|
(M/MF205) Paleoecotoxicology: the chemical stress hypothesis and the Cretaceous-Tertiary mass extinction event. Herkovits, J.1, Domínguez, O.1, 1 ABSTRACT- The fossil record of biota reveals as a distinct phenomena mass extinction events which result in a succession of species assemblages that existent for a time and were then replaced. The Cretaceous-Tertiary (C-T) episode led about 65 million years ago to the transition from the age of the dinosaurs to the age of mammals. At that time influx of extraterrestrial materials like iridium as well as huge amounts of pulverised rocks were ejected into the atmosphere as a consequence of a large asteroid impact in the Yucatan Peninsula. The worldwide distribution by atmosphere and subsequent water bound transport of the pulverised material implicated an extraordinary increase in the pollution of siderophite and crust materials like Al, Fe, O, Li, Zn, Ni, Co, Cr, Cu, Ir, etc. most of them well known as toxic substances. Data on iridium toxicity, a no priority chemical for present environmental conditions, is reported by means of the AMPHITOX test. The environmental stress on the biota exerted by the adverse effects of the tiny particles ejected into the atmosphere as well as the toxic substances pulverised and by this means highly bioavailable from air, water, soil, sediments and the food web could be viewed as the development of a worldwide chemical bomb scenario. The adverse effects on living organisms including the synergistic effects of the complex mixture of chemicals could result in a highly selective mass extinction phenomena based on differential exposure conditions, toxicity resistance, habitat-refugees features, food web and preference, etc. of the existing species at the Cretaceous-Tertiary boundary period. The iridium as a stratigraphic marker provide evidence of a rapid recovery after the chemical storm allowing the surviving species, with less competition than ever before, to multiply radiate and re colonised the Earth. Key words: Biodiversity, mass extinction, Paleoecotoxicology, AMPHITOX |
