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Mineral Resources > Online Spatial Data > Geology > by state > Colorado Geology

Geologic units in Fremont county, Colorado

[Additional scientific data in this geographic area]

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 17 % of this area

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;

Lithology: granite; granodiorite; quartz monzonite

Eocene prevolcanic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1 % of this area

South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)

Lithology: sandstone; conglomerate; mudstone

One or more Ordovician fms (Phanerozoic | Paleozoic | Ordovician) at surface, covers 2 % of this area

Fremont Limestone, Harding Sandstone, and Manitou Limestone

Lithology: limestone; sandstone

Niobrara Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 4 % of this area

Calcareous shale and limestone

Lithology: shale; limestone

Laramide intrusive rocks (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 1 % of this area

Mainly intermediate to felsic compositions; some mafic

Lithology: granitoid

Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic) at surface, covers 3 % of this area

Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks

Lithology: biotite gneiss; schist; migmatite; quartzite; marble

Oligocene sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.6 % of this area

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 (lime

Lithology: sandstone; shale; conglomerate

Pierre Shale--Lower unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Sharon Springs Member (organic-rich shale and numerous bentonite beds) in lower part

Lithology: shale; bentonite

Morrison and Ralston Creek Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.3 % of this area

Ralston Creek Fm: Claystone, sandstone, limestone, and gypsum

Lithology: mudstone; sandstone; limestone; evaporite

Mafic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 0.9 % of this area

Gabbro and mafic diorite and monzonite

Lithology: gabbro; diorite; monzonite

Santa Fe Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1 % of this area

Siltstone, sandstone, and conglomerate

Lithology: siltstone; sandstone; conglomerate

Sangre de Cristo Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 2 % of this area

Arkosic conglomerate, sandstone, and siltstone

Lithology: conglomerate; sandstone; siltstone

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 1 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Vermejo Fm and Trinidad Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Shale, sandstone, and major coal beds; sandstone

Lithology: sandstone; shale; coal

Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic) at surface, covers 19 % of this area

Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks

Lithology: felsic gneiss; mafic gneiss; meta-basalt; meta-graywacke

Poison Canyon Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Arkosic conglomerate, sandstone, and shale

Lithology: sandstone; conglomerate; shale

Quartzite, conglomerate, and interlayered mica schist (Proterozoic | Paleoproterozoic) at surface, covers 0.2 % of this area

Quartzite, conglomerate, and interlayered mica schist

Lithology: quartzite; conglomerate; mica schist

Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic) at surface, covers 6 % of this area

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

Lithology: granite; granodiorite; quartz monzonite

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Includes dune sand and silt and Peoria Loess

Lithology: dune sand; silt; loess

Landslide deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.9 % of this area

Locally includes talus, rock-glacier, and thick colluvial deposits

Lithology: landslide; talus; colluvium

Dry Union Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.7 % of this area

Siltstone, sandstone, and conglomerate. Includes Wagontongue Fm (Miocene) in South Park

Lithology: siltstone; sandstone; conglomerate; tuff

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest

Lithology: gravel; alluvium

Raton Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.9 % of this area

Arkosic sandstone, siltstone, and shale; contains major coal deposits in Raton Basin

Lithology: sandstone; mudstone; coal

Mesozoic rocks (Lower Phanerozoic | Mesozoic | Cretaceous-Triassic) at surface, covers < 0.1 % of this area

Mainly Lower Cretaceous, Jurassic, and Triassic Fms

Lithology: clastic

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 (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 2 % of this area

Lithology: sandstone; mudstone

Wall Mountain Tuff (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.4 % of this area

Early ash-flow tuff of Sawatch Range provenance

Lithology: ash-flow tuff

Middle Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.6 % of this area

Intermediate to felsic compositions

Lithology: plutonic rock (phanerit

Dakota Sandstone or Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone

Minturn and Belden Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 4 % of this area

Lithology: sandstone; shale; limestone; conglomerate

Pierre Shale--Upper unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Lithology: shale

Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian(?) Carboniferous Mississippia) at surface, covers 2 % of this area

Lithology: limestone; sandstone

Dakota Sandstone and Purgatoire Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Sandstone and shale

Lithology: sandstone; shale

Dakota and Morrison Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 0.1 % of this area

Lithology: sandstone; mudstone; shale

Carlile Shale, Greenhorn Limestone, and Graneros Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

Lithology: shale; limestone

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences

Lithology: basalt; tuff; volcanic breccia (agglomerate); conglomerate

Intra-ash flow andesitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.5 % of this area

Lithology: andesite

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary) at surface, covers 3 % of this area

Includes many named units

Lithology: ash-flow tuff

Evaporitic facies of Minturn And Belden Fms in South Park and southward (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.4 % of this area

Gypsum, siltstone, and shale

Lithology: siltstone; shale; evaporite

Pierre Shale, undivided (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Lithology: shale

Lykins Fm and Lyons Sandstone (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Lithology: sandstone; mudstone; limestone

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers 5 % of this area

Includes several named units

Lithology: andesite; tuff; volcanic breccia (agglomerate)

Pierre Shale--Middle unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

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

Lithology: shale; sandstone

Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 1 % of this area

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 2 % of this area

Arkosic sandstone and conglomerate

Lithology: sandstone; conglomerate

Intrusive rocks (Phanerozoic | Paleozoic | Cambrian) at surface, covers 1 % of this area

Alkalic and mafic intrusive rocks in small plutons, and diabase dikes

Lithology: diabase

Lykins Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 0.1 % of this area

Red siltstone, shale, and limestone

Lithology: siltstone; shale; limestone

Colorado Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1.0 % of this area

Consists of Niobrara Formation (Kn) and either Benton Shale or Carlile, Greenhorn, and Graneros Fms (Kcg)

Lithology: shale; limestone

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.5 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift