Indicadores de contaminación extraterrestre en secciones distales del tránsito Cretácico-Terciario

Resumen

Several Unes of evidence have been cited to support the Chicxulub structure as the crater site forthe major extraterrestrial impact occurred at the end of the Cretaceous. The location of the craterexplains the different nature of proximal and distal Cretaceous-Tertiary (K/T) boundary deposits.The impact produced distinctive dispersal materials, mostly derived from target rocks and the vaporized bolide. Within distal sites, those located closer to Chicxulub, as it is the case for Blake Nose(NW Atlantic), a higher contribution of target rocks is recorded in the ejecta materials, whereas atthe most distal sections as those from Agost and Caravaca (SE of Spain) spherules and trace-metalanomalies evidence a significant bolide contribution. At Blake Nose, K/T boundary spherule compositions can be related to different precursors materials: Si-rich and Ca-rich materials, which is inagreement with the composition of impact glasses reported in the Gulf of Mexico area and Chicxulub pre-impact stratigraphy. Here there is little evidence for significant extraterrestrial contribution suggesting that the spherule-bed material mainly originated from the alteration oftarget-rock-derived material, which is also evidenced by REE Cl-normalized patterns.