X-ray fluorescence scanning of discrete samples - a new tool for the geochemical characterization of loess-paleosol sequences

Abstract

Loess-paleosol sequences (LPS) are among the most important terrestrial archives of paleoclimate for the Quaternary and provide valuable information about past environmental changes on millennial to multi-millennial time scales. Magnetic susceptibility and grain-size are proven as reliable proxies for pedogenesis and wind activity. Thus, to analyse these proxies, LPS are sampled in high spatial resolutions down to 2 cm. In contrast, geochemical data indicating weathering intensity, dust provenance and grain-size dynamics are often acquired with 10 cm resolution at best by using time- and cost-intensive quantitative analytical methods. However, results derived from X-ray fluorescence (XRF) scanning in the marine and lacustrine realm demonstrate that determining qualitative, relative changes in the elemental composition of a profile is generally sufficient to track paleoenvironmental changes at a high spatial resolution down to 100 micrometre. With the design of sample holders that allow measurements of discrete samples with an ITRAX XRF core-scanner, it becomes possible to exploit the unused potential of high-resolution samples previously taken for grain-size analysis as to geochemistry. Consequently, the aim of this study is to benchmark XRF scanning of discrete samples against other proxy data to evaluate the potential of high-resolution qualitative geochemistry unravelling weathering intensity, dust source changes and grain-size variations. For this purpose, three well-studied European LPS (Schwalbenberg II, Germany; Susak, Croatia; Süttö, Hungary) have been considered. They cover different time periods from Marine Isotope Stage (MIS) 7 to MIS 2 and are predominantly influenced either by oceanic, continental or Mediterranean climate respectively.