Multivariate Statistical Analysis of Late Mississippian Paleosol Trace Element Chemistry and Application to Interpreting Pedogenic Processes and Climate Through Time

Paleosol geochemistry has primarily focused upon bulk analyses of major elements and stable isotopes. Trace elements in bulk samples, in contrast, are rarely studied, primarily due to very low concentrations and a fundamental lack of knowledge of chemical behavior in analogous modern soil-forming environments. Late Mississippian (Chesterian) paleosols of the US Appalachian region serve as a case-study to investigate temporal relationships in paleosol trace element chemistry as a function of changing climatic conditions. Both linear (coorelation matrices) and multivariate statistical techniques (cluster, principal components and canonical variates) were employed to identify statistically significant relationships between trace elements, including Ti, Ga, Ge, Y, Zr, Nb, Cs, La, Hf, Ta, W, Ce, Th. Results indicate that trace element chemistry of this Late Mississippian suite of paleosols is controlled by either organic matter content or lessivage (clay formation and accumulation by feldspar weathering). Mean annual precipitation (MAP), estimated using the CIA-K geochemical proxy, controls soil hydrology, redox chemistry, and organic matter accumulation, in addition to clay accumulation. Soil orders through time are statistically separable, with variable success in discriminating between changes in soil drainage. Our results provide a new tool to evaluate pedogenic processes and to draw inferences regarding intensity of chemical weathering and its relationship to climate change.