EVOLUTION OF QUATERNARY MAPPING IN ALBERTA: MEETING CLIENT'S CHANGING NEEDS

East of the Rocky Mountains and Foothills, Alberta has an extensive cover of preglacial, nonglacial and glacial unconsolidated sediments that exceeds 300 m in thickness in places. Multiple glaciations, in which ice sheets advanced up-drainage into Alberta, eroded the soft Cretaceous bedrock and buried the valleys that were incised during the late Tertiary and early Quaternary. This resulted in a present surface topography that has subtle relief compared to the underlying bedrock topography. Surficial and subsurface stratigraphic mapping continues to be an essential activity of the Alberta Geological Survey (AGS) by providing baseline information for the efficient and effective development of the energy resources and more recently for diamond and aggregate exploration. Current map products provide baseline information in digital vector format, 3-D visualizations of modeled surfaces, as well as grid data needed by other geological processing applications.

Recent demands by government, industry and academia provide impetus for creating additional map information, by processing and analyzing the baseline data to produce digital derivative maps with specific themes. Examples include aggregate and landslide inventory maps; key sediments initially identified on surficial geology maps are further analyzed to produce a derivative product that highlights a land resource or an geoenvironmental indicator, respectively.

The design of a glacio-stratigraphic architecture enables the differentiation of multiple glacial events in the Quaternary sedimentary succession, each of which have an associated diamicton (till) and stratified sediment assemblage. Subsurface mapping has identified major preglacial aquifers resting on bedrock valley floors, as well as intertill glacial aquifers, both types of which are major suppliers of high-quality water needed in the steam-enhanced thermal recovery methods used to extract bitumen from oilsands. Recent discoveries of economical deposits of natural gas that have migrated into permeable glacial aquifers at depths as shallow as 70 m from surface illustrate the importance of mapping for energy resource and drilling-safety needs.