長崎県佐世保市東浜町の礫岩質ビーチロックから採取した試料の放射性炭素年代測定

書誌事項

タイトル別名
  • Radiocarbon Measurements of Samples Collected from Conglomeratic Beachrock Developing at Higashihama-cho, Sasebo, Nagasaki Prefecture

抄録

<p> A total of four muddy–fine sand deposits attached to the undersides of cobles and boulders and three Claudiconcha japonica fossils were collected to determine the formation age of conglomeratic beachrock developing at Sasebo, Nagasaki prefecture. The geology of the surveyed coast consists of non-limestone rocks. Radiocarbon dating using Accelerator Mass Spectrometry (AMS14C dating) for the collected samples was conducted to determine the formation age of the beachrock. It was not possible to determine the age of four muddy–fine sand deposits because of their low CaCO3 concentrations (1.4%); however, the Claudiconcha japonica fossils yielded an age of Modern (102.5 ± 0.3 pMC–101.6 ± 0.3 pMC). The elemental composition of the cement samples analyzed with ICP-MS showed Al and Fe concentrations of 6.9% and 4.9%, respectively; however, the Ca concentration was low at 0.6%. The analytical results lead to the conclusion that the formation age of conglomeratic beachrock at Sasebo could not be determined with AMS14C dating, and that cobles and boulders, including mud and fine sand deposits, were cemented with Al2O3 and Fe2O3, or probably with SiO2, and formed conglomeratic beachrock.</p>

収録刊行物

  • 地学雑誌

    地学雑誌 131 (4), 473-478, 2022-08-25

    公益社団法人 東京地学協会

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