ABSTRACT

Field measurement of 863 joints at six locations in the Devonian Waterways limestone of the Fort McMurray area reveals the rocks to be fractured by two orthogonal regional joint systems. One system is made up of sets striking roughly north-south and east-west, whereas the other has sets striking approximately parallel and normal to the trend of the Cordilleran orogen to the west (about 50 degrees and 145 degrees). These strike directions of regional joint sets are present throughout central and southern Alberta (Babcock, 1973, 1974).

Two types of fractures are commonly seen in the McMurray Formation oil sands. Regional joints are present in ironstone horizons and at man-made outcrops distant from steep scarps in the oil sands. These regional joints have strike directions similar to joints in the Waterways Formation. Fractures parallel and perpendicular to the adjacent scarp face at valley sides and man-made scarps are most commonly seen at oil-sand outcrops. These are attributed to the exfoliation weathering of the sandstone.