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.