Dinosaurs Connections

Aftermath of Extinction

What is the Cretaceous/Tertiary boundary and what does it indicate about the extinction at the end of the Cretaceous period?

The mass extinction at the end of the Cretaceous period is evident in the Cretaceous/Tertiary (K/T) boundary, a thin layer of rock found in various areas around the world—all dominated by a large amount of iridium, a chemical element found in abundance in comets and asteroids but rare on Earth. It was this K/T boundary that first clued scientists in to the fact that there was a mass extinction about 65 million years ago. According to this layer and other evidence in the fossil record, mass extinctions of animals and plants—in both oceans and on land—occurred around the same time.


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