A review of worldwide sediment core dating research including fallout radionuclides to reconstruct erosion and sedimentation processes
Résumé
Dating recent sediment archives (<150 years) constitutes a prerequisite for reconstructing soil erosionand deposition processes during the last several decades. Radiocesium ($^{137}$Cs) emitted duringthermonuclear bomb testing ($^-$1950 - $^-$1980) and nuclear accidents (1986 and 2011) was generally used for identifying sediment sources or for establishing sediment core chronology based on discrete time markers. Although this method has been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of both natural and artificial fallout radionuclidesused for dating sediment cores in environmental and Earth sciences. The current literature overview wasbased on 573 articles published between 1977 and 2020, reporting the collection of 1351 individualsediment cores. This synthesis led to the identification of the worldwide distribution of discrete timemarkers associated with the thermonuclear bomb testing peak in 1963, the Chernobyl fallout, theFukushima fallout, and the identification of 25 events induced by local accidents or nuclear tests (e.g.,Sellafield, la Hague accidents, Chinese nuclear tests). With a growing number of studies focusing on the analysis of recent sediment cores and the increasinginterest in sediment fingerprinting techniques, this spatialized synthesis provides a unique worldwide foridentifying the distribution of $^{137}$Cs sources across the globe. The potential associated with the analysis of other fallout radionuclides, including excess-lead-210 ($^{210}$Pb$_{xs}$) and plutonium atom ratios ($^{240}$Pu/$^{239}$Pu), is also discussed to improve the dating of environmental archives for reconstructing soil erosion and sedimentation processes.
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