Although not useful to industry it does contain rare and diverse fossils, some of which are only known in Illinois such as Tentaculites oswegoensis, a small unclassified fossil named after Oswego, Illinois and found in the basal Brainard.
It ranged from Oswego, IL (Kendall County) to possibly Kankakee River State Park (KRSP) in Will County, Illinois.
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In Oswego, Illinois it is found mostly in clusters at Waubonsie Creek in the Basal Brainard Formation, just west of the railroad tracks.