We’ve just uploaded the next of our free STATEMAP quadrangle map products to our online store: the Geologic Map of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado. The STATEMAP series in general provides a detailed description of the geology, mineral and ground-water resource potential, and the geologic hazards of an area. Digital PDF/ZIP download.
Matt Morgan, Senior Research Geologist and CGS Deputy Director, along with Senior Engineering Geologist (Emeritus) Jon White generated this map with special input from Richard Madole (surficial geology) and Shannon Mahan (OSL analysis), both of the USGS. This free release from the CGS includes two PDF plates (with a geologic map, cross-section with correlation, oblique 3D view, and legend) along with the corresponding GIS data package that allows for digital viewing, all in a single ZIP file.
This mapping project was funded jointly by the U.S. Geological Survey through the STATEMAP component of the National Cooperative Geologic Mapping Program, which is authorized by the National Geologic Mapping Act of 1997, and also by the CGS using the Colorado Department of Natural Resources Severance Tax Operational Funds. The CGS matching funds come from the severance paid on the production of natural gas, oil, coal, and metals. Geologic maps produced through the STATEMAP program are multi-purpose information sources useful for land-use planning, geotechnical engineering, geologic-hazard assessment, mineral-resource development, and ground-water exploration.
Surficial deposits consist of middle Pleistocene to Holocene flood-plain and terrace-forming alluviums and Holocene sand deposits of predominantly eolian origin. The sand deposits are composed of disaggregated sediments derived from the weathering and subsequent mobilization of the underlying Dawson Arkose. New Optically Stimulated Luminescence (OSL) ages, collected during this project, indicate that these eolian deposits were first active during the lowermost Holocene. High-level gravel deposits of Neogene-early Quaternary age cap isolated buttes in the southern half of the quadrangle. These gravels consist of cobbles and boulders of granite, quartzite, sandstone and tuffaceous igneous rocks and were likely derived from the erosion of the late Eocene Castle Rock Conglomerate.