Paleontology and geology
During the Tertiary, sea level decreased from the high mark it reached during the Cretaceous, but much of the southern half of the state still consisted of shifting shallow coastal marine environments. Rivers brought in large amounts of mud and sand from the eroding Appalachian Mountains to the north. The muds were deposited in estuaries and other coastal environments in thick layers that later became economically valuable clay deposits. Small reefs formed in marine environments where there was little mud or sand being deposited. Fossils from the Tertiary include corals, sea urchins, whales, and the giant shark, Carcharodon megalodon.