The CRONUS-Earth inter-comparison for cosmogenic isotope analysis

• Published in: Quaternary Geochronology
• Main Authors: Jull, A.J.Timothy, Scott, E.Marian, Bierman, Paul
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2015
• Subjects: Antarctic; Cronus; The Antarctic; Antarc*
• Online Access: http://eprints.gla.ac.uk/229024/; http://eprints.gla.ac.uk/229024/1/229024.pdf

As part of the NSF-funded program CRONUS-Earth, a series of natural reference materials for in situ produced 26Al, 10Be, 14C, and 36Cl were prepared and circulated to United States, Australian, and European laboratories for analysis to explore the comparability of results from the different laboratories and generate preliminary consensus values for a range of reference material. Such reference materials, which did not exist for these isotopes, assist laboratories in independently assessing quality and are useful to quantify precision and accuracy. Currently, most researchers report only internal analytical uncertainties for all results. While researchers have acknowledged the need for realistic inter-laboratory uncertainties for in situ produced cosmogenic isotopes, few previous studies have addressed this issue. Two samples (denoted A and N) were provided for 26Al, 10Be and in situ 14C analysis, one from the Antarctic, high in 26Al and 10Be and the other from Australia, lower in both 26Al and 10Be. Both samples were prepared to quartz at the University of Vermont. For each sample, results have been summarised in terms of the mean reported concentration, standard deviation both between (inter) and within (intra) laboratories to describe inter- and intra-laboratory variability. Coefficients of variation (CoV) expressed as a percentage of the mean are also reported. For in-situ 14C, a small number of laboratories reported results, so they are summarised separately. Initial uncorrected results for 10Be for samples A and N showed significant variation (greater than 8% CoV) in results. When corrected to a common standardisation basis, the CoV was 2.9% for 10Be measurements of sample A (high concentration) and to 4.1% for sample N (lower concentration), which is closer to typical cosmogenic samples. 26Al measurements had greater variation; a CoV of 4.9% was achieved for sample A (high concentration) but for the lower concentration sample N, the CoV was 10.1%.