At least one of the petroglyph panels from Long Lake was buried by ash from an eruption of the nearby Mount Mazama volcano roughly 6,700 years ago, proof that it was carved sometime before the eruption.
"We have no idea what they mean," Benson said of the Winnemucca Lake petroglyphs.
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.
"Prior to our study, archaeologists had suggested these petroglyphs were extremely old," said Benson, also an emeritus USGS scientist.
There are few petroglyphs in the American Southwest that are as deeply carved as these, and few that have the same sense of size." Benson obtained permission to non-invasively examine the petroglyphs from the Pyramid Lake Paiute Tribe, which owns the land.
Study co-author John Southton, a faculty member at University of California, Irvine, radiocarbon dated the material for the study.
Scientists deciphered maternal genetic material from two babies buried together in Alaska 11,500 years ago.
Some look like multiple connected sets of diamonds, and some look like trees, or veins in a leaf.Co-authors on the study included Eugene Hattori of the Nevada State Museum in Carson City, Nev., John Southon of the University of California, Irvine and Benjamin Aleck of the Pyramid Lake Paiute Tribe Museum and Visitor's Center in Nixon, Nev. 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."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." While Native American artifacts found in the Lahontan Basin -- which encompasses the Winnemucca Lake subbasin -- date to the time period of 11,300 to 10,500 years ago, it does not rule out the possibility that the petroglyphs were carved as early as 14,800 years ago, Benson said.The oldest dates calculated for the Winnemucca Lake petroglyph site correspond with the time frame linked to several pieces of fossilized human excrement found in a cave in Oregon, said Benson, who also is affiliated with CU's Institute of Arctic and Alpine Research.Now, the fuller that barrel gets the more water is going to leak out the thoroughly perforated sides, just as more carbon-14 will decay if you have more of it around.