This dataset is a GIS version of part of Map 227, which is a regional synthesis of various published and unpublished maps. The data represent drift isopachs for Alberta. The southern part of Alberta, from 49 to 56 degrees north, was primarily compiled from existing 1:250,000 bedrock topography maps. The interpretation of the remaining northern portion of the province was based mostly on limited borehole data and information from existing 1:250,000 hydrogeological maps. The exposed areas represent areas where drift is absent or thin and discontinuous. Contour intervals are irregular and depend on local data density.