Soil Taxonomy adapted to buried paleosols: First approximation

Abstract

Buried paleosols are important reservoirs of paleoenvironmental information, yet there is no unified system to taxonomicallyclassify them on geological timescales. Here we present the first approximation of a soil-paleosol taxonomy modified from properties in the Soil Taxonomy thatcan be reasonably and reliably described, measured, and interpreted. The rationale for this approach follows theconcept of uniformitarianism that the twelve soil orders recognized in Soil Taxonomy were present during the Phanerozoic. The diagnostic information required for application of the soil-paleosol taxonomy is obtained from field descriptions, bulk geochemical assays, and petrographic thin sections. The key to the soil-paleosol taxonomy is evaluated in the same sequence as soils in the Soil Taxonomy, and are: paleo-Gelisols (permafrost) > paleo-Histosols (organic materials) > paleo-Spodosols (illuvial organics, sesquioxides) > paleo-Andisols (volcanic glass, phosphorus retention), paleo-Oxisols (residual sesquioxides) > paleo-Vertisols (shrink-swellclays) > paleo-Aridisols (aridic soil moisture regime) > Paleo-Ultisols (low fertility, illuvialclays) > paleo-Mollisols (high fertility, surface horizon) > paleo-Alfisols (high fertility, illuvialclays) > paleo-Inceptisols (incipient subsoil) > paleo-Entisols (surface horizon). The paleopedologist will ultimately determine when diagenetic alterations prevent application of the soil-paleosol taxonomy. However, diagnosticcriteria were successfully evaluated against some 30 paleosols reported in the literature that had been minimally altered by diagenesis. Nearly one-half of those paleosols were misclassified, significantly altering the original interpretation of associated environmentalconditions. The soil-paleosol taxonomy for paleosols will enhance our understanding of the soil forming factors, lead to the development of new analytical tools, promote stratigraphiccorrelation both spatially and temporally, andcontribute to the development of acomprehensive database.