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Keywords:

  • glacial erosion;
  • quarrying;
  • abrasion;
  • overdeepenings;
  • glacial geomorphology;
  • Uinta Mountains

Abstract

We explore the relationships amongst bedding dip, basin aspect, and glacial landforms using field observations and GIS analyses of the northwestern Uinta Mountains of Utah. We examine basins on opposing sides of three ice divides in which quartzite beds of the Mount Watson Formation maintain a near constant dip. These areas provide contrasting relationships between ice flow and bedding dip directions while holding rock type and climate constant. We map the occurrence of three glacial erosional landforms: cliffs showing evidence of quarrying, scoured surfaces polished by abrasion, and overdeepenings. Cliffs and overdeepenings are more common in basins where bedding dips up-basin, while scoured surfaces are more prevalent where bedding dips down-basin. The significance of jointing in controlling glacial erosional forms is well established and we propose that bedding, as well as joints, dictates the geometry of quarried blocks and influences the spatial patterns of process dominance. Where bedding dips up-basin, the geometry of pre-existing weaknesses favours quarrying creating both cliffs and overdeepenings. In contrast, where bedding dips down-basin, block geometry does not favour the creation of overdeepenings via quarrying and exposed bedding planes are subjected to glacial abrasion, producing scoured surfaces.