2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 6
Presentation Time: 9:25 AM

Early Permian Vegetational Patterns across Equatorial Pangea and Climatic Implications

DIMICHELE, William A., Department of Paleobiology, NMNH Smithsonian Institution, Washington, DC 20560, TABOR, Neil J., Department of Geological Sciences, Southern Methodist University, P.O. Box 750395, Dallas, TX 75275-0395, MONTANEZ, Isabel, Geology, University of California, Davis, CA 95616 and KERP, Hans, Forschungsstelle für Paläobotanik, Geologisch-Paläontologisches Institut, Westfälische Wilhelms-Universität Münster, Hindenburgplatz 57, Münster, 48143, Germany, dimichel@si.edu

The latest Pennsylvanian-earliest Permian has been established as a time of massive glaciation in the southern hemisphere. Paleoclimate analyses, based on proxy data and modeling studies, suggest that, on-average, wetter climates were prominent proximate to Tethys, in the eastern parts of the equatorial region, with progressive drying and seasonality to the west. Terrestrial rocks of this age are preserved in a string of basins that run across the equatorial region. The non-marine character of the rocks, consistent with globally lowered sea level, makes determination of the Pennsylvanian-Permian boundary, internal temporal subdivision, and interbasin correlation difficult. Plant fossils from these basins also support east-to-west increase in the predominance of drier climates on which shorter-term climatic oscillations, probably reflecting smaller-scale changes in ice volume, were superimposed. In the eastern most regions, plants typical of humid/perhumid conditions and associated peat/coal deposits remain conspicuous. In central Europe (Rotliegends), peats/coals are thin and less common and biomes characteristic of both humid and seasonally dry conditions are represented. Similarly in the Appalachians (Dunkard) the flora largely reflects humid conditions, though peat/coal formation was rare and both floras and paleosols indicative of strong seasonality are interspersed. Floras of the western part of the continent (North-Central Texas – Markley and Archer City formations; New Mexico – Bursum and Abo formations) indicate progressive spatio-temporal increase in dominance of the seasonally dry biome. Vegetation thus changes significantly across the tropics with an overall spatial trend toward dominance of assemblages tolerant of drier conditions to the west.