CHARACTERIZATION OF PALEOSOLS ACROSS THE K-T BOUNDARY USING PEDOTRANSFER FUNCTIONS: A CASE STUDY FROM BIG BEND NATIONAL PARK, U.S.A., INTEGRATING BIOGEOCHEMICAL AND CLIMATE CONTROLS on EVOLVING TERRESTRIAL ECOSYSTEMS

Paleosol properties are routinely determined from morphological features and whole-rock geochemistry, diminishing the interpretation of important paleopedological and paleoenvironmental information. Here we explore a group of fine-grained alluvial paleosols across the K-T boundary and into the early Paleocene in Big Bend National Park, U.S.A. to: 1) reconstruct physical, chemical, and biological properties through pedotransfer functions of whole-rock molecular oxides, 2) infer redox potentials (Eh) from morphological features and reconstructed pH, and 3) assess climate and paleosol biogeochemical controls on evolving terrestrial ecosystems. Four paleoseries (i.e. pedotypes) characterize the range of properties within the late Maastrichtian to early Paleocene terrestrial succession, which includes Vertisols, Inceptisols, and Entisols. All soils possessed optimal water holding capacity based on strong pedality (macroporosity), low bulk density (total porosity), and low to moderate moisture stress as inferred from soil and climate parameters. Fertility levels were sufficient for the growth of most mesophytic and hydrophytic plants because of high retention (cation exchange capacity) of base cations (base saturation), low solubility of aluminum assumed from nonacid pH, and limited salinity (electrical conductivity) and sodicity (exchangeable sodium percentage) inferred from pedality and low sodium content. Unlike Subtropical and alkaline woodland soils of the late Maastrichtian (i.e. calcialkaphytes), early Paleocene soils supported Warm Temperate forests adapted to plant available iron, manganese, and phosphorous because of eH-pH controlled solubility (i.e. typineutraphytes). Carbon, nitrogen, phosphorous, and sulfur cycling through microbially-mediated mineralization of organic matter increased in the early Paleocene apparently because of greater litter input from mixed evergreen and deciduous angiosperms. Early Paleocene soils seem to have been responding to general climate trends and were fully recovered from the deleterious effects of the K-T impact.