The subglacial geomorphology of southeast Alberta: evidence for subglacial meltwater erosion

Abstract

A coherent pattern of landforms in southeast Alberta forms a subglacial landform continuum. Scoured bedrock tracts, flutes, transverse bed forms, and tunnel channels in this continuum are inferred to be products of erosion by turbulent subglacial meltwater flows beneath the Laurentide Ice Sheet. Bedrock and glacigenic sediment are truncated by an erosional surface. Flutes and extensive boulder lags across the truncation surface strongly suggest erosion by high-velocity turbulent flows. Tunnel channels dissect the erosion surface and record channelization of earlier sheet flows. Convex longitudinal profiles of channels indicate subglacial meltwater flow. Northeast-southwest trending transverse bed forms are superimposed on the preglacial divide and may be either glaciotectonic ridges or fluvial bed forms. Landforms reflect the dominance of erosion in the subglacial environment, likely by catastrophic meltwater flows of the Livingstone Lake megaflood event. The subglacial meltwater hypothesis accounts for each of the above landforms observed in southeast Alberta and suggests a less complex subglacial system than hypotheses requiring multiple processes to account for the landforms.