Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
Siltstone, sandstone, and conglomerate
Includes Broadway and Louviers Alluviums
Arkosic conglomerate, sandstone, and siltstone
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
Includes some unclassified glacial deposits
Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest
Minturn and Belden Fms
Intra-ash flow quartz latitic lavas
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
Intermediate to felsic compositions
Arkosic sandstone and conglomerate
Includes many named units
Carlile Shale, Greenhorn Limestone, and Graneros Shale
Gabbro and mafic diorite and monzonite
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.
Sharon Springs Member (organic-rich shale and numerous bentonite beds) in lower part
Intra-ash flow andesitic lavas
Mainly as in Mesozoic unit (MZ) plus Permian and Pennsylvanian Fms
Calcareous shale and limestone
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 basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences
Alkalic and mafic intrusive rocks in small plutons, and diabase dikes
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
Pierre Shale, undivided
Shale and sandstone. Includes Farisita Conglomerate in northwestern Huerfano County