Multianalytical Pedosystem Approach to Characterizing and Interpreting the Fossil Record of Soils
Lee C. Nordt, Charles T. Hallmark, Steven G. Driese, Stephen I. Dworkin, 2013. "Multianalytical Pedosystem Approach to Characterizing and Interpreting the Fossil Record of Soils", New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems, Steven G. Driese, Lee C. Nordt
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Interpretations of critical zones, past and present, are dependent on the comprehensive characterization of morphological, physical, chemical, biological, and mineralogical properties of soils as the biogeochemical mediator of Earth’s surface processes. The traditional approach of studying fossil soils (paleosols), however, is modeled after methods developed during the advent of pedology in the early 20th century. Even though there have been remarkable advances in the development of analytical procedures for modern soils (pedology), advancements in paleopedology have not proceeded past whole-rock geochemical characterization. Here, we develop multianalytical strategies combining traditional and modern approaches to studying paleosols that include direct laboratory measurement, petrographic analysis, and pedotransfer functions. In addition to standardizing the characterization of paleosols, doing so will also contribute to more robust geoinformatic compilations and strengthen interpretations of soil processes, soil taxonomic classification, edaphic controls, and climate conditions in the past. We applied the multianalytical approach to a paleosol from the Late Triassic and demonstrate that it classifies as a Vertisol based on slickensides identified in the field, sepic fabric in thin section, and high values for variables such as total and fine clay content, coefficient of linear extensibility (COLE), smectite content, and available water capacity (AWC). Reconstructed cation exchange capacity (CEC), pH, and base saturation point to a plentiful supply of plant available nutrients. Most reconstructed properties appear to have been reasonably preserved because of shallow burial depths and the formation of slowly permeable claystones. Further testing of direct analytical techniques and the development of pedotransfer functions beyond Vertisols are needed to improve the characterization of the full range of properties expected in the fossil rock record of soils.
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New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems
After initial breakthroughs in the discovery of fossil soils, or paleosols in the 1970s and early 1980s, the last several decades of intensified research have revealed the much greater role that these deposits can play in reconstructing ancient Earth surface systems. Research currently focuses on terrestrial paleoclimatology, in which climates of the past are reconstructed at temporal scales ranging from hundreds to millions of years, using paleosols as archives of that information. Such research requires interdisciplinary study of soils conducted in both modern and ancient environments. These issues and many others were discussed at the joint SEPM-NSF Workshop “Paleosols and Soil Surface Analog Systems”, held at Petrified Forest National Park.