Arkosic sandstone, shale, and conglomerate; contains abundant volcanic materials; Upper Cretaceous volcaniclastic McDermott Member at base
Siltstone, shale, and sandstone
Cliff House Sandstone
Arkosic sandstone, conglomerate, shale, and limestone. Includes at base in some areas siltstone and shale of Molas Fm or Larsen Quartzite
Arkosic sandstone, siltstone, and conglomerate
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
Includes Broadway and Louviers Alluviums
Pictured Cliffs Sandstone and Lewis Shale
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 Frontier and Mowry Members (Kmfm), or these and the Dakota Sandstone (Kfd) are distinguished, map unit (Km) consists of shale above Frontier Member. In Southwest: Lower part contains Juana Lopez Member (Kmj)
Shale and sandstone
Includes Piney Creek Alluvium and younger deposits
Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest
Shale, sandstone, and major coal beds
Morrison, Wanakah, and Entrada Fms
Red siltstone, shale, sandstone, and limestone-pellet conglomerate
Sandstone, shale, and conglomerate. In northwest and west-central: Lower Cretaceous. In southwest: Lower and Upper Cretaceous.
Elbert Fm: shale and sandstone.
Sandstone, shale, and coal; sandstone
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.
Mainly intermediate to felsic compositions; some mafic
Quartzite, conglomerate, and interlayered mica schist
Quartzite, slate, and phyllite
Includes some unclassified glacial deposits
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
San Juan Basin
Locally includes talus, rock-glacier, and thick colluvial deposits
Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes
Older glacial drift
San Juan Basin
Parting Fm: quartzite and shale.
Transgressive marine sandstone.
Prominent cliff-forming marine sandstone.
Marine shale and mudstone.
Mudstone, shale, and sandstone; coal-bearing.
Intermediate to felsic compositions
Coal-bearing, primarily in the Fruitland.
Volcaniclastic sedimentary rocks of intermediate composition in northern San Juan Basin.