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MULTIANALYTICAL PEDOSYSTEM APPROACH TO CHARACTERIZING
AND INTERPRETING THE FOSSIL RECORD OF SOILS
LEE C. NORDT
Department of Geology, Baylor University, One Bear Place #97354, Waco, Texas 76798, USA
e-mail: Lee_Nordt@baylor.edu
CHARLES T. HALLMARK
Department of Soil and Crop Sciences, Texas A&M University, 370 Olsen Blvd., College
Station, Texas 77843, USA
STEVEN G. DRIESE AND STEPHEN I. DWORKIN
Department of Geology, Baylor University, One Bear Place #97354, Waco, Texas 76798, USA
ABSTRACT: 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 wholerock
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.