Pennsylvanian and Permian strata in the Whetstone Mountains are 4,700 feet thick and include, in ascending order: the Black Prince Limestone, Horquilla Limestone, Earp Formation, Colina Limestone, Epitaph Formation, Scherrer Formation, Concha Limestone, and Rain Valley Formation. Early Pennsylvanian (Morrowan) fusulinids are present locally in the Black Prince Limestone. Fusulinids are abundant in the lower and upper parts of the Horquilla Limestone and the lower part of the Earp Formation. Those from the lower 450 feet of the Horquilla are of late Atokan and early Desmoinesian age; those from the upper 250 feet of the Horquilla are of Missourian to early Virgilian age; and those from the lower part of the Earp Formation of middle to late Virgilian age-the highest collection from the Earp may be as young as early Permian. Fusulinids are also present locally in the upper part of the Concha Limestone and suggest an early Guadalupian age.

New species of fusulinids include Schubertella whetensis, Fusulina mescalensis, JWedekindellina pseudomatura, Dunbarinella sp. A, Triticites mcgrewensis, T. coronadoensis, T. bensonensis, T. whetstonensis, and T. southensis.