Friday Headlines, August 23, 2013
THE LATEST IN THE GEOSCIENCES
After a hiatus due to field work, I’m back to this fun weekly post.
Today’s round-up:
For the first time in 35 years, a new species of carnivore has been discovered in the West.
Rock art older than 10,000 years has been discovered in Nevada.
The olinguito is found the the cloud forests of Columbia and Ecuador. Its presence hasn’t been unknown to science, however it has been mistaken for years for its larger cousin the olingo.
Though it looks a little like a cross between a bear and a cat, it’s really most closely related to raccoons. Though superficially similar to the olingo, its skull, teeth, and skin are distinct from other members of the raccoon family.
And it’s cute.
Oldest rock art in North America revealed.
In northwest Nevada is a dried-up lake bed called Winnemucca. Along its west side are limestone boulders with carvings on them, which have now been dated between 10,500 and 14,800 years old.
All right. So, how do you date carved rocks?
In this case they used radiometric dating on carbonate crusts on the rock. Carbonate formed when Winnemucca Lake was actually a lake and the crusts precipitated from the lake waters with the help of bacterial processes.
Carbon in the carbonate retains its isotopic signature from when it formed, this includes radioisotopes like carbon-14. So if we carbon-date the rock the petroglyphs are carved into, we know that the petroglyphs can be no older than that. This rock is dated to about 14,800 years ago.
Some of the petroglyphs have younger carbonate over the top, that clearly formed after the petroglyphs were carved. So if we date those, we know the carvings can be no younger than that. The over-growing carbonate is dated to between 10,200 and 9,800 years ago.
Hence, the petroglyphs were carved sometime between 14,800 and 10,200 years ago, making them the oldest rock art in North America.
Penny Higgins - Storyteller • Artist • Scientist 
Does the younger carbonate in the petroglyph carvings require water to form? Would its presence imply that the rock was re-submerged after the carvings were made?
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