History of I-129 Deposition in Marine Sediments

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ABSTRACTOCE-9907024The isotope 129I is a cosmic ray produced species with a decay half-life of 15.7 million years. If its distribution is well known, it could be applied to various geologic and paleoceanographic studies. This work will determine the 129I/I ratio and I concentrations in sixteen samples from four ODP cores in order to establish the history of I-129 deposition in marine sediments of the open ocean over the period of the last 25 million years. The cores are representative of different paleoceangraphic and sedimentological conditions from the Atlantic and Pacific Oceans. The work will incorporate micropaleontological and stable isotope studies in order to put the I-129 results into the appropriate time scale. By measuring the 129I/I ratio in independently age-dated cores, the time history of 129I deposition will be reconstructed.