Surficial Geology of the Calgary Urban Area

This study presents the results of mapping of the surficial material in an area of approximately 2985 sq. km with the city of Calgary at its centre. The mapping was conducted to determine the distribution and stratigraphic relationships of the surficial materials. Such information provides an important database on resources, construction conditions, and potential geological hazards to assist development planning.

No significant geological hazards are in the Calgary area, although slope failures are not uncommon on steep slopes, especially along the Bow River valley. Although failures have occurred in nearly all geological settings, the most common setting is in thick lacustrine sediment, especially where saturated permeable beds occur in the succession. The silt and very fine sand that make up much of the lacustrine sequence through the city are susceptible to rapid and severe gully erosion where exposed on even gently unvegetated slopes. The presence of quartzite gravel or very hard sandstone bedrock beneath a thin cover of till or lake sediment in many parts of the area results in difficult digging conditions that can significantly increase construction costs.