Portable X-ray fluorescence (PXRF) as a field tool for high-resolution global biogeochemical studies

When studying global biogeochemical events in the stratigraphic record it is frequently difficult to pinpoint areas where higher resolution data analysis needs to be done. Identifying the position of events in any given outcrop or core is critical to determine the number and position of samples to be taken while in the field. Many global biogeochemical events in the rock record exhibit significant variations in redox-sensitive elemental abundances (e.g. Mo, V, Cr, etc.). These variations are typically harbingers of the larger biogeochemical perturbations and can be used to help to determine the rough position of events in the stratigraphic record. The availability of portable X-ray fluorescence (pXRF) provides the opportunity for rapid and inexpensive determinations of redox-sensitive trace metal abundances in the field or core repository that can be used to help to identify stratigraphic intervals that should be sampled at higher resolution. To test this methodology we utilized pXRF to obtain elemental abundances from Silurian strata in the Schlamer #1 core drilled by the Illinois State Geological Survey from SW Illinois. The first step in this proof-of-concept approach is to demonstrate the reliability of pXRF data by comparing it to ICP-MS data from identical sample horizons. Preliminary results demonstrate that the pXRF can be a useful tool to help to determine where higher resolution data analysis should be conducted.