Cretaceous extinctions

Cretaceous extinctions
Name	Cretaceous extinctions
Epoch	Cretaceous
Period	Mesozoic
Time	~145–66 Ma
Major events	Early Cretaceous turnovers; Cenomanian–Turonian event; end-Cretaceous mass extinction
Notable causes	volcanism, bolide impact, climate change, sea-level change

Contents

Cretaceous extinctions describe multiple biotic crises during the Cretaceous Period that reshaped Mesozoic life. The interval includes pulsed losses that affected marine and terrestrial biota across continents such as North America, South America, Africa, Eurasia, Australia, Antarctica, and India and intersected with provinces studied by institutions like the Smithsonian Institution, Natural History Museum, London, American Museum of Natural History, and research programs at Caltech and University of Oxford. Paleontologists, stratigraphers, and geochemists from organizations including Geological Society of America, International Union of Geological Sciences, Royal Society, and laboratories at Massachusetts Institute of Technology and University of California, Berkeley have documented the events using cores from the Kumano Basin, DSDP, and ODP expeditions.

Overview and Timeline

The Cretaceous spans from the Jurassic–Cretaceous boundary through the Cretaceous–Paleogene boundary and includes chronostratigraphic markers such as ammonite zonations tied to sites like Gubbio, El Kef, and DSS core 763A. Geochronology from laboratories at Utrecht University, University of Cambridge, ETH Zurich, and Columbia University refines ages using methods developed by teams at Los Alamos National Laboratory and Geological Survey of Canada. Major turnovers are recognized in the Early Cretaceous, the Cenomanian–Turonian boundary (also called the Oceanic Anoxic Event 2 by some researchers), and the end-Cretaceous event around 66 Ma linked to the Chicxulub crater. Stratigraphic correlations rely on work by stratigraphers affiliated with INQUA, PAGES, and regional surveys from USGS and British Geological Survey.

Early Cretaceous faunal changes documented in formations such as the Lagerstätten of Liaoning, Portuguese Lusitanian Basin, Wealden Group, and collections at the Natural History Museum, Berlin involve turnovers among ammonites, bivalves, and dinosaur clades studied by researchers at Yale University, Harvard University, Seoul National University, and University of Tokyo. The Cenomanian–Turonian event, recorded in the Western Interior Seaway cores and sections in New Jersey, Morocco, and Italy, is associated with organic-rich shales reported by teams from University of Texas at Austin, University of Barcelona, and Instituto Geológico y Minero de España. The end-Cretaceous crisis, characterized by abrupt losses in non-avian dinosaurs, ammonites, marine reptiles, and plankton, is preserved in the Hell Creek Formation, Paleogene boundary sections at Gubbio, K-Pg boundary sections of Seymour Island, and museums like the Denver Museum of Nature & Science.

Volcanism: Large igneous province eruptions such as the Deccan Traps and flood basalts in Siberian Traps-adjacent studies are analyzed by geochronologists at GFZ Potsdam, CARNEGIE Institution for Science, and Arizona State University for links to CO2 and sulfur emissions. Impact: The discovery and analysis of the Chicxulub crater by teams from UNAM, University of Arizona, Brown University, and University of Copenhagen provided iridium anomalies, shocked quartz, and spherules correlated with abrupt extinctions. Climate: Paleoclimate reconstructions from isotope labs at WHOI, Lamont–Doherty Earth Observatory, Max Planck Institute for Chemistry, and Scripps Institution of Oceanography show warming and ocean acidification episodes consistent with modeling by groups at Princeton University, ETH Zurich, and Pacific Northwest National Laboratory. Sea-Level Change: Eustatic shifts documented by the International Commission on Stratigraphy and regional syntheses from Geological Survey of India, Geological Survey of Japan, and Bureau of Mineral Resources altered shelf habitats and are integrated with paleoecological work by scientists at University of Leeds and University of Queensland.

Taxonomic selectivity appears across studies in paleobiology labs at University of Chicago, University of Oslo, University of Buenos Aires, and Monash University. Marine plankton groups such as foraminifera, calcareous nannoplankton, and radiolarians show differential extinction and recovery patterns documented in cores from the South Atlantic Ocean, Indian Ocean, and Pacific Ocean by IODP researchers. Terrestrial impacts on clades like Theropoda, Ornithopoda, Hadrosauridae, Ankylosauria, Ceratopsia, Pterosauria, and early Aves are reconstructed from bonebeds at Laramie Formation, Hell Creek, Dinosaur Provincial Park, and collections at Royal Tyrrell Museum. Recovery phases involve opportunistic radiations comparable to post-extinction patterns analyzed by the Paleobiology Database and modeled by groups at Stanford University and Brown University.

Shallow marine shelves such as the Western Interior Seaway, European Chalk Sea, and Tethys Ocean experienced carbonate platform collapse and turnover recorded by teams at University of Hamburg, Universidade de São Paulo, and CNRS. Terrestrial ecosystems from the Santonian to Maastrichtian stages show provincialism between faunas in Madagascar, India, Antarctica, and Iberia documented by field teams affiliated with Paleontological Research Institution, Museo Argentino de Ciencias Naturales, and Natural History Museum of Los Angeles County. Freshwater and estuarine assemblages preserved in the Liaoning Biota, Río Negro Province, and Neuquén Basin indicate selective survivorship patterns investigated by researchers at University of Alberta and University of São Paulo.

Active debates involve attribution of causality among proponents linked to Deccan Traps timing studies by teams at University of Oxford and impact-focused groups at Imperial College London, with integration efforts by consortia including IODP, ICDP, NSF, and European Research Council. New geochronology from U–Pb and 40Ar/39Ar labs at ETH Zurich, Geological Survey of Canada, and UC Santa Barbara refine synchronicity between volcanism and impact. Emerging techniques—sedimentary ancient DNA sequencing pioneered by labs at University of Copenhagen and Max Planck Institute for Evolutionary Anthropology, microfossil morphometrics from Smithsonian collaborators, and climate modeling at NASA Goddard Institute for Space Studies—aim to resolve patterns at regional scales. Interdisciplinary projects with museums such as American Museum of Natural History, Field Museum, and Natural History Museum, London continue to archive specimens that constrain extinction dynamics.

Category:Mass extinctions