Ozarks Fossil Hunting

Hiking in Northwest Arkansas is always satisfying. As the leaves fall and meadows of wildflowers die back, though, you might want to add an extra element to your hikes. Why not look for fossils?

In 2003, a team of students from the University of Arkansas found the largest fossil of a cephalopod (think octopus) on record while digging in a ditch along Interstate 540. It was the 2nd of its kind found in Fayetteville, joining a slightly smaller specimen that was unearthed forty years before. Just this year, a portion of a spine from a prehistoric shark was documented in a cave just south of Springfield, Missouri.

The mountain vistas of the Ozark Mountains may not make you think immediately of an ocean floor, but that’s exactly what much of our region was just over 300 million years ago. The rich limestone deposits and shale in these mountains are a result of ancient sea life living and dying in the seas of prehistoric Earth. For that reason, hiking through the mountains (or sitting on the banks of a river) provide an excellent opportunity to pick up a little memento in the shape of a fossilized creature such as an ammonite or chrinoid.

Paleontologists tell us that the Ozark Mountain plateau was what is called a “dome” under the surface of the ocean, a shallow area that was home to all manner of sea-living invertebrates. By contrast, the Ouchita Mountains were the bottom of a deep sea ocean, which is why it is not as littered with fossils as the Ozarks.

It’s easy enough to find fossils if you just know what to look for. Exposed limestone bluffs are a perfect spot to sit and scan your surroundings. Many chunks of limestone contain the little rings of chrinoid fossils – resembling stone replicas of rubber gaskets. If you’re lucky you might find a section of the rings still stuck together – the spine of the plant, in essence – and lying right on the ground, unattached to surrounding rock.

Ammonites are also fairly easy to recognize in the limestone, and you may find nautiloids, trilobites, and stromatolites as well. Check out the Arkansas Geological Survey’s poster to get a sense of what the common fossils look like.

Are you allowed to pick them up? On public land, invertebrate fossils may not be protected, but vertebrate fossils usually are. On private land, you just need the permission of the owner of the land.

If you can’t — or don’t care to — take the fossil as a souvenir, take a picture or a rubbing for your naturalist notebook.

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