Impact events are a ubiquitous geologic phenomenon across the Universe affecting all planetary bodies, yet aspects of their geologic ramifications remain poorly understood. Impacts can generate extremely high temperatures and pressures that profoundly alter impacted materials, both within the crater and material ejected during the impact process. Additionally, impact events can partially and fully reset host rock geochronologic systems, often introducing complexities and uncertainties in constraining the timing of discrete impact events. A clearer understanding of how impact processes affect host rock material properties and the geochronology record is essential to refine our knowledge of planetary histories.

This dissertation investigates the effects of impacts on rock materials and radiometric systematics through microtextural and geochronologic analyses of impact crater rocks (host and newly created from host rocks) and ejecta. Project 1 examines materials within the Kamestastin Lake crater, using shock microtextural analysis of thin sections and bulk rock ⁴⁰Ar/³⁹Ar geochronology to explore the relationship between temperature, pressure, and microtextures, and how these factors influence ⁴⁰Ar diffusion, retentivity, and ultimately ⁴⁰Ar/³⁹Ar ages. Projects 2 and 3 shift focus to ejecta materials, specifically investigating how the mineral zircon is altered from the high pressure-temperature environment of an impact event and how U-Pb ages derived from these altered zircons are affected in the ejecta environment. Project 2 analyzes Chicxulub impact ejecta, while project 3 examines Apollo sample 14311, an impact melt breccia, and also evaluates zircon mineral separation processing techniques to optimize lunar zircon recovery.

Collectively, this dissertation advances our understanding of the pressure-temperature complexities of impact cratering and the impact environmental effects on rocks, mineral material properties, and geochronologic systems. The findings demonstrate that high temperatures, evidenced by specific microtextures, can result in fully resetting geochronometers, therefore producing true impact ages. However, the impact cratering process is highly heterogeneous and produces heterogeneous temperature and pressure conditions, resulting in variable effects across an impact structure and different geochronologic systems (e.g., U-Pb, ⁴⁰Ar/³⁹Ar). By elucidating these processes in this dissertation, this research enhances our ability to interpret and date materials from impact events across the Solar System.