CHISHOLM, Minn. — The Mesabi Range in northern Minnesota is known for its rich deposits of iron ore underground.
But just above that layer, yet still deep below the surface, is a 90-million-year-old formation rich in something else: fossils.
In Minnesota, most of that Cretaceous Period layer and its fossils are unreachable by researchers, but thanks to miners who dug up that layer of rock and piled it to the side to reach the marketable ore underneath, paleontologists such as John Westgaard of the Minnesota Discovery Center can easily sift through it.
Since 2013, he and others have found thousands of shark teeth, snails and clams. There’s even evidence of ancient crocodiles. So far, they’ve uncovered three dinosaur fossils, mainly at the Hill Annex Mine State Park in Calumet, Minn.
“Boy, there was a lot of disbelief when we first started telling people,” Westgaard said. “We got used to carrying around a display mount of shark teeth so we could just show people that no, we found all these here — we really did."
But that’s changing. Through outreach and continued exploration, more people are grasping which creatures once wandered in what is now Minnesota.
An ancient shoreline
Approximately 90 million years ago, the Mesabi Range was near the eastern coastline of — and sometimes covered by — an ocean called the Western Interior Seaway, which ran down the middle of North America.
Evidence of this was left behind in a layer called the Coleraine Formation. Thanks to the walls of the open pit at Hill Annex serving as a geologic cross-section, it’s a visible layer. And beside the pit, piles of overburden (soil or rock overlying a mineral deposit) containing the layer’s materials are easily accessible by paleontologists and volunteers.
Mining at the park ended in 1978, and the property became a state park 10 years later. Westgaard said the presence of fossils there was “heavily referenced” in past research, but it had been a while since anything was written. So in 2013, he and a research partner, both at the Science Museum of Minnesota at the time, scouted out the site “to make sure it’s still there.”
Almost immediately, a park staff member turned over a bone found by his grandson. The bone was later determined to be from an ancient sea turtle.
They now find several thousand fossils there each year.
Among the finds are three confirmed dinosaur fossils.
They uncovered a hadrosaur vertebra, but believe it was pulled into the region by a glacier from Alberta or Saskatchewan.
Two other dinosaur fossils they found on site — a claw bone from a dromaeosaur (like raptors from the movie “Jurassic Park”) and a vertebra from an ornithomimus (“The ostrich-like dinosaurs … about human-sized,” Westgaard said) — are believed to have once lived in what is now Minnesota.
A fourth potential dinosaur bone — a vertebra found in a rock — will need to be confirmed using a CT scan.
Westgaard teased another recent significant find, but would not offer more details as researchers are still working to confirm what it is.
“It would be another first,” Westgaard said.
Paleontology program housed at Minnesota Discovery Center
Westgaard had been working at the Science Museum of Minnesota in St. Paul and volunteering with the Minnesota Discovery Center and often at Hill Annex searching for fossils, but after COVID 19-induced layoffs at the museum, the center hired him.
As of this month, he’s now officially a paleontologist at the Minnesota Discovery Center and will continue what he started at the museum.
Donna Johnson, executive director of center, said including paleontology at the center fits into its recently rewritten mission statement.
“Adding that science direction is exciting,” Johnson said. “Because it’s never really been a focus … and I think in this process, we may find some scientific, groundbreaking fossils that may have not ever otherwise been identified if we didn’t keep this program moving forward.”
Johnson and Westgaard said having the program based at the Minnesota Discovery Center means the fossils they find can stay on the Iron Range rather than be stored in the Twin Cities.
“The majority of the fossil material that we have is all from the Mesabi, so it should be here where the community can enjoy it,” Westgaard said.
It also means expanded programming, like more public presentations and showcases, the chance for volunteers to help search for fossils and youth camps.
Cyrie Michelson, 13, and Deena Dougherty, 12, both of Hibbing, had just finished a four-day paleontology camp through the center, where they learned to tell the difference between fossils and rocks, then went out and found their own fossils at Hill Annex.
At a public event about fossils Thursday, July 22, the two sat behind cases about the size of 8-by-11-inch paper displaying fossils they found this week — mostly shark teeth and snails.
They both didn’t expect to find so many.
“It was a really good learning experience,” Michelson said. “I got to know what a lot of fossils were and how old they were. It was also really cool and interesting building confidence in what you find because a lot of these, I didn’t know what they were.”
And it was exhilarating every time they determined they had a fossil and not just a rock.
“You’re actually touching an ancient thing,” Dougherty said. “It was like blowing my mind.”
The future of Hill Annex
Though it’s been a state park for 33 years, Hill Annex Mine State Park could revert back to mining, which could put the fossils on site in jeopardy.
That’s because it’s on school trust land leased to the DNR’s Parks and Trails Division. The primary purpose of that land is “to provide an economic return” to the fund supporting the state’s K-12 schools, said Philip Leversedge, deputy director of the DNR’s Division of Parks and Trails.
“The legislation authorizing the state park stipulates the opportunity for the park to revert back to active mining if it becomes economically feasible to do so in the future,” Leversedge said in an email. “This possibility encompasses any and all of the school trust lands.”
Hill Annex is considered a “rustic state park with limited services,” Leversedge said. Besides the fossils, the park has a visitor center that details the mine’s history, open on weekdays during the summer, and a scenic overlook of the mine pit, now filled with water.
But the water level is rising, and Iron Range lawmakers have sought $2 million to solve that and other safety issues.
Johnson said the lack of investment in Hill Annex concerns her and she wants to make sure the paleontology program can continue if mining were to resume.
“I’ve been offering MDC to step in and help, or hopefully, maybe someday be able to relocate some of that overburden on-site so we can continue the (paleontology) work if that relationship changes at Hill Annex so it doesn’t just go away,” Johnson said.
Hill Annex is just one of many former mines where fossils could have been brought to the surface.
Westgaard noted there are more than 400 historic mines along the 90-mile Mesabi Range and hopes research can expand to more areas going forward. And then there are the active mines.
“Mining isn’t done ... There is a lot yet to explore,” Westgaard said. “Every year, more soil comes out of the ground because mining is active, so the chances for us to really just blow the cover off of the darkness of this coastline and to share a picture of so much detail — it’s just right there in front of us.”