COEXISTENCE CLIMATE ANALYSIS OF THE LATE EOCENE FLORISSANT FLORA, COLORADO

The late Eocene Florissant flora has long been utilized for interpretation of paleotemperature using various paleobotanical proxies, including nearest living relative (NLR) and physiognomic methodologies. These have produced a range of mean annual temperature (MAT) estimates from 10.7 to 18^oC. Our study applies the coexistence approach (CA) in the first application at Florissant to methodically and rigorously analyze climate based on data from nearest living relatives at the generic level. Several variations of the floral list were utilized, including lists of both macrofossil and pollen genera based on previously published works. Results for MAT were lowest in analyses based exclusively on macrofossils and on lists that include only confidently identified pollen and leaf taxa, and were highest in analyses based exclusively on pollen lists and on lists that include less confident identifications. Previous studies have demonstrated that a significant amount of pollen can be dispersed over long distances, raising the probability that the fossil pollen assemblage consists of a mixture of both local (cool high elevation) and distant (warm low elevation) pollen influx. Thus, we consider that the macrofossil assemblage, which indicates MAT of about 10-18^oC, better represents local climate. By contrast, analysis of the pollen assemblage indicates MAT of about 15-20^oC. The Palaeoflora database itself proved to be problematic in terms of the consistency of the climate data and its Eurasian bias, and therefore we supplemented climate from alternate sources when available. These alternate sources focused on flora from North America and China. Generic values from the Palaeoflora database and supplemental sources indicate MAT of about 10-13^oC from the confidently recorded macrofossil assemblage.