From Weyburn we drive southeast to Halbrite, then west a few kilometres to what we refer to as Valley of the Rocks--a "moonscape" of meltwater-eroded, complexly stratified, highly deformed bedrock (Fig. 18 and 19) upon which rest (often precariously) large clusters of glacial boulders of every size, shape and rock type (Fig. 20). The exposed strata must be close in age to the Cretaceous-Tertiary (KT) contact--a time, we are told, when the dinosaurs were "done in." The breathtaking panorama of broken and bent multicolored rock strata and myriad scattered boulders bring great joy and delight to the enthusiastic rock hound. How would you explain to a six-year-old how a slab of limestone rock came to perch on a clump of brown clay, the whole arrangement looking just like a giant toadstool (Fig. 21)? To the geotechnical engineer constructing

dams and impounding reservoirs, this landscape has quite another significance: a window into the effects of glaciotectonic disturbance of bedrock strata. Glacial ice thrusting has destroyed much of the continuity, strength and other engineering properties of the deformed beds. Being able to view such glacier-deformation effects--from the air (Fig. 22) and on the ground (Fig. 23) --is a rare occurrence on the prairie landscape of Western Canada. Close-up inspection of Valley of the Rocks suggests a further geotechnical problem: piping erosion of holes, called "jugs", in dispersive clay shale (Fig. 24). Their formation is a concern in dam foundations, where piping erosion channels in dam abutments often preferentially follow bedding and joint partings opened from the unloading effects of valley erosion and glacial rebound.

This window into folds and faults in the Souris River valley is also located close to PanCanadian Petroleum's multi-million dollar carbon dioxide injection project, with the CO2 piped from coal mines in North Dakota.

Q. Figs. 18, 19, 23 - From looking at bedding detail in highly deformed Cretaceous bedrock strata at Valley of the Rocks, west of Halbrite, how would you distinguish rock deformation effects (folds and faults) that might be associated with:

• glaciotectonic activity (glacial thrusting and shearing)?
• salt tectonics (salt dissolution in underlying Prairie Evaporite beds)?
• deep crustal tectonics (pervasive plate tectonic motion)?

Q. Fig. 24 - At Valley of the Rocks, what is the geotechnical explanation for the formation of vertical 'jugs' in Cretaceous bentonitic marine clay shale? What are the roles played by clay particles and by percolating pore water?