EXPLORING THE HYDROTHERMAL AND BIOLOGIC LEGACY OF CHICXULUB

The Chicxulub impact, which ended the Cretaceous and caused the Cretaceous-Paleogene (K-Pg) mass extinction event, also fundamentally restructured the northern Yucatán Peninsula crustal structure into a peak ring basin. Shock deformation including generation of an impact melt sheet and enhancements to porosity, as well as rock displacements from impacts fundamentally alter the thermal setting, architecture, and permeability of the target rocks. Here we discuss our studies into the rock properties including permeability of impact materials that affect the plumbing and temperature through time of the impact generated hydrothermal system and report on results of hydrologic modeling of Chicxulub’s convective system. Full waveform seismic data and depth converted images provide the key geometric constraints. International Ocean Discovery Program Site M0077 drilled into the peak ring constain physical properties of the post-impact sediment, sorted and unsorted melt-rich polymict breccia (suevite), impact melt rock, and uplifted granitic crystalline basement. From Site M0077 data, thermochronology and extant thermophilic species present in the cores suggest that the Chicxulub hydrothermal system is remarkably long lasting and spawned a robust subsurface ecosystem. Our results suggest there are some critical aspects of large impact processes that drive the dynamics of the hydrothermal system and thus timescales of habitability of the impact structure for chemosynthetic life. These aspects include: 1) the physical property inversion caused by the collapsed sedimentary transient crater rim being emplaced beneath the peak ring, 2) the shock and transport enhanced porosity and permeability of the peak ring, 3) the limited permeability of the overlying suevite impact breccia, 4) the evolution of permeability and temperature of impact melt sheet which is the primary heat source and also initial barrier to flow.