Mammoth Site Sinkhole revealed to be at least 140,000-years-old

HOT SPRINGS, S.D. (KEVN) - It has been nearly 30 years since dating was done on a sinkhole once filled with warm water and struggling mammoths, and scientists at The Mammoth Site it was time to try something new.

"There's been a lot of improvements in the last 30 years and so we were interested in seeing some of these new dating techniques," said Dr. Sharon Holte, scientific educator at The Mammoth Site.

One of those techniques and the one used for The Mammoth's Site Sinkhole was the Optically Stimulated Luminescence Method. "This OSL dating method looks at mineral grains that have not been exposed to light so those mineral grains have been buried underground and the more light that's exposed to them, they start to decay so what we do is we sample these specimens in the dark and we look a the decay rates coming off of mineral grains such as quartz and feldspar," Dr. Holte said.

After collecting the samples, researchers found the sinkhole to be 50,000 years older than they originally thought. The surprise and real interesting part about The Mammoth Site is that it hosts the real remains of mammoths that existed over 140,000 years ago.

"At 190,000 years ago, we were coming out of a very cold glacial period where the ice sheets were covering most of North America and just starting to recede. By 140,000 years ago, we are right in the middle of a very prominent inter-glacial period where it was a lot warmer, considerably warmer than it is today," Dr. Holte continued.

Dr. Holte and Justin Wylkins, bone bed curator, says the process took them about two years and it's one several sites around the region are using to get answers. They say the in-depth study lets the public know about the significant environmental changes around the continent and in the hills.

"We did take samples from other areas around the Black Hills and compare them to our site as well so we can get a better framework and understanding of some of these major changes that are happening," Holte said.

"The earth is not just a static environment. We can come here to the Mammoth Site and we can see not only how the layers of dirt change that we can observe and touch in some cases but we can see how the animals change over time," Wylkins expressed.

All of the exhibits at The Mammoth Site are undergoing renovation. The site is open from 8 a.m. to 8 p.m. daily and the last tour goes out at 7 p.m.