Development, Stratigraphy and Summary Diagenetic History of the Athabasca Basin, Early Proterozoic of Alberta and Its Relation to Uranium Potential

The Athabasca Group in Alberta was deposited between 1730 Ma and 1600 Ma in four sequences, separated by unconformities, and largely deposited in separate sub-basins, in a tectonic environment dominated by regional compressive stress. Reorganization of basin architecture, major changes in grain size and changes in drainage directions distinguish the sequences. During sequence 1 and 2, the locus of deposition shifted from west to east in response to the after effects of the Trans-Hudson Orogen and coeval orogens. Sequence 1 is largely restricted to the Jackfish Basin in the northwestern quarter of the Athabasca Basin. Sequence 2 is developed most prominently in the Cree Basin in Saskatchewan. Sequences 3 and 4 appear related to more distant compressional forces along the margins of the continent and were deposited in the more central Mirror Basin, partitioned by later faulting into a number of troughs. Sediments deposited during later deepening of the basin have been removed by erosion and are likely to have been deposited under conditions of regional tensile stress.

Uranium mineralization in and near Alberta is related to repeated, but minor, reactivation of major shear zones bordering the Athabasca Basin and its sub-basins, and is usually found where two major fault systems intersect. Disruption of the basal unconformity by faulting, accompanying the later stages of basin growth or deformation, facilitated the development of the hydrothermal systems that emplaced the uranium.