Geologic units in Park county, Colorado

Biotitic gneiss, schist, and migmatite (Early Proterozoic) at surface, covers 18 % of this area

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

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Tertiary) at surface, covers 11 % of this area

Includes several named units

Granitic rocks of 1700-m.y. age group (Early Proterozoic) at surface, covers 8 % 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; also, unnamed granitic rocks

Granitic rocks of 1400-m.y. age group (Middle Proterozoic) at surface, covers 8 % 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

Rocks of Pikes Peak Batholith (1000-m.y. age group) (Middle Proterozoic) at surface, covers 7 % of this area

Includes Pikes Peak, Mount Rosa, Windy Point, and Redskin Granites and unnamed rocks

Gravels and alluviums (Quaternary) at surface, covers 6 % of this area

Includes Broadway and Louviers Alluviums

Oligocene sedimentary rocks (Tertiary) at surface, covers 4 % 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 (limestone tuff, tuffaceous sandstone, and conglomerate). Southwest: includes Creede Fm (tuffaceous siltstone, sandstone, conglomerate) and gravels interbedded with volcanic rocks northeast and southeast of Gunnison

South Park Fm (Tertiary) at surface, covers 4 % of this area

Arkosic sandstone and shale, volcaniclastic conglomerate, and andesite flows and breccia

Evaporitic facies of Minturn And Belden Fms in South Park and southward (Pennsylvanian) at surface, covers 4 % of this area

Gypsum, siltstone, and shale

Pierre Shale, undivided (Cretaceous) at surface, covers 3 % of this area

Pierre Shale, undivided

Felsic and hornblendic gneisses, either separate or interlayered (Early Proterozoic) at surface, covers 3 % of this area

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

Glacial drift (Quaternary) at surface, covers 3 % of this area

Includes some unclassified glacial deposits

Dry Union Fm (Tertiary) at surface, covers 2 % of this area

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

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

Minturn and Belden Fms

Minturn Fm in west-central and south-central and other units (Pennsylvanian) at surface, covers 2 % 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.

Older gravels and alluviums (Quaternary) at surface, covers 2 % of this area

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

Intra-ash flow andesitic lavas (Tertiary) at surface, covers 2 % of this area

Intra-ash flow andesitic lavas

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 2 % of this area

Mainly intermediate to felsic compositions; some mafic

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Mississippian-Cambrian) at surface, covers 2 % of this area

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite

Middle Tertiary intrusive rocks (Tertiary) at surface, covers 1 % of this area

Intermediate to felsic compositions

Wall Mountain Tuff (Tertiary) at surface, covers 0.8 % of this area

Early ash-flow tuff of Sawatch Range provenance

Modern alluvium (Quaternary) at surface, covers 0.8 % of this area

Includes Piney Creek Alluvium and younger deposits

Maroon Fm (Permian-Pennsylvanian) at surface, covers 0.8 % of this area

Arkosic sandstone, siltstone, conglomerate, and local limestone

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 (Early-Middle Proterozoic) at surface, covers 0.8 % 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

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 (Cretaceous-Jurassic) at surface, covers 0.7 % of this area

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

Colorado Group (Cretaceous) at surface, covers 0.6 % of this area

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

Older glacial drift (Quaternary) at surface, covers 0.3 % of this area

Older glacial drift

Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone (Mississippian-Ordovician) at surface, covers 0.3 % of this area

Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone

Bouldery gravel on old erosion surfaces in Front Range and Never Summer Mountains (Tertiary) at surface, covers 0.3 % of this area

Bouldery gravel on old erosion surfaces in Front Range and Never Summer Mountains

Laramie Fm and Fox Hills Sandstone (Cretaceous) at surface, covers 0.2 % of this area

Laramie Fm and Fox Hills Sandstone

Landslide deposits (Quaternary) at surface, covers 0.1 % of this area

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

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

Dakota and Morrison Fms

Fox Hills Sandstone (Cretaceous) at surface, covers 0.1 % of this area

Fox Hills Sandstone

Ash-flow tuff of main volcanic sequence (Tertiary) at surface, covers 0.1 % of this area

Includes many named units

Eocene prevolcanic sedimentary rocks (Tertiary) at surface, covers 0.1 % 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)

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

Mainly Lower Cretaceous, Jurassic, and Triassic Fms

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

Dakota Sandstone or Group

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Tertiary) at surface, covers < 0.1 % of this area

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

Chinle Fm (Triassic) at surface, covers < 0.1 % of this area

Red siltstone, sandstone, and limestone-pellet conglomerate