L'iridium a la limite Cretace-Tertiaire du site d'El Kef, Tunisie

摘要: The Cretaceous-Tertiary (K/T) boundary is marked by the collision of Earth with an asteroid or a comet. This event produced high concentrations iridium and other PGEs in K/T sediments. Although delivered very brief event, Ir observed over sizeable thickness sediments simulating long duration phenomenon (several tens thousands years). In order to understand this point we have analysed rocks from section El Kef (Tunisia), site which offers ideal conditions (high deposition rate low bioturbation) for detailed stratigraphic study. distribution shows millimetre thick pulse-like feature occurring perfect coincidence beginning biological crisis. superimposed diffuse component extending about two metres sediment upper Maastrichtian top Globigerina eugubina zone Danian. associated crystals Ni-rich spinel, mineral derived meteoritic material. pulse, reminiscent brevity results prompt large amount debris projectile dispersed world-wide as result impact event. As far concerned, its agrees estimated residence time sea water. explained transit through oceanic reservoir finely divided fraction projectile.