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Deformation is a ubiquitous process that occurs to rocks during impact cratering; thus, quantifying the deformation of those rocks can provide first‐order constraints on the process of impact cratering. Until now, specific quantification of the conditions of stress and strain within models of impact cratering has not been compared to structural observations. This paper describes a methodology to analyze stress and strain within numerical impact models. This method is then used to predict deformation and its cause during peak‐ring formation: a complex process that is not fully understood, requiring remarkable transient weakening and causing a significant redistribution of crustal rocks. The presented results are timely due to the recent Joint International Ocean Discovery Program and International Continental Scientific Drilling Program drilling of the peak ring within the Chicxulub crater, permitting direct comparison between the deformation history within numerical models and the structural history of rocks from a peak ring. The modeled results are remarkably consistent with observed deformation within the Chicxulub peak ring, constraining the following: (1) the orientation of rocks relative to their preimpact orientation; (2) total strain, strain rates, and the type of shear during each stage of cratering; and (3) the orientation and magnitude of principal stresses during each stage of cratering. The methodology and analysis used to generate these predictions is general and, therefore, allows numerical impact models to be constrained by structural observations of impact craters and for those models to produce quantitative predictions. 

Highly expanded Cretaceous–Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)–International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to form a peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarse-grained suevite, including clasts possibly generated by melt–water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting. Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impact-induced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms. 

The ~180-km-diameter Chicxulub peak-ring crater and ~240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth’s crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified ~1.4 × 10 5 km 3 of Earth’s crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 10 6 years.