Abstract: 3-D Geometry and Structural History of the Southern MacKenzie Mountains, Northwest Territories, Yukon and British Columbia, Canada

At 60 degrees N latitude, the Rocky Mountain fold and thrust belt has a prominent deflection to the northeast. The southern MacKenzie Mountains study area was selected to examine this deflection by mapping the 3-D geometry of observed and interpreted surface and subsurface structures and to decipher the complex structural history of the study area. The objective is to determine what causes the oblique trend of several structural elements and the changes in structural style associated with facies variations in Paleozoic strata. Palinspastic restoration of these structures and facies is constrained by all available surface and subsurface data.

Seismic interpretation has examined two structures that are oblique to the general E-W trend of Laramide compression: the NE-SW trending Pointed Mountain Thrust and a NW-SE trending anticline. The interpretation shows a number of key features: the existence of an original extensional geometry, which is evident from the thickening and thinning of strata; subsequent overprinting by Laramide compression involving either reactivation of the normal faults or development of new thrusts localized at sites of normal faulting; and the existence of a middle to lower Devonian detachment fault. High resolution aeromagnetic data show numerous cross-trending features that coincide with the trend of the NW-SE trending anticline and appear to offset structures at the surface. In addition, a magnetic high occurs at the southern termination of several of the structures and is sub-parallel to the NE deflection of the fold and thrust belt. A second magnetic high occurs along the easternmost extent of the deformed belt.
 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid