Special Report 072

Special Report 072

SPE 072

Basement structure in central and southern Alberta: insights from gravity and magnetic maps

Author(s) Lyatsky, H.V. Pana, D.I. Grobe, M. Date 2005-10-01

Identification of brittle faults in the Alberta Basin is critical to hydrocarbon and mineral exploration, as well as to greenhouse-gas geological sequestration studies. Many faults affecting the Phanerozoic sedimentary rocks of this basin are well known to be basement controlled. Potential-field data can give valuable information on the location of faults in the basement. These faults may have propagated into the overlying sedimentary rocks and influenced fluid flow and distribution of hydrocarbon traps and mineralization zones, as well as salt dissolution and carbonate alteration. The present study used regional, publicly available gravity and aeromagnetic data compiled and levelled by the Geological Survey of Canada to identify geophysical lineaments that may represent basement faults in the central and southern Alberta (south of 56 degress N latitude).

The crystalline basement in central and southern Alberta includes Archean and Early Proterozoic ductile orogenic structures and Middle Proterozoic to Recent cratonic structures.

Although anomaly signatures of the ancient ductile basement structures predominate in potential-field maps, it is brittle, high-angle block-bounding faults that had the most influence on the evolution of the Alberta Basin. These steep, brittle basement faults are much more subtle and less easily detectable; many of them are sub-resolution seismically. Gravity and magnetic data processing and anomaly-enhancement experiments revealed many gravity and magnetic lineaments defined by gradient zones, alignments of separate local anomalies of various types and shapes, aligned breaks or discontinuities in the anomaly pattern, etc. Such lineaments are commonly associated with brittle basement faults.

The results of gravity and magnetic data processing are provided here as a catalogue of maps with inferred lineaments, as well as geographically referenced geotiff files (potential-field maps) and DXF files (lineament maps).

Lyatsky, H.V., Pana, D.I. and Grobe, M. (2005): Basement structure in central and southern Alberta: insights from gravity and magnetic maps; Alberta Energy and Utilities Board, EUB/AGS Special Report 072, 76 p.