The long half‐life of 129 I makes it useful for dating marine sediments aged 2–90 Ma. However, the lack of initial value dating hinders its application for dating terrestrial sediments. A large scatter of 129 I/ 127 I in prenuclear terrestrial samples has been reported; however, the key influencing factors remain unclear. This study presented iodine isotope data from three Argentine Entisol profiles and developed an iodine‐source model to determine the influence of the source on iodine isotopic composition. The temporal patterns demonstrated clear climate modulations in natural terrestrial iodine isotopes over the last ∼15 Kyr. The model identified rock weathering as a major source of iodine in continental sediments. Higher 129 I/ 127 I ratios at mid‐high latitudes arise from weak geomagnetic shielding of cosmic rays and thus a high production rate, implying limited meridional diffusion of atmospheric iodine. These findings reveal that environmental factors are significant for constraining the initial value of terrestrial 129 I.
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Fan et al. (2024) studied this question.
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