Abstract

The drumlins in the Dollard area, Saskatchewan, are short streamlined hills, composed of stratified drift and till. Some of these drumlins are believed to represent former kames overridden by the ice. Extensive exposures of one drumlin reveal its internal stratigraphy and structure. The frontal part, facing the direction of ice movement, consists of stratified sand and gravel. The tail probably consists of till, with minor intercalations of gravel. Separating these two parts is a vertical wall of stratified drift consisting of large boulders, cobbles, and pebbles in a matrix of coarse sand. The boulders in this wall have fractures which can be considered joints as they are arranged in a well-oriented system. Analysis of the joints shows two sets of shear joints and one of extension joints. Boulders of dolomite and limestone have both extension joints and shear joints; boulders of granite have shear joints only. The joint pattern indicates that a simple compressive force acted on the wall in the drumlin which was confined above and below. The direction of this force was parallel to that of the ice movement as indicated by the long axis of the drumlin. The joints are, therefore, interpreted to be the result of pressure by moving ice against the frontal part of the drumlin.

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