Ice-shoved hills of Saskatchewan compared with Mississippi Delta mudlumps - Im plications for glaciotectonic models

The Dirt Hills and Cactus Hills of southern Saskatchewan are outstanding examples of large ice-shoved hills. Glaciotectonic models for the genesis of these and other ice-shoved hills fall into two groups: (1) models in which the glacier thrusts permafrozen strata and (2) models in which permafrost is not considered a prerequisite. Mudlumps of the prograding Mississippi Delta are deforming in a style and magnitude much like ice-shoved ridges. Mudlumps may be regarded as modern nonglacial analogs to large ice-shoved hills of Pleistocene age. Both situations share several traits in common; the only significant difference is the nature of the advancing load--glacier ice or delta sand. The increased load, in either case, caused compaction and overpressuring of incompetent strata and led to deformation and uplift of ridges in front of the advancing load. Loading by glacier ice during deformation of the Dirt Hills is estimated to have been triple the magnitude of loading associated with Mississippi mudlumps. Permafrost is not necessary for this style of deformation in either glacial or nonglacial settings.