The formation is exposed only in a small area of the southern Nacimiento Mountains.

No tabulate corals are found in the upper part of the formation, but here the diversity of chonetid brachiopods increases.

[1] Northrop and Wood recognized fossils of Schizophoria oklahomae, a lower Pennsylvanian brachiopod, at Guadelupe Box during their 1945 survey.

[3] Armstrong found additional examples of what he termed the Schizophoria oklahomae strata, and recognized that these were separated from the overlying middle Pennsylvania stata by an erosional surface, but did not assign a formal unit name to the beds.

[4] The formation was formally named by H. DuChene in 1973 for exposures near the Gilman Tunnels in the Jemez Mountains of New Mexico.