The Geology and Paleontology of Tule Springs Fossil Beds 

National Monument, Nevada

A Brief History of Tule Springs

Vertebrate fossils have been known 

from the Las Vegas Valley for more than 

a century, beginning in 1903 when Josiah 

Spurr of the U.S. Geological Survey 

reported teeth and bones in the sediments exposed in the wash between Corn 

Creek Springs and Tule Springs (Spurr, 

1903). Several scientific investigations 

followed, including the extensive and 

multidisciplinary Tule Springs Expedition of 1962–63 that sought to determine 

if humans and Pleistocene megafauna 

coexisted in the area. In what came to be 

known as the Big Dig, the Tule Springs 

Expedition combined traditional field 

techniques with massive earth-moving 

activities. Heavy construction equipment 

carved enormous trenches into the sediments at Tule Springs to expose vertical 

walls as deep as 13 meters (nearly 

43 feet!), which allowed the sediments to 

be studied in detail. Geologist C. Vance 

Haynes, Jr., directed the geological investigations and subdivided the fossil-rich 

sediments into distinct units of the Las 

Vegas Formation. He also assigned ages to 

the units using the newly developed radiocarbon dating technique. Haynes’ targeted 

approach demonstrated that human-made 

artifacts only occurred in the youngest 

levels of the formation—those layers lacking the fossilized remains of Pleistocene 

animals (Haynes, 1967). Consequently, 

the hypothesis that early humans coexisted 

with Pleistocene megafauna at Tule 

Springs was disproven, and interest in the 

site faded. A long intermission in scientific 

research followed, lasting until the 2000s 

when museum scientists conducted comprehensive and systematic paleontological 

excavations of the area. The scientists 

discovered nearly 600 new fossil localities and collected and curated more than 

40,000 vertebrate fossils. Work in Tule 

Springs Fossil Beds National Monument 

continues today through the efforts of 

scientists from the U.S. Geological Survey, 

National Park Service, and academic institutions across the country.

On December 19, 2014, Tule Springs Fossil Beds National Monument in Nevada was established by Congress as the 405th unit of 

the National Park Service to “conserve, protect, interpret, and enhance for the benefit of present and future generations the unique and 

nationally important paleontological, scientific, educational, and recreational resources and values of the land” (P.L. 113-291, sec. 3092).

The upper Las Vegas Wash cuts through sediments formed by ancient springs and marshes that blanketed the Las Vegas Valley floor during 

the Pleistocene Epoch. These deposits have yielded thousands of vertebrate fossils and contain valuable information on past climatic and 

environmental conditions. This is Tule Springs Fossil Beds National Monument.

Photograph by Eric Scott, Cogstone Resource Management, Inc., used with permission.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3038

December 2018
A Story of Water

Tule Springs Fossil Beds National Monument preserves nearly 23,000 acres of the fossil-rich Las Vegas Formation. The formation’s silty, light-colored sediments were once thought to be the remnants of a large Pleistocene lake, but it is now known that they 

actually represent a vast spring ecosystem that existed throughout the Las Vegas Valley for millennia (Quade, 1986). During the 

Pleistocene, the climate was wetter than today, and the water table was so high that groundwater flowed up to the ground surface. 

The soggy ground and dense vegetation trapped dust and sand transported by water and wind, which mixed with organic material and 

chemical precipitates to form wetland deposits. Specific spring environments, such as marshes and wet meadows, spring pools and 

ponds, and spring-fed streams, can be recognized through careful examination of the deposits. These environments are comparable to 

modern spring ecosystems and help reconstruct past environmental and hydrologic conditions in the valley.

Examples of spring environments in present-day wetlands (upper panels) and their counterparts from the geologic past (lower panels). The 

types of springs and their distribution throughout the upper Las Vegas Wash are directly related to the location of buried faults, the complexity 

of local and regional aquifers, and the height of the water table both today and in the past. The two lower left photographs by Eric Scott, 

Cogstone Resource Management, Inc., used with permission.

Marshes/wet meadows Spring pools/ponds Spring-fed streams

Timing is everything...

The Las Vegas Formation consists of 17 different geologic 

units that collectively span more than 500,000 years (Springer and 

others, 2018). Each unit dates to a specific period of geologic time 

and exhibits a unique set of physical characteristics that can be used 

to distinguish one from another. This is important because ages of 

the units can be used to date vertebrate fossils that are found within 

them. Radiocarbon dating saw its first widespread use during the Tule 

Springs Expedition in the early 1960s. Never before had a fossil site 

been dated in this way. Scientists have continued to refine the chronology of the deposits by radiocarbon dating charcoal (left), which 

determines when plants found in the sediment were last alive, and 

luminescence dating (right), which determines when the sediments 

were last exposed to light or heat.
A Story of Life

The vertebrate fossil assemblage found in Tule Springs Fossil Beds National Monument, called the Tule Springs local fauna, 

represents one of the most important Pleistocene vertebrate faunas in the American Southwest. The fauna occurs throughout most 

of the Las Vegas Formation and spans from approximately 100,000 years ago to 12,500 years ago (Scott and others, 2017). The 

Tule Springs local fauna is both abundant and diverse and includes numerous species of large mammals, as well as smaller animals 

such as frogs, lizards, snakes, birds, and rodents. Invertebrates such as aquatic and terrestrial snails, tiny clams, and ostracodes are 

also common. All of the fossils and geologic deposits in the monument are protected for posterity. Ongoing and future scientific 

studies should continue to reveal a wealth of information about the ever-changing ecosystems in the Las Vegas Valley and the 

plants and animals that once called it home.

The Columbian mammoth (Mammuthus columbi) is the iconic animal of Tule Springs Fossil Beds National Monument. Mammoth remains have been discovered throughout the monument and dominate the Tule Springs local fauna in terms of sheer numbers 

of fossils. Yesterday’s camel (Camelops hesternus) was widespread in western North America during the late Pleistocene and is the 

second most common animal found at Tule Springs. Two species of bison were also present in the valley, a long-horned species (Bison 

latifrons) and a smaller species (Bison antiquus). A large stout-legged horse (Equus scotti), a small stout-legged horse (Equus sp.), 

and a small stilt-legged species (Haringtonhippus francisci) also lived there during the late Pleistocene, as did Jefferson’s ground 

sloth (Megalonyx jeffersonii) and Shasta ground sloth (Nothrotheriops shastensis). In addition, rare fossils of American lion (Panthera 

atrox), and new findings of dire wolf (Canis dirus) and saber-toothed cat (Smilodon fatalis), show that carnivores prowled the valley 

(Scott and Springer, 2016). All of these majestic animals went extinct as the Pleistocene Epoch came to a close.

Drawings by Adrienne Picchi, Pasadena, California

...and context is critical!

The thousands of Pleistocene fossils from Tule Springs Fossil 

Beds National Monument are spectacular, but it is their geological 

context that makes them truly special. The geologic framework of 

fossil sites in the monument allows scientists to assess the age of the 

fossils, determine what the environment was like when the animals 

were alive, evaluate how extinct species lived and died, measure 

how populations changed over time, and understand how the animals adapted to the challenges of life under a changing climate.

Left: Fossil horse tooth from Tule Springs. Right: U.S. Geological Survey 

research geologist Kathleen Springer examining a sequence of wetland 

deposits in the upper Las Vegas Wash. Photograph by Eric Scott, 

Cogstone Resource Management, Inc., used with permission.
Ice Age Climate

The Pleistocene Epoch began about 

2.6 million years ago and ended 11,700 years 

ago. During this period of time, Earth’s 

climate saw numerous swings from cold to 

warm and back again. Massive continental 

ice sheets, extensive alpine glaciers, numerous large lakes, and expansive spring-fed 

wetlands characterized the cold periods, 

called glacials. During the warm periods, or 

interglacials, the ice sheets retreated and the 

deserts dried. These glacial-to-interglacial 

cycles were long, lasting tens to hundreds of 

thousands of years. During both glacial and 

interglacial times, numerous rapid climate 

fluctuations operating over decades to centuries also affected the availability of water on 

the landscape.

Although glaciers were not present 

in the Las Vegas Valley during the Pleistocene, water was in abundance, and wetlands 

blanketed much of the valley floor. These 

ecosystems were extremely sensitive to 

changes in climate. Multiple cycles of erosion, deposition, and soil formation occurred 

as the wetlands expanded and contracted in 

sync with abrupt global cooling and warming events before largely disappearing as the 

last glacial period came to a close (Springer 

and others, 2015). 

Geologic deposits in the valley also 

show evidence of megadroughts, which 

typically lasted for a few centuries. These 

events severely impacted flora and fauna 

that depended on the springs and wetlands 

for water. Scientists continue to investigate 

the geologic, chronologic, and hydrologic 

context of vertebrate fossil localities in Tule 

Springs Fossil Beds National Monument 

to determine how the animals, and early 

human inhabitants, survived times of rapid 

climate change in the recent geologic past.

Megafauna Extinctions

Mammoths, sloths, camels (jaw 

shown at right), horses, and dozens of 

other large animals disappeared from 

North America at the end of the Pleistocene. The question of what caused this 

extinction has never been fully answered. 

Hypotheses that seek to explain the demise 

of the Pleistocene megafauna include 

climate change, increased competition 

for resources, overhunting by humans, 

By Kathleen B. Springer and Jeffrey S. Pigati of the U.S. Geological Survey and Eric Scott of 

Cogstone Resource Management, Inc.

widespread disease, and even an extraterrestrial impact event. The deposits 

in the upper Las Vegas Wash may offer 

important clues that could help solve this 

mystery. Scientists are using the Tule 

Springs fossils to track the abundance of 

mammals as the Pleistocene came to a 

close, allowing them to relate changes in 

populations to climate fluctuations and 

the arrival of humans to assess how the 

extinctions may have unfolded.

Carbonate Rivers

About 10,600 years ago, a network of spring-fed streams meandered 

across the Tule Springs area. The stream 

channels became frozen in time in the 

form of tufa. Tufa is calcium carbonate 

that precipitates from cool, spring-fed 

waters. This variety of tufa forms in 

the presence of algae and water-loving 

plants, coating leaves, twigs, branches, 

and logs. At first, it is soft and spongy, 

but when the springs dry up, it hardens 

into the rocky form that is seen today 

throughout the park. Tule Springs is 

home to the only braided fluvial tufa 

system in North America, preserving a 

network of stream channels just as they 

appeared on the landscape thousands of 

years ago. (Left, spectacular tufa from 

an ancient stream channel)

References

Haynes, C.V., Jr., 1967, Quaternary geology of the 

Tule Springs Area, Clark County, Nevada, in

Wormington, H.M., and Ellis, D., eds., Pleistocene studies in southern Nevada: [Carson City] 

Nevada State Museum Anthropological Papers 

no. 13, p. 15–104.

Quade, J., 1986, Late Quaternary environmental 

changes in the upper Las Vegas Valley, Nevada: 

Quaternary Research, v. 26, p. 340–357.

Scott, E., and Springer, K.B., 2016, First records of 

Canis dirus and Smilodon fatalis from the late 

Pleistocene Tule Springs local fauna, upper Las 

Vegas Wash, Nevada: PeerJ, v. 4, e2151, 17 p.

Scott, E., Springer, K.B., and Sagebiel, J.C., 2017, 

The Tule Springs local fauna—Rancholabrean 

 vertebrates from the Las Vegas Formation, Nevada: 

Quaternary International, v. 443A, p. 105–121.

Springer, K.B., Manker, C.R., and Pigati, J.S., 2015, 

Dynamic response of desert wetlands to abrupt 

climate change: Proceedings of the National 

Academy of Sciences of the United States of 

America, v. 112, no. 47, p. 14522–14526.

Springer, K.B., Pigati, J.S., Manker, C.R., and 

Mahan, S.A., 2018, The Las Vegas Formation: U.S. 

Geological Survey Professional Paper 1839, 62 p. 

[Also available at https://doi.org/10.3133/pp1839.]

Spurr, J.E., 1903, Descriptive geology of Nevada 

south of the fortieth parallel and adjacent portions of California: U.S. Geological Survey 

Bulletin 208, 229 p.

U.S. Geological Survey Science in the Park

Acknowledgments

We extend our appreciation to the National Park 

Service and the leadership of Tule Springs Fossil Beds 

National Monument for their support of our ongoing 

work there.

For More Information

U.S. Geological Survey,

Geosciences and Environmental Change Science 

Center,

https://www.usgs.gov/centers/gecsc

National Park Service,

Tule Springs Fossil Beds National Monument,

https://www.nps.gov/tusk/

A contribution of the Paleohydrology of Desert Wetlands 

project, https://www.usgs.gov/desertwetlands

Photograph by

Eric Scott, Cogstone

Resource Management, Inc.

ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20183038