Paleontology and geology
During the Devonian, a shallow sea covered the southern part of Minnesota. Within these waters the skeletons of marine organisms slowly accumulated and contributed to the limy sediments on the sea floor. These sediments eventually formed limestone. Organisms such as brachiopods, cephalopods, trilobites, and corals dominated life in this sea. The North American continent was located much closer to the equator during the Devonian, and the climate was warm and tropical.