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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 center. The mapping was conducted to determine the distribution nd stratigraphic relationships of the surficial materials. Such information provides an important data base on resources, construction conditions, and potential geologic hazards and as such will assist in planning of development as well as in the early design stages of specific projects in the Calgary urban area.The area extends from the foothills in the southwest to the plains in he east The eroded bedrock surface, with local relief of as much as 200 m, is draped by surficial deposits that range in thickness from less than a metre to more than 85 m. Underlying the plains in the east, the bedrock consists of flat lying to gently dipping sandstone, siltstone, and shale of the Porcupine Hills Formation of Cretaceous or Paleocene age. In the foothills zone in the western art of the area, steeply dipping folded and faulted Cretaceous marine hale alternates with marine marginal and continental sandstone and siltstone beneath the north-northwest trending valleys and foothill ridges respectively.The surficial materials, which were mapped to a depth of 6 m, consist dominantly of loamy to clayey glacial till and clayey to silty glacial lake sediment. Six distinct stratigraphic units have been mapped within the glacial six sequence. The various stratigraphic nits within the till sequence are differentiated by both field- ecognizable and laboratory determined compositional differences including pebble composition, grain size, carbonate mineral content, clay mineral composition, and petrology of the very coarse sand.The gravel deposits throughout the area constitute the most significant economic resource within the surficial materials. Extensive deposits of gravel of Tertiary age cap the Broadcast and Big Hill-Nose Hill uplands beneath a till cover. Other major gravel deposits include as much as 10 m of early Pleistocene gravel covering the floor of the preglacial Bow River valley, and the late Wisconsinian valley floor deposits along the Bow and Elbow Rivers and their major tributaries. This resource has been rapidly consumed or een made unavailable for development by the rapid expansion of the City of Calgary during the past two decades.No significant geologic hazards are present 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 geologic 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 eneath a thin cover of till or lake sediment in many parts of the area results in difficult digging conditions that can significantly ncrease construction costs.The surficial materials in the Calgary area are the products of erosional and depositional activities of rivers, lakes and glaciers cting over a period of several tens of millions of years. During the middle and late Tertiary, rivers flowing out of the mountains eroded the early Tertiary and Cretaceous bedrock, leaving remnants of their gravel-covered valley floors on the major uplands in the area. Erosion continued into the early Pleistocene with the ancestral Bow River cutting its valley nearly to the level of the present valley floor. The gravel deposits of this river are buried beneath the earliest glacial sediment recognized in the area, the weathered pre- py Hill till. This till was deposited by a prelate Wisconsinian lacier that advanced from the mountains to the west. Some time around 25 000 years before present, the late Wisconsinian
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