One of the most iconic works of Ancient American art is likely hundreds, perhaps thousands, of years younger than was previously believed, according to new research.
The giant display of ghostly, larger-than-life-size, ochre-colored figures painted on a remote sandstone wall in Utah’s Canyonlands National Park is considered the defining example of a rock art technique known as the Barrier Canyon Style.
The style, recognized by its wraith-like, often limbless, anthropomorphic figures painted on a heroic scale, is found throughout the Colorado Plateau.
But since the original Barrier Canyon panel, known as the Great Gallery, was first discovered by scientists in the 1920s, experts have debated how old the images are, and what culture created them.
Some archaeologists have theorized that the rock art may be as much as 4,000 to 7,000 years old.
But new chemical analysis of the Great Gallery, combined with some other geological detective work, suggests it was painted much more recently, and may even be little more than 1,000 years old.
“The painting of the Great Gallery occurred during a window between late Archaic time, around A.D. 1, through the introduction of maize and the bow and arrow to Utah, and on to the peak of the Fremont culture A.D. ∼1100,” writes a team of archaeologists in today’s issue of the Proceedings of the National Academy of Sciences.
While the team limited its research to the famous Great Gallery, they say that their findings may have important implications for the origins of the Barrier Canyon Style.
If their data are correct, they say, the rise of this style of art may coincide with the advent of agriculture in the northern Four Corners region, perhaps inspired or influenced by immigrants from the south who introduced farming to the area.
If that’s the case, the Barrier Canyon Style and its hallmark grandiose forms “may not have been limited to a specific archaeological culture,” the team writes.
Rock art is notoriously difficult to date, but paintings on rock, or pictographs, like those found at the Great Gallery, usually offer an advantage, because they have pigments that can be tested. [Learn what technology has revealed about pictographs in Texas: “Ancient Rock Art in Texas Yields ‘Surprising’ New Finds“]
But previous research at Barrier Canyon, also known as Horseshoe Canyon, had found that the pigments contained no organic materials, and couldn’t be radiocarbon dated.
However, new technology — known as optically stimulated luminescence dating — has proven extremely useful in determining when mineral deposits that have been buried were last exposed to sunlight, and for how long.
This may not help date the Great Gallery itself, but it proved crucial in analyzing the canyon’s other features — namely, the layers of sediment on which ancient artists likely stood, and the fragments of their art that fell off the canyon wall centuries later.
An international team of researchers, led by Utah State University archaeologist Joel Pederson, first set about setting a maximum age for the Great Gallery, by using luminescence to date the layers of sediment on the canyon floor.
The team found two strata that revealed important geological events.
The first was a thick layer of flood-driven sediment that filled the canyon high above the level of the Great Gallery, up until about 8,000 years ago.
Over the following 5,000 years, most of this layer eroded away, eventually exposing the sandstone panel in the canyon for the first time.
Therefore, the team writes, “the art is incontrovertibly younger than the top” of that layer.
Then, their analysis showed, a second, newer layer of sediment was laid down between 3,000 and 800 years ago. This became the modern canyon floor.
“It is, in fact, possible,” Pederson’s team writes, “that … [these] deposits provided a standing platform for [the Great Gallery] artists.”
Taken together, these dates seem to disprove the oldest proposed dates for the gallery, the archaeologists say.
“This reasoning alone makes an early Archaic (>5000 B.C.) origin for the Great Gallery improbable, and any older hypotheses are ruled out,” they write.
But then there was the matter of how young could the artwork be.
To find a minimum date, Pederson’s team focused on that remnant of the Great Gallery that had collapsed in an ancient rockfall.
Again using luminescence dating, the researchers tested quartz grains from the face of the fallen rock, as well as the sediment that the boulder landed on.
Both of the luminescence dates — along with the radiocarbon date of a leaf that was serendipitously pinned between the boulder and the sediment — returned the same date range: about 900 years old.
Since the Great Gallery must have been painted before the rockfall, the scientists conclude, “these three convergent dates provide a very solid minimum age constraint of A.D. 1100, the height of the Fremont culture.”
Finally, the luminescence technique provided one last data point that allowed the team to zero in on the art’s age even further.
Luminescence technology can be used not only to measure the last time a mineral was “charged” by exposure to sunlight, but also to determine how long it was exposed to light, in a process called “bleaching.”
Using this approach, the team determined that the face of the rockfall had been exposed to sunlight for at least 700 years before it collapsed, putting the approximate date of the artwork’s creation in the 5th century.
Judging conservatively, the team concludes that Canyonlands’ Great Gallery was created between 900 and 2,000 years ago. [Learn about the discovery of the oldest known rock art in North America.]
This is the period, Pederson’s team points out, when immigrant groups from the Four Corners region were thought to have first moved into the area north of the Colorado River, introduced local foragers to the game-changing practices of agriculture and village settlement patterns.
Some experts suspect that this interaction gave rise to the Fremont culture, which in time developed its own distinctive, more geometrical rock art style.
So rather than being the signature of a single, elusive group, the Barrier Canyon Style may be the artistic expression of multiple cultures as they mingled to form a larger and more enduring society, they say.
“If so,” the team concludes, “then it was made by peoples of contrasting heritage, but who nevertheless maintained a common tradition, expressed in the compelling iconography of the Barrier Canyon Style.”