Criteria for Differentiating the McMurray and Clearwater Formations in the Athabasca Oil Sands

In the absence of fossil evidence the presence of the following minerals in a sample of Athabasca oil sand identifies it as belonging to the Clearwater Formation: (1) glauconite pellets, (2) euhedral biotite flakes, (3) montmorillonite, (4) euhedral grains of plagioclase feldspar. Other diagnostic characteristics of the oil sands of this formation include the presence of felsite grains and of more than 10 per cent of chert grains in the sand fraction.