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ArticleIntercomparison of XRF core scanning results from seven labs and approaches to practical calibration(American Geophysical Union, 2020-09-09) Dunlea, Ann G. ; Murray, Richard W. ; Tada, Ryuji ; Alvarez-Zarikian, Carlos A. ; Anderson, Chloe H. ; Gilli, Adrian ; Giosan, Liviu ; Gorgas, Thomas ; Hennekam, Rick ; Irino, Tomohisa ; Murayama, Masafumi ; Peterson, Larry C. ; Reichart, Gert-Jan ; Seki, Arisa ; Zheng, Hongbo ; Ziegler, MartinX‐ray fluorescence (XRF) scanning of marine sediment has the potential to yield near‐continuous and high‐resolution records of elemental abundances, which are often interpreted as proxies for paleoceanographic processes over different time scales. However, many other variables also affect scanning XRF measurements and convolute the quantitative calibrations of element abundances and comparisons of data from different labs. Extensive interlab comparisons of XRF scanning results and calibrations are essential to resolve ambiguities and to understand the best way to interpret the data produced. For this study, we sent a set of seven marine sediment sections (1.5 m each) to be scanned by seven XRF facilities around the world to compare the outcomes amidst a myriad of factors influencing the results. Results of raw element counts per second (cps) were different between labs, but element ratios were more comparable. Four of the labs also scanned a set of homogenized sediment pellets with compositions determined by inductively coupled plasma‐optical emission spectrometry (ICP‐OES) and ICP‐mass spectrometry (MS) to convert the raw XRF element cps to concentrations in two ways: a linear calibration and a log‐ratio calibration. Although both calibration curves are well fit, the results show that the log‐ratio calibrated data are significantly more comparable between labs than the linearly calibrated data. Smaller‐scale (higher‐resolution) features are often not reproducible between the different scans and should be interpreted with caution. Along with guidance on practical calibrations, our study recommends best practices to increase the quality of information that can be derived from scanning XRF to benefit the field of paleoceanography.
ArticleHigh-resolution and high-precision correlation of dark and light layers in the Quaternary hemipelagic sediments of the Japan Sea recovered during IODP Expedition 346(Springer, 2018-03-26) Tada, Ryuji ; Irino, Tomohisa ; Ikehara, Ken ; Karasuda, Akinori ; Sugisaki, Saiko ; Xuan, Chuang ; Sagawa, Takuya ; Itaki, Takuya ; Kubota, Yoshimi ; Lu, Song ; Seki, Arisa ; Murray, Richard W. ; Alvarez-Zarikian, Carlos A. ; Anderson, William T. ; Bassetti, Maria-Angela ; Brace, Bobbi J. ; Clemens, Steven C. ; da Costa Gurgel, Marcio H. ; Dickens, Gerald R. ; Dunlea, Ann G. ; Gallagher, Stephen J. ; Giosan, Liviu ; Henderson, Andrew C. G. ; Holbourn, Ann E. ; Kinsley, Christopher W. ; Lee, Gwang Soo ; Lee, Kyung Eun ; Lofi, Johanna ; Lopes, Christina I. C. D. ; Saavedra-Pellitero, Mariem ; Peterson, Larry C. ; Singh, Raj K. ; Toucanne, Samuel ; Wan, Shiming ; Zheng, Hongbo ; Ziegler, MartinThe Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter- to decimeter-scale alternation of dark and light clay to silty clay, which are bio-siliceous and/or bio-calcareous to a various degree. Each of the dark and light layers are considered as deposited synchronously throughout the deeper (> 500 m) part of the sea. However, attempts for correlation and age estimation of individual layers are limited to the upper few tens of meters. In addition, the exact timing of the depositional onset of these dark and light layers and its synchronicity throughout the deeper part of the sea have not been explored previously, although the onset timing was roughly estimated as ~ 1.5 Ma based on the result of Ocean Drilling Program legs 127/128. Consequently, it is not certain exactly when their deposition started, whether deposition of dark and light layers was synchronous and whether they are correlatable also in the earlier part of their depositional history. The Quaternary hemipelagic sediments of the Japan Sea were drilled at seven sites during Integrated Ocean Drilling Program Expedition 346 in 2013. Alternation of dark and light layers was recovered at six sites whose water depths are > ~ 900 m, and continuous composite columns were constructed at each site. Here, we report our effort to correlate individual dark layers and estimate their ages based on a newly constructed age model at Site U1424 using the best available paleomagnetic datum and marker tephras. The age model is further tuned to LR04 δ18O curve using gamma ray attenuation density (GRA) since it reflects diatom contents that are higher during interglacial high-stands. The constructed age model for Site U1424 is projected to other sites using correlation of dark layers to form a high-resolution and high-precision paleo-observatory network that allows to reconstruct changes in material fluxes with high spatio-temporal resolutions.