P.E. Jardine and G.J. Harrington: The Red Hills Mine palynoflora: Late Paleocene, Mississippi, U.S.A. 183 THE RED HILLS MINE PALYNOFLORA: A DIVERSE SWAMP ASSEMBLAGE FROM THE LATE PALEOCENE OF MISSISSIPPI, U.S.A. PHILLIP E. JARDINE GUY J. HARRINGTON School of Geography, Earth, and Environmental Sciences University of Birmingham Birmingham B15 2TT United Kingdom e-mail: pej083@bham.ac.uk Abstract Lignites from the Red Hills Mine in Mississippi, U.S.A. contain pollen and spores derived from paratropical swamp vegetation on the U.S. Gulf Coast during the Late Paleocene. Most previous studies of the Gulf Coast sporomorph record have been limited to a restricted taxonomic group, or merely those taxa that are relevant to biostratigraphy, meaning that the true sporomorph diversity may be higher than previously appreciated. Eight samples were collected for palynological analysis from the Red Hills Lignite Mine in Ackerman, Mississippi. All the taxa observed during counting (a minimum of 300 grains per sample) were included in the sample count. Rarefaction, relative abundance distributions, and non-metric multidimensional scaling were used to analyze floral composition, richness, and evenness. The lignite samples are heterogeneous in terms of composition and relative abundances, indicating patchiness in the swamp communities. Clay horizons representing temporary marine incursions contain significantly higher proportions of bisaccate pollen, which may have originated a considerable distance inland from the swamps. These samples therefore represent a much larger source area (regional to sub-continental), compared to the local signal contained in the lignite samples. Richness in the Red Hills Mine assemblage is higher than has previously been recorded for the Late Paleocene of the eastern Gulf Coast. This, combined with the recognition of 23 previously undescribed taxa, suggests that a detailed reappraisal of the Gulf Coast Paleocene sporomorph record is needed to improve understanding of the evolution of the North American vegetation type. Key words: Paleocene; U.S. Gulf Coast; pollen; spores; diversity; statistics; swamp. Palynology, 32 (2008): 183–204 © 2008 by AASP Foundation ISSN 0191-6122 INTRODUCTION The Paleocene (65.5–55.8 Ma; Gradstein and Ogg, 2004) strata of the U.S. Gulf Coast contain a well-preserved sporomorph (pollen and spore) record, which has received decades of study (Jones, 1961; Elsik, 1968a ,b; Tschudy, 1973a; 1975; Christopher et al., 1980; Frederiksen, 1991; 1994; 1998; Harrington, 2001; 2008; Harrington and Kemp, 2001; Harrington and Jaramillo, 2007). During the Late Paleocene, the U.S. Gulf Coast experienced mean annual temperatures of around 27°C (Wolfe and Dilcher, 2000), and a diverse, paratropical vegetation type developed on the coastal plain. This flora consisted of a mixture of plant families with modern temperate to subtropical/tropical distributions (Jones, 1961; Harrington and Jaramillo, 2007; Harrington, 2008). The Gulf Coast flora was a geographi- cally constrained ‘island’ ecosystem (Harrington, 2004; Harrington and Jaramillo, 2007), which was substantially different from other regions of North America (Harrington, 2003; 2004), and South America (Jaramillo and Dilcher, 2001; Harrington and Jaramillo, 2007). The Gulf Coast sporomorph record can be used as a proxy for reconstruct- ing vegetational changes during the Paleocene. This allows for testing of hypotheses concerning the responses of highly diverse, warm-adapted plant communities to envi- ronmental changes over extended periods. Most previous studies on Gulf Coast Paleocene sporo- morphs have focused on marginal marine deposits (e.g., Tschudy, 1973a; 1975; Frederiksen, 1991; 1998; Harrington, 2001; Harrington and Kemp, 2001; Harrington and Jaramillo, 2007). However, lignites are also present which represent episodes of regression, delta progradation, and the establishment of interdistributary swamp communities (Nichols and Traverse, 1971; Mancini and Tew, 1995; Thomson, 1995). Forested swamp palynofloras are of par- ticular interest because they are dominated by sporomorphs