Indiana Limestone: The Beginning
During the Mississippian Period (359–318 million years ago), a shallow inland sea covered much of what is now the Ohio valley of North America. These warm, tropical waters teemed with life, hosting an array of invertebrate organisms that extracted calcium carbonate from the seawater to form their shells and skeletons. Bryozoans, brachiopods, corals, and echinoderms (especially crinoids) were abundant in …