Chicxulub Impact : The Paleogene Started with a Bang

The Chicxulub impact event at the Cretaceous–Paleogene (K–Pg) boundary (~66 Ma) represents one of the most abrupt and consequential perturbations of the Earth system, marking both a large mass extinction and the onset of the Paleogene. A ~10–15 km-diameter asteroid, probably originating beyond Jupiter, struck the Yucatán carbonate platform, forming a ~200 km-wide crater and releasing ~ 10^23 J of energy, initiating immediate global-scale physical and biological disruption. The impact generated shock waves, vaporization of target lithologies, and an ejecta plume dispersing silicates, sulfates, carbonates, and melt droplets globally within hours to days. This produced the now world-famous, globally distributed K–Pg boundary layer enriched in iridium and other platinum-group elements, shocked minerals, and micro-spherules, providing a unique and ultra-precise global chronostratigraphic marker. Environmental consequences included gigantic earthquakes, megatsunamis, wildfires, atmospheric heating, and rapid injection of aerosols and dust into the stratosphere. The dominant extinction mechanism is linked to a prolonged “impact winter” marked by a major temperature decline (15 to 30ºC), especially on the continents. Recent work demonstrates that fine silicate dust (<~10 μm) was a critical, and previously underestimated, driver of this impact winter. Climate modeling in that study indicates that, within hours to days, silicate dust excavated from deep within Chicxulub rapidly dispersed globally, sustaining atmospheric opacity and darkness for up to ~2 years. The total shutdown of photosynthesis severely disrupted both marine and terrestrial food webs. Importantly, this view challenges earlier paradigms that emphasized sulfate aerosols released from the vaporization of target rock evaporites and soot from global wildfires as dominant forcings. Based on the silicate dust model, photosynthesis might even have recovered faster in the Southern Hemisphere. Meticulous, high-resolution (<mm) examination of K-Pg stratigraphic records further refines geochemical constraints on quantifying volatile release, their origin, transport, and K-Pg boundary deposition processes. These data indicate that sulfur emissions were likely significantly lower than previously estimated. The extinction scenario emerges as a multi-phase cascade dominated by dust-driven radiative forcing, with sulfur and soot as secondary modifiers. The integration of sedimentological, geochemical, and modeling approaches highlights rapid Earth system feedbacks operating on timescales from hours to millennia. After, the Ir-peak identification within the crater impactite sequence in core from IODP-ICDP 364, stratigraphic temporal coincidence unequivocally supports the impact-extinction linkage. The Chicxulub impact event defines the base of the Paleogene and the transition from Mesozoic to Cenozoic ecosystems. Extreme environmental instability, including cooling followed by a greenhouse-gas rebound due to CO₂ emissions, marks the aftermath of the event. Biotic recovery during the early Paleogene likely began in a highly dynamic, stressed Earth system with reorganized trophic structures. The Chicxulub impact represents both a catastrophic endpoint and a transformative beginning, initiating the Paleogene as a period of major global changes, with rapid ecological and climatic reorganization.