Geologic record of climate change in soils and paleosols

This work started with a National Science Foundation supported study of A modern test of the assumptions used for determining paleo-atmospheric carbon dioxide from goethite-bound carbon. The concept of using goethite-bound carbon isotopes as a proxy for estimating paleo-atmospheric PCO2 throughout the Phanerozoic has been a kingpin for paleoclimatic modeling efforts such as Bob Berner's GEOCARB model. In this study we tested the underlying assumptions used by Crayton Yapp, developer of the goethite inferred paleo-atmospheric PCO2 barometer. Work has been performed on soil/saprolites found overlying granite terrains in the Piedmont of Georgia, including Panola Mt. Georgia and the USDA (now UGA) Phil Campbell Resource Center.  We have discovered that carbon is bound in gibbsite. Samples collected from a residual weathering profile developed on a Paleozoic granite in the Georgia Piedmont, were examined for 14C content and found to be geologically young. Combining the results of 14C, 26Al, and 10Be analyses offers the potential to assess differential rates of chemical weathering and continental denudation in order to understand better the links between rates of silicate rock weathering, climate, and soil residence times. We are now moving on to other regions of the Georgia Piedmont with study of the Cahloun Critical Zone Observatory.

  1. Austin, Jason C. and Paul A. Schroeder. 2014 Assessment of pedogenic gibbsite as a paleo-PCO2 proxy using a modern Ultisol. Clays and Clay Minerals, Vol. 62, No 5, 235-266.
  2. Austin, Jason 2011 Soil CO2 efflux simulations using Monte Carlo method and implications for recording paleo-atmospheric PCO2 in pedogenic gibbsite Palaeogeography, Palaeoclimatology, Palaeoecology, v. 305,  280-285.
  3. Schroeder, P.A., 2010 Natural occurrence of elevated arsenic and selenium in Georgia regolith: Implications for their relative mobility in Piedmont soils. Southeastern Geology, v. 47, No. 1, p. 15-26.
  4. Schroeder, Paul A., Jason C. Austin, John F. Dowd 2006 Estimating long-term soil respiration rates from carbon isotopes occluded in gibbsite, Geochimica et Cosmochimica Acta. v. 70/23, 5692-5697
  5. Schroeder, P. A., J..J. Le Golvan and M. Roden. 2002 Weathering of ilmenite from granite and chlorite schist in the Georgia Piedmont, USA American Mineralogists. v. 87 (12) 1616-1625.
  6. Schroeder, P. A., Melear, N. D., Bierman, P., Kashgarian, M., and Caffee, M., 2001 , Gibbsite growth ages for the regolith in the Georgia Piedmont: Geochimca et Cosmochimica Acta , v. 65 (3) p. 381
  7. Schroeder, P. A., Melear, N. D., West, L. T., and Hamilton, D. A., 2000 Meta-gabbro weathering in the Georgia Piedmont, USA: Implications for global silicate weathering rates: Chemical Geology, v.163, 235-245
  8. Schroeder, P. A., and Melear, N. D., 1999 Stable carbon isotopic signatures preserved in authigenic gibbsite from a forested granitic regolith: Panola Mt., Georgia, USA.: Geoderma, p. v 91 p. 261-279.
  9. Schroeder, P. A., Kim, J. G. and Melear, N. D. 1997 Mineralogical and textural criteria for recognizing remnant Cenozoic deposits on the Piedmont: Evidence from Sparta and Greene County, Georgia, U.S.A. Sedimentary Geology. v. 108, 195-206

For a complete listing of Schroeder's publication activities, see Curriculum Vitae

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