This report isolates the two primary geologic divisions, the bedrock and the overlying unconsolidated material, by superimposing a topographic map of the present land surface upon a topographic map of the bedrock surface. To reconstruct the preglacial landscape it is necessary to identify and add to the existing bedrock surface the modifications effected by glacial and recent erosion upon the preglacial surface. The preglacial drainage is then shown by marking the ''thalweg'' (a line along the deepest part of the ancient valley) for various preglacial drainage ways. The alluvial gravels of these ancient valleys are commonly of economic significance.
Geiger, K.W. (1965): Bedrock topography of southwestern Alberta; Research Council of Alberta, RCA/AGS Earth Sciences Report 1965-01, 18 p.