Geologic units in Lake county, Colorado

Granitic rocks of 1700-m.y. age group (Early Proterozoic) at surface, covers 18 % 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

Glacial drift (Quaternary) at surface, covers 16 % of this area

Includes some unclassified glacial deposits

Granitic rocks of 1400-m.y. age group (Middle Proterozoic) 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

Biotitic gneiss, schist, and migmatite (Early Proterozoic) at surface, covers 11 % of this area

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

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 8 % of this area

Mainly intermediate to felsic compositions; some mafic

Minturn Fm in west-central and south-central and other units (Pennsylvanian) at surface, covers 7 % 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.

Gravels and alluviums (Quaternary) at surface, covers 5 % of this area

Includes Broadway and Louviers Alluviums

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Mississippian-Cambrian) at surface, covers 4 % of this area

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

Dry Union Fm (Tertiary) at surface, covers 4 % of this area

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

Older gravels and alluviums (Quaternary) at surface, covers 4 % of this area

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

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

Older glacial drift

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

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

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

Includes Piney Creek Alluvium and younger deposits

Minturn and Belden Fms (Pennsylvanian) at surface, covers 0.8 % of this area

Minturn and Belden Fms

Middle Tertiary intrusive rocks (Tertiary) at surface, covers 0.7 % of this area

Intermediate to felsic compositions

Ash-flow tuff of main volcanic sequence (Tertiary) at surface, covers 0.7 % of this area

Includes many named units

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Tertiary) at surface, covers 0.6 % of this area

Includes several named units

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 0.3 % 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

Felsic and hornblendic gneisses, either separate or interlayered (Early Proterozoic) at surface, covers 0.1 % of this area

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