High-Fidelity Cretaceous-Paleogene Boundary Investigations: Records of Impact and Transport

Abstract

The Chicxulub impact on the Yucatán Peninsula triggered the end-Cretaceous mass extinction 66 million years ago, but physical models still struggle to accurately describe ejecta generation and transport from this and other large meteorite impacts. To better constrain these processes, Kaskes et al. (2025), https://doi.org/10.1029/2024gc012151 completed detailed micro-X-ray fluorescence (μ-XRF) mapping of a K-Pg boundary sequence preserved at Starkville South (Raton Basin, Colorado, USA). Their results directly challenge the previous “dual layer” model of ejecta sequences exemplified in the North American K-Pg outcrops, where one layer hosts the ballistically emplaced impact spherules and the overlying layer hosts the shocked minerals that were atmospherically transported. The new Kaskes et al. (2025), https://doi.org/10.1029/2024gc012151 model describes four distinct layers: (a) the ballistically emplaced spherules, (b) the ballistically emplaced shocked minerals, (c) an initial settling of atmospherically transported Ni- and Cr-rich dust, and (d) a gradual decrease of impact-generated dust back to background concentrations. Kaskes et al. (2025), https://doi.org/10.1029/2024gc012151 provide high-resolution geochemical analyses offering new insights into the timing and mechanisms of ejecta production, transport and deposition after a large meteorite impact event, which the community can apply to other K-Pg sites around the world.