Chicago Rants

Tully monster fossil and model at Chicago Field Museum - photo © Brian Smith on Flickr

Once in a while, its nice to get out of the city for some decent fishing on a nice day and Braidwood State Fish and Wildlife Area is a solid escape. My trip to the area and Braidwood lake yielded some good weather, decent fishing, hiking, and a few fossils.

Some background: The Mazon Creek area is loaded with Pennsylvanian age fossils, the 300 million year old remnants of the swampy inland ocean that once covered Illinois. These rocks were dug up in the 1960′s when the area used to be a coal strip mine. It has since been turned into a fishing, game, and fossil hunting area. Some common fossils at Mazon Creek are worms, jellyfish, plants and ferns, but rarer concretions will hold small fish, shrimp, spiders, beetles, or even Illinois’ rare state fossil of the Tully Monster.

You need a day permit to collect fossils to state that you know the rules (no digging up plants, only one 5-gallon bucket per person). It’s free and only takes a second to print out, but it seemed unnecessary since nobody was even there to check it or enforce anything. And from what I could see, it is very unlikely that someone could find a 5-gallon-bucket full of fossils in the area.

The first stop was at Mazonia State Fish and Wildlife Area as seen on the map below:
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 The DNR website for the area has information on fossil hunting and fishing, so it seemed like a promising area… however despite it being early spring, the lakes are completely overgrown and the only fishing access was via the few boat ramps on the various lakes. Before leaving to the next lake, we scouted around for a fossil dig site to try our luck finding some concretions, but as I said, the area is completely overgrown and any area that was once a ‘dig site’ years ago, now looks more like these photos:

I have read that the DNR occasionally bulldozes areas of the park for researchers and fossil collectors, but that info is not easily available to a casual day visitor and we had no luck in finding anything other than knee-high brush along a few trails.

The second stop was a more popular dig site on Braidwood Lake. Below is a map of the parking lot and 2 mile walk to the site:

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We brought our fishing poles along and fished the somewhat more open and scenic bank of Braidwood Lake en route to the fossil dig site. We caught several catfish and a few bluegill using nightcrawlers as bait. Despite the area’s fame for fossils, you won’t find any along the way, as it is just as overgrown as the Mazonia area. However, the islands, only accessible by boat, look decent for fossil hunting and fishing.
50 years ago, I’m sure the area was loaded with fossils, but the inactive strip mine turned into a forest over the decades. Here’s some before and after pictures of what the transformation likely looked like:

Those few ridges are all that remains of what was once a vast fossil-collecting area. But despite all, we were able to collect a few concretions and crack them open. I know most people recommend a freeze-thaw method that reveals the fossils inside, but that requires a lot of time and patience, and is not quite as fun as smashing them open with a hammer.

Even the most promising-looking nodules held nothing more than little silver blobs, but there were a few fern leaves and plant stems mixed in, along with something that looked like a tadpole or a shrimp.
If I were to go again, I would go with a more knowledgeable group. I know that the Field Museum arranges fossil hunting trips and the Earth Science Club of Northern Illinois has several trips at different areas throughout the year. However, I would gladly take any pointers on better spots in the area via a comment or email to contact@chicagorants.com