August 14, 2013
Nevada Rock Carvings Found To Be Oldest Petroglyphs In North America
redOrbit Staff & Wire Reports - Your Universe Online
Petroglyphs cut into boulders in at the Winnemucca Lake site in western Nevada have been identified as the oldest known rock engravings in North America, researchers from the University of Colorado Boulder (CU-Boulder) report in a new study.
The pictogram images pictured include a series of “vertical, chain-like symbols and a number of smaller pits deeply incised with a type of hard rock scraper,” the researchers said, but there are no people, animals or handprint symbols depicted. Benson and his co-authors published their findings in this month’s edition of the Journal of Archaeological Science.
“Prior to our study, archaeologists had suggested these petroglyphs were extremely old,” Benson said in a statement. “Whether they turn out to be as old as 14,800 years ago or as recent as 10,500 years ago, they are still the oldest petroglyphs that have been dated in North America.”
“We have no idea what they mean,” he added. “But I think they are absolutely beautiful symbols. Some look like multiple connected sets of diamonds, and some look like trees, or veins in a leaf. There are few petroglyphs in the American Southwest that are as deeply carved as these, and few that have the same sense of size.”
One of the methods used to date the rock engravings was determining when the Winnemucca Lake subbasin water level reached the specific elevation of 3,960 feet. That information was important to the study because it marks the maximum height in which the subbasin – which at one time was a single body of water connecting two lakes – could have reached before it started spilling excess water over Emerson Pass to the north.
Once the lake level reached that height, the boulders upon which the petroglyphs were discovered would have been submerged, meaning that they could not have been accessible for carving, Benson said.
He added that a white layer of limestone carbonate, which originated from ancient Winnemucca Lake, had coated some of the carvings near the base of the boulders. He had previously demonstrated that the carbonate coating elsewhere in the basin at that elevation had a radiocarbon date of roughly 11,000 years ago.
“Benson sampled the carbonate into which the petroglyphs were incised and the carbonate that coated the petroglyphs at the base of the limestone boulder,” the university explained. “The radiocarbon dates on the samples indicated the carbonate layer underlying the petroglyphs dated to roughly 14,800 ago.”
“Those dates, as well as additional geochemical data on a sediment core from the adjacent Pyramid Lake subbasin, indicated the limestone boulders containing the petroglyphs were exposed to air between 14,800 and 13,200 years ago and again between about 11,300 and 10,500 years ago,” they added.
Benson’s co-authors on the study included Eugene Hattori of the Nevada State Museum, John Southon of the University of California, Irvine and Benjamin Aleck of the Pyramid Lake Paiute Tribe Museum and Visitor’s Center. The research was funded by the US Geological Survey’s National Research Program.