OF-06-06 Geologic Map of the Palmer Lake Quadrangle, El Paso County, Colorado


The purpose of this map is to describe the geologic setting and mineral resource potential of the 7.5-minute quadrangle located in the northwestern part of El Paso County. Geologic maps produced by the CGS through the STATEMAP program are intended as multi-purpose maps useful for land-use planning, geotechnical engineering, geologic-hazards assessment, mineral resource development, and ground water exploration. Digital ZIP/PDF download. OF-06-06D

From the Author’s Notes:

The Palmer Lake quadrangle is located in the northwestern corner of El Paso County, Colorado, along the eastern flank of the Rampart Range. The U.S. Air Force Academy campus is in the southeastern part of the quadrangle. The small towns of Palmer Lake and Monument are in the northeastern part of the map area. Interstate Highway 25 is located just east of the quadrangle boundary. The Mount Herman Road transects the quadrangle from east to west and is the only public road passable by passenger vehicles to provide access into the Rampart Range.

The Rampart Range rises abruptly west of the Rampart Range Fault, which transects the quadrangle north to south. East of the fault zone is the comparatively subdued topography of the Colorado Piedmont. Elevation within the quadrangle ranges from roughly 6,800 feet along Hay Creek and Beaver Creek in the southeastern part of the quadrangle to 9,378 feet on an unnamed knoll along the Schubarth Trail in the southwestern part of the quadrangle. Mount Herman, which rises to 9,063 feet along the range front, is the most prominent peak in the quadrangle as viewed from the flatter and more populated eastern part of the mapped area and Interstate 25. Several creeks and ephemeral streams that originate in the Rampart Range flow from west to east across the quadrangle and are part of the Arkansas River drainage basin. The principal streams and drainages within the quadrangle are, from north to south, Monument Creek, North Monument Creek, North and South Beaver Creeks, Hay Creek, Deadmans Creek, and Goat Camp Creek. Most of the forested land in the Rampart Range is administered by the U.S. Forest Service (Pike Peak Ranger District, Pike National Forest). The flatter land in the eastern one third of the quadrangle, aside from the U.S. Air Force Academy, is mostly privately owned.

The oldest rocks exposed in the Palmer Lake quadrangle are granitic rocks of the late Mesoproterozoic Pikes Peak batholith, which forms the Rampart Range. Rocks of the batholith are faulted against Laramide-age synorogenic sedimentary rocks of the Dawson Formation along the Rampart Range Fault, a major north-south reverse fault that separates the Rampart Range from the Denver Basin. The fault also serves as the physiographic demarcation between the Colorado Piedmont and the Rampart Range physiographic provinces.

The Dawson Formation forms the bedrock in the eastern one-third of the Palmer Lake quadrangle. A 140- to 180-feet-thick remnant of Lower Paleozoic strata rests unconformably on Pikes Peak Granite in a fault-bounded block just west of the Air Force Academy, near Deadmans Lake. A wedge of Upper Cretaceous marine sedimentary strata is present in a tectonic sliver along the Rampart Range Fault in the northwestern corner of the Air Force Academy.