ABSTRACT

Reinterpretation of reflection seismic profiles shows a well defined Proterozoic compressional orogeny in the Anderson Plains of the Northwest Territories. Industry reflection seismic data reveal that beneath a thin (1-3 km) and relatively undeformed Phanerozoic section there are large, southeast-directed thrust faults. These faults have strike lengths at least as large as 60 to 70 km and individual displacements of approximately 5 to 10 km. The total shortening is estimated to be at least 20 per cent over 150 km. A northwest-dipping detachment to these faults is inferred to exist at 12 to 15 km, at or near the base of the seismic profiles. The age of the deformation is seen to be syn- and post- the deposition of the Dismal Lakes Group. It is also found that some Proterozoic-aged faults appear to have been reactivated during Phanerozoic deformation periods. The stratigraphy of the Proterozoic rocks is not well defined but with correlations from well data to the south and seismic character correlation ties from the Campbell Uplift, it is interpreted that the sub-Paleozoic unconformity overlies the Mackenzie Mountains supergroup in the western part of the study area and the Dismal Lakes Group in much of the eastern part. The Dismal Lakes unconformably overlies the Hornby Bay Group, the base of which may or may not be identified near the maximum record length of the seismic profiles.

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