The Army Corps spillway below Caesar Creek Lake cut straight through Ordovician limestone and left one of the richest, most accessible invertebrate exposures in the Midwest. You need a free permit from the visitor centre, there is a size limit (roughly palm-sized), and it is surface collecting only, no digging or hammering the bedrock. Isotelus, Ohio’s state fossil, comes out of here.
Brachiopods, bryozoans, trilobites · Ordovician, ~440 mya
Open to the public for collecting, and what you find is yours to keep. Check the posted rules before you start: they can change with the season and the landowner.
Other places on the map within a couple of hours.
