Toward direct, micron-scale XRF elemental maps and quantitative profiles of wet marine sediments

Here we describe a chemical analysis technique for Ca, Fe, K, Sr, Ti, and S using a recently developed Micro-XRF analyzer (Micro-XRF) with a 100-mm resolution and an XRF whole-core scanner (XRF-S) with a 5-mm resolution for selected sediment sections from a continental margin sediment core. The Micro-XRF produces highly resolved element maps of individual sections, and the calculation of individual continuous element profiles is based on overlap measurements of successive sections. By means of discrete subsamples analyzed by ICP-OES, the two XRF data sets are successfully calibrated to provide quantitative profiles of Ca, Fe, K, Sr, and Ti. We discuss the advantages and limitations of both XRF techniques. A comparison of the two independent XRF data sets demonstrates the overall high consistency and accuracy of both techniques. The resulting element profiles and detailed XRF maps clearly show that the Micro-XRF is a powerful tool for studying at high resolution the chemical transitions linked to paleoenvironmental changes. For example, the discrimination between provenance changes and diagenetical effects on the Fe profile can be achieved by the combined inspection of the Fe/Ti profile and S maps. This highlights the usefulness of the XRF maps for clarification of profile ambiguities and clearly distinguishes the Micro-XRF from other technical devices producing elemental profiles only.