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Petroglyph-inscribed rocks.

Petroglyph-inscribed rocks.

Photograph courtesy Larry Benson, University of Colorado

Ker Than

for National Geographic

Published August 15, 2013

Ancient symbols etched onto the sides of boulders lying along the western edge of a desiccated lake in Nevada are the oldest confirmed rock carvings in North America—possibly dating back to the first peopling of the New World, scientists say.

The so-called petroglyphs, carved in soft limestone millennia ago, range from simple lines, pits, and swirls to more complex and ambiguous shapes that resemble diamonds, trees, flowers, and veins in a leaf. They range from about 8 inches (20 centimeters) up to about 3 feet (1 meter) in width.

In a new study, published in this month's issue of the Journal of Archaeological Science, geochemist Larry Benson and his team concluded that the petroglyphs, located about 35 miles (56 kilometers) northeast of Reno at Winnemucca Lake, are at least 10,500 years old, and perhaps as much as 14,800 years 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, who is at the University of Colorado Natural History Museum in Boulder, said in a statement. (See video of rock art in Arizona.)

Clues in Carbonate

To date the petroglyphs, Benson and his colleagues began by figuring out just when they could have been made.

Though Winnemucca Lake is dried up now, it was once so full of water that the boulders upon which the petroglyphs are etched were submerged.

As the water levels slowly dropped, crusts of a mineral called carbonate formed on the boulders. Radiocarbon testing of these carbonate layers revealed them to range in age from about 14,800 to 10,300 years old.

The carbonate ages, combined with an analysis of sediment cores taken from neighboring Pyramid Lake, suggest that the boulders were exposed to air—and thus accessible for carving by humans—between about 14,800 to 13,100 years ago, and again from about 11,300 to 10,500 years ago. In between the two time periods, the boulders were submerged, the scientists say.

It's unknown what method was used to create the petroglyphs, but one possibility is the artists used hard volcanic rock to chip away at the carbonate, which is porous and relatively soft, said Benson, who conducted the dating research while with the U.S. Geological Survey.

As a result, the rock art would not have taken very long to carve, but "whether all of them were done within a short period of time or over a span of hundreds of years, I don't know," Benson said in an interview on Wednesday.

 

Rocks with petroglyphs of trees and diamonds.

Photograph courtesy Larry Benson, University of Colorado

 

Non-invasive Examination

Benson said it might be possible to better pinpoint the age of the petroglyphs, but it would require sampling carbonate from inside the etchings themselves—something that he has agreed not to do.

Benson obtained permission to non-invasively examine the carvings from the Pyramid Lake Paiute Tribe, which owns the land.

"One of the deals I made was that I would only work to the side of the glyphs, and not touch any of the glyphs themselves," Benson said.

Mystery Artists

Prior to the new dating of the Lake Winnemucca petroglyphs, the oldest rock art in North America was thought to be carvings found at Long Lake in Oregon that date to roughly 7,300 years ago.

Benson says he doesn't know what the symbols at Lake Winnemucca mean, or who might have made them, but he notes that their ages roughly match those of several pieces of fossilized human feces, or coprolites, that were discovered in Paisley Cave in Oregon and dated to around 14,400 to 13,000 years ago.

This date is close to when scientists think humans first began settling the Americas. In a new study published in this week's issue of the journal of the Proceedings of the National Academy of Sciences, scientists say they have found genetic evidence that a first wave of migrants crossed into the Americas from Asia about 15,000 to 18,000 years ago by slowly creeping down the continent's coasts.

A few thousand years later, according to the study, a second wave of humans entered North America, this time by slipping across the Bering Strait into Alaska and then crossing through an ice-free corridor into Canada.

Benson speculated that members of the first wave of settlers might have been responsible for the Lake Winnemucca rock art.

"It's possible that those people did occupy areas farther south, like the Lake Winnemucca area ... [but] it is also possible that paleoindians occupying the Winnemucca Lake basin between 11,300 and 10,500 years ago carved the petroglyphs," he said.

"At the moment we have no way to decide between the two possibilities."

Follow Ker Than on Twitter.

5 comments
James John
James John

"The carvings shown in photo looks like the rock carvings seeing in Kerala Stone Age Caves and sites. I think all ancient man have same style of drawing skill. Each carving shows his strong emotional output, because he had excited mind or tensed thoughts, that lead him to express those by carve his emotions on a hard rock."

Robert Peterson
Robert Peterson

It is interesting to see such nice photos of these panels.  I photographed them in the 1980s at night using off camera flash.  It was very difficult to get good daylight shots of them, as the lighting was rarely as nice as that and idiots had been chalking them to try to make them show up better.  I did get some very nice photographs but it was quite difficult and required very long exposures, multiple flashes and crawling around in the dark with no lights.  A couple of my photos were at one time on display at Pyramid lake along with a large number of other peoples photographs of the area. It is fascinating to get a handle on the age.  I had been under the impression that the Great Basin Rectilinear and Curvilinear styles were a lot younger than that.  It is interesting to see the dates for rock art pushed back that far.  When were the boulders exposed to the air for the last time?  Could they, however,  have been carved subsequent to lake levels dropping after the 11,300 - 10,500 exposure?  Determining that would probably require tests in the glyphs themselves.

Ron Prondzinski
Ron Prondzinski

Hello,

In my profession as a stained glass artist I must often reconstruct broken pieces of painted glass. I have also had a long time interest in archaeology where similar reconstruction is done using various methods. 

When  I viewed these pieces of rock and the various patterns on them I immediately could see that the boulders were fragile and appeared to have fallen over from the main rock above. Obviously, one cannot move the pieces and re-stack them for the reasons mention in your article. 

The solution I believe, is to use a 3-D scanning method called Metrology, which involves laser scanning the pieces. I have been doing some research into this for use in my profession. There are many different machines and software available that would capture a great deal of the boulder shape and surface texture, and allow for approximate reconstruction in 3-D. Here is the address of a company that I believe could help: http://www.exactmetrology.com/services/applications/art-architecture/

Something that would need to be figured into the reconstruction is how long have the pieces been broken from their original position. There is the erosion of the once joined matching surfaces, and the accumulation and subsequent erosion of that said material around the bases of the boulder. You may need to ask if would be okay to dig a small trough under one of the boulders simply to inspect the depth it is embedded, Perhaps ground sonar might work on this exploration.

I'd like to hear some feed-back on this, and would really be excited to see if anyone is willing to carry the ball here.

Great work!

Ron Prondzinski

 

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