Oligocene sedimentary rocks

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
State Colorado
Name Oligocene sedimentary rocks
Geologic age Tertiary
Lithologic constituents
Sedimentary > Clastic > Sandstone (Tuffaceous)
Sedimentary > Clastic > Mudstone > Shale (Tuffaceous)
Igneous > Volcanic (Pyroclastic-tuff)
Sedimentary > Clastic > Conglomerate (Tuffaceous)
Sedimentary > Clastic > Siltstone (Tuffaceous)

Tweto, Ogden, 1979, Geologic Map of Colorado: U.S. Geological Survey Special Geologic Map, scale 1:500,000.

NGMDB product
Counties Fremont - Gunnison - Mineral - Moffat - Park - Rio Blanco - Saguache - Teller