Micro-XRF Core Scanning in Palaeolimnology: Recent Developments

Abstract

Within the last ten years, micro-XRF (µXRF) core scanning has become an important addition to the suite of techniques for investigating lacustrine sediments. Most studies to date have focused on records of detrital material. These have typically used elements such as Si, K, Ca, Ti, Fe, Rb, Sr and Zr as single element profiles or ratios. Inferences are made about changing catchment dynamics such as glacier advance and retreat, variations in run-off and soil erosion, weathering rates and processes and grain-size fluctuations. These can be linked, depending on the context of the individual basin, to factors such as climatic variability, meteorological events, seismic activity, tephra deposition or anthropogenic disturbance such as agriculture or deforestation. Studies of in-lake dynamics focus on elements affected by redox changes (e.g., Fe, Mn) or those which can be produced authigenically either as a result of evaporative concentration or biological processes (e.g., Ca). Here, we review the use of µXRF core scanning on lake sediments and summarise the range of elements and ratios that have been applied as a reference point for users. We consider some of the challenges involved in interpreting elemental data, given the wide variety of internal and external factors that can affect lake sediment composition.

Cirque Glacier on South Georgia Shows Centennial Variability over the Last 7000 Years

“…To disentangle the different processes acting on the archives, it is increasingly common to employ multiple proxies (e.g., Bakke et al, 2010;Vasskog et al, 2012). Sediment variables, commonly reflecting the glacial signal include elements such as Si, K, Ca, Ti, Fe, Rb, and Zr (Davies et al, 2015), variations in bulk organic matter as given by loss-on-ignition (e.g., Karlén, 1976), DBD (e.g., Bakke et al, 2005) and grain size (e.g., Matthews and Karlén, 1992), as well as a range of magnetic properties (e.g., Paasche et al, 2007). In this study, we use mass specific magnetic susceptibility (χbulk) as an indicator of change in the suspended glacigenic input to the bog and lake.…”

Modern sedimentation processes in Laguna de Medina, southern Spain, derived from lake surface sediment and catchment soil samples

“…The evaluation of the concentration of the minerals was evaluated using TOPAS Rietveld (Coelho, 2003). Relative element intensities were determined on pressed powder samples using an Xray fluorescence (XRF) scanner (ITRAX; Cox Analytical Systems; Davies et al, 2015). Measurements were performed with 1 mm resolution and an exposure time of 60 s using a Cr-tube (settings: 50 kV, 38 mA), which provides a general overview of the elements lighter than Cr (Löwe-mark et al, 2011).…”

Palaeoecology of the South Wellesley Archipelago. A history of human occupation and environmental change

“…Micro X-ray fluorescence (µXRF) core scanning rapidly records continuous, high-resolution and non-destructive measurements of relative geochemical variations downcore (Croudace et al, 2006;Francus et al, 2009). XRF scanning of lake sediments record local and regional environmental change (Davies et al, 2015).…”

“…Ti is often used to normalise data as it indicates allochthonous inputs from the catchment (Cohen, 2003), is immobile in sediments and resists post depositional influences (Montero-Serrano et al, 2010). Ratios of Ca, Mn and Fe over Ti can identify within site processes such as biogenic production or evaporative concentrations rather than detrital deposition (Davies et al, 2015). Mn/Ti and Ca/Ti profiles of all cores show a general increasing trend from the base.…”

“…At WS01 sampling with a sand auger below the reach of the D-Section revealed an unconsolidated, sandy sediment with shell hash and pisoliths comparable to zone 1 of MARR04. Increased Ti is often cited as an indicator of increased rainfall or runoff (Davies et al, 2015). However, high counts of Ti in WS01 and WCS01 between 500-300 cal.…”