HR: 17:30h
AN: PP14A-07    [Abstracts]
TI: Major Transient Floral Change During the Paleocene-Eocene Thermal Maximum
AU: * Wing, S L
EM: wings@si.edu
AF: Smithsonian Institution, Dept. of Paleobiology, Washington, DC 20013-7012 United States
AU: Harrington, G J
EM: g.j.harrington@bham.ac.uk
AF: University of Birmingham, Earth Sciences Department, Aston Webb Building, Birmingham, B15 2TT United Kingdom
AU: Bloch, J I
EM: carpo@umich.edu
AF: University of Florida, Florida Museum of Natural History, Dickinson Hall, Gainesville, FL 32611-7800 United States
AU: Boyer, D M
EM: dboyer@ic.sunysb.edu
AF: Stony Brook University, Dept. of Anatomical Sciences, Stony Brook, NY 11794-8081 United States
AU: Smith, F
EM: fsmith@geosc.psu.edu
AF: Smithsonian Institution, Dept. of Paleobiology, Washington, DC 20013-7012 United States
AB: New continental sections representing the Paleocene-Eocene Thermal Maximum (PETM) have been discovered in the southern Bighorn Basin, Wyoming. Three localities preserving leaves and fruits are the first megafossil record of plants from this geologically short (about 150ky) period of intense warming. The localities produce fossil pollen and spores as well. The plant remains are in sections that preserve vertebrate fossils characteristic of the Wa-0 faunal zone that elsewhere is restricted to the period of negative carbon isotopic values that occurred during the PETM. The megaflora and palynoflora from the three localities contain a small number of long-ranging taxa that are common in many late Paleocene and early Eocene localities from the Bighorn Basin (e.g., {\it Macginitiea}, {\it Caryapollenites}, {\it Ulmipollenites}, {\it Alnipollenites}), however they also produce up to 10 taxa that have not been seen before in either the Paleocene or Eocene of this area. In the palynoflora, several of these previously unrecorded taxa (e.g, {\it Labropollis}, cf. {\it Bombax}, and a distinctive large tricolpate grain) are common in the Gulf Coastal Plain Paleogene. Although the number of dicot leaf species so far is too small to produce a robust physiognomic estimate of temperature or precipitation, it is notable that one locality near the base of the PETM is dominated by small-leaved legumes, and another near the top by an undetermined dicot leaf with an extremely long drip-tip. Preliminary analysis of the floral data strongly suggests that some types of plants extended their ranges up to 1500 km northward during the PETM, where they became sympatric with native mid-latitude taxa. These range extensions are restricted to the PETM. Furthermore, PETM floral change was essentially synchronous with the better-known mammalian turnover event. The unusual physiognomy of PETM fossil leaves raises the possibility of major changes in seasonality or amount of precipitation. We plan to measure stable carbon isotope ratios in organic matter and soil carbonates from the new sections in order to establish more precisely the relationship between biotic and geochemical change during the PETM.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting