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LOGAN — Utah's most famous display of ancient rock art is apparently not so ancient after all.
“The most accepted hypotheses pointed to the age of these paintings as 2,000 to 4,000 years old, or perhaps even 7,000 to 8,000 years old,” said Joel Pederson, professor of geology at Utah State University.
New scientific studies reveal that the world-renowned painting known as The Great Gallery is significantly younger than most experts believed.
Researchers at Utah State used the luminescent side-effect of natural radioactivity to uncover some secrets of The Great Gallery.
To see the famous rock art requires one of the most memorable 3-mile hikes in Utah through scenic Horseshoe Canyon. It used to be named Barrier Canyon.
I've heard archaeologists suggest that it's actually the most impressive and most famous rock art in North America.
–Joel Pederson, professor of geology at Utah State University
That's why the haunting panel of warriors, ghosts or priests came to be known as the Barrier Canyon-style of rock art.
"I've heard archaeologists suggest that it’s actually the most impressive and most famous rock art in North America,” Pederson said.
The brooding, evocative, possibly threatening figures have attracted worldwide interest and many international hikers.
Indeed, when adventurer Aron Ralston was pinned by a boulder and forced to cut off his own arm to escape, as portrayed in the film "127 Hours," he hiked to The Great Gallery.
Ralston was rescued by a family from The Netherlands, drawn to the rugged canyon by paintings that have reverberated with art lovers for decades.
Pederson, anthropologist Steven Simms and their team used technology called "luminescence dating" to answer part of the mystery: Who created The Great Gallery? When? And why?
"I don't think we will ever know the meaning to the original maker," Simms said.
Barrier Canyon-style is very different from most Utah rock art, which is usually attributed to the so-called Fremont culture.
"This Barrier Canyon rock art, which is very distinctive, was agreed to be older, was thought to be a separate culture. It predated Fremont,” Pederson said.
So how old is it? To get answers, researchers used USU's light-proof luminescence laboratory, the only one of its kind in Utah.
They examined quartz crystals collected from The Great Gallery. When exposed to blue light, quartz emits ultraviolet light — luminescence — caused by natural radiation. But that luminosity fades away when quartz crystals are exposed to the sun.
"So we're looking at the stored signal from radioactivity and how it is bleached away with the sun in minerals," Pederson said.
By measuring the luminosity of quartz crystals, the lab procedures can determine when sand eroded away from the cliff face, when the cliff was exposed to the sun and when part of it flaked off. Using those techniques, the researchers came up with an 1,100-year span when the painting must have been done.
"The time window is right from the time of Christ, A.D. one or zero, up until about 1,100 A.D.,” Pederson said.
The new evidence puts the artwork closer to modern times, to the dawn of Fremont culture. It was a time of great upheaval as Native Americans who knew how to grow crops were moving into the region from the south.
"You have immigrants coming into a landscape that had been occupied for thousands and thousands of years by hunters and gatherers,” Simms said, “and together out of that interaction, they are making a brand new culture."
Many mysteries remain. The science is zeroing in on the "when," but the "who" and the "why" remain elusive.