It preserves fossils dating back to the Moscovian to Kasimovian Ages of the early Pennsylvanian.

[1][2] The formation consists of brown to gray shale alternating with thin ray ledges of limestone.

[1] Opercula of cephalopods (possibly Liroceras) have been found in the formation, as have shells of Bellerophon, Phestia, and Euphemites.

[5] The unit was designated the Bishop Cap Member of the Magdalena Group by L.A. Nelson in 1937.

[6] In 2001, B. Kues recommended abandoning the Magdalena Group and raising its members, including the Bishop Cap, to formation rank.