urban geology of edmonton - bulletin 32
DESCRIPTION
An urban geology study of the Edmonton area was undertaken by the Alberta Research Council in response to the increasing demand for the geologic information needed to formulate land use plans based on natural capabilities and limitations of the area. Initially, the geologic framework was established; this was then used as the basis for outlining geologic factors that may affect development.The near-surface bedrock in the Edmonton area is the Upper Cretaceous Edmonton Formation except to the northeast of the city where the Belly River and Bearpaw Formations are present. The Edmonton formation consists primarily of bentonitic sandstone, siltstone and silty claystone, with coal seams and bentonite beds. The Belly River Formation consists of bentonitic sandstone, silty to sandy shale and carbonaceous claystone.The basic configuration of the bedrock surface was essentially determined during preglacial times by rivers flowing eastward from the Rocky Mountains; these established a series of dendritic drainage basins separated by low bedrock divides. In the Edmonton area, the Beverly Valley passes through the northern portion of the city and is the dominant feature of the bedrock topography; numerous tributary stream valleys are separated by flat-topped bedrock uplands. Preglacial sediments deposited along these ancient river channels are termed Saskatchewan gravels and sands.During the Pleistocene Epoch, the Edmonton area was glaciated, and sediments were deposited on the bedrock and on the Saskatchewan gravels and sands. Landforms resulting from glaciation include ground moraine, hummocky dead-ice moraine, stream trenches, kames, outwash deposits, pitted delta deposits and glacial Lake Edmonton sediments.Subsequent to glaciation, the North Saskatchewan River and several tributaries cut their present valleys, and alluvium has been deposited along the banks of most of these streams.The thickness of the surficial deposits overlying the bedrock is variable, ranging from only a few feet on bedrock uplands to greater than 250 feet (76 m) in the Beverly Valley.The most important natural resources in the Edmonton area are groundwater in the bedrock and buried channels, and sand and gravel in the buried channels and the North Saskatchewan River terraces. Other resources of lesser importance or lower potential include oil sand gas, coal, marl, ceramic and brick clay, silica sand, peat and salt.Data on the engineering properties of the geologic deposits have been integrated with information on the nature and distribution of the sediments and used as-a basis for preparing a series of land use maps on which the Edmonton area is rated in terms of the following factors:1.general construction conditions 2.suitability for solid waste disposal 3.susceptibility to erosion 4.slope stability 5.deep sewer construction.The main intent of these maps is that they be used as general guidelines for regional development or as a basis for conducting further studies. The maps should not be used in place of detailed site investigations because of the variability of geologic deposits over short distances.TRANSCRIPT
