Mines student recognized for research on fossil dissolution rates

RAPID CITY — A South Dakota Mines graduate student has published research on the rate that fossils erode when they’re exposed to the surface.

Colleen Sullivan’s research has just been published in the peer-reviewed open-access scientific journal PLOS ONE.

In a news release from Mines, Sullivan said she was studying the effect of rain on exposed fossils and noticed there was little research on the subject.

“This is the first time someone has put a numerical value on the rate of fossil dissolution due to interaction with rainfall,” she said.

Sullivan, who completed her master’s in paleontology at Mines this year, tested fossil vertebrae to determine how long they would take to dissolve with various levels of acidity mimicking the chemistry of average rainfall. She found higher rates of acidity lead to faster dissolution. She then calculated how long an exposed fossil might stay at the surface before being lost to weathering and erosion.

“If we just focus on rain, the smaller fossils will be dissolved and unrecognizable in about a decade,” Sullivan said. “Something like a skull or larger fossilized bone with more mass is going to vary; bigger fossils could last longer on the surface maybe a century.”

Sarah Keenan, Ph.D., an assistant professor in the Department of Geology and Geological Engineering at Mines, said the research adds to the understanding of what types of fossils are preserved overall.

“This is important for addressing biases in our fossil collections as a whole,” says Keenan. “Not everything gets fossilized in the first place, and then the limited selection of fossilized remains are exposed and degraded at the surface, further reducing the selection. So, when we are talking about the whole fossil record, we are looking at a snapshot of a snapshot of life on earth.”