Evidence from seismic reflection profiling, drill holes, potential field measurements and regional geology shows that an east verging Proterozoic thin-skinned thrust and fold belt is situated beneath the Interior Platform of northwestern Canada. Balanced cross sections and associated palinspastic reconstructions provide constraints on the extent of the shortening in the thrust belt and suggest that at least 50--90 km of compression can be accounted for.

Although the Proterozoic stratigraphy in the subsurface is not well known, the cross sections are constrained essentially by seismic reflection geometry. Shortening occurred on subhorizontal detachment(s) that lie above the autochthonous (Hudsonian?) basement. Seismic reflection data from the area west of the major thin-skinned thrust structures show that the Proterozoic strata there can be traced for up to 100 km and are characterized by broad, open folds with wavelengths of 10 km or more. Uniform potential field anomalies and subhorizontal seismic reflections further indicate that there ae no mjaor crustal boundaries (such as sutures) in the area between the thrust belt and the Campbell uplift near Inuvik, Northwest Territories, that were associated with the thrusting. The detachment(s) that carried the folded and thrust faulted allochthons must therefore extend for a considerable distance to the northwest of the thrust belt. New deep crustal seismic reflection data from the Campbell uplift, however, show evidence for crustal-penetrating Proterozoic structures that dip northwestward and that were probably reactivated during late Paleozoic compression and Mesozoic extension.

Taken together, the various data thus indicate that the area from Great Bear Lake to the Campbell uplift (about 400 km) is underlain by a mid-Proterozoic decollement above which the compressional deformation took place, and that the deformation extended to the north side of the present Campbell uplift where steeply north dipping structures indicate that the underlying autochthonous basement is characterized by a ramp structure that was probably associated with the southern edge of a Proterozoic basin. ¿ American Geophysical Union 1988