To evaluate climatic conditions through the geologic past, the stable isotopes of carbon and oxygen in paleosols have been evaluated to assess ancient atmospheric CO2 concentrations and paleo-atmospheric circulation patterns. Yet, these records may be compromised if they do not precipitate in equilibrium with soil CO2 and soil water. Michel et al. assess this possibility by examining the isotopic record of modern Vertisols (a soil class) that include a range of material incorporated from underlying marine limestone, a potential contaminant. The results indicate the roles that soil development, weathering, and topographic position can play in compromising the soil signal. They suggest that inheritance (contamination) from precursor substrates can alter a “climate” signal in some cases, and should be assessed in application of geological soils for paleoclimate studies.
Stable-Isotope Geochemistry of Vertisols Formed On Marine Limestone and Implications for Deep-Time Paleoenvironmental Reconstructions by Lauren A. Michel, Steven G. Driese, Lee C. Nordt, Daniel O. Breecker, Dana M. Labotka, and Stephen I. Dworkin