I'm no expert in the Great Lakes but I'm surprised they found something that far north that old. From a little reading the glaciers were retreating from that area around the same time frame. I guess +/- 1,000 years is a big deal.
There are a bunch of cool signs of the precursor to Lake Michigan around Chicago from the time when the lake was "capped" in the north and drained to the south. Blue Island and Stony Island were real islands. Ridge road to the north marks where the shore once stood. Pretty cool to imagine.
Edit: Just looked at the article, and see that Ridgeland avenue is listed as one of the shoreline areas in the article.
[0] https://en.wikipedia.org/wiki/Palos_Forest_Preserves [1] https://en.wikipedia.org/wiki/Site_A [2] https://en.wikipedia.org/wiki/Argonne_National_Laboratory