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. 2
Presentation Time: 8:20 AM

Paleotropical Climate and Vegetation Linkages to Southern Gondwanan Glaciation: Extending the Early Permian Record into the Late Mississippian

MONTANEZ, Isabel1, TABOR, Neil J.2, DIMICHELE, William3, CECIL, Blaine4, EROS, James M.5, GULBRANSON, Erik L.5 and POULSEN, Chris6, (1)Department of Earth and Planetary Sciences, University of California, Davis, One Shields Dr., Davis, CA 95616, (2)Department of Geological Sciences, Southern Methodist University, P.O. Box 750395, Dallas, TX 75275-0395, (3)Smithsonian Institution, Washington, DC 20560, (4)US Geological Survey, National Center (Emeritus), Reston, VA 20192, (5)Department of Geology, Univ of California, Davis, CA 95616, (6)Dept. of Geological Sciences, University of Michigan, 2534 C.C. Little Building, Ann Arbor, MI 48109, ipmontanez@ucdavis.edu

The longest-lived icehouse of the past half billion years, the Late Paleozoic Ice Age (LPIA) came to a close in the Early Permian, transitioning into an ice-free warm period that was sustained arguably until the onset of our current glacial state ~34 million years ago. For the final stage of the LPIA, integration of newly developed paleo-high-latitude glacigenic and paleotropical marine and terrestrial records document covariance between repeated shifts in inferred paleoprecipitation, pCO2, paleotropical SSTs, and extent of Gondwanan glaciation consistent with CO2-forcing of climate. Here we present new results from several basins across paleotropical Euramerica (Appalachian Basin, USA; Donets Basin, Ukraine; Paganzo Basin, northwest Argentina) that extend the apparent CO2-climate-glaciation link down into the Carboniferous. Integration of soil carbonate δ13C and δ18O, fossil plant matter δ13C and δ15N, paleosol morphologies, and lithologic trends from late Mississippian through Pennsylvanian paralic to fully terrestrial successions delineates discrete intervals (2 to 4 Myr) of decreased effective moisture and increased seasonality likely associated with elevated atmospheric pCO2. Drier intervals are intercalated with those characterized by humid climate paleosol morphologies and lithologies, significantly lower pedogenic and meteoric calcite δ18O values, and estimated present-day pCO2. Two inferred ‘drier' intervals (late Mississippian and latest Moscovian through Kasimovian) – possibly greenhouse gas-forced - coincide with periods of normal marine and fluvio-deltaic sedimentation, or long-lived pedogenesis in high-latitude southern Gondwana, indicating drier periods coincided with periods of glacial minima or possibly ice-free conditions. Integration of our proxy records with tropical paleobotanical records reveals repeated major restructuring of flora in-step with climate and pCO2 shifts. Notably, major floral shifts documented across the middle-late Pennsylvanian boundary and Permo-Carboniferous transition are coincident with mineral isotopic and sedimentologic evidence for increased aridity and seasonality; abrupt shifts in fossil plant isotope values record the impact of these climate transitions on tropical flora.