Samples from an almost complete core of the basal part of the Clearwater Formation and the McMurray Formation were examined for their microfaunal content. Twenty-one species of Formaninifera and one species of Ostracoda are reported from the Clearwater Formation, along with seven species of Foraminifera are described and figured.

The upper part of the McMurray Formation is demonstrated to be marine, deposited in a shallow, brackish-water lagoon, and is transitional from the lower, presumably continental beds of the Formation, upwards into the marine, epineritic shales of the Clearwater Formation. Using Foraminifera, the base of the Clearwater Formation and the upper part of the McMurray Formation are correlative with the upper part of the Loon River Formation, and the lower part of the Moosebar Formation.

Examination of heavy mineral residues from the McMurray Formation shows two distinct suites are present: first-cycle minerals derived from an igneous-metamorphic terrane, and second-cycle tourmaline and zircon derived from pre-existing sediments. Unstable and metastable minerals, such as amphiboles and pyroxenes, are absent or very rare.

Conclusions reached are that the upper part, and possibly all, of the McMurray Formation is middle Albian in age, deposited contemporaneously with and marginal to the westward-lying Loon River sea. Source of the sediments is to the east, derived in part from Precambrian igneous and metamorphic rocks, and in part from pre-existing sediments.

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