Paleozoic Tropics

One day, last summer, I was pleased to discover a railcut not far from my house. I decided to check it out. It doubles as a bowling ball graveyard. The exposure is a short distance away. Silurian rocks. I'm not sure of the exact strata, but I want to say interreef upper Racine Formation.  My time was limited and after a brief look around, it seemed barren of fossils. The rock was embedded with chert nodules and a sort of dull beige color when split. Because it was summer and the foliage made it difficult to fully investigate, I decided to return in the fall. Below is some exposed strata after the leaves had fallen. The layers are dipping slightly to the east. I walked a little west and came across a large tabulate coral loose on the ground.  When I returned home, I noticed it was silicified and completely covered in tiny quartz crystals- a change from the dolomitized corals I'm used to finding in this region. Not a particularly attractive specime...

After about two hours of finding absolutely nothing, I found thoracic segments of a Calymene peeking out of a sledged rock. I carefully exposed more of the trilobite in the field, mainly just to see if it was complete, then waited to get home to fully prepare it. A beautiful Gravicalymene celebra!  Here, my lovely assistant helps prepare a latex mold. After layering latex all day, it is ready for casting.

On some days, when scouting new areas for fossils, this is all that can be found...

Pictured below is a very nice, large Dalmanites cephalon. A collections manager from the Field Museum brought it to a Chicago Rocks & Minerals Society meeting last year. The label says it's from the collection of Rollin Thomas Chamberlin, (1881-1948) professor of geology, University of Chicago. It was found at McCook Quarry, which unfortunately, is not accessible to collectors these days. Luckily, there are still a few localities to find Dalmanites in the Chicago area. To find one complete is extremely rare, but their disarticulated cephali and pygidia remains can be found with some luck and  persistence. Here are a few I have found. Had to glue eye back on. Below is a larger one measures about 4cm across, Glyptambon verrucosus, though not as exquisite as Mr. Chamberlin's specimen. This is how I found it after splitting open the rock. Dolostone can be tricky to work with, but with trial and error, and some luck, it can be rewarding. Had to glue it ba...

Pictured below is a nice Eucalyptocrinites  crinoid calyx I found in a Racine Formation spoil pile. The sedimentary rocks in this formation are from the Wenlockian Epoch, mid-Silurian Period (approx. 430 million years old). These are carbonate rocks formed when Illinois was submerged in an epicontinental tropical sea, not unlike the coral reefs of the Bahamas today. The fossils found in the Racine Formation are extinct reef faunas preserved through deep time, long before the dinosaurs or humans. Corals, crinoids, trilobites, cephalopods and brachiopods are some of the common faunas. The fossils are considered "steinkerns," which means the original skeletal material of the organisms have dissolved away during diagenetic processes leaving perfect internal molds. Some taphonomic features can be easily observed in some fossil assemblages of the Racine Formation, but others are not so obvious as they seem to be floating in a sort of void with seemingly little context. Here, with ...

I've been slicing up Silurian corals in order to experiment with some histological carbonate staining techniques and analysis, mostly just to have fun following crystal diagenesis, observe morphological changes through coral life/death, mineralogy, etc.. I still have a lot of learning and work to do. This is just a first test using Alizarin Red S diluted with hydrochloric acid. For photos, I used my old Canon PowerShot SX120IS 10MP. Favosites sp. with Alizarin Red staining. Bridgeport Quarry, Chicago, IL Zoom I need to fix lighting! Above is an unknown specimen found at Hawthorne Quarry, Cicero, IL. It could be Alveolites sp or possibly a Chaetitid sponge. Above is another Favosites slice from the same coral, vertical slice. from Bridgeport showing corallites. Dolomite slice with echinoderm skeletal fragments. From Hawthorne. Zoom Mostly need to figure out a different lighting set up and timing of staining. These were all stained at the sa...

Some fossils found in unusual places in Chicago. On an elevator. Trilobites at Children's Memorial Hospital. Moroccan trilobites at the Park Hyatt across street from the water tower. Skeletal remains in alley dumpster.

Early one January morning, I returned to Hawthorne. As I descended the hill to the frontage road, a couple of the men from the encampment appeared to be on their way to work. I decided to enter the homeless camp to see if I could find any promising looking rocks on the other side. There was a woman standing under a tarp. It was raining and getting colder. I gave her a few bucks. I didn't really want to bother her. I went about looking for fossiliferous rocks. Cement blocks, bricks and weird conglomerate deceptively weathered appearing as reef material. I didn't find much. Lots of trash, hundreds of malt liquor bottles everywhere. There was even a bed made out of bottles and cardboard. Eventually, I did find this one rock next to a bottle of King Cobra. I had to pry it out of the mud with a crobar and lug it back to my car. When I got home, I noticed a Calymene impression on the outside of the rock. When I split it open there was a large Bumastus   cephalon insid...