Geology of the Athabasca Formation

A systematic study was made of the Athabasca formation to determine the history of its sedimentation, its regional correlation, and its age. This formation, covering an area of 40,000 square miles in northern Saskatchewan, is predominantly sandstone with minor shale and conglomerate beds. Shale chip fragments are abundant on bedding planes throughout the formation. The measurement of 1,200 crossbeds and other current features showed that the sands were carried into the basin from the east and southeast and that the lines of transportation converged as they passed towards the northwest. As the Martin formation north of Lake Athabasca was deposited in an area of high relief and the direction of transport of the Athabasca is towards this area, it seem unlikely that the two formations were deposited contemporaneously. The crossbedding of the Athabasca is predominantly in the form of narrow 'troughs' and the coarse material is poorly sorted and lensy, suggesting scour and fill deposition in the beds of fluctuating streams. The shale chips probably indicate extremely shallow water and temporary withdrawals. These and other data suggest that the Athabasca was predominantly a fluviatile deposit in a coastal plain environment. The sandstones are mature, with a small heavy mineral content and considerable chart. These data suggest that the sandstone is a multicycle product derived from a largely sedimentary terrain. The Carswell formation, a dolomite sequence overlying the Athabasca, is present as a ring of intensely folded strata about 18 miles in diameter. Basement gneiss outcrops within the ring suggesting a domal structure. The dolomite indicates that the predominantly fluviatile environment of the Athabasca was replaced by a marine environment. The Athabasca formation is locally folded and intruded by diabase dykes. Pitchblende veins that cut the formation have been dated as about 4x10 years. The Athabasca formation is probably of Precambrian age.