Fossil dissolution study propels student to a Ph.D. program

RAPID CITY, S.D. (KOTA) - A South Dakota Mines student set out to find answers on fossil dissolution rates. Her findings landed her a spot in the paleontology Ph.D. program at the University of Kansas.

Erosion due to weather is a constant process on Earth, and rainwater is one of the primary ways rocks and minerals break down. According to the South Dakota Mines website, “paleontologists have not yet gained a complete understanding of the rate fossils erode once they are exposed at the surface.”

“What we wanted to look at is what their longevity was when they’re exposed to these conditions,” said University of Kansas Ph.D. student Colleen Sullivan, “We did laboratory experiments with different fossils from a mosasaur, cause that’s a really common fossil to find in this area.”

Takeaways from the project according to Sullivan were the look into taphonomic biases that aren’t really researched in the field, since not everything gets fossilized, and to give field paleontologists a better understanding of how long they have to collect a fossil once it’s dug up and exposed to the surface.

“Give new information to field paleontologists and to kind of give them more info on the longevity of fossils because we didn’t really have a quantitative value for this before, it was very qualitative, we know it’s bad, but we can’t put a number to it,” said Sullivan.

According to Sarah Keenan, an assistant professor at South Dakota Mines, it was the lack of research into the subject of fossil dissolution that helped propel the research on how acidity in pH levels affects the rate fossils erode at.

“We knew from prior work on pure mineral dissolution people have done experiments looking at apatite dissolution, which is the primary mineral found in bone, but no one had done bone dissolution and fossil bone is a composite of multiple minerals fazes,” said Keenan, “So, we had an idea with increasing acidity or lower pH and expected to find dissolution rates to increase; which is what we observed.”

Keenan noted that acidity levels vary from area to area making it a significant factor they had to look into while researching the topic.

“A lot of precipitation is naturally acidic, certain areas have higher acidity rainfall and snowfall,” said Keenan, “So, by knowing how different precipitation will affect bones we’re able to come up with a number and numerically quantify how fast will a fossil dissolves under certain conditions.”

Keenan added this was only the first step in a process that will hopefully help paleontologists understand what types of fossils are preserved overall.

“Once we have things that enter the fossil record, they exist for millions of years and then come back to the surface,” said Keenan, “Hopefully, this will help to stimulate some ideas on what are we missing, what else are we missing that we haven’t thought of yet?”

Fossils are rare, so anyone who finds a fossil should leave it in place and contact experts to assess it. According to South Dakota Mines, those who collect fossils on their own run the risk of destroying scientific information about their location and context that can’t be recreated.

If you are interested in learning more about Sullivan’s findings you can find her research in the peer-reviewed open-access scientific journal PLOS ONE.

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