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

Geologic units in Pitkin county, Colorado

[Additional scientific data in this geographic area]

Mesaverde Group or Fm--Upper part (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 3 % of this area

In Moffat and Rio Blanco Counties, sandstone, shale, and coal beds above Sego Sandstone. Along Grand Hogback south of Colorado River, sandstone and shale above coal-bearing sequence

Lithology: sandstone; shale; coal

Morrison, Entrada, and Chinle Fms (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers 0.8 % of this area

Along southern Grand Hogback, Chinle is represented only by basal Gartra Sandstone Member

Lithology: mudstone; sandstone

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 10 % of this area

In northwest and west-central: Intertongues complexly with units of overlying Mesaverde Group or Fm; lower part consists of a calcareous Niobrara equivalent and Frontier Sandstone and Mowry Shale Members; in areas where the Frontie

Lithology: shale; sandstone

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

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

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 (Proterozoic | Paleoproterozoic Mesoproterozoic) at surface, covers 0.2 % of this area

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

Lithology: granitoid

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.1 % of this area

Includes several named units

Lithology: andesite; tuff; volcanic breccia (agglomerate)

Morrison Fm and Entrada Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.4 % of this area

Lithology: mudstone; sandstone

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 10 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift

Eagle Valley Fm - evaporitic facies (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.1 % of this area

Gypsum, siltstone, and shale; salt present in deep borings. Intertongues with Minturn and Lower Maroon Fms. Diapiric structure in many places

Lithology: siltstone; shale; evaporite

Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area

Locally includes Peerless Fm

Lithology: quartzite; sandstone; dolostone (dolomite)

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

Lithology: basalt

Ancient alluvium (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers 2 % of this area

In isolated patches that may not all be of the same age

Lithology: alluvium

Minturn and Belden Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 1 % of this area

Lithology: sandstone; shale; limestone; conglomerate

Dakota Sandstone or Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

Lithology: sandstone

Maroon Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 21 % of this area

Arkosic sandstone, siltstone, conglomerate, and local limestone

Lithology: sandstone; siltstone; conglomerate; limestone

Middle Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 7 % of this area

Intermediate to felsic compositions

Lithology: plutonic rock (phanerit

Chinle And State Bridge Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 0.6 % of this area

Red siltstone and sandstone

Lithology: siltstone; sandstone

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

Includes many named units

Lithology: ash-flow tuff

Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic) at surface, covers 14 % 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

Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic) at surface, covers 0.3 % 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

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous) at surface, covers 2 % of this area

Lithology: limestone; quartzite

Belden Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.4 % of this area

Shale, limestone, and sandstone. Includes Kerber Fm in south-central

Lithology: shale; limestone; sandstone

Minturn Fm in west-central and south-central and other units (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 1.0 % of this area

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.

Lithology: sandstone; conglomerate; shale; limestone

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

Mainly Lower Cretaceous, Jurassic, and Triassic Fms

Lithology: clastic

Landslide deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.8 % of this area

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

Lithology: landslide; talus; colluvium

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, Morriso (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 1 % of this area

Lithology: sandstone; mudstone; limestone

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.5 % of this area

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

Lithology: gravel; alluvium

Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic) at surface, covers 8 % 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 0.3 % of this area

Mainly intermediate to felsic compositions; some mafic

Lithology: granitoid

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

In northwest and west-central: Major coal beds in lower part; Rollins Sandstone Member at base in Delta, Gunnison, and Pitkin Counties. In southwest: sandstone and shale.

Lithology: sandstone; shale; coal

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

Siltstone, shale, and local gypsum

Lithology: siltstone; shale; evaporite

Mesaverde Group or Fm--Lower part (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.7 % of this area

Sandstone, shale, and major coal beds

Lithology: sandstone; shale; coal

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 0.2 % 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

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

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

State Bridge Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 3 % of this area

Red and orange siltstone and sandstone

Lithology: siltstone; sandstone

Frontier Sandstone and Mowry Shale Members of Mancos Shale, and Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Locally includes, at base, Burro Canyon Fm (shale and sandstone) or, in western Moffat County, Cedar Mountain Fm (conglomerate and shale)

Lithology: sandstone; shale; conglomerate

Wasatch Fm (including Fort Union equivalent at base) and Ohio Creek Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 3 % of this area

Claystone, mudstone, sandstone, and conglomerate

Lithology: mudstone; sandstone; shale; conglomerate

Older glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.8 % of this area

Lithology: glacial drift