This element is associated with the end of the Cretaceous period 65 million years ago, when a massive comet or asteroid struck the Earth, which led to disastrous consequences for all living organisms. This celestial event, which occurred in Mexico, created a crater 180 kilometers in diameter and 20 kilometers deep and threw about 50,000 cubic kilometers of rock into the atmosphere in the form in the form of dust, droplets of molten rock (spherules) and micro diamonds.
The collision immediately wiped out all forms of life over several thousand square kilometers around the site of the collision. As for Tunisia, and in the region of Oued Mellègue in the Kef Governorate; This event led to a sharp decrease in planktonic activity results in a sharp drop in the carbonate content of the ancient sedimentary layer of that period, with a yellowish millimetric layer of clays exceptionally rich in Iridium, which is an element found abundantly in metallic meteorites.
Thus, this geological stratotype found in Tunisia provides strong evidence to support the theory of the impact of the meteorite in the occurrence of extinction.

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The Stratotype of the Cretaceous-Tertiary Boundary was submitted in 2016 to the UNESCO Tentative List in Tunisia.