Mastodon, Hemlock and Freshwater Wetlands – New Evidence of Terrestrial Environments Along the Coastal Zone of the Southeastern US

A new American mastodon site was discovered in a dried creek bed in North Charleston, SC, an area that was within the proposed late Pleistocene thermal enclave of southeastern North America. The site produced a tusk, both mandibles, three molars, a humerus, four vertebrae, and several ribs from a single individual. The mastodon is male, based on femur size and tusk circumference, and died between 43 and 47 years of age, based on molar wear and stage of molar eruption. Sediment surrounding the fossil was brownish-gray silt-to-granule sized, indicative of a fluvial/overbank depositional environment. Palynological analysis revealed palynomorphs of probable northern, southeastern coastal plain, and freshwater origins (e.g., Pinus resinosa, Tillandsia usneoides, and Myriophyllum sp., respectively). Pollen from what are believed to be similarly aged strata have been reported from Reid’s and Bell’s bluffs, on the Georgia–Florida state line, and from the Central Depression on St. Catherines Island, GA. Northern taxa include Tsuga (hemlock) from the Florida locales, and Tilia (basswood) and Juglans (walnut/butternut) from the island. Polygonum (jointweed), Nuphar (yellow waterlily), and abundant grasses and composites indicative of freshwater marshes have also been recovered from strata of the Central Depression. The three sites had to have been inland locales during the Pleistocene lowstand, and, based on the striking similarities of the microfloras, we believe the Florida, Georgia, and South Carolina sites represent a more-or-less continuous coastal plain environment where Pleistocene megafauna, northern and southern plant taxa, and freshwater wetlands were commonplace where barrier islands and other coastal landforms now exist.