Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
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 several named units
Calcareous shale and limestone
Minturn and Belden Fms
Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest
Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks
Includes many named units
Arkosic conglomerate, sandstone, and siltstone
Sandstone and shale
Dakota Group and Morrison And Ralston Creek Fms at mountain front between Boulder and Colorado Springs. Dakota, Purgatoire, Morrison, and Ralston Creek Fms in Canon City area
Arkosic sandstone and conglomerate
Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences
Fremont Limestone, Harding Sandstone, and Manitou Limestone
Pierre Shale--Upper unit
Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone
Shale, sandstone, and major coal beds; sandstone
Sharon Springs Member (organic-rich shale and numerous bentonite beds) in lower part
Includes Broadway and Louviers Alluviums
Includes Piney Creek Alluvium and younger deposits
Alkalic and mafic intrusive rocks in small plutons, and diabase dikes
Mainly intermediate to felsic compositions; some mafic
Carlile Shale, Greenhorn Limestone, and Graneros Shale
Siltstone, sandstone, and conglomerate
South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)
Consists of Niobrara Formation (Kn) and either Benton Shale or Carlile, Greenhorn, and Graneros Fms (Kcg)
Gabbro and mafic diorite and monzonite
Arkosic sandstone, siltstone, and shale; contains major coal deposits in Raton Basin
Locally includes talus, rock-glacier, and thick colluvial deposits
Siltstone, sandstone, and conglomerate. Includes Wagontongue Fm (Miocene) in South Park
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
Intermediate to felsic compositions
Intra-ash flow andesitic lavas
Includes some unclassified glacial deposits
In Boulder-Fort Collins area, contains Richard, Larimer, Rocky Ridge, Terry, and Hygiene Sandstone Members; elsewhere shale between zones of Baculites reesidei and B. scotti
Early ash-flow tuff of Sawatch Range provenance
Gypsum, siltstone, and shale
Pierre Shale, undivided
Ralston Creek Fm: Claystone, sandstone, limestone, and gypsum
Arkosic conglomerate, sandstone, and shale
Quartzite, conglomerate, and interlayered mica schist
Dakota and Morrison Fms
Red siltstone, shale, and limestone
Includes dune sand and silt and Peoria Loess
Mainly Lower Cretaceous, Jurassic, and Triassic Fms
Lykins Fm and Lyons Sandstone
Dakota Sandstone or Group