Print this page3-D Geometry of Compressional and Oblique Structures and Reactivated Normal Faults, southern Mackenzie Mountains, Canada
HODDER, DENISE N., DEBORAH A. SPRATT, AND DON C. LAWTON
Renewed seismic exploration and interpretation of the southern Northwest Territories and Yukon reveal a complex structural history of compressional and oblique motion on low angle thrusts, high angle reverse faults, and reactivated normal faults. Near 60 degrees N latitude, the Rocky Mountain fold and thrust belt deflects to the northeast across a northeast-trending lineament known as the Liard Line. Parallel to it, but oblique to the east-west trend of Laramide compression, are inherited features: the northeast-trending Bovie Lake Normal Fault and a zone of erosional and depositional pinchout of Lower Paleozoic strata whereby the thick strata of the Liard Basin (Depression) are absent to the southeast on the Liard High. The Devonian Arnica, Landry and Headless formations shale out northwestward into the basin and display changes in structural style. Numerous oblique structures point to a transpressional setting: asymmetric systems of northwest-trending normal faults at surface in the hanging wall of the LaBiche Thrust, several northeast and northwest-trending reactivated normal faults and associated folds recognized in the subsurface, the northeast-trending Liard Syndine, and the northeastward deflection of the Pointed Mountain Thrust.
National Energy Board and more recent industry seismic data, well data and surface maps are compiled and interpreted to analyze the 3-D variations in structural style and geometry. Seismic interpretations, balanced and restored cross-sections, and strike sections display the shaling out of facies to the northwest and reactivated high angle northeast-trending normal faults, particularly beneath the Beaver River, Kotaneelee and Pointed Mountain gas fields.