PORTABLE X-RAY FLUORESCENCE (PXRF) AS A RECONNAISSANCE TOOL FOR HIGH-RESOLUTION GLOBAL BIOGEOCHEMICAL STUDIES

Biogeochemical events, such as carbon isotope excursions, typically do not leave a macroscopic signal in the stratigraphic record, so it is hard to determine where higher resolution data collection is required. Effectively and efficiently sampling these events out in the field or in core can prove to be extremely difficult without prior knowledge of the exact location of the biogeochemical event in the given sampling area. However, global biogeochemical events have distinctive variations in the proportions of redox-sensitive elements, e.g. Mo, V, Cr, etc., which make up a ‘chemical fingerprint’. Theses variations prove to be very helpful pinpointing a close position of these events in both core and outcrop samples.

The availability of portable X-ray fluorescence (pXRF) technology provides high-resolution data collection for redox-sensitive elements much more quickly than traditional laboratory ICP-MS methods. This technique also gives users the ability to sample in situ in the field or in a core repository. However, it is necessary to test whether pXRF results are truly comparable to laboratory results. To test the methodology and reliability we used the pXRF to collect the elemental abundances from Silurian strata in the Schlamer #1 core drilled by the Illinois State Geologic Survey from SW Illinois. The first step in this proof-of-concept approach is to demonstrate the reliability of pXRF data by comparing ICP-MS data from identical sample horizons. Preliminary results demonstrate that the pXRF can be a useful tool to help determine where higher resolution data analysis should be to effectively sample biogeochemical events.