It preserves fossils dating back to the early Cretaceous period.

[1][2][3] The formation consists mostly of red to red-brown to gray or green shale, mudstone, and arkosic siltstone.

The base of the formation is a well indurated conglomerate derived from the underlying Paleozoic beds.

[1] The total thickness is up to 1,700–3,500 feet (520–1,070 m) but varies considerably over the region.

[5] The formation was first defined by Zeller in 1965 for exposures near the Hell-to-Finish tank in the southern Big Hatchet Mountains of New Mexico.