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Prehistoric McHenry County

Eurypterus, a common Upper Silurian eurypteid, by Obsidian Soul.
Eurypterus, a common Upper Silurian eurypteid. Photo: Obsidian Soul.

An Oakwood Hills man discovers traces of life on Earth – even before dinosaurs – right under his feet.

Nothing is more satisfying than taking a trip back in time and losing yourself in the past. You only have to pretend that you have a time machine and set the dial for the time and place you want to explore.

Let’s set our time machine for McHenry County, 420 million years ago during Earth’s Silurian Period.

The reign of the dinosaurs was still roughly 200 million years into the future during this period, but the shallow tropical sea that covered Illinois teemed with life. Shelled animals like brachiopods, clams, snails and trilobites called this sea home. A massive coral reef that contained sponges, crinoids and bryozoans stretched from Racine, Wis., to Thornton, Ill.

“Hidden in plain sight is a lost world of marine fossils just waiting to be discovered.”

It was by accident that James Iverson, 54, ended up taking a trip to this prehistoric period, and it’s a trip he can’t resist taking regularly. It started right in his back yard.

“I found my first McHenry County fossil about 20 years ago while landscaping on my property in Oakwood Hills,” Iverson said. “The hexagon pattern made me think it was a fossilized bee’s nest. A trip to the local library and a couple geology books later and I had a new appreciation for what I had found. It turned out to be a piece of coral – hundreds of millions of years old. I was fascinated and hooked.”

Since then, Iverson has searched quarries, gravel pits, farm fields and river banks throughout McHenry County.

“I’m always amazed by my discoveries,” he said. “Hidden in plain sight is a lost world of marine fossils just waiting to be discovered.”

An ancient brachiopod from a quarry in Crystal Lake was followed by numerous pieces of coral discovered in Oakwood Hills, Bull Valley and Cary. Sedimentary rocks with varying layers of color and, from a much more recent time, an expertly crafted arrowhead from a Fox River Grove riverbank also made their way into Iverson’s collection.

“With the approahcing spring weather, I encourage others to get outside and take a trip back in time to uncover the geology of McHenry County,” Iverson said.

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