Geologic units in Chaffee county, Colorado

Granitic rocks of 1700-m.y. age group (Early Proterozoic) at surface, covers 23 % 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

Middle Tertiary intrusive rocks (Tertiary) at surface, covers 13 % of this area

Intermediate to felsic compositions

Felsic and hornblendic gneisses, either separate or interlayered (Early Proterozoic) at surface, covers 10 % of this area

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

Dry Union Fm (Tertiary) at surface, covers 9 % of this area

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

Gravels and alluviums (Quaternary) at surface, covers 9 % of this area

Includes Broadway and Louviers Alluviums

Glacial drift (Quaternary) at surface, covers 8 % of this area

Includes some unclassified glacial deposits

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

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

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 5 % of this area

Mainly intermediate to felsic compositions; some mafic

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 4 % 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

Biotitic gneiss, schist, and migmatite (Early Proterozoic) at surface, covers 4 % of this area

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

Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone (Mississippian-Ordovician) at surface, covers 3 % of this area

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

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

Includes many named units

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

Minturn and Belden Fms

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Tertiary) at surface, covers 1 % of this area

Includes several named units

Evaporitic facies of Minturn And Belden Fms in South Park and southward (Pennsylvanian) at surface, covers 0.9 % of this area

Gypsum, siltstone, and shale

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

Early ash-flow tuff of Sawatch Range provenance

Older glacial drift (Quaternary) at surface, covers 0.5 % of this area

Older glacial drift

Landslide deposits (Quaternary) at surface, covers 0.4 % of this area

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

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Mississippian-Cambrian) at surface, covers 0.3 % of this area

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

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

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite (Tertiary) at surface, covers 0.1 % of this area

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite

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

Gabbro and mafic diorite and monzonite

Intra-ash flow andesitic lavas (Tertiary) at surface, covers < 0.1 % of this area

Intra-ash flow andesitic lavas