Cretaceous-Tertiary extinction event

The Cretaceous-Tertiary (K-T or KT) extinction event, also known as the KT boundary, was a period of massive extinction of species, about 65.5 million years ago. It corresponds to the end of the Cretaceous Period and the beginning of the Tertiary Period. (K is the traditional abbreviation for the Cretaceous period. Cretaceous comes from the Latin for chalk, creta. The K comes from the German word for chalk kreide, or possible Greek kreta. The K is used so as to avoid confusion with the Carboniferous period which uses the letter C.)

Deccan traps

Several paleontologists remained skeptical about the impact theory, as their reading of the fossil record suggested that the mass extinctions did not take place over a period as short as a few years, but instead occurred gradually over about ten million years, a time frame more consistent with longer term events such as massive volcanism. Several scientists think the extensive volcanic activity in India known as the Deccan Traps may have been responsible for, or contributed to, the extinction. A partial reason for the rejection of the impact theory may have been a certain general distrust of a group of physicists intruding into the paleontologists' domain of expertise.

Related Topics:
Fossil - Volcanic - India - Deccan Traps - Physicist

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Luis Alvarez, who died in 1988, replied that paleontologists were being misled by sparse data. His assertion did not go over well at first, but later intensive field studies of fossil beds lent weight to his claim. Eventually, most paleontologists began to accept the idea that the mass extinctions at the end of the Cretaceous were largely or at least partly due to a massive Earth impact. However, even Walter Alvarez has acknowledged that there were other major changes on Earth even before the impact, such as a drop in sea level and massive volcanic eruptions in India (Deccan Traps sequence), and these may have contributed to the extinctions.

Related Topics:
1988 - Sea level

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A very large impact crater has been recently reported in the sea floor off the west coast of India 2. This, the Shiva crater (450/600 km diam.), has also been dated at about 65 million years at the K-T boundary. The researchers suggest that the impact may have been the triggering event for the Deccan Traps. However, this feature has not yet been accepted by the geologic community as an impact crater http://www.spacedaily.com/news/deepimpact-04r.html.

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