This GIS dataset is part of a digital compilation of the Precambrian geology of the Alberta portion of the Canadian Shield and Athabasca Basin. It is one of the datasets used to produce Alberta Geological Survey (AGS) Map 537.
For the Alberta shield, the compilation integrates detailed mapping by both AGS and the Geological Survey of Canada (GSC) at scales ranging between 1:31,680 and 1:250,000. Geochronological data and interpretations also helped prepare this dataset.
For the Athabasca Basin, the compilation incorporates the geology of the basin presented in the ExTech IV volume, published in 2007 by the GSC.
This dataset tries to present the geological information in a neutral manner, unbiased by the three mutually exclusive, regional tectonic concepts existing at the time of compilation. Users are encouraged to view AGS Map 537, which contains overviews of the geology of the respective areas and a complete reference list.
The polygon feature dataset came from existing, though largely unpublished, digital sources. Areas of the shield are mainly from digitized versions of AGS Maps 180 and 25: the shield north of Lake Athabasca and south of the Athabasca Basin, respectively.
The selected polygons were from GSC maps, which Alberta Geological Survey digitized, generalized and integrated into the compilation. The author gave new or updated descriptions to the map units and assigned them to the polygon attribute table.
1. North Shield: We started with an ArcGIS polygon coverage digitized from Alberta Geological Survey (AGS) Map 180 (unpublished). We generalized and/or edited the selected map units (high- and low-grade mylonites, Wallace Island Granite, Fishing Creek Granodiorite) to coincide with equivalent map units published by the Geological Survey of Canada. We coded the attributes for the map-unit labels and descriptions.
2. Athabasca Group: We started with a polygon shapefile of the Athabasca Basin supplied by Saskatchewan Industry and Resources. We also updated the attributes for the map-unit labels and descriptions.
3. South Shield: We started with an ArcGIS coverage of polygon linework digitized from Alberta Geological Survey Map 25 (unpublished). After which, we tagged the polygons with their original classifications, then grouped and reclassified them into one of five categories as defined by the author. The polygon boundaries were dissolved based on new classifications. We coded the attributes for the map-unit labels and descriptions.
The three datasets were appended into one layer of contiguous polygons. The layer incorporates the Devonian outliers from AGS Map 236 and AGS Earth Sciences Report 2004-01, Figure 5. The final dataset corrected misalignment errors at the edges of the differing data sources.