Rock Carvings Found in Nevada may be 15,000 Years Old

The oldest known petroglyphs in North America may be nearly 15,000 years old, according to a new analysis by researchers at the University of Colorado Boulder.

The petroglyphs, also known as a rock engravings, are cut into boulders in western Nevada about 35 miles northeast of Reno. Researchers have known about the carvings for decades, but understanding how old the carvings are and what they could mean has been an ongoing puzzle for those involved in their study.

Research leader Larry Benson said the petroglyphs consist of deeply carved grooves and complex dot patterns. The glyphs appear to be a "series of vertical, chain-like symbols and a number of smaller pits deeply incised with a type of hard rock scraper," the researchers wrote in a statement, noting that depictions of humans, animals or hand symbols are notably absent from the carvings.

"We have no idea what they mean," said Benson of petroglyphs. "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."

To date the petroglyphs, Benson and his colleagues used a variety of methods, including determining when an ancient lake system reached a specific elevation of 3,960 feet, which is key to the study because it marked the marked the maximum height the lake system could have reached before excess water started spilling out of the basin. When the water was at such a level, the boulders would have been submerged and inaccessible for carving.

Thousands of years ago, petroglyphs near the base of the boulders were coated by a layer a white layer of carbonate made of limestone which precipitated from the ancient, overflowing lake system, Benson said.

"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 radiocarbon dates on the samples indicated the carbonate layer underlying the petroglyphs dated to roughly 14,800 ago," the university explained in a statement. "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."

Benson added: "Prior to our study, archaeologists had suggested these petroglyphs were extremely old. 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."

Benson and his colleagues research is published in the Journal of Archaeological Science.