A single column separation method has been developed for the determination of radiogenic ¹⁴³Nd/¹⁴⁴Nd ratios for natural geological samples. Conventional radiogenic Nd isotope ratio measurements require rigorous column chemistry involving multiple steps to extract a pure Nd fraction. Elements that cause isobaric interference during analysis are removed using a multi-column separation method, which is often time consuming and/or expensive. In this work, we use a single cation exchange column to extract a Nd fraction, and a novel method of mass fractionation correction to circumvent the isobaric effect of Sm during analysis. The developed method allows accurate measurement of the ¹⁴³Nd/¹⁴⁴Nd ratio without the elimination of Sm. The ratio of two non-radiogenic Nd isotopes with no natural isobars, ¹⁴⁵Nd/¹⁴⁶Nd, is used to correct for instrumental mass fractionation on ¹⁴³Nd/¹⁴⁶Nd. The corrected ¹⁴³Nd/¹⁴⁶Nd ratios can be converted to the ¹⁴³Nd/¹⁴⁴Nd form using the conventionally used constant ratio of ¹⁴⁶Nd/¹⁴⁴Nd of 0.721900, allowing direct comparison with published literature and databases. We have implemented this sample preparation scheme to generate accurate and precise radiogenic ¹⁴³Nd/¹⁴⁴Nd ratios for nine natural reference materials including basalts, granites, sediments and sedimentary rocks, confirming the applicability and robustness of this technique.

Conodonts are tooth-like apparatuses of extinct marine animals and their geochemical composition is a key tool in reconstructions of paleo-marine environmental conditions. Previous geochemical studies focused on conodont fossils with weak thermal maturation from shallow-marine sedimentary rocks. However, the geochemical features of conodont fossils in pelagic deep-sea sedimentary rocks, which are suitable for reconstructions of paleo-environmental conditions of pelagic Panthalassa, are poorly understood. This study presents geochemical data of conodont fossils from the Triassic deep-sea pelagic sedimentary rocks from the Inuyama area, central Japan and examines their potential as a paleo-environmental indicator. The examined conodonts were composed of fluorapatite and possessed almost the same major elemental fractions as conodonts from Early Triassic limestone. Concentrations of REEs in conodonts in the pelagic deep-sea sedimentary rocks (~1000 ppm in average) are much higher than that of the conodonts from limestone (~89 ppm in average). Cathodoluminescence images and elemental mapping of conodont cross-sections reveal that conodonts in pelagic deep-sea sedimentary rocks have a few μm-thick REEs-rich layers composed of diagenetically precipitated euhedral apatite at the surfaces of the denticles and along cracks. Furthermore, Y/Ho ratios and Ce anomalies of the conodont fossils are different from those of modern seawater and, instead, are similar to those of the surrounding siliceous sedimentary matrix. These results suggest that their REE signatures were acquired from the surrounding siliceous material during diagenesis. The Ce anomalies of conodonts could reflect the presence of Fe-Mn oxides at the paleo-sea floor and indirectly record the redox condition of paleo-ocean floor.

Radiocarbon (¹⁴C) has been widely used to understand the ages in archeology and paleo-environmental sciences. In marine environments, the dissolved inorganic radiocarbon (expressed as DIC Δ¹⁴C) of seawater has been used as a reliable tracer in the research of carbon cycling and studies in global to regional water mixing. Here, we present the first high-resolution dataset of DIC Δ¹⁴C values in the Tokara Strait collected at eight stations during a cruise on the Research Vessel (R/V) Hakuho-Maru in March 2022. The DIC Δ¹⁴C ranges from –211‰ to 28‰ in the upper 1200 m depth of the Tokara Strait. High and modern values (bomb ¹⁴C; DIC Δ¹⁴C ≥ 0‰) were observed above ~400 m depth at station T3 and above ~200 m depth at other stations. These are indicative of the influence of anthropogenic carbon from above-ground nuclear bomb tests conducted in the Pacific Ocean during the 1940s to 1960s. The dataset also includes hydrographic information (temperature, salinity, and density), all of which may help interpret the DIC Δ¹⁴C variations in the Tokara Strait. These datasets are expected to improve our understanding of water mixing processes and the carbon cycle in the Tokara Strait, which has important implications for understanding climate variability.