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

Geologic units in Saguache county, Colorado

[Additional scientific data in this geographic area]

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

Includes some unclassified glacial deposits

Lithology: glacial drift

Unclassified surficial deposits and underlying Alamosa Fm in San Luis Valley (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers 21 % of this area

Alamosa Fm: gravel, sand, silt

Lithology: alluvium

Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 7 % of this area

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers 29 % of this area

Includes several named units

Lithology: andesite; tuff; volcanic breccia (agglomerate)

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.6 % 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

Parting, Fremont, and Harding Fms (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian) at surface, covers < 0.1 % of this area

Lithology: quartzite; sandstone; limestone; shale

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

Lithology: sandstone; mudstone; shale

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary) at surface, covers 18 % of this area

Includes many named units

Lithology: ash-flow tuff

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % 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 1 % of this area

Lithology: andesite

Dakota, Burro Canyon, Morrison, and Junction Creek Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 0.8 % of this area

Burro Canyon is locally absent

Lithology: sandstone; mudstone; shale

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 0.2 % of this area

Lithology: sandstone

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 0.5 % of this area

Lithology: limestone; sandstone

Minturn and Belden Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 2 % of this area

Lithology: sandstone; shale; limestone; conglomerate

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

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

Lithology: siltstone; sandstone; conglomerate; tuff

Landslide deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

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

Lithology: landslide; talus; colluvium

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.4 % of this area

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

Lithology: gravel; alluvium

Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic) at surface, covers 5 % 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

Minturn Fm in west-central and south-central and other units (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % 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

Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic) at surface, covers 0.1 % 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

Intra-ash flow quartz latitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1.0 % of this area

Lithology: quartz latite

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

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

In Gunnison River area east of wedgeout of all units of Wanakah Fm (Jmw) except the Junction Creek Member

Lithology: mudstone; sandstone

Oligocene sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % 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

Mafic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 0.1 % of this area

Gabbro and mafic diorite and monzonite

Lithology: gabbro; diorite; monzonite

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

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

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

Santa Fe Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Siltstone, sandstone, and conglomerate

Lithology: siltstone; sandstone; conglomerate

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 3 % 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

One or more Ordovician fms (Phanerozoic | Paleozoic | Ordovician) at surface, covers < 0.1 % of this area

Fremont Limestone, Harding Sandstone, and Manitou Limestone

Lithology: limestone; sandstone

Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic) at surface, covers 0.7 % 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