The Coon Creek Formation is a Late Cretaceous sandy marl deposit in western Tennessee and northeastern Mississippi, laid down about 70 to 71 million years ago in a shallow arm of the Gulf of Mexico. Formed in coastal water, it preserves an ancient shoreline ecosystem rich in shellfish, crustaceans, ammonites, sharks, and marine reptiles. Storm-buried, clay-rich sediments sealed many remains in their original state, making the site an exceptionally fossil-rich and well-preserved deposit. More than 600 species have been recorded there, including Tennessee’s state fossil, and its discovery by Bruce Wade in 1915 helped establish its major scientific importance.