The Quilici Formation was named for exposures along Quilici Creek in T. 44 N., R. 64 E., south of Blanchard Mountain in the HD Range (Riva, 1970).

The Quilici Formation is Middle Pennsylvanian (Desmoinesian) in age based upon fusulinid fauna (Riva, 1970). It is considered equivalent with the Tomera Formation. The Quilici Formation unconformably overlies Ordovician western assemblage rocks and is unconformably overlain by the Permian Buckskin Mountain Formation.

The Quilici Formation is composed of intensely fractured limestone and chert-pebble conglomerate. The basal 120 feet of the formation are composed of chert-pebble conglomerate with varicolored chert clasts in beds 1 to 3 feet in thickness (Riva, 1970). Thick ledge-forming gray limestone beds first occur in the upper 30 feet of the conglomerate and alternate with thin-bedded red weathering siltstone, and lenticular beds of chert-pebble conglomerate in the upper 230 feet of the formation. Two 3 foot thick rugosoid coral biostromes are present in the upper 60 feet of the unit (Riva, 1970).

The Quilici Formation is 350 feet thick in the HD Range.

The Quilici Formation has only been mapped in the HD Range.

The Quilici appears to be a time and probable lithologic equivalent of the Tomera Formation and may be allochthonous with respect to its initial depositional site. It represents shallow marine carbonate and clastic deposition in the Antler foreland to the east of the exposed and eroding allochthon. The Quilici like the Tomera probably was deposited relatively near the foreland margin with periodic influxes of coarse clastic debris as submarine sediment flows. Overall the unit probably represents submarine fan delta sedimentation.