The Kootenai was deposited in a foreland basin east of the Sevier thrust belt in western Montana.

The lithology consists of a basal conglomerate with overlying non-marine sandstones, shales and lacustrine limestones.

[1] The most common fossils found within the Kootenai Formation are gastropod, ostracod, and pelecypod shells.

Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

This article about a specific stratigraphic formation in the United States is a stub.