Paleontology and geology
Rocks of Devonian age occur in southeastern Tennessee and in several areas in the western and central parts of the state. Warm tropical seas covered Tennessee during much of the Devonian, and marine fossils include brachiopods, corals, bryozoans, crinoids, and trilobites. By the Late Devonian, a restricted water flow caused oxygen to be severely depleted near the seafloor. Few organisms could live in these conditions. The lack of oxygen prevented the decay of plant and animal remains, and organic-rich muds were deposited on the seafloor. One of the black shales formed from these muds, the Chattanooga Shale, is exposed in several parts of the state.