Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks
Includes several named units
Includes Boulder Creek -M.Y. AGE GROUP (AGE 1650-1730 M.Y.)--Includes Boulder Creek, Cross Creek, Denny Creek, Kroenke, Browns Pass, Powderhorn, Pitts Meadow, Bakers Bridge, and Tenmile Granites, Quartz Monzonites, or Granodiorites; also, unnamed granitic rocks
Includes Silver Plume, Sherman, Cripple Creek, St. Kevin, Vernal Mesa, Curecanti, Eolus, and Trimble Granites or Quartz Monzonites; also, San Isabel Granite of Boyer (1962) and unnamed granitic rocks
Includes Pikes Peak, Mount Rosa, Windy Point, and Redskin Granites and unnamed rocks
Includes Broadway and Louviers Alluviums
Northwest: includes Duchesne River Fm (sandstone and shale; includes some rocks of Eocene age) and Bishop Conglomerate near Utah border. South-central: includes Florissant Lake Beds (tuffaceous shale and tuff) and Antero Fm (limestone tuff, tuffaceous sandstone, and conglomerate). Southwest: includes Creede Fm (tuffaceous siltstone, sandstone, conglomerate) and gravels interbedded with volcanic rocks northeast and southeast of Gunnison
Arkosic sandstone and shale, volcaniclastic conglomerate, and andesite flows and breccia
Gypsum, siltstone, and shale
Pierre Shale, undivided
Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
Includes some unclassified glacial deposits
Siltstone, sandstone, and conglomerate. Includes Wagontongue Fm (Miocene) in South Park
Minturn and Belden Fms
Arkosic sandstone, conglomerate, shale, and limestone. Includes Madera Fm and Sharpsdale Fm of Chronic (1958) in Sangre de Cristo Range and Gothic Fm of Langenheim (1952) in Elk Mountains. Other units of Middle Pennsylvanian age.
Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest
Intra-ash flow andesitic lavas
Mainly intermediate to felsic compositions; some mafic
Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite
Intermediate to felsic compositions
Early ash-flow tuff of Sawatch Range provenance
Includes Piney Creek Alluvium and younger deposits
Arkosic sandstone, siltstone, conglomerate, and local limestone
Granitic rocks of 1400- and 1700-m.y. age groups, undivided, or, in Taylor River region, rocks with characteristics of Xg but U-Th-Pb zircon ages of Yg
Dakota, Purgatoire, Morrison, Ralston Creek, and Entrada Fms in southeast. Dakota, Morrison, and Entrada Fms in central mountains. Dakota, Burro Canyon, Morrison, Wanakah, and Entrada Fms in Gunnison River area. Dakota, Morrison, Curtis, And Entrada Fm
Consists of Niobrara Formation (Kn) and either Benton Shale or Carlile, Greenhorn, and Graneros Fms (Kcg)
Older glacial drift
Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone
Bouldery gravel on old erosion surfaces in Front Range and Never Summer Mountains
Laramie Fm and Fox Hills Sandstone
Locally includes talus, rock-glacier, and thick colluvial deposits
Dakota and Morrison Fms
Fox Hills Sandstone
Includes many named units
South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)
Mainly Lower Cretaceous, Jurassic, and Triassic Fms
Dakota Sandstone or Group
Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences
Red siltstone, sandstone, and limestone-pellet conglomerate