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

Geologic units in Boulder county, Colorado

[Additional scientific data in this geographic area]

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

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 0.2 % of this area

Lithology: sandstone; mudstone

Laramie Fm and Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 8 % of this area

Lithology: sandstone; mudstone; coal

Ingleside Fm and Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.4 % of this area

Ingleside Fm: Limestone and calcareous sandstone. Fountain Fm: arkosic sandstone and conglomerate

Lithology: sandstone; limestone; conglomerate

Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic) at surface, covers 19 % 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

Quartzite, conglomerate, and interlayered mica schist (Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Quartzite, conglomerate, and interlayered mica schist

Lithology: quartzite; conglomerate; mica schist

Denver and Arapahoe Fms (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.1 % of this area

Sandstone, mudstone, claystone, and conglomerate; Denver is characterized by andesitic materials

Lithology: sandstone; mudstone; conglomerate

Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic) at surface, covers 0.8 % 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

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes dune sand and silt and Peoria Loess

Lithology: dune sand; silt; loess

Lykins Lyons and Fountain Fms (Phanerozoic | Paleozoic Mesozoic | Carboniferous Pennsylvanian Permian(?) Triassic) at surface, covers 0.8 % of this area

Red siltstone, sandstone, and conglomerate

Lithology: siltstone; sandstone; conglomerate

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Bouldery gravel on old erosion surfaces in Front Range and Never Summer Mountains (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Lithology: gravel

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

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 16 % 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

Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic) at surface, covers 13 % 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

Laramide intrusive rocks (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 3 % of this area

Mainly intermediate to felsic compositions; some mafic

Lithology: granitoid

Laramie Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.3 % of this area

Shale, claystone, sandstone, and major coal beds

Lithology: shale; claystone; sandstone; coal

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 6 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift

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

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

Lithology: shale; limestone

Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

Pierre Shale--Middle unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % 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

Lykins Fm and Lyons Sandstone (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 2 % of this area

Lithology: sandstone; mudstone; limestone

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 3 % of this area

Lithology: sandstone

Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 1 % of this area

Arkosic sandstone and conglomerate

Lithology: sandstone; conglomerate

Dakota, Morrison, and Sundance Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 2 % of this area

Lithology: sandstone; mudstone

Pierre Shale--Upper unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 7 % of this area

Lithology: shale