'Golden' fossils reveal new secrets; provide clues to Jurassic extinction event
AUSTIN (KXAN) - Fossils that have been making "fools" out of scientists for decades are getting a new look. Researchers with the University of Texas' Jackson School of Geosciences published a paper in Earth Science Reviews showing that fossils commonly thought to be coated in pyrite, also known as 'Fool's Gold," had been deceiving scientists for decades.
"There's a lot of work being done in paleontology that relies on assuming that we're seeing everything. And we're very rarely seeing everything," said Rowan Martindale, Ph.D., an associate professor with the Jackson School. She oversaw the team that did the research.
The study, led by Drew Muscente, a former Jackson School postdoctoral researcher, examined fossils found in Germany.
"These iconic fossils, so many of them have this beautiful, sort of golden sheen," Martindale said.
Fool's Gold and Fossils
The fossils are of creatures from the early Jurassic period, about 165 million years ago.
"It's the time where organisms were dying, going extinct. But it's also the same time we find like organisms are well preserved," said Sinjini Sinha, a doctoral student at UT Austin who worked on the project.
Sinha said that the fossils from the period show not just bone, but skin and hair.
"They preserve In exquisite detail with even embryos and babies preserved in in their mothers," Martindale said.
The creatures were killed due to a change in the ocean's oxygen levels. We're not sure what caused this extinction event. "Anything that swam around in the surface ocean died, fell to the sea floor, and then there was no oxygen," Martidale said.
Fool's Gold forms in these low oxygen environments, which is why scientists assumed that was what gave the fossils their sheen.
But when Muscente and Sinha looked at the fossils under an electron microscope, they discovered something intersting. "I found like the pyrite is present minimally on the fossils," Sinha said.
"The ones that we thought for sure, pyrite, they're they glitter, they're beautiful, they're golden. There's no pyrite or there's maybe a little bit of pirate," Martindale said.
The pyrite was instead found on the rocks around the fossils. "When we zoomed in, like 500 microns, we could see the features of the shell," Sinha said the new view revealed the fossils themselves were getting their sheen from phosphate, a different mineral that needs oxygen to develop.
Clues to extinction
The researchers took a closer look at the fossils, which had been studied for decades, after notcing two things.
For one, many of the fossils had not developed "pyrite disease." When pyrite is exposed to oxygen, it frequently blooms and crumbles. These fossils did not.
The other thing is that we often get things like lobsters, we get things like oysters and clams," Martindale said these creature live in areas that require oxygen.
The team checked fossils from around the world. Samples from Canada and the United Kingdom also contained phosphate.
In the end, researchers checked 70 samples under an electron microscope. Larger samples were sent to the University of Missouri, which has a larger microscope. All of the samples showed the same result.
Many scientists believe that the extinction event was a direct result of oxygen levels in the oceans plummeting. The new discovery means that oxygen likely still existed in the ocean, but the extinction event still happened.
"There's no evidence of low oxygen. So that might make us think more carefully about what's going on today," Martindale said.
One of the issues arising in our oceans today is de oxygenation. According to the International Union for Conservation of Nature, warmer ocean water holds less oxygen and is more buoyant than cooler water. As the ocean warms, less oxygen is available for sea creatures.
The new research means that oxygen being completely removed from the oceans isn't required for the an extinction level event. Only slight changes can have a massive impact.