Crustal Refraction Experiment: Yellowknife 1966

A crustal refraction experiment was carried out around Yellowknife, Northwest Territories, in 1966. The pattern of shots and stations was designed for time-term interpretation over a wide area, traversed by a more detailed line of interspersed shots and stations. The records were unusually simple, and nearly all arrival could be explained by a shallow surface layer (3.5±1.2 km at 5.5 km/sec) overlying a uniform crust (6.1±0.04 km/sec). No significant difference was found between the crustal thicknesses under the Slave and Churchill Precambrian provinces, but they are separated by a narrow belt corresponding to the east arm of Great Slave Lake, under which the crust is about 4 km thicker. The structural interpretation is supported by a study of the amplitudes of Pn. The upper mantle velocity west of the Precambrian margin (8.23±0.04 km/sec) was found to be higher than that east of the margin (8.10±0.03 km/sec). This may be related to an orogenic belt parallel to but west of the margin in late Aphebian time.