OF-24-01 Geologic Map of the Fort Collins Quadrangle, Larimer County, Colorado

The purpose of this publication is to describe the geology, mineral and groundwater resources, and geologic hazards of the Fort Collins 7.5-minute quadrangle. It is a continuation of field mapping work in the northern Front Range and Colorado Piedmont areas where the CGS has mapped multiple quadrangles, this one covering the area around the city of Fort Collins. Nearby published quadrangles include Timnath, Loveland, Windsor, and Severance. CGS geologists Kassandra Lindsey, Alexander Marr, and Emily Perman completed the field work on this project during the mapping seasons of 2023-24. Digital ZIP download. OF-24-01D

From the abstract:

The Fort Collins quadrangle is located in the northern part of the Colorado Piedmont section of the Great Plains, the northern part of the Colorado Front Range, and on the western edge of the Denver Basin. The Upper Cretaceous Niobrara and Pierre Shale underlie the quadrangle and record some of the final sequences of the Cretaceous Western Interior Seaway. They dip at around 25 degrees east on the western border of the mapped area, where the units form portions of the characteristic Front Range hogbacks. Bedding dips rapidly decrease to the east, reaching around 9 degrees east. A Laramide-aged anticline-syncline pair underlies the northern part of the mapped area. From the Middle Pleistocene through the Holocene, fluvial, mass-wasting, and eolian systems have deposited sediments that mantle much of the bedrock in the quadrangle. Alluvial deposits record periods of deposition and erosion associated with climate fluctuations during glacial and interglacial periods. Fluvial units in the quadrangle are quarried for aggregate resources. The most common natural hazards that occur in the mapped area are flooding in low-lying areas, especially adjacent to the Cache al Poudre River, and swelling and collapsing soils in areas underlain by the Pierre Shale and eolian sediments.