Here's a field trip report from ESCONI Vice President Dave Carlson for the Starved Rock Clay Pit field trip back on July 24th, 2021.
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Usually we are concerned about mud at the clay pit, but not this time. It was quite dry for this trip, even to the point where some rain would have been welcome in order to clean things off and keep the dust down. As always, we do the best with the conditions we have.
Recent work had changed the configuration of pits. Some of the underclay was brought to the surface forming blue/gray/purple piles. The Colchester coal was exposed intact showing cracks filled with calcite. Calcite has also mineralized the black shale but that didn't stop some folks from breaking large pieces open. The calcite cement varies from clear to tan to brown and the crystals can be showy. They are also fluorescent in LW UV.
These pictures are from Ceal Tobias.
Fossils were also recovered in the black shale like this stick found by Rob Russell.
Also some invertebrate fossils like these found by Connor Puritz.
Above, Pseudorthoceras, and below, Desmoinesia.
The only vertebrate specimens were Listracanthus, a shark denticle, like this one found by Kyle Schroeder.
A few plant fossils were found in the gray shale. This Annularia was found by Melissa Parages.
This fern was found by Ceal Tobias.
This location always produces stable pyrite in various forms, such as balls and cylinders, and pyritized wood which is unstable and subject to pyrite disease.
This is a unique and geologically complex location. It can be challenging to collect at the clay pit but with persistence and patience, interesting fossils and minerals can be found.
