The limestones and shales visible in outcrops here contain museum specimen invertebrate fossils of Ordovician age.  The rocks were formed when Ohio was just north of the equator and lush tropical waters of the Tippecanoe Sea covered the area.  Because of the abundance of fossils, visitors are allowed to collect.  Horn coral can be found in significant abundance along with brachiopods, cephalopods, crinoids, and the most sought after fossils of trilobites.