Dr. Alexis K. Ault has been granted an NSF Earth Sciences Postdoctoral Fellowship to carry out research and an education plan at the University of Arizona. This research investigates the surface response of cratons to near-field plate boundary activity including deformation, sedimentation from regions of high topography, foreland basin development, flexural uplift, and exhumation-related fluid-circulation. The proposed research focuses on the Rae craton, exposed on Baffin Island, Canada, a unique cratonic locality given its proximity to plate boundaries throughout the Phanerozoic, and aims to constrain the magnitudes and patterns of cratonic burial and unroofing with a suite of thermochronometers including apatite (U-Th)/He, apatite fission-track, and zircon (U-Th)/He dating. Fluid flow and secondary mineralization associated with rock exhumation, will be dated via hematite (U-Th)/He dating. An innovative aspect of this proposal is the coupling of paleomagnetic data with the hematite dating to provide a backdrop to evaluate Fe-oxide data and potentially "double-date" fluid flow events in two Western U.S. pilot studies. Accurate interpretation and understanding of the significance of hematite (U-Th)/He dates is necessary before application of the technique to other settings like Baffin Island.
How and why cratonic regions, or the cores of continents long considered to be immune to tectonism, are reactivated and the signatures of such processes on the surface evolution of cratons remain outstanding questions in continental dynamics. The results of this research will be of interest to the geochronology and tectonics communities. Reconstruction of the past extent and thickness of sedimentary rocks deposited across the Rae craton and quantification of burial temperatures will aid glaciologists and geomorphologists exploring the impact of Laurentide ice sheet dynamics on the Baffin Island landscape, but will also provide critical information for understanding regional hydrocarbon reservoir potential in the Canadian Arctic. The development and successful application of the hematite (U-Th)/He dating technique to constrain near-surface fluid flow will benefit those in the active tectonics and economic geology communities. Education activities associated with this research include mentoring University of Arizona undergraduate and graduate students and co-teaching an intensive summer student workshop on the method and application of the new hematite (U-Th)/He dating technique.
