Iodine diagenesis in non-pelagic deep sea sediments

Measurements of sediment geochemistry and porewater speciation have been made using light cores containing turbidite sections from the Madeira and Nares Abyssal Plains. The results have been used to evaluate how the diagenetic chemistry of iodine in these sediments compares with that in sediments undergoing steady-state diagenesis. The behaviour of iodine is related to the development of a redox front within the turbidite, between the organic-rich unoxidised sediment and its oxidised cap, and its downward migration through the turbidite with time. Comparison with Mn data demonstrates that the I enrichment above the redox front is supplied by upward diffusion from the oxidising turbidite, the increasing I content with depth being accounted for by progressive diagenetic enrichment with time. (author)