Chicxulub impact

Chicxulub impact
Name	Chicxulub impact
Caption	Gravity anomaly map of the Chicxulub structure
Location	Yucatán Peninsula
Coordinates	21.4°N 89.5°W
Diameter	~180 km
Age	~66 million years
Event	Bolide impact
Discovered	1978–1991

Chicxulub impact The Chicxulub impact is the Cretaceous–Paleogene boundary bolide event associated with a large buried impact structure on the Yucatán Peninsula, linked to the mass extinction at the end of the Cretaceous and the demise of non-avian Dinosauria. Evidence from geophysics, stratigraphy, and paleontology ties the event to global signals recorded in marine and terrestrial sections studied by institutions such as the Smithsonian Institution, the Geological Society of America, and the International Ocean Discovery Program. The impact remains central to debates involving planetary science, stratigraphy, and paleobiology.

Discovery and Identification

The buried structure was first inferred from aeromagnetic and gravimetric anomalies detected by oil companies operating in the Gulf of Mexico and by researchers at the University of Cambridge, the University of Arizona, and the National Autonomous University of Mexico during surveys in the 1970s and 1980s. Subsequent synthesis of evidence by scientists like Luis Alvarez, Walter Alvarez, Hervé (sic), and researchers at the Carnegie Institution for Science and Brown University connected ejecta layers and shocked minerals to a single origin, while drilling campaigns such as those organized by the Integrated Ocean Drilling Program and the International Continental Scientific Drilling Program provided cores confirming a buried multi-ring basin structure. The naming derives from the nearby town of Chicxulub Pueblo and was popularized through publications in journals associated with the American Geophysical Union and the Geological Society of London.

Impact Structure and Geology

The impact structure is a peak-ring basin with an estimated rim-to-rim diameter of roughly 150–200 km identified through gravity, magnetic, and seismic surveys conducted by teams at the US Geological Survey, the Centro de Investigación Científica de Yucatán, and universities such as the Massachusetts Institute of Technology and the University of Texas at Austin. The target sequence comprises carbonate platform lithologies of the Yucatán Platform, evaporites, and pelagic sediments overlain by Palaeogene deposits; these were disrupted to form a central uplift and concentric rings analogous to features studied in the Sudbury Basin and the Vredefort Dome. Cores recovered during drilling expeditions reveal suevite, impact melt rock, breccia units, and high-pressure polymorphs of SiO2 such as coesite and stishovite, consistent with cratering processes observed in the Chicxulub structure's analogues.

Impact Mechanics and Ejecta

Numerical modeling by groups at institutions including Caltech, the University of California, Berkeley, and the Max Planck Institute for Chemistry indicates an impactor roughly 10–15 km in diameter, likely a carbonaceous chondritic asteroid with kinetic energy comparable to the output of large supervolcano eruptions and modeled using hydrocodes developed at the Los Alamos National Laboratory. The impact produced a transient cavity, collapse to form a peak ring, and global dispersal of ejecta including spherules, tektites, and shocked minerals found in K–Pg boundary sediments at sites such as Stevns Klint, El Kef, and Río Puerco. Massive vaporization of target carbonates and sulfates generated sulfur-rich plumes and sulfate aerosols documented in sulfate anomaly records studied by researchers at the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution.

Environmental and Climatic Effects

The injection of dust, soot, and sulfate aerosols into the stratosphere caused rapid sunlight attenuation and photosynthetic collapse documented in paleobotanical and isotopic studies undertaken at the Natural History Museum, London, the American Museum of Natural History, and the Royal Society. Climatic models developed at the National Center for Atmospheric Research and the UK Met Office simulate short-term extreme cooling ("impact winter") followed by longer-term greenhouse warming due to CO2 release from vaporized carbonates, paralleling mechanisms discussed in literature from the Intergovernmental Panel on Climate Change and modeled by groups at the University of Cambridge. Ocean acidification and deoxygenation signals appear in marine carbonate isotope excursions recorded in cores analyzed by the Oregon State University and the University of California, Santa Cruz.

Biological Consequences and Extinction

The event coincides with the mass extinction at the Cretaceous–Paleogene boundary that affected marine plankton such as foraminifera and calcareous nannoplankton, terrestrial vertebrates including non-avian Dinosauria, and numerous plant groups; this pattern emerges from fossil records curated at institutions like the Field Museum, the Naturhistorisches Museum Wien, and the Royal Ontario Museum. Recovery dynamics, biotic selectivity, and survival of clades such as Aves and certain mammalian lineages have been explored by paleontologists from the American Museum of Natural History and the Smithsonian Institution using stratigraphic sections at Hell Creek Formation, Danian sections, and global K–Pg reference sites. Comparative mass-extinction studies draw on precedents such as the Permian–Triassic extinction event for context.

Evidence and Dating

High-precision radiometric ages from shocked zircons, isotopic stratigraphy, and argon–argon dating performed by laboratories at the Geological Survey of Canada, the ETH Zurich, and the University of Chicago converge on an age near 66.04–66.05 Ma, matching the K–Pg boundary layer identified by biostratigraphy and chemostratigraphy at global localities such as K–Pg boundary sections at Kola Peninsula analogues and well-studied outcrops like Gubbio. Geochemical tracers including anomalous iridium concentrations, platinum-group elements, and chromium isotope signatures link distal ejecta and boundary clay layers to an extraterrestrial source demonstrated by teams at the Vanderbilt University and the University of Vienna.

Ongoing Research and Debates

Active research continues on aspects including the precise impactor type and provenance explored via isotopic fingerprinting studies at the Lunar and Planetary Institute and the Smithsonian Astrophysical Observatory, the relative roles of impact versus volcanism debated relative to Deccan Traps timing by researchers at the Indian Institute of Science and the Purdue University, and the detailed mechanisms of ecological selectivity addressed by teams at the Swiss Federal Institute of Technology in Zurich and the University of Chicago. New drilling initiatives, remote sensing campaigns by the NASA and the European Space Agency, and advances in climate and ecological modeling at institutions like the Princeton University and the University of Oxford aim to refine chronology, quantify forcing agents, and resolve outstanding questions about post-impact recovery and the interplay with contemporaneous Earth system processes.

Category:Impact craters