| The study of the ice-thrust terrains found in central and southern Alberta indicates that macroscopic deformations due to ice thrusting include concentric folds, fault-bend folds, disharmonic folds, normal faults, strike-slip faults, thrust faults with stair-case geometry, sole thrusts or decollements in the form of shear zones, and duplex structures.;Facies and fabric models were applied to show the relationship between the regional bedrock topographic configuration and the occurrence and attitudes of ice-thrust features. Three glaciotectonic facies are recognized in central and southern Alberta: (1) Escarpment, (2) Valley, and (3) Plains.;Field observations and stability analyses suggest that glaciotectonism in the study areas is caused by foundation failure at the snout of a subpolar ice sheet when its marginal stagnant and frozen area is compressed by the active-flowing upglacier ice and the corresponding earth pressure in the strata.;Applications of glaciotectonics include ice direction indicators, site investigations, interpretation of laboratory test results, slope stability problems, and mechanics on glacier surge and ice-rock avalanches.;The ice-thrust argillaceous sediments found in the shear zone or sole thrust in Highvale mine were studied by means of the polarizing microscope and the scanning electron microscope. The observed fabric indicates that in addition to glaciotectonism, the ice-thrust sediments found in Highvale mine probably have been disturbed by permafrost, cycles of loading and unloading, and surface weathering. Laboratory work on fissured and brecciated ice-thrust sediments sampled from a bentonitic mudstone in the mine, indicates that the strength of these brecciated deposits is below the peak and, in general, close to residual. Slope stability problems found in the mine are related to the local joint systems and the horizontal shear zone or sole thrust formed by ice thrusting. The intersection of the steeply-inclined local joint sets with the flat-lying shear layer, which has a strength close to residual, permits slope failure to take place readily. |
