In this study, we investigate the distribution of radiocarbon and uranium in the calcified opercula of Turbo sp. collected from Ryukyu region and Chiba, Japan, to explore the potential of U/Th dating using mollusks collected from the Japanese archipelago. We acquired high-resolution radiocarbon and uranium concentration measurements using single-stage accelerator mass spectrometry and laser ablation−inductively coupled plasma−mass spectrometry. Our results show that uranium in the opercula of modern Turbo sp. is unevenly distributed at concentrations 1000 times less than those in coral skeletons. Radiocarbon found in the calcified opercula samples record ambient seawater radiocarbon values as well as coral skeletons. Uranium in the calcified opercula of Holocene Turbo marmoratus were also unevenly distributed and concentrated within the opercula in a different manner than observed in modern samples, suggesting uranium exchange after death. Our results suggest variable uptake of uranium isotopes into mollusk shells and highlights the need for rigorous sample selection criteria when choosing mollusks species for U/Th dating around Japan.

中文翻译：

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日本列岛周围海洋腹足动物的放射性碳和铀分布

在这项研究中，我们研究了放射性碳和铀在钙化鳃盖中的分布。涡轮sp。从琉球地区和日本千叶收集，探索使用从日本群岛收集的软体动物进行 U/Th 测年的潜力。我们使用单级加速器质谱法和激光烧蚀电感耦合等离子体质谱法获得了高分辨率放射性碳和铀浓度测量结果。我们的研究结果表明，现代人的鳃盖中含有铀。涡轮sp。分布不均匀，浓度比珊瑚骨骼中的浓度低 1000 倍。在钙化鳃盖样本中发现的放射性碳记录了周围海水以及珊瑚骨骼的放射性碳值。全新世钙化盖中的铀涡轮斑鳀与现代样本中观察到的不同，它们在鳃盖内的分布和集中方式也不均匀，这表明死后发生了铀交换。我们的结果表明，软体动物壳对铀同位素的吸收存在差异，并强调在日本各地选择软体动物物种进行 U/Th 测年时需要严格的样本选择标准。