Tongue River Member

The Tongue River Member is the uppermost geologic member of the Fort Union Formation in Montana, North Dakota, Wyoming. The strata are yellow or light-colored massive sandstones and numerous thick coal beds.

The vertebrate fossil fauna includes fishes, turtles, crocodiles, and mammals. Mammalian genera known from rocks of both the Torrejonian and the Tiffanian land mammal ages (middle and late Paleocene) are present.