Integrating DEM and field data to unravel the impact of bedrock topography on Late Quaternary ice flows: A case study of the Lake Mistassini area, Canada

The topography of bedrock beneath an ice sheet is one of the several factors that influence the flow of ice. It has the potential to change the direction of ice movement, which can lead to confusion when interpreting glacial striae and landforms. In the Mistassini area in Canada, formerly glaciated by the Laurentide Ice Sheet during several phases of the Quaternary, we used a high-resolution digital elevation model to calculate hillshade, slope gradient, and slope aspect. These derived topographic parameters were then combined with mapped glacial indicators to investigate how the underlying bedrock topography potentially influenced the direction of ice flow. The results show that during the older southeastward (SE) event, there was a notable deflection of the ice towards the south in the southern part of the study area. During the southward (S) event, and to a lesser extent south–southeastward (SSE) event, the impact of bedrock topography on ice movement appears to be less pronounced than during the previous southeastward phase (SE). As the ice gradually thinned during the final south–southwestward flow (SSW), the ice sheet became increasingly sensitive to the local bedrock topography. This sensitivity was particularly pronounced in the southern part of the area, where a dominant north-south topographic pattern constrained the ice to flow towards the south. This study demonstrates the feasibility of conducting a quick assessment of the influence of bedrock topography on paleo-ice flows through morphometric analysis of current topography and glacial evidence preserved on bedrock surfaces.