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‘Dem Bones’

Dinosaur Quarry
Yields Answers

IUP geoscience faculty member Jonathan Warnock with a Camarasaurus shoulder blade his group unearthed in 2016 at the Cleveland-Lloyd Dinosaur Quarry in Utah. (Joseph Peterson)

Talk about a cold case—the one IUP geoscience faculty member Jonathan Warnock is investigating dates back 147 million years.

Since 2012, when he was a PhD candidate at Northern Illinois University, Warnock has been traveling to the Utah desert to study the Cleveland-Lloyd Dinosaur Quarry, famous for its dense deposit of Jurassic-aged dinosaur bones. In his two years at IUP, he has taken students along to help with the sleuthing.

The mystery: How did such a hodgepodge of dinosaur bones come together in that area? And, why—when compared with other dinosaur quarries—is the percentage of bones from predatory dinosaurs so high?

Over the summer, Warnock and his colleague, paleontologist Joseph Peterson from the University of Wisconsin Oshkosh, published a paper in the science journal PeerJ that connects at least some of the dots in this case from the Late Jurassic. Because of the decades-long debate over the quarry’s formation, these new developments have resounded in the science community.

Set in the Morrison Formation—colorful layers of Upper Jurassic sedimentary rock spanning 600,000 square miles—the quarry has been the site of excavations that, in nearly a century, have unearthed more than 12,000 dinosaur bones.

But while similar bone beds—so labeled because of their abundance of fossils—are filled mostly with the remains of long-necked, plant-eating sauropods, Cleveland-Lloyd is teeming with carnivore bones. Sixty-six percent of the remains found at the site belong to Allosaurus, a bipedal predator slightly smaller and lighter than the Tyrannosaurus rex and predating the better-known dino by nearly 100 million years.

A full Allosaurus skeleton in the quarry visitors’ center. (Josh Colasante)

A full Allosaurus skeleton in the quarry visitors’ center. (Josh Colasante)

Scientists have long had theories explaining the bone bed’s unusual composition. Many believed the quarry was a predator trap—similar to the La Brea Tar Pits in Los Angeles—in which animals got stuck in the muck, and the predators who came to feast on them became trapped as well. Some declared drought the cause of death, suggesting the site was a dried-up watering hole, and the parched dinosaurs that arrived there could walk no farther. Still others thought the quarry was the site of a poison spring.

None of the hypotheses, in and of themselves, had enough evidence to support them, Warnock said. Bones at the quarry lack chew marks from predators or scavengers, which would have existed in a trap or in a drought, and a spring would have needed to be “hideously toxic” to kill creatures that size before they could walk away, he said.

Instead, he and Peterson believe the quarry was once a seasonal pond, and major floods in the Late Jurassic swept the surrounding area and washed dinosaur bodies into this reservoir.

In this “bloat and float” theory, as the dinosaur corpses decomposed, they became bloated with gas and floated and drifted in the floodwaters—similar to whales that wash up on the beach.

“The idea at the quarry is that these animals were washed in early in the decomposition,” Warnock said. “As they’re in this pond and continuing to rot, parts fall off. When we look at the distribution of the bones, we don’t have nice, laid-out skeletons. Here’s an arm, here’s a section of vertebrae, here’s most of a skull. Parts drop off and accumulate at the bottom.”

The unblemished bones—along with the metals detected in the bones and in the sediment—support the idea of a pond so full of decay from decomposing dinosaurs that it repelled scavengers, as well as fish, turtles, crocodiles, and most other aquatic life.

“It’s just a super scummy pond,” Warnock said. “Having that amount of rotting organic matter helps explain the different, awkward chemistries that we see, the lack of typical pond fossils, and the lack of scavenging on the bones.”

Because they’ve found layers of the quarry with near-perfect bones and layers without them, Warnock and Peterson say the pond was seasonal, sometimes giving way to drought conditions. 

“Bone flakes and crumbles when it sits at the surface,” Warnock said. “We see that component of bone sitting out in hot, dry weather and disintegrating. But it’s mixed in with really well-preserved bone that represents flood periods—it implies very rapid burial.

Jonathan Warnock and his students and volunteers camped at the Cleveland-Lloyd quarry for about two weeks. (Josh Colasante)

Jonathan Warnock and his students and volunteers camped at the Cleveland-Lloyd quarry for about two weeks. (Josh Colasante)

“Some of the old, competing hypotheses went back and forth—this is drought based, this is flood based—but it’s both.”

The researchers believe the dinosaurs washed in during several major floods. “We don’t know if it’s a 100-year flood or a 1,000-year flood, but it would have been a very large flood to create the conditions to wash in the dinosaurs and create that bone layer,” Warnock said.

How many floods occurred and when, whether the dinosaurs were killed in the floods or already dead, and what the landscape—including the river systems that fed into the pond—looked like are questions Warnock and Peterson are still trying to answer.

“And, really, all of that goes into why so many Allosaurus,” Warnock said. “That’s sort of the whole mystery, because every other bone bed in the Jurassic—and nearly every other bone bed we find—is overwhelmingly prey items and only a couple predators. We’ve always approached Cleveland-Lloyd as being the exception to the rule, but maybe it represents a better snapshot—because of the conditions in which it formed—and we really had a landscape full of predators.”

Some of Warnock’s students are helping to unravel mysteries of the quarry. Nicole Lees is analyzing oxygen isotopes in bones to determine if the Allosaurus are likely from the same area or from vastly different areas, and Justin Petricko is studying sediment samples to see if the metals in the quarry came from the bones or from the sediment.

For the past two summers, Warnock has also taken vanloads of students across the country to continue the work he and Peterson began five years ago. That’s when Peterson began planning a summer field course in dinosaur paleontology for UW Oshkosh and contacted his friend from Northern Illinois University’s graduate school to help.

Warnock’s research has focused on paleoclimatology, the study of climate change through Earth’s history, but as a former “dinosaur kid” who went on to do dinosaur research as an undergraduate, he eagerly stepped in. When they learned no one else was working at the Cleveland-Lloyd quarry, they jumped at the chance.

Last May, Warnock agreed to lift the cap on his summer field class so that all 18 IUP students who expressed an interest could go to the quarry.

At the Utah border, the group took a break from driving. (Courtesy of Jonathan Warnock)

At the Utah border, the group took a break from driving. (Courtesy of Jonathan Warnock)

“Some of them came because they needed to check that box to graduate, but it was 18 students because it was dinosaurs,” Warnock said. “I could write dinosaurs on a sandwich board and walk up and down the street, and I’d have dozens of volunteers by tomorrow.”

In fact, Warnock and Peterson do bring along some volunteers, in addition to students, as part of a “citizen science” initiative.
“I’ve had people who come year after year, and this is how they spend their summer vacation,” Warnock said. “They come and sweat and haul rocks and live without electricity and running water.”

On the road to Utah, the group stopped for a few days in Colorado—still under a coat of snow—where Tom Moore ’76, a former faculty member who worked for years in the oil and gas industry, led a tour of the state’s geology. For the next couple weeks, the group camped out on the rocky terrain of the Cleveland-Lloyd quarry, where temperatures stayed mostly in the 80s, but intense winds leveled at least a half-dozen tents.

Warnock, who is also co-director of IUP’s new sustainability studies minor, considers the quarry the “best teaching laboratory there is,” with ready-made lessons on rock layers, geological mapping, and of course, dinosaurs.

“It’s one of the few places in the world where I can guarantee, if you sit there and poke at the ground for a while, you’re going to find something,” he said. 

In 2016, the group’s major find was a four-foot shoulder blade belonging to a Camarasaurus—one of the rare herbivores in the quarry. This past summer, the students found their first, definite skull material—a young Allosaurus’s right, lower jaw. All the bones will stay in Utah for permanent curation.

Currently, only a portion of the quarry is being actively excavated. Sheltered by two aluminum buildings, that area is roughly 10 feet by 40 feet, and the bone bed itself is about 3 feet deep. An area at least that large remains untouched, leaving Warnock, Peterson, and their respective students as much of the quarry yet to explore as there are mysteries to solve.

“One of the goals of our upcoming field season—and however long it takes—is to figure out the areal extent of this deposit,” Warnock said. “But there’s more work there than will fill my career.”

Click on any image below to launch a slideshow of full-size images.

Of all the bones found at the Cleveland-Lloyd Dinosaur Quarry, 66 percent are from the Allosaurus. (Jonathan Warnock)
An Allosaurus jaw that Warnock and his students found last summer. The dark color of the teeth and bone distinguishes them from the rock. (Dave Hola)
Students described rock at the San Rafael Swell in Utah. (Josh Colasante)
Students checked out Utah’s geology, not far from the Colorado border. (Josh Colasante)
On the road to Utah, former faculty member Tom Moore ’76 led a tour of Colorado’s geology. (Josh Colasante)
Jonathan Warnock and his students discussed geology at the Cleveland-Lloyd quarry. (Josh Colasante)
Statue of a Camarasaurus at George S. Eccles Dinosaur Park in Ogden, Utah. IUP students found a four-foot shoulder blade from this long-necked, plant-eating sauropod at the Cleveland-Lloyd quarry in 2016. (Eccles Dinosaur Park)