Construction Trucks May Have Damaged 112-Million-Year-Old Dinosaur Tracks at Mill Canyon in Utah

Nearly 30 percent of the site’s irreplaceable paleontological resources may have been impacted

An image of dinosaur tracks at the Mill Canyon Tracksite with vehicle tracks running through them
More than 200 preserved footprints trek across the canyon's limestone surface and give clues about what life was like millions of years ago. Jeremy B. Roberts

At the Mill Canyon Dinosaur Tracksite near Moab, Utah, a section of 112-million-year-old dinosaur footprints may have been damaged by construction equipment in the area.

Paleontologists and residents were shocked after reports of disruption to early cretaceous era dinosaur tracks. The news first emerged on social media when visitors to the site noticed vehicle tracks has skid across some prehistoric prints where a wooden boardwalk once was, reports Amy Joi O'Donoghue for Deseret News. The walkway had been removed as part of a construction project approved last year by the Bureau of Land Management (BLM).

The Mill Canyon Dinosaur Tracksite is one of the most significant and most diverse known tracksites in the Cedar Mountain Formation in Zion National Park. It contains as many as ten different kinds of ichnotaxa, which is the scientific term for prehistoric bird, crocodile or dinosaur tracks and other trace fossils.

Together, more than 200 preserved footprints cover the canyon's limestone surface and provide clues about what life in the region was like millions of years ago. For example, the area was once a lake, so prints of ancient crocodiles sliding onto the shore to sun themselves have been found, as well as footprints of a swimming dinosaur that may have pressed its feet into the lake's bottom, reports Tess Joosse for Science.

An image of the dinosaur footprints across the Mill Canyon site in Moab, Utah. The photo shows a wooden boardwalk where visitors could view the prints without disturbing them.
After the prints' initial discovery in 2009, the BLM designed the area as a public site and built a raised wooden boardwalk in 2013, so visitors could view the prints without disturbing them. Bureau of Land Management - Utah via Flickr

After the prints' initial discovery in 2009, BLM designated the area as a public site and built a raised wooden boardwalk over the prints in 2013, so visitors could view them without disturbance, reports Salt Lake Tribune's Brian Maffly.

By 2021, the path was warping, and BLM decided to replace it with sturdier, elevated concrete poured into a metal platform, the Salt Lake Tribune reports. After approving the project, BLM stated that any risk to the tracks would be mitigated by flagging and outlining fragile areas while also providing inspections during the construction, Deseret News reports.

However, according to various local experts, including Utah's state paleontologist Jim Kirkland, some key stakeholders were not aware of the work done at Mill Canyon, per Deseret News.

"They didn't talk to any of us," Kirkland said to Science. "I had no clue."

Experts were only made aware of the construction last week, and without a public comment period, they were not able to give input on the environmental assessment, Jeremy Roberts, a Utah local, told Science.

The site's damage was first reported by Sue Sternberg, a Moab resident who has regularly monitored the area since its discovery, per the Salt Lake Tribune. Both Sternberg and Kirkland attribute the lack of communication and misstep to BLM's inability to fill a position for a staff Moab-based paleontologist after the previous expert left in 2018, per Deseret News.

Lee Shenton, the Moab chapter president of the nonprofit Utah Friends of Paleontology, shares concerns about the need for an on-location expert. If a paleontologist was on staff, he says, they could have understood the risks involved and pointed out areas to avoid, per the Salt Lake Tribune.

"The [federal land management] agencies designated these sites as important, so it is surprising there is this sudden change of plan [at Mill Canyon] and a reorganization of the site without consulting the paleontology community. This is the reason why there is all this fuss," Martin Lockley, a paleontologist who led one of the first studies of the site in 2014, told the Salt Lake Tribune.

Some reports state that between 20 and 30 percent of the tracks were damaged, Kirkland tells Science.

BLM spokesperson Rachel Wooton claims in a statement that heavy equipment is on location but was not used near the protected tracks, per Science.

“The Moab Field Office is working to improve safe public access with an updated boardwalk that is designed to protect the natural resources of this site. During that effort, heavy equipment is on location, but it is absolutely not used in the protected area," per the BLM statement.

Recent weather and erosion may have partially covered the tracks, leaving them concealed under sand and hard to see, Shenton tells the Salt Lake Tribune. The contractor and crew hired by the BLM to conduct the renovations were supposed to preserve the paleontological treasure, but the location of the prehistoric footprints may have been unclear. It appears as if a heavy backhoe was driven over them.

"The weather and erosion ended up covering up significant portions of the site, especially after a heavy rain, so the guys that were doing the work couldn't see the tracklayer. That was the problem," Shenton said to the Salt Lake Tribune. "They just drove across it thinking this is just more sand. I don't think there's any bad guys here."

The Center for Biological Diversity has filed a cease-and-desist letter to the BLM's Utah office to halt construction in the area.