OF-15-06 Geologic Map of the Crawford Quadrangle, Delta and Montrose Counties, Colorado


The purpose of Open-File Report OF-15-06 is to describe the geologic setting of this 7.5 minute quadrangle. Field work for the project was conducted in 2014. Two plates (map, cross-section, and 3-D oblique view) and GIS data. Digital ZIP download. OF-15-06

From the Geologic Setting

This quadrangle includes the town of Crawford, the Crawford Reservoir, and Saddle Mountain. The regional dip of sedimentary strata in the Crawford quadrangle is at gentle angles, typically less than 10°, toward the northeast. This marks the regional tilting of the Gunnison uplift, a feature that was formed during the Laramide orogeny during Late Cretaceous to Early Tertiary time (Hansen, 1965; Dickinson and others, 1988). The regional dip is interrupted in places by monoclinal folding, or by intrusive igneous bodies. The monoclinal folding is best seen along Fruitland Mesa in the southwestern part of the map area, where the Dakota Sandstone is broken by local anticline-syncline pairs or limbs of steeper strata (with dips of 20° to 34°), having NW-SE and N-S axial orientations. Gentler folding of the same type, having NW-SE axial orientations, is indicated in the Mancos Shale in the south-central part of the quadrangle, although the outcrop exposures are poor.