ABSTRACT

The glaciated northern Great Plains contains a number of major escarpments separating various upland and lowland regions. Numerous divergent hypotheses to explain the origin of these escarpments, proposed in the geological literature, are briefly reviewed. The method of multiple working is then applied in a brief analysis of the problem.

Hypotheses suggesting structural origins for the escarpments are rejected because they imply complicated patterns of folding and/or faulting. Hypotheses proposing preglacial erosion are likewise rejected because 1) they require erosion rates slower than expected, 2) they are inconsistent with the apparent lack of pre- Wisconsin glacial drift and 3) they imply a major northern sedimentary basin which does not exist.

A new hypothesis which combines elements of previously proposed hypotheses suggests the escarpments are the walls of large-scale regions initially produced by catastrophic floods related to advancing and retreating icesheets. The scour regions then channelled future glacial ice movements. Glacial ice streamlined the scour region floors and walls producing the modern landforms. This "new" working hypothesis suggests the northern Great Plains region has experienced significant erosion during one or more glacial episodes.