A detailed structure contour map of the sub-Cretaceous unconformity within the Western Canada basin was analyzed by spatial filtering to display the sizes and trends of contained features for interpretation. Spatial filters are applied by computer to digital maps for the extraction and display of individual features free from the distracting presence of conflicting larger and smaller scale trends. The original maps were automatically posted using well information, well identification (X-Y location), and geologic correlations obtained from a computer file of drilling history on over 70,000 wells. This file contains information on wells in the sedimentary basin east of the structurally disturbed belt from Alberta to Manitoba.

The data were contoured manually then the contours were digitized for the computer analysis. Four nondirectional, bandpass filters were used to display structures ranging in width from 20 to 40 km (12 to 25 mi) and two directional filters to enhance structures with northeast-southwest and northwest-southeast trends.

The filtered maps indicate that the structures are controlled largely by the basement trends and are dominantly tectonic in origin with the frequency of structures increasing toward the disturbed belt. In addition to the tectonic structures, there are areas of Manitoba and Saskatchewan where solution of the Devonian salt formations produced prominent collapse features. The filtered structures suggest that Precambrian basement trends have controlled both the tectonic and erosional patterns of the sedimentary section and have subsequently influenced the migration and entrapment of petroleum and natural gas.

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