The late Upper Cretaceous non-marine Whitemud Formation of south-central and southwestern Saskatchewan and southeastern Alberta consists of kaolinitic, metamorphic lithic sands and silts, and kaolinitic clays. The sands and silts are not highly feldspathic as was originally thought. The major constituent is metamorphic lithic grains with minor kaolinitic clay and vermicular kaolin, clear angular quartz, chert, muscovite and minor amounts of volcanic lithic grains and feldspar. The upper part of the late Upper Cretaceous Eastend Formation, which conformably underlies the Whitemud Formation, consists of non-marine sands, silts and clays. Kaolin is very rare. The bulk of the sands and silts are composed of volcanic lithic (tuffaceous) grains with minor amounts of metamorphic lithic grains, clear angular quartz, chert, feldspar, muscovite and biotite.

The contact between the two formations may be transitional or sharp. It is characterized by the following changes from the Eastend Formation into the Whitemud Formation: an abrupt decrease in volcanic lithic grains; the appearance of kaolin; the disappearance of biotite and apatite; a slight increase in clear angular quartz and muscovite; a decrease in feldspar; a general increase

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in metamorphic heavy minerals; an increase in the percentage of ilmenite (both as solitary grains and intergrown with magnetite) which is altered to leucoxene.

The sediments of both formations were deposited on alluvial flood plains. The climate was warm and temperate with sufficient rainfall to produce periodic flooding.

On the basis of mineralogy, the Whitemud Formation is definitely a correlative of the Colgate Member of the fox Hills Formation in Montana and North Dakota.

The Eastend and Whitemud Formations were derived from Late Upper Cretaceous volcanic rocks, Precambrian and Paleozoic metamorphic rocks, and Paleozoic carbonates, all situated in Montana. Eastend sediments represent fast mechanical weathering of mountains of freshly extruded volcanic rocks, whereas the Whitemud sediments represent slow chemical weathering and leaching which predominated once the mountainous volcanic rocks were worn down. This deep chemical weathering altered the volcanic tuffs into kaolinitic clay at the source area; the kaolin of the Whitemud Formation is not derived from the weathering of feldspars at the site of deposition. The Whitemud Formation essentially represents an altered, concentrated form of the Eastend Formation.

It is suggested that the Frenchman and Ravenscrag Formations were also derived from late Upper Cretaceous and early Tertiary volcanic rocks in Montana. The Whitemud-like sediments in the Ravenscrag Formation have the same genesis as the Whitemud Formation.

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