OF-20-04 Geologic Map of the Cedaredge Quadrangle, Delta County, Colorado


The purpose of this publication is to describe the geology, geologic resources, and geologic hazards of this 7.5-minute quadrangle. It is a continuation of field mapping work on the Western Slope of Colorado where the CGS has cumulatively mapped 18 other quadrangles. CGS Senior Engineering Geologist Jon White (emeritus) completed the field work on this project during the summer and fall of 2020 and 2021. Digital ZIP download. OF-20-04D

From the Physiographic Setting:

The Cedaredge quadrangle lies in Delta County, Colorado, approximately 20 km northeast of the town of Delta. The town of Cedaredge is in the lower central part of the quadrangle along the north-to-south aligned State Highway (SH) 65 that bisects the map area before meandering up into steeper slopes towards Grand Mesa. These steeper slopes in the upper third of the map area are part of the southern flank of Grand Mesa and are characterized by higher elevations and hummocky, south-facing slopes underlain by landslide deposits with abundant basaltic surface boulders. The upper hummocky terrain transitions southward to lower-gradient mid-elevation bouldery mesa surfaces near Cedaredge. The highest elevation of Cedaredge quadrangle is 2,986 m above mean sea level (AMSL) at the northwest map corner within higher elevation landslide terrain in the Grand Mesa National Forest. The lowest is 1,662 m AMSL at its southern boundary where Ward Creek exits the quadrangle. The annual precipitation in the map area ranges from 91 cm along the northern map area where alpine forest is predominant, through a mid-elevation semi-arid pinyon-juniper woodland climate of the high alluvial mesas, and to a low of 31 cm at the more arid, lower elevation, southwest flank of the map area where sparsely vegetated shale (“adobe”) badlands occur. Average temperatures in Cedaredge are correspondingly about 6°C cooler than at Delta along the Gunnison River and the Grand Junction/Grand Valley area at the confluence with the Colorado River.