensity and lithology leads to the following general interpretation. A 60-mgl. negative anomaly a.cross the Rocky Mountains has been attributed to a 16,000-foot crustal downwarp, while an anomaly of similar magnitude but with steeper gradients across the Cassiar Mountains is considered to be due to a mass of low-density granite occurring within the mountain system.