163-1 Insights from Chicxulub: Continued Exploration into the Geological and Biological Effects of Impacts

Session: Impact Cratering Processes Across the Solar System: In Memory of Dr. Bevan M. French

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The Chicxulub impact, infamous for its causal link to the mass extinction at the end-Cretaceous and deposition of the global Cretaceous-Paleogene boundary sequence, produced the best-preserved impact basin on Earth. The crater provides access to key structures including: ring faults, terrace zones, a peak ring, a submerged central uplift, a central melt sheet, and an annular trough. Impactites include impact melt rocks as well as melt-bearing impact breccias (suevites). These features are overlain by a transitional unit bridging impact to marine sedimentary processes. In 2016, International Ocean Discovery Program Expedition 364, with support from the International Continental Scientific Drilling Program, drilled into the peak ring of the Chicxulub impact structure at Site M0077. Here, we discuss key findings from Expedition 364 that provide insights into the cratering process, marine ecosystems and recovery after the mass extinction, and the post-impact hydrothermal system and habitability of the impact structure. Select results include: 1) confirmation of the dynamic collapse model of peak-ring formation, 2) insights into impactite emplacement processes on Earth, where water is a key component, 3) discovery of the Iridium anomaly within the impact basin unequivocally linking Chicxulub to the global K-Pg boundary layer, 4) evidence for key atmospheric inputs of dust, sulfate aerosols, and soot all contributing to global cooling and reduction of photosynthesis as drivers for extinction, 5) recovery of life within the ocean overlying the crater including a primary succession driven by first picoplankton before a transition over 100s Kyr to diversifying nanoplankton and plankton communities, and 6) presence of a long-lived hydrothermal system with extant thermophilic life in the buried peak ring 66 Myr later. In short, research at the Chicxulub crater bridges planetary science, impact dynamics, and astrobiology, and paves the way for future research into the transformative power of asteroid impacts as a geologic and biologic process.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8216

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