X‐ray fluorescence core scanning of wet marine sediments: methods to improve quality and reproducibility of high‐resolution paleoenvironmental records

Abstract

X‐ray fluorescence (XRF) core‐scanning is a convenient non‐destructive tool to rapidly assess elemental variations in unprocessed sediments. However, substantial analytical deviations may occur in such data due to physical sedimentary properties. The consequences of these artifacts on element intensities are important for paleoclimatic studies, but as yet have not been adequately studied for high resolution (≤ 1‐cm interval) records. We have done a high resolution comparison between results from XRF scanning and from two more conventional methods: XRF with beads and inductively coupled plasma optical emission spectrometry (ICP‐OES), both on discrete samples. Our XRF scan data concord reasonably well with those from the conventional methods for most elements. In several discrete intervals large deviations occur that could have been attributed to major paleoceanographic events. However, these deviations appear to be mainly related to water content and distribution. We show that the variability in the water film thickness underneath the plastic foil is highly variable, causing significant apparent variability in all elements from Al to Fe. The unverified use of these elements in ratios can thus lead to deviations in the paleoenvironmental interpretation. Erroneous element (ratio) variability can, however, be recognized and corrected using conventional analytical data of a few discrete samples. The antipathetic behavior of Ca to K or Ti, and their similar behavior to water absorption, leaves their ratios relatively unaffected at variable water film thicknesses. Hence, Ca/K and Ca/Ti ratios are recommended for a preliminary down‐core overview of sedimentary variability and for stratigraphic correlations between unprocessed marine cores.

Late Oligocene obliquity-paced contourite sedimentation in the Wilkes Land margin of East Antarctica: implications for paleoceanographic and ice sheet configurations

“…Similar variations have been previously described in sediment cores to indicate substantial analytical deviations due to physical sedimentary properties (i.e. Tjallingii and Röhl et al, 2007;Hennekam and de Lange 2012). Accordingly, for this study we have concentrated our interpretations on Al, Si and K 235 values from the XRF analyses in discrete samples (see below).…”

Soil Organic Carbon in Mangrove Ecosystems with Different Vegetation and Sedimentological Conditions

“…On the other hand, the source of OC has been studied as the qualitative determination of mangrove OC because OC source has a major impact on the overall carbon dynamics in intertidal mangrove ecosystems. C/N ratio is a useful parameter to predict the source of OC [18] reflecting levels of OC degradation, and X-ray fluorescence (XRF) analysis has been conducted to study the source of sediment deposited at different times [19]. Not only the source of OC, but also the quantity and the composition of the OC, may differ depending on the vegetation type [20].…”

The last interglacial (MIS 5e) cycle at Little Bahama Bank: A history of climate and sea-level changes

“…Because enhanced seawater content in the sediment appears to reduce only Ca intensities, leaving measures of elements with higher atomic numbers (e.g., Fe, Sr) less affected (Tjallingii et al, 2007;Hennekam and de Lange, 2012), normalization of Sr counts to Ca results in very high Sr/Ca intensity ratios across the Cl-rich intervals. The general consistency of the measured Sr intensities argues against an early marine diagenesis that would strongly reduce and homogenize the Sr/Ca intensity ratio, 170 altering isotopic signatures and often causing a change in sediment color (Chabaud, 2016) that is not observed in our sediment core.…”