The Bull Canyon formation is part of the Chinle Group. These Upper Triassic sediments date from the Norian Stage, between 208.5 and 228 million years ago. Exposures can be found in Harding, Quay and San Miguel counties in eastern New Mexico. Primarily comprised of mudrock with bands of sandstone, this area is believed to have been an ancient floodplain.
Fossil remains of the following have been found in this formation: