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The Cretaceous–Paleogene (K–Pg) extinction event, [a] also known as the K–T extinction, [b] was the mass extinction of three-quarters of the plant and animal species on Earth [2] [3] approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs.
A study aiming to quantify the habitat of latest Cretaceous North American dinosaurs, based on data from fossil occurrences and climatic and environmental modelling, and evaluating its implications for inferring whether dinosaur diversity was in decline prior to the Cretaceous–Paleogene extinction event, was published by Chiarenza et al ...
In ascending order, they are the Horseshoe Canyon, Whitemud, Battle and Scollard Formations. [ 2 ] [ 1 ] The Cretaceous-Paleogene boundary occurs within the Scollard Formation, based on dinosaurian and microfloral evidence, [ 5 ] as well as the presence of the terminal Cretaceous iridium anomaly .
For older periods, the potassium-argon dating process is more accurate. Radiocarbon dating is carried out by measuring how much of the carbon-14 and nitrogen-14 isotopes are found in a material. The ratio between the two is used to estimate the material's age. Suitable materials include wood, charcoal, paper, fabrics, fossils and shells. It is ...
For example, the Cretaceous–Paleogene extinction event, marks the lower boundary of the Paleogene System/Period and thus the boundary between the Cretaceous and Paleogene systems/periods. For divisions prior to the Cryogenian , arbitrary numeric boundary definitions ( Global Standard Stratigraphic Ages , GSSAs) are used to divide geologic time.
End Cretaceous: 66 million years ago, 76% of species lost, including all ammonites, mosasaurs, plesiosaurs, pterosaurs, and nonavian dinosaurs; Smaller extinction events have occurred in the periods between, with some dividing geologic time periods and epochs. The Holocene extinction event is currently under way. [12]
The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula.The strata date from the end of the Late Cretaceous (upper-lower Maastrichtian stage [1]) to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.
Badlands near Drumheller, Alberta, where erosion has exposed the Cretaceous–Paleogene boundary. The End Cretaceous extinction, or the K–Pg extinction (formerly K–T extinction) occurred at the Cretaceous (Maastrichtian) – Paleogene transition. [19] The event was formerly called the Cretaceous-Tertiary or K–T extinction or K–T ...