Scientists may have found the oldest petroglyphs in North America.
The "large, deeply carved grooves and dots forming complex designs on several large limestone boulders," are estimated to be from between 10,500 and 14,800 years ago, a University of Colorado news release reported.
The ancient carvings, discovered at the Winnemucca Lake petroglyph site in Nevada, exhibit "a series of vertical, chain-like symbols and a number of smaller pit" that were most likely created with a rock-scraper tool.
"We have no idea what they mean," study leader Larry Benson, an emeritus USGS scientist, said. "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."
In order to date the rocks the research team determined the history of the surrounding Winnemucca Lake subbasin's water level. When the basin was at an elevation of 3,960 feet, the rocks would have been under water and inaccessible for carving.
When the basin was at this height it would have spilled water over the Emerson Pass.
The petroglyphs and surrounding area were coated with a white limestone carbonate caused by the water that once covered it.
Radiocarbon dating of the boulders' coating suggested they were exposed to air between 14,800 and 13,200 years ago, and then again between 11,300 and 10,500. The carvings must have been created during one of these periods when the rocks emerged from the water.
"Prior to our study, archaeologists had suggested these petroglyphs were extremely old," Benson said. "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."
Researchers had also found fossilized human excrement in an Oregon cave dating back to 14,400 years ago, which agrees with the carvings' estimated timeframe.
Oregon petroglyphs (once believed to be the oldest in North America) have a similar appearance to the Nevada boulders. The carvings were buried in ash after the eruption of a volcano, which allowed scientists to determine they were at least 6,700 years old.
Some of the oldest-known carvings in the world date back to before the last ice age 22,000 years ago, Australian Geographic reported.
The Australian rocks depicted "human-like figures, human faces and animals that no longer inhabited the region, including the Tasmanian tiger."
