It preserves fossils dating back to the late Pennsylvanian.

[1] The Holder Formation consists of limestone, red and gray calcareous shale, sandstone, and conglomerate.

[2] The formation is interpreted as a shallow-shelf marine formation of Virgilian (latest Pennsylvanian) age[3] during a global ice age.

[4] The unit was first named by Lloyd C. Pray in 1954[1] and a type section was designated in 1959.

[6] Pray originally assigned the formation to the Magdalena Group, but the Magdalena Group has subsequently been abandoned.