Fossil Butte National Monument


Fossil Butte National Monument
IUCN category V (protected landscape/seascape)
Fossil Butte National Monument entrance sign.jpg
Fossil Butte National Monument
Map showing the location of Fossil Butte National Monument
Map showing the location of Fossil Butte National Monument
Fossil Butte
Map showing the location of Fossil Butte National Monument
Map showing the location of Fossil Butte National Monument
Fossil Butte
LocationLincoln County, Wyoming, USA
Nearest cityKemmerer, WY
Coordinates41°51′52″N 110°46′33″W / 41.86444°N 110.77583°W / 41.86444; -110.77583Coordinates: 41°51′52″N 110°46′33″W / 41.86444°N 110.77583°W / 41.86444; -110.77583
Area8,198 acres (33.18 km2)[1]
EstablishedOctober 23, 1972 (1972-October-23)
Visitors16,552 (in 2011)[2]
Governing bodyNational Park Service
WebsiteFossil Butte National Monument
Heliobatis radians, an extinct stingray, had small teeth for crushing snails and other mollusks and barbed spines on the tail for defense. This specimen is about 35 centimetres (14 in) long, including the tail.
This 1.7-meter (5 foot 6 inch) Axestemys byssinus is one of the largest turtles known from Fossil Lake.

Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located 15 miles (24 km) west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch (56 to 34 million years ago) animal and plant fossils associated with Fossil Lake—the smallest lake of the three great lakes which were then present in what are now Wyoming, Utah, and Colorado. The other two lakes were Lake Gosiute and Lake Uinta. Fossil Butte National Monument was established as a national monument on October 23, 1972.

Fossil Butte National Monument preserves the best paleontological record of Cenozoic aquatic communities in North America and possibly the world, within the 50-million-year-old Green River Formation — the ancient lake bed. Fossils preserved include fish, alligators, bats, turtles, dog-sized horses, insects, and many other species of plants and animals — suggest that the region was a low, subtropical, freshwater basin when the sediments accumulated, over about a 2 million-year period.[3]

Geologic formations

Map of major Wyoming geological formations, showing Fossil Butte (lower left) far south of Yellowstone (upper left), southwest across the state from Devils Tower (upper right).

During the Eocene this portion of Wyoming was a sub-tropical lake ecosystem. The Green River Lake System contained three ancient lakes, Fossil Lake, Lake Gosiute, and Lake Uinta. These lakes covered parts of southwest Wyoming, northeast Utah and northwestern Colorado. Fossil Butte is a remnant of the deposits from Fossil Lake. Fossil Lake was 40 to 50 miles (64 to 80 km) long from north to south and 20 miles (32 km) wide. Over the two million years that it existed, the lake varied in length and width.[4]

Fossil Buttes National Monument contains only 13 square miles (8,198 acres (33,180,000 m2)) of the 900-square-mile (595,200 acres (2.409×109 m2)) ancient lake. The ancient lake sediments that form the primary fossil digs is referred to as the Green River Formation. In addition to this fossil-bearing strata, a large portion of the Wasatch Formation, river and stream sediments, is within the national monument. The Wasatch Formation represents the shoreline ecosystem around the lake and contains fossil teeth and bone fragments of Eocene mammals. Among these are early primates and horses.[4]


Coal mining for the railroad led to the settlement of the nearby town of Fossil, Wyoming.[5] When the fossils were discovered, miners dug them up to sell to collectors. In particular, Lee Craig sold fossils from 1897 to 1937. Commercial fossil collecting is not allowed within the National Monument, but numerous quarries on private land nearby continue to produce extraordinary fossil specimens, both for museums and for private collectors.


The Fossil Butte National Monument Visitor Center features over 80 fossils and fossil casts on exhibit, including fish, a crocodile, turtle, bats, birds, insects and plants. A 13-minute video is shown about the fossils found at the site and what scientists have learned. Interactive exhibits let visitors create fossil rubbings to take home, and a computer program discusses fossils, geology and the current natural history of the monument.


During the summer, lab personnel prepare fossils in public. Summer activities also include ranger programs, hikes, paleontology and geology talks, and participation in fossil quarry collections for the park.

Stingray prepared by R. Lee Craig (Asterotrygon maloneyi). In the collection of Fossil Shack. Prepared circa 1920.

A Junior Ranger program can be completed by children aged 5–12 (with exercises scaled to the child's age) in 3–4 hours. A highlight is hiking 3/4 mile up the butte to the dig, where interns from the Geological Society of America talk about their excavation and let children help them flake apart sedimentary deposits to discover fish fossils and coprolites.

List of fossil species recovered at Fossil Butte National Monument








Primary source:[7]


See also

Other NPS Cenozoic Era sites in the western U.S.:


  1. ^ "Listing of acreage as of December 31, 2011" (PDF). Land Resource Division, National Park Service. Retrieved 2012-05-14.
  2. ^ "NPS Annual Recreation Visits Report". National Park Service. Retrieved 2012-05-14.
  3. ^ Geologic travel guide from American Geological Institute
  4. ^ a b "Geologic Formation". Fossil Buttes National Monument. National Park Service. Retrieved 7 December 2016.
  5. ^ "Geologic Formations". National Park Service. Retrieved 7 December 2016.
  6. ^ Kemmerer, Mailing Address: P. O. Box 592; Us, WY 83101 Phone:877-4455 Contact. "Fossils - Fossil Butte National Monument (U.S. National Park Service)". Retrieved 2019-01-29.
  7. ^ a b c d e Green River Formation Fossils at Fossil Butte

External links

  • National Park Service: official Fossil Butte National Monument website
  • Photo Gallery of Green River Formation Fossils from FBNM