Utah State University's luminescence geochronology laboratory is helping archaeologists and geologists study ancient sites threatened by erosion by the Colorado River.
Last month, the U.S. Bureau of Reclamation awarded $2.3 million to study archaeological sites below Glen Canyon Dam, including at least one that may have been in danger of further erosion during the recent high-flow experiment.
In the test, bureau officials released about 41,500 cubic feet of water per second for 60 hours. The experiment is to check whether spring flooding, curtailed since construction of Glen Canyon Dam began in 1963, would benefit native fish, rebuild sandbars and return fine sediment to the Colorado River system.
But one concern is that the release could further erode riverbanks that preserve archaeological evidence. The grant was awarded to USU and the Zuni Cultural Resources Enterprise, fielded by the Zuni Pueblo. USU does geology while Zuni scientists carry out the archaeology. Over the next five years, they are to document and study ancient sites that may be in danger of eroding away.
Recently they worked near Nine Mile Draw, about five miles downstream from Glen Canyon Dam, notes USU. There, an eroded riverbank showed the presence of scientifically valuable information.
The contract covers "archaeological sites along the river in both Grand Canyon National Park as well as the reach of Glen Canyon that's below the dam," said Joel Pederson, principal investigator for geology and an associate professor at USU in Logan. He is also director of the university's new luminescence lab.
Four USU specialists are working on the project: Pederson, grad student Erin Tainer, project manager Gary O'Brien, and Tammy Rittenour, who oversees the luminescence laboratory operations.
The laboratory, the only one of its kind in Utah, can date sand sediments up to about 300,000 years old, Pederson noted last year when it opened. Grains of quartz in sand and pottery retain information about how long ago they were exposed to sunlight. The lab can test these and calculate when that was.
The teams think archaeological sites exist in both Glen Canyon and the Grand Canyon that are older than previously been believed. "There's the potential for finding archaeological sites that are many thousands of years old," he said. Evidence for an Anasazi presence is well-known, but the archaeologists are "very excited" about earlier material lower in the sediments.
They would like to learn whether people in the region were farming or following a hunter-gatherer lifestyle. If farming and "there have been some indications" of farming, he said archaeologists want to discover "when they might have started farming."
So far, the work has been close to Lee's Ferry, Ariz. The National Park Service provided a shuttle boat so researchers could go to facilities each day at Lee's Ferry "and we could shower," he said. But soon the teams will move to more remote areas, using river expeditions, and the scientists will need to camp.
Near Lee's Ferry, the group studied a site "right on this eroding, cut bank on the river," he said. Loose sediment was falling off the escarpment and into the Colorado River.
"Here and there, sort of peeking out of that beautiful sediment, were little hearths or little campfire sites," he said. Some seemed to be older material, camps used by hunter-gatherers. There were stone-tool flakes, and, in the later sites that were higher on the bank, evidence of pottery.
A couple of weeks before the high-flow experiment began on March 5, "we actually did excavate out some of these campsites and remove it, in case this flood caused a bank collapse," he said. Camps in the lower strata may be about 2,500 years old, he said.
Sediment samples were taken to the luminescence lab, and the experts will continue gathering samples as the survey proceeds. "Maybe this summer we'll start to get results back" from the first samples, he said. Meanwhile, the USU team found the experience rewarding."You get to work in a beautiful place," Pederson said, "and it's really exciting as a geologist to work with the archaeologists."