A group of 6,700-year-old carvings in Oregon just lost their title as oldest rock carvings in North America, LiveScience reports. Researchers just discovered that ornately designed petroglyphs in Nevada may be more than twice as old as the Oregon rocks.

The true age of this rock art had not been known, but a new analysis suggests these petroglyphs are the oldest North America, dating back to between 10,500 and 14,800 years ago.

The rocks occupy a spot in the Nevada desert once covered by Winnemucca Lake. After a dam was built in the early 20th century, however, the lake dried out. Years ago, however, this lake sometimes became quite deep. Researchers decided to use ancient water marks to estimate the rock art’s age.

The overflowing lake left telltale crusts of carbonate on these rocks, according to study researcher Larry Benson of the University of Colorado Boulder. Radiocarbon tests revealed that the carbonate film underlying the petroglyphs dated back roughly 14,800 years ago, while a later layer of carbonate coating the rock art dated to about 11,000 years ago. Those findings, along with an analysis of sediment core sampled nearby, suggest the petroglyph-decorated rocks were exposed first between 14,800 and 13,200 years ago and again between about 11,300 and 10,500 years ago.

The carvings feature depictions of nature and geometrical motifs, although “we have no idea what they mean,” Benson writes in a press release. “But I think they are absolutely beautiful symbols.”

More from Smithsonian.com:

Oldest American Rock Art Found in Brazil

Dampier Rock Art Complex, Australia