ABSTRACT

Most lineament interpretations from satellite imagery display the idealized picture of "single line" regional linear features generally trending northwest-southeast and northeast-southwest in the plains of Western Canada.

Thematic Mapper imagery, however, reveals distinctive and complex zones of intensive faulting and mega-fracturing, which may vary in width from a few kilometres to about 20 km. Most of these features have been active during the latest orogenies. However, a number of them must have been developed earlier as a result of interaction of repeatedly reactivated, deep-seated basement faults and "thin skin tectonics" of the overlying sedimentary sequences.

The regionally predominant rhomboidal pattern of faults appears to have played a significant role in the following geological processes, which are essential for successful exploration:

1. depositional control and diversification of facies
2. migration of hydrocarbons along concentrated pathways
3. creation of reservoirs and porosity; secondary migration

The mechanism that has reactivated faulting and controlled development of these regional fault patterns should be interpreted in the light of plate tectonics. Of particular importance is the recognition of westward continental drift, combined with collision(?), rotation, and transpressional underthrusting of the Canadian Shield Plate beneath the Cordilleran "semiplate". The interaction of "thin skin tectonics" with the basement structural grain has been combined with apparent eastward sliding of the top sedimentary sequences. This has resulted in partly displaced regional fault patterns at the surface, relative to the present position of basement faults.

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