[2] The formation contains fossil conodonts indicating that it ranges from Tournaisian to Visean (Early to Middle Mississippian) in age.

[1] The lower Caloso Member contains fossils of the brachiopods Beecheria chouteauensis and Spirifer centronatus and the fusulinids Latiendothyra, Medioendothyra, and Tuberendothyra.

The upper Ladron Member contains a diverse fossil assemblage, including brachiopods such as Rhipidomella and Linoproductus, blastoid echinoderms such as Pentremites conoideus, cnidarians such as Zaphriphyllum casteri, and numerous species of microscopic algae and foraminiferans.

[2] The Kelly Limestone was the principal ore-bearing formation of the historic Magdalena, New Mexico mining district.

The ore takes the form of replacement deposits in the limestone produced by nearby igneous intrusions.