REVISITING THE MIDDLE EOCENE FLORA FROM THE CLAIBORNE GROUP IN WESTERN KENTUCKY AND TENNESSEE, USA

During the early Paleogene Earth experienced a long-term global temperature increase punctuated by hyperthermal events. The warming resulted in a reduction of the latitudinal temperature gradient, in addition to a global increase in seasonality and drought. Changes in faunal and floral distribution and composition have been well documented in the western part of North America. Several studies have supported the hypothesis that a widespread band of thermophilic plant communities existed and expanded into the mid latitudes, consistent with biota tracking climate change. It is not clear how well these floras are connected, and how exactly they responded during these rapid and long-term global warming events. My goal is to gain insight in the response of the middle Eocene Gulf Coastal Plain plant communities to these warming events using various leaf physiognomic traits (e.g., DILP, CLAMP, leaf mass per area, leaf margin analysis, leaf area analysis) and systematic census of several floras. For this, I have visited and collected several well-preserved floras from the Claiborne group in Tennessee and Kentucky. Cuticular analysis was used to describe leaf morphotypes and narrow down their botanical affinity, as well as measure stomatal density, stomata index, stomata characteristics, undulation index, and δ¹³C to reconstruct paleoatmospheric CO₂ concentrations. Initial analysis of floras from two collections suggests low diversity with morphotypes indicative of a warm, wet environment, high pCO₂ concentrations, and an open canopy structure.