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DESCRIPTION MILE 0 Stop R1. Red Rocks overlook at RMAG plaque. From the aquifer standpoint, the following should be noted: The Fountain Formation (Pennsylvanian) and Lyons Sandstone (Permian) are most important aquifers in areas adjacent to and immediately east of the Precambrian terrain. Most wells completed in Fountain and Lyons strata yield less than 15 gpm. Overlying Lykins and Morrison strata are normally not developed as aquifers. The Dakota Group (South Platte and Lytle members) is utilized in localities on the dipslope and a short distance east of its contact with the Benton Formation. Fountain Formation - Unconformably overlying the Precambrian basement rocks in the northern part of the Denver Basin and conformably overlying the Glen Eyrie Formation in the Colorado Springs area are the continental deposits of the Fountain Formation. The dominant constituents of the for- mation are red, pink, and gray, cross-bedded, poorly sorted micaceous and arkosic, sandstones and conglomerates. Unevenly distributed throughout the formation are micaceous shales and mudstones, and locally thin beds of fresh-water limestone. Particle size ranges from silt to cobbles up to about six inches in diameter. The predominantl}~ red color of the formation is due to iron oxide cement, hematite films on sand grains, pink feldspar, and red interstitial argillaceous material. Silica and calcareous cement are present, but do not add to the formation's red color. The Fountain Formation ranges in thickness from about 800 feet near Golden to about 4, 400 feet in the Colorado Springs area. The reduction in thickness in the northern part of the project area is probably the result of thinning by one or more strike faults which occur along the foothills belt. The forma- tion dips eastward at slopes ranging from 35 to 85 degrees. 1.0 Road -left. Fountain/Lyons contact. Lvons Sandstone -The Lyons Sandstone of Permian age overlies the Fountain Formation and forms a continuous resistant hogback that dips eastward at slopes ranging from 35 to 75 degrees. The formation consists of yellowish- gray (south) to brownish-yellow, tan and pink (north) fine to medium-grained, thin bedded to massive, quartzose sandstone. The Lyons is locally arkosic and cross laminated. Lenticular layers of coarse channel conglomerate occur near its base near the vicinity of Kassler. Throughout most of the area where the Lyons is exposed, it is found to be friable. Predominant cementing materials are iron oxide and calcareous material. Iron oxide cement is more common in the lower portion of the formation and forms resistant sheets of maroon and dark reddish-brown sandstone. 8