AuthorFabryka-Martin, June Taylor.
Committee ChairDavis, Stanley N.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractIodine-129 (t ½, 16 My) is a naturally-occurring tracer which can be used to study hydrologic and geologic processes on time scales up to 100 My. Global modelling suggests that the pre-bomb atmospheric ratio ¹²⁹I/I should have been constant in time and space. This ratio is the starting value in ground-water recharge, and subsequent ratio changes are determined by isotope contributions from three sources: recharge water, iodine leached from the formation, and in situ uranium fission. This expected behavior is compared to field study results. Ground-water samples from the Great Artesian Basin, Australia, provide an estimate of the atmospheric equilibrium ratio, 6 x 10⁻¹³. Down-gradient changes in water up to 1 My old suggest that subsurface production can be significant. The usefulness of ¹²⁹I as an indicator of brine source and age is verified in brines collected in and around Louisiana salt domes. The method leads to ages of 7 and 9 My for two brine pockets trapped within Jurassic salt, and 32 to > 40 My for oil-field brines in Miocene sands adjacent to the domes.
Degree ProgramHydrology and Water Resources