Isaac Humburg and Jim Pollard are shown on the side of the hill looking for enigmatic spheres along the banks of Elk Creek in South Dakota.

For several years, Blue Earth resident, amateur fossil hunter and curator at the Southern Minnesota Museum of Natural History, Jim Pollard, has sponsored taking a local youth and his/her parent on a fossil dig adventure somewhere.

This year’s summer fossil dig included 10-year-old Isaac Humburg and his mother, Marissa, of Blue Earth.

They were on the trip during the days of June 23-25.

They were guided by paleontologists Don and Karly Litchfield as they hunted for ancient sea animals along Elk Creek in South Dakota.

“Ammonites, baculites, clams, and scaphites lived within a narrow seaway that cut North America in half, stretching from the Gulf of Mexico to the Arctic Ocean during the ‘Age of Dinosaurs,'” says Pollard.

Hunting for fossils differs from place to place, but at Elk Creek, they are hidden inside enigmatic stone spheres, Pollard explained. These can be as small as soccer balls or giant, thousand-pound behemoths. Finding the spheres is not a problem; they are laid out in horizons along the creek embankment, laid to rest by tidal wave action. However, accessing their hidden treasures is another matter. Drills, hammers, and crowbars must be deployed.

“While swinging hammers at stone, we talked among ourselves, wondering what life might have been like in this underwater realm,” Pollard says.

After cracking open a sphere, Isaac exclaimed, “I found ammonites, and a baculite with a Mosasaur bite mark!”

One can only guess how the other creatures in the sphere died. It was a perilous place where every animal could become another’s next dinner.

Isaac was relentless in his quest for the next fossil, and by the end of the day, his mother Marissa’s car was filled with treasures.

Was it fun?

“It was great!” Isaac says. “We found a lot of stuff that we were looking for, and they were really well preserved fossils.”

He adds that he learned a lot on the trip, too.

“I learned about how to open a fossil ball,” he says. “I thought you just used a pick axe and smashed it open. I like how when you crack open a fossil ball, there is always something in there.”

Isaac’s mother, Marissa Humburg also was impressed with the trip.

“Don and his daughter Karly were excellent teachers, they showed Isaac how to locate fossil balls and how to open them up,” Marissa says. “Don took Isaac to dig sites where he knew Isaac would be able to find lots of fossils. You could tell that Don and Karly enjoy working with kids, teaching them everything they know about the process. I also liked that it was a safe dig site, that Isaac could roam around freely, exploring the ground for fossil balls.”

Marissa says she and Isaac met Jim Pollard two years ago when his fossil display was in the Blue Earth Community Library. Isaac, who already had a strong passion for fossils and rocks, loved being able to walk around with Pollard and listen to him explain about the different fossils.

“We also learned during that time that Jim takes kids out on fossil digs, but Isaac had to be 10 before he could go,” Marissa says. “Now, two years later, Isaac finally got the chance to go. I can’t thank Jim enough for setting up the fossil dig with Don, it was a wonderful experience. Isaac learned a lot and it has only helped to grow his passion for fossils and rocks even more.

Isaac is already planning his next dig. Dinosaurs in Montana? Ancient mammals in Wyoming? Marissa says he would like to go on another fossil dig in Lusk, Wyoming.

This was only day one of what could be a lifetime of adventures.

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enigmatic spheres

by Jim Pollard

Enigmatic spheres found on the soaring banks of Elk Creek in South Dakota have long puzzled scientists. What conditions created them? Why are they only found in certain locations? How is it that some are densely packed with shell fragments, while others are mostly mud with a fossil in the center?

For answers, we go back 100 to 66 million years, when North America was divided by the Western Interior Seaway. These warm, shallow waters were teaming with life. Algae and kelp forests provided a diverse food chain for swimming reptiles, fish, and shell-bearing mollusks, including baculites, ammonites, scaphites, and clams.

When a mollusk died, it fell to the seafloor and became covered in sediment. Bacteria fed on the soft tissue remains and, through a process only recently understood by scientists, encapsulated the dead mollusk in a calcium carbonate covering called a “concretion.”

Intermittent, high-energy events, including solar and lunar tides and storms, rolled the small concretions over the clay-rich sea floor, growing them in size. But to develop into the heavy spheres like those found today along Elk Creek required significantly more energy than what these forces could supply.

Recent discoveries show a link between meteorite impacts and the formation of these large spherical objects that often weigh hundreds of pounds. Each meteorite generated a powerful tsunami that scoured the shallow sea floor, rolling small sphere-like concretions into larger ones, in the same manner as when making a snowman. The “mud balls” grew in size until the tsunami exhausted its energy and the spheres rolled to a stop, forming an extensive horizon.

Over a 12-million-year period, more than six scientifically dated meteorite impact sites have been identified within the Western Interior Seaway region, and the dates match the horizons exposed on the banks of Elk Creek.

Some of these spheres are found densely packed with shell fragments, while others were mud with a mollusk shell at the center, and it was random luck as to which was which. It all depended on the shell debris field on the seafloor where the mud ball was rolling.

The spheres not only preserve forensic details of ancient fauna, but are also manifestations of the tremendous extraterrestrial forces that led to their creation. And who knows, maybe one of these spheres was rolled by the shock wave produced by the asteroid that ended the age of dinosaurs!