The bulk of the formation is dark shale with minor sandstone and black limestone.

The upper beds are tuffaceous sandstone with minor black limestone.

A basalt flow and an andesite breccia are present in the upper beds.

[3] Dinosaur remains of tyrannosaurs and hadrosaurs are among the fossils that have been recovered from the formation.

[5] These include possible remains of Albertosaurus[6] and a hadrosaur tail skin impression.