Annual Pembina Gorge Fossil Dig digs up exciting finds

The Pembina Gorge Fossil Dig that is held every year was a success of prehistoric proportions.

fossil dig

Posted on 8/8/15

By Melissa Anderson

With between 9-15 volunteers attending each day over the course of the week, the paleontologists and organizers were able to get a lot of fossils out of the ground.

The Pembina Gorge dig site was once part of the western interior seaway which connected the Arctic with the Gulf of Mexico. This seaway fluctuated in size and depth over the years but covered large chunks of North Dakota about 80 million years ago.

“This is different than Lake Agassiz, which people often confuse with it. Lake Agassiz was a very recent glacial lake,” Becky Barnes, a paleontologist with the North Dakota Geological Survey (NDGS), explained.

To the west of the seaway the Rocky Mountains were forming, producing volcanic events in the process.  Within the site itself,  volunteers can see the results of the volcanic eruptions in thin bands of volcanic ash.

The site was initially discovered in 1999 and dug in 2000 when the roadway nearby was being widened. Since then the NDGS and the Department of Parks and Recreation have teamed up to care for the site and the fossils it contains.

“It’s a slow process, as Mother Nature constantly erodes new fossils each year,” Barnes said.

Each day started with a PowerPoint presentation covering the site’s history. Demo fossils were passed around, typical of what the site produces. Participants were then brought to the site where tools were distributed and a demonstration of proper digging techniques was given. After that, people found their lucky spots and dug for the remainder of the day with a break in the middle for lunch.

“The best part of the dig always fluctuates – enthusiasm spikes each time someone finds something, and ripples of excitement spread.  The lure for digging varies between people – some like sea monsters, some have always wanted to try a fossil dig, some like the great outdoors,” Barnes said.

Typical fossils found at the site include fish scales and vertebrae which are the most common fossils at the site.

“It’s a numbers game – if a fish has thousands of scales and hundreds of bones, you’re more likely to find scales than bones, but both are common,” Barnes explained.

Among the more rare finds of the dig were two partial fish skeletons that included chains of vertebrae or backbones. The most exciting find on the dig was a mosasaur skull found on the very first day, which then took the rest of the week to excavate and place in protective casts for transport.

Mosasaurs were large marine reptiles that lived at the same time as dinosaurs but were not dinosaurs themselves. According to Barnes, the closest living relatives would be varanid lizards such as the komodo dragon.

The NDGS has found mosasaurs in the area before, but a new one is always a happy find for the crew. Barnes explained that when most people visualize skulls or skeletons of fossilized animals, they probably think back to Jurassic Park, with a nice, perfect specimen. This is not the case.

“That almost never happens,” Barnes said.

The NDGS teams work with what they call “prehistoric leftovers” or “road kill”, if you will. Scavengers, rot, and time all take their toll on the animals long before they ever become a fossil and are found by those searching for them.

“That was what we found with the mosasaur skull this year–all of the bones were jumbled, but you could identify individual pieces such as the jaw and nasal,” Barnes explained.

Digging each summer is exhilarating for Barnes and her fellow paleontologists. North Dakota has a wide variety of different types of fossils to offer, and each site is so different from one another.

“It’s a really unique experience. We’re lucky to have sites spread all across the state, offering people from all regions different excursions,” Barnes said.

Summer digs are immensely important to the NDGS as they have to hit a “sweet spot” concerning fossils in the field. Barnes explained that if the teams get there too early, and the fossil is still buried, they won’t see it/find it. But on the flip side, if they get there too late after a rain, frost, wind, cows or machines have done their damage. Then the fossil may be beyond saving.

The NDGS team strives to find that happy medium, where the fossil is exposed a little but still mostly protected. This careful and purpose-filled excavation has to happen each year, as every rainstorm or summer thaw exposes new material.

“It keeps us on our toes for sure,” Barnes stated.

Over the course of the week a major component to the success of the dig is the weather. For the Pembina Fossil Dig, the weather did cooperate for the most part.

“We hit a little rain on Thursday night which made the site too gummy to dig in during the morning hours. ,” Barnes said.

While the dig site dried out, the NDGS and its crew of volunteers instead toured the various local museums. By afternoon the site had dried enough to allow the crew to return to digging,  staying later than the normal end time.

For Barnes and her fellow paleontologists, it’s hard to compare between digs. Each one has different materials, digging requirements, and fossils. The Pembina Gorge Dig, Barnes explained, is one of the easier access sites; a quarry that is returned to year after year, instead of hiking around and prospecting. It’s also rare for the dig teams to have amenities at other sites, such as port-a-potties or shade tents.

“It’s really quite cushy,” Barnes said.

Attendance at the Pembina Fossil Dig was typical when compared to other sites. The NDGS places a cap for each dig’s numbers based on the numbers of staff that will be available for that dig in order to make sure the digger-to-paleontologist ratio isn’t too skewed.

“This way everyone gets their questions answered and given help if needed,” Barnes stated.

Once the fossils from each site are carefully excavated, they are brought back to the paleontology lab in Bismarck where they are cleaned and prepared for exhibition or storage. In this way, the paleontologists can assist researchers when they come to study.

“We also try and bring those fossils back into the public eye and give them an appreciation for what goes on behind the scenes in a museum,” Barnes said.

The experience of a NDGS fossil dig gives people that attend the digs the chance to see first-hand all the time and patience it takes just to get the bones out of the ground. For those that take it another step and volunteer in the lab, the appreciation only grows as they become part of the process of repairing and caring for those fossils.

“Because the fossils come from state land, they belong to everyone. This way we can ensure that the fossils are properly cared for and exhibited across the state appropriately,” Barnes explained.