It preserves fossils dating back to the early to middle Pennsylvanian.

[1] The Flechado Formation consists of low-feldspar sandstone and shale alternating with thin beds of limestone.

[3] The formation grades laterally into the La Pasada Formation to the south of the Rio Pueblo, with the clastic beds of the Flechado abruptly thinning and transitioning to carbonate beds of the La Pasada over a distance of about 5 miles (8.0 kilometres).

[1] The terrigenous sediments of the Flechado Formation were likely derived from the southern part of Uncompahgre uplift during uplift on the west side of the Picuris-Pecos fault.

[1] Fossils are scarce in the upper portion of the Flechado Formation, but middle Desmoinesian (upper Moscovian) brachiopods are found about 800 feet (240 meters) below the top of the formation.