Geohydrology Section

Aquifer Systems in Wyoming

Aquifer systems within the State of Wyoming occur as:

• Unconsolidated deposits overlying bedrock formations may be composed of river alluvial deposits, terrace deposits, eolian sand/silt deposits, glacial deposits, and lacustrine deposits, typically of Quaternary age.
• Volcanic rock formations range in age from Eocene to Quaternary and most of these are located within the northwestern portion of the state in the Absaroka Mountains and Yellowstone National Park area.
• Upper Tertiary age aquifers in Wyoming include the High Plains Aquifer located in southeastern Wyoming, Star Valley, Bear River Valley, Sweetwater River Valley, south flank of the Wind River Mountains, Saratoga Valley, and along the flanks of the Sierra Madre-Medicine Bow Mountains. Examples of Upper Tertiary aquifers include portions of the White River, Browns Park, Salt Lake, Split Rock, Moonstone, Arikaree, and Ogallala Formations.
• Lower Tertiary age aquifers are generally located within the large structural basins of the state. Examples of Lower Tertiary aquifers include portions of the Fort Union, Evanston, Pinyon Conglomerate, Hoback, Ferris, Hanna, Wasatch, Green River, Battle Spring, Wind River, Wagon Bed, and Willwood Formations.
• Triassic, Jurassic, Lower Cretaceous, and Upper Cretaceous age aquifers are generally located along the margins of the structural basins in the state and in the Overthrust Belt of western Wyoming. Examples of these aquifers include the Nugget Sandstone, Twin Creek Limestone, Muddy Sandstone, Newcastle Sandstone, and Fox Hills Sandstone, and the Chugwater, Jelm, Preuss, Stump, Cloverly, Lakota, Fall River, Bear River, Frontier, Mesaverde, Medicine Bow, Lance, and Ferris Formations.
• Paleozoic age aquifers include the Casper Formation, Tensleep Sandstone, Madison Limestone, Hartville Formation, and Bighorn Dolomite, and are commonly located along the flanks of the mountain uplifts of the state and in the Overthrust Belt of western Wyoming.
• Precambrian aquifers are commonly exposed at the ground surface in the cores of large mountain uplifts of the state and include both granitic and metamorphic crustal bedrock formations.