First used as a field name for a thick (in excess of 4,260 feet) coarse red and green conglomerate on and near Hilton Ranch in Davidson Canyon, Pima Co, AZ in the Basin-and-Range province. Conglomerate is dusky red and of cobbles and boulders derived from underlying Cretaceous sedimentary rocks and volcanic flows. The matrix is medium- to coarse-grained, angular to subrounded sand cemented with silica. Conglomerate is interbedded with white to light-gray tuff, purple andesite flows, and white or gray quartzite. Lenses of black or gray sedimentary breccia composed of platy cobbles and pebbles of laminated limestone and siltstone derived from the Apache Canyon or Shelleburg Canyon formations. Lateral rapid changes in grain size and color. No fossils found. Unconformably overlies Turney Ranch formation (first published use). Thought to be the same age as Fort Crittenden formation, or Late Cretaceous.

Source: GNU records (USGS DDS-6; Denver GNULEX).