Geochronology of impact structures - constraining syn- and post-impact processes using the 40Ar/39Ar and U-Pb techniques

My PhD project is focused on the development and application of different radiometric dating techniques on impact structures. Impact structures are formed by one of the most spectacular and fastest surface-modifying process on Earth, which can change the geo- and biosphere in a couple of seconds. In order to understand how impact events influence the Earth’s geological and biological evolution, especially with regard to possible future events, it is crucial to determine precise and accurate ages of impact structures. Unfortunately the ages of many craters are not well-constrained or unknown. This is largely attributable to the lack of suitable dating material due to erosion, post-impact alteration, thermal overprinting, and contamination.

My PhD project will therefore focus on 40Ar/39Ar and U-Pb ages of different mineral phases in target rocks, to obtain impact-related data. Impact-generated shock waves are able to reset different isotopic systems, i.e., a loss of daughter isotopes and a re-start of the isotopic clock. Biotite, amphiboles and zircon are to be investigated to see if the shock waves can induce a reset of the isotopic systems of the different mineral phases and if there is a correlation between the ages and different shock pressure levels. The first working area is the Siljan impact structure in Sweden.