Ice-thrust features and the Maymont landslide in the North Saskatchewan River valley

Abstract

The Battleford glacier created shearing and softening of bedrock clays, contributing to widespread slope instability along the valley of the North Saskatchewan River. The Battleford glacier flowed southeastward down the valley of the North Saskatchewan River during its final stage in west-central Saskatchewan. It created flutings, crevasse fillings, folding and faulting in ice-thrust ridges, and extensive horizontal gouge zones filled with soft, malleable clay. Extensive drilling and testing for the foundations of the Maymont bridge provided definitive data outlining at least three gouge zones. The shallowest gouge zone at an elevation of 465 m defines the base of the most severe glacial folding and deformation of the bedrock in at least one of the ice-thrust ridges. The deeper gouge zones are at about 433 and 438 m elevation. Postglacial landslides (slumps) along the southern side of the North Saskatchewan River are controlled by the gouge zones, which are low-friction slide surfaces along which large horizontal movements took place. Multiple normal faults and graben structures in the landslide mass could have been the mechanism for horizontal movement and extension with little or no rotation. Two main slide masses have been identified: the lower one moved on the middle gouge zone (438 m), and the upper one moved on the upper gouge zone (465 m).