Identification and Paleoecological Implications of a Late Pleistocene Pteridophyte-dominated Assemblage Preserved in Brown Peat From St. Catherines Island, Georgia

A Late Pleistocene/Holocene sediment core from St. Catherines Island, Georgia (31°37'N latitude, 81°09'W longitude), was found to contain dense peat at a depth of 5.02-5.12 meters. The peat was radiocarbon dated (AMS) at 47,620 ± 2,500 years BP, and contains a palynoflora consisting of 85% monolete pteridophyte spores. No perispores were recovered, so unequivocal identification of the spores based on surface morphological characteristics is impossible. The associated palynoflora of the peat (taxa such as Chenopodiaceae-Amaranthaceae, Asteraceae, and Liquidambar) was used to infer the habitat and environmental conditions which were present at the depositional site; these inferred conditions were used in combination with comparisons of mean spore size to modern fern taxa (e.g., Woodwardia, Thelypteris, Dryopteris) in order to identify the probable producer of the fossil spores. The data indicate that the most likely candidate for the pteridophyte is Woodwardia virginica. Paleoecological reconstructions suggest the presence of a dense stand of ferns growing alongside characteristically southeastern floral elements. The long-term stability of southeastern coastal plant communities is supported by this pteridophyte-dominated assemblage.