SOIL SURVEY

-11-Glacial processes are not however, the only factors which have influencedthe landscape of Yoho . Water erosion and mass wasting processes have also beenimportant since the retreat of the glaciers, and are still actively changing th elandscape . Drew (1975) indicates that the glacial activity was less extensive i nthe western portions of Yoho Park . Consequently, the valleys in the western portio nof the Park show more effects of water erosion and less of ice erosion than the valley sin the eastern portions of the Park, and there is a change from predominantly U-shape dvalleys in the east to predominantly V-shaped valleys in the west .As with the glacial deposits, alluvial and colluvial deposits generally contai na mixture of materials from various stratigraphic units . These deposits are generallycalcareous, reflecting the dominant bedrock . Textures of the alluvial deposits varywith the mode of deposition and the nature of the source materials, but in genera lare coarser than silt loam, and usually are gravelly and cobbly. Textures of thecolluvial deposits are influenced by the softness and composition of the local bedrock ,but again are usually coarser than silt loam and generally have abundant coarse fragments. Exceptions to the usually calcareous fans are found in the Lake O'Hara are awhere our observations indicate that there are alluvial fans whose compositions aredominated by Gog Group materials . These alluvial fans are coarse textured an dnon-calcareous . Also, in the Ice River area, there are alluvial fans which ar ecomposed mainly of igneous rocks . These fans are coarse textured and non-calcareou sand are unique to the Ice River area in Yoho . However the more usual (for Yoho )medium textured calcareous fans are also found in the Ice River Valley adjacent to ,and to some extent alternating with, the igneous fans .A recent report on the surficial geology of Yoho National Park by Drew(1975) provides a map at a scale of 1 :50,000 and a generalized discussion o fmaterials .