Name Horseshoe Mountain Group applied to rocks of the Sauk sequence in central CO of Late Cambrian and Early Ordovician age. In its northwest province near Glenwood Springs, Garfield Co in the Piceance basin, the group is divided into the Sawatch Sandstone, Dotsero Formation (and its Glenwood Canyon and Clinetop Members), and Manitou Limestone (and its Deadhorse and Tie Gulch Members). In its southeast province--near Salida, Gunnison Co in the Piceance basin, Colorado Springs, El Paso CO in the Denver basin, and Fairplay, Park Co in the South Park basin--the group is divided into the Sawatch Sandstone, Peerless Formation, and Manitou Limestone (and its Helena Canyon, Ptarmigan (provisional), and Fairplay (provisional) Members). The group is named for exposures on Horseshoe Mountain (the type section) near Fairplay in Park Co. Rocks of the group include conglomerate, sandstone, shale, limestone, and dolomite. Correlation chart. Thickness of group at type (southeast facies--sec. 12, T. 10 S., R. 79 W.) is 352 ft: Manitou, 167 ft; Peerless, 35 ft; and Sawatch, 150 ft. Thickness of group in northwest facies (sec. 15, T. 5 S., R. 87 W.) is 772 ft: Manitou, 156 ft; Dotsero, 96 ft; and Sawatch, 520 ft.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Named as middle member of Manitou Formation (rank term changed from Limestone) in its southeastern facies; upper formation of Horseshoe Mountain Group (new). Geographic name derived from a locality near Horseshoe Mountain. Type section measured on north wall of cirque on east side Horseshoe Mountain about 1/4 mi east of Park Co line along west extension of line between secs 7 and 18, T10S, R78W, Park Co, CO in the South Park basin. At type, member unconformably overlies the Helena Canyon Member of the Manitou and conformably underlies Leavick Tarn Dolomite Member (new), upper member of Manitou. Upper contact arbitrarily placed at first well-developed bedding plane above the highest chert. Consists of pink to gray dolomite 95.4 ft thick at type. The dolomite beds vary from platy to flaggy to massive to blocky bedded. Some beds are cherty; some are siliceous. Is characterized by abundant bedded chert. Is 95.4 ft thick at type; is 160.8 ft thick at type of Manitou. Correlated with upper part of Deadhorse Conglomerate Member and lower part of Tie Gulch Dolomite Member of the northwestern facies of the Manitou. Measured sections; correlation chart. Of Early Ordovician age.

Source: GNU records (USGS DDS-6; Denver GNULEX).