Crystal Peak Dolomite

The Crystal Peak Dolomite is a geologic formation in Utah. It preserves fossils dating from the Ordovician period.

This geographic stratum is named for its dolomite (used to describe a sedimentary carbonate rock composed predominantly of the mineral dolomite, or dolostone). It is named for exposures at the Crystal Peak section 10 mi southwest of Smooth Canyon, Millard County, Utah in the Great Basin province. It separates the Watson Ranch Quartzite tongue of Swan Peak quartzite from the younger Eureka quartzite. The stratum generally consists of brown, gray to black, usually fine- to medium-grained, but may be coarse-grained, dolomite. Thin (about 6 ft thick) quartz sandstone and siltstone occur about 50 ft from base. The layer is 85 ft thick in Smooth Canyon. The stratum is fossiliferous; it has been shown to contain orthocone cephalopods, and corals. The thickness has been measured between 61 ft thick in Tule Valley, Utah to 92 ft thick in Desert Range Experiment Station, Utah; it is 89 ft thick at Crystal Peak. It is classified as Middle Ordovician age. The Crystal Peak equivalent has been recognized in the Lehman Formation in the Snake Range of Nevada, but was not specifically identified in adjoining eastern Nevada.