LINKING MODERN AND FOSSIL SOILS: FORECASTING FUTURE SOIL CHANGES BASED ON PALEOSOL RECORDS

Understanding future changes in soil systems, in response to both anthropogenic-as well as naturally-induced climate change forcing mechanisms–is essential for addressing several important 21^st century challenges. Dialogue and cross-linkages between geoscientists and soil scientists are essential to the success of this endeavor. Since the late-1800s, scientists have made huge strides in documenting distributions of different soil types and their ranges in physical and chemical properties, across the world, in essentially all global biomes and climatic zones. Similar advances have not occurred in understanding changes in soils across time (i.e., “deep” geologic time, arbitrarily defined here as pre-Quaternary). Paleosols, which are fossil soils preserved in the geologic record, provide a method for understanding soil changes across multiple time scales ranging from short- to long-term, including “deep” time. There is need to bring together a diverse group of scientists studying chemical, isotopic, physical, mineralogical, and biological processes occurring in modern soils and recorded in paleosols. Particularly important are questions pertaining to influences of changes in past climates (precipitation and temperature), biomes, landscape conditions (aggradation or degradation), and paleo-atmospheric chemistry (including pCO₂ and pO₂), to soil properties impacting soil ecosystem function. Understanding soil changes by linking modern soils and paleosols requires multidisciplinary approaches that integrate field morphological, microscopic, and geochemical data, geochronology, and evolutionary changes in terrestrial biota and flora that have occurred over time. Important advancements have been made in some areas (e.g., bulk geochemical proxies) and for some soil types (e.g., Vertisols) but these must be expanded to other soil types and geochemical approaches. We will describe examples of changes in paleosols that record abrupt changes in temperature and precipitation.