OF-13-05 Geologic Map of the Orchard City Quadrangle, Delta County, Colorado


The purpose of this map is to describe the geology, mineral and ground-water resource potential, and geologic hazards of this 7.5-minute quadrangle located west of Delta in western Colorado. CGS staff geologist David Noe and field assistant Michael Zawaski completed the field work on this project during the summer of 2009. The geologic map plates and the Authors’ Notes report were created using field maps, structural measurements, photographs, and field notes generated by the investigators. This mapping project was funded jointly by the U.S. Geological Survey (USGS) and CGS. USGS funding comes from the STATEMAP component of the National Cooperative Geologic Mapping Program, award number G09AC00192, authorized by the National Geologic Mapping Act of 1997, reauthorized in 2009. CGS matching funding comes from the Colorado Department of Natural Resources Severance Tax Operational Funds, from severance taxes paid on the production of natural gas, oil, coal, and metals in Colorado. Digital ZIP download. OF-13-05D

From the authors notes:

The Orchard City 7.5-minute quadrangle is located in Delta County, Colorado. The town of Orchard City lies within the quadrangle. It incorporates three former settlements: Austin, Cory, and Eckert (for a community history, see Delta, the largest town and county seat of Delta County, lies 4 miles to the southwest. The area is known for its orchards and agriculture. The highest elevation is on Cedar Mesa at the northeastern corner (6,370 ft). The lowest elevation (4,975 ft) is where the Gunnison River exits at the western edge. Four geomorphic areas comprise the quadrangle: (1) The Gunnison Uplift, in the southeastern corner is, where the Gunnison River carves a 500-ft deep gorge. (2) The broad, Gunnison River valley near Austin, in the southwestern part. (3) The southern flank of 11,200 ft Grand Mesa, in the northern and central part. This area contains tributary streams such as Tongue, Surface, and Currant Creeks. The tributary valleys are separated by gravel-capped mesas that include Cedar and Redlands Mesas, the “Surface Creek Surface” that extends from Cedaredge to south of Cory, and numerous smaller mesas. (4) Finally, shale badlands known locally as the “Adobe hills,” or simply, “the Adobes,” occur in the east-central part along State Highway 92, in the southern part around Peach Valley, and in the western part near the valley of Tongue Creek. Adobe hills flank many of the tributary valleys and mesas throughout the quadrangle.