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In 1980, a team of researchers led by Nobel prize-winning physicist Luis Alvarez, his son, geologist Walter Alvarez, and chemists Frank Asaro and Helen Vaughn Michel, discovered that sedimentary layers found all over the world at the Cretaceous–Paleogene boundary (K–Pg boundary, formerly called Cretaceous–Tertiary or K–T boundary) contain a concentration of iridium hundreds of times ...
The Cretaceous–Paleogene (K–Pg) extinction event, [a] also known as the Cretaceous–Tertiary (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.
The date of the impact coincides precisely with the Cretaceous–Paleogene boundary (K–Pg boundary), slightly more than 66 million years ago. [7] The crater is estimated to be over 150 km (93 mi) in diameter [10] and 20 km (12 mi) in depth, well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth.
Deeper in time, a mass extinction event that ended the Devonian Period, a geological era when life thrived on land for the first time, was also attributed to a hyperthermal event likely triggered ...
By the end of the year, 50 K–T boundary sites with anomalously high iridium levels had been identified. [46] Peucker-Ehrenbrink and others studied osmium isotope ratios from sediments ranging in age from recent to 80 million years old. They found only the osmium at the K–T boundary to preserve an anomalous extraterrestrial-like ratio. [114]
The climate across the Cretaceous–Paleogene boundary (K–Pg or formerly the K–T boundary) is very important to geologic time as it marks a catastrophic global extinction event. Numerous theories have been proposed as to why this extinction event happened including an asteroid known as the Chicxulub asteroid, volcanism, or sea level changes.
The Paleocene–Eocene thermal maximum (PETM), alternatively ” Eocene thermal maximum 1 (ETM1) “ and formerly known as the " Initial Eocene " or “ Late Paleocene thermal maximum ", was a geologically brief time interval characterized by a 5–8 °C global average temperature rise and massive input of carbon into the ocean and atmosphere ...
Principles. The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [5] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or ...