A KINEMATIC DISCUSSION OF THE FORMATION OF GLACIAL FLUTINGS

Abstract

ALTHOUGH MANY STUDIES have been made of so-called ice-moulded landforms, drumlins, drumlinoids, and flutings, their mode of genesis remains unsolved. The form of drumlins is quite distinctive; a quotation from Alden (1905) used by Chorley (1959) clearly sets down their salient features: “We may regard as a typical drumlin a hill of glacial drift which approximates the form of a segment of an elongated ovoid, of which the widest part of the basal outline and the highest point of the crest are not more distant from the stoss-end than one-third the length of the major axis and whose major axis is oriented parallel to the direction of movement of the glacier which formed it.” With extension of the length of the characteristic drumlin a gradation occurs into extensive linear features known as flutings. The longitudinal profile of flutings differs from that of drumlins in that the maximum crest elevation is maintained for large distances. However, flutings show the same parallelism with ice-flow direction and general streamlined form as drumlins. In this paper flutings refer to both the ridges and the adjacent grooves that make up the total landform. Generally this paper will be confined to larger-scale flutings as described by Smith (1948), Gravenor and Meneley (1958), Lemke (1958), and Freschauf (1971). The large-scale features range in scale from two to three metres high and several kilometres in length. Such flutings appear to be confined to North America. Smaller-scale features have been described from a variety of recently deglaciated areas (Hoppe and Schytt 1953; McPherson and Gardner 1969; Baranowski 1970), but these are not analogous with the large-scale features. Drumlins and flutings clearly differ in form, and it is pertinent to consider other properties which may provide information on their mode of origin. A wide variety of internal composition has been noted. Till is most commonly observed, but stratified drift is often found in both drumlins and flutings. The influence of bedrock may also be important; drumlins with bedrock cores have been widely described (Chamberlin 1883; Crosby 1934), and flutings in Alberta, Saskatchewan and the Northwest Territories, Canada, may also be developed in crystalline bedrock (Smith 1948). Long-axis orientation of stones in drumlins has been shown to parallel drumlin axes approximately (Hoppe 1951; Donner and West 1955; Wright, 1957). Hill (1971) shows similar results but emphasizes a significant scatter in mean directions obtained from different samples from a single drumlin. Andrews and King (1968) show increasing deviation between stone and drumlin orientations in samples taken from successively higher positions in a drumlin section. However, micro-fabric analysis on samples from glacial flutings (Gravenor and Meneley 1958) gave orientations of silt and sand particles parallel to the fluting crest to a depth of three metres. Below three metres particle long axes were found to deviate from the fluting crest. Some authors have proposed that there is a relationship between the occurrence of drumlins