There is a rocky cliff outside Colorado Springs called Corral Bluffs. It looks similar to many of the cliffs and bluffs found around this state, with layers of brown and red earth sparsely covered with brush, but this place is unlike any other site on the planet.
Earlier this fall, scientists revealed that they had found some of the best-preserved mammal fossils from the time period immediately after the extinction of the dinosaurs and geologist Ken Weissenburger of Grand Junction was there in the thick of the action.
Weissenburger, who earned an undergraduate degree at University of Colorado-Boulder and earned master's and doctorate degrees at Stanford University, has spent his life working as a geologist in the energy sector, but after retiring from that life, traveling around the world on projects, he and his wife moved to Colorado Springs.
While he was living there Weissenburger started to volunteer for the Denver Museum of Science and Nature. He took on a protege, Sharon Milito, a schoolteacher who also volunteered for the museum.
"The museum trains a lot of people to help them with their field work in particular, especially on the vertebrate side," Weissenburger said. "On public lands it's illegal to collect vertebrate fossils because of their rarity and their importance, but they train people to help them."
Milito helped the museum, as a citizen scientist, by doing paleontological resource evaluation on sites around Colorado Springs. If a development or trail was proposed for a site, she would visit and help determine if the site had a value to paleontologists.
Two proposed developments near Corral Bluffs drew the attention of Milito and Weissenburger around 2008. The first was a motorcycle trail and the other was a proposed reservoir. Neither development came to be, but the review got the attention of the museum.
"This is a special place, Corral Bluffs, because it's on the prairie and the prairie is generally pretty flat out there, but here you have 100 meters-plus, 400 feet of cliff," Weissenburger said. "If you're approaching it from the north you just see prairie in front of you until you get to the edge to the precipice. Suddenly you've got the whole world at your feet looking down."
That large cliff section was important because it exposed rock that formed during a very important time — right before and right after the dinosaurs became extinct. That point in time to paleontologists is called the K-T Boundary. Below the boundary you find dinosaurs. Above it you find mammals.
"We knew that this was an important place," Weissenburger said. "We knew that the K-T Boundary was out there somewhere and we had no vertebrate paleontologist at the museum at the time that owned this project."
With no lead scientist Weissenburger and Milito continued to search the site on a volunteer basis. They didn't find very much during that time, at least they thought. Weissenburger was mostly focused on determining the geology to pinpoint what layers of rock belonged to what time.
"So we're doing this from 2008 up until 2016 in fits and starts," Weissenburger said. "This was not a full-time project, it's a part-time thing."
Then in 2016 a paleontologist named Tyler Lyson took on the project for the museum. He didn't have much luck either at first, Weissenburger said. That is until he opened a drawer and found a jaw bone in a concretion that Milito had previously collected.
A concretion is a ball of sediment that can sometimes form around organic matter, Weissenburger said, but that is not what they'd been looking for in the past. Lyson returned to the site, this time hunting for concretions.
"One day he was looking at some of the concretions and he whacked one open," Weissenburger said. "To his surprise inside it was the skull of a mammal looking back at him. So that was his eureka moment."
Up until that find, the work had mostly been done by volunteers with limited resources, Weissenburger said. All that changed with Lyson's discovery.
"In September of 2016 he made the magic discovery that opened the door that led to us finding a big trove of fossils out there and that changed the world for us in terms of this project," Weissenburger said. "We suddenly were not resource limited."
The museum devoted more manpower and resources to the project. Geologists determined specific layers of rocks could be accurately dated based on how the Earth's magnetic field had flipped at that time.
Another scientist found the K-T Boundary using fossilized pollen. Paleontologists found fossils from mammals, reptiles and plants that filled in a critical gap in geologic time.
"We've got a trifecta," Weissenburger said. "We've got all of these animal fossils. We've got all of these plant fossils. These things together are giving you an idea of the whole ecosystem that was there at all these different levels. The other leg that you have in the trifecta is you have time."
Time is where Weissenburger has been focused. Using the magnetic signatures in the rock as starting points, along with some other geologic indicators, he is able to determine with accuracy how old each fossil is based on where they were in the layers of rock.
"My role is to find out what's up and what's down and how old it all is," Weissenburger said. "So when they find fossils we know where they fit in the picture of time."
Weissenburger, who moved to Grand Junction in 2013, is continuing that work as more fossils are found. He goes out to help when the museum researchers are in the field a few times a year. All of this work is detailed in an article in the journal Science, of which Weissenburger is a co-author.
Weissenburger said he enjoys the science aspect of the work, but he's also very interested in the educational and public outreach portion. He said he plans to teach courses in the spring about the find.
"My interest in working with these guys is in large part the education piece of it," Weissenburger said. "I'm a scientist, but I'm also an educator. So this fills two of my boxes."
Weissenburger said he's happy to play the part he has in the discovery and hopes finds like this one encourage people to get out and explore the natural world.
"A big part of this story is that it's been out there right under our noses," Weissenburger said. "You never know when you're going to find the next one."
If you would like more information about the find, Weissenburger recommended a video done by Nova that is available at PBS.com.