Tunisia - The Cretaceous-Tertiary boundary Stratotype (K-T limit)

At the end of the Cretaceous, 65 million years ago, a huge meteorite struck the Earth with catastrophic consequences. Before the cataclysm, dinosaurs and other groups of reptiles dominated the earth, the seas and the heavens. Their extinction left the field open to mammals and birds. The meteorite, about 10 km in diameter, fell near the current village of Chicxulub, on the Yucatan coast in Mexico. Its fall dug a crater 100 km in diameter and 12 km deep and had to annihilate immediately all life over several thousand square kilometers around the site of impact. Some 50 000 Km3 of rocks were projected into the atmosphere in the form of dust, droplets of molten rocks (spherules) and micro diamonds. In Tunisia, in the region of Oued Mallègue (El Kef governorate), the sharp decrease in planktonic activity results in a sharp fall in the carbonate content of the sediments. In this site, chosen as a stratotype, the KT limit corresponds to a thin yellowish millimetric layer of clays exceptionally rich in Iridium, an element found abundantly in metallic meteorites, thus supporting the theory of meteorite impact at the origin of extinctions. large-scale massive animal and plant species. Located on the bank of the Oued Mallègue, the Cretaceous-Tertiary crossing section is easily recognizable on the ground and presents the most advantageous outcrop conditions that are threatened by erosion, especially during periods of high water. The K-T boundary of the El Kef site extends steadily over hundreds of meters. It is uniform and without any gap.