Análisis paleoceanográfico de las extinciones de radiolarios cretácicos

Resumen

The analysis of major extinction-radiations events and the fluctuation of diversity are compared with major paleoceanographic events and variation of diversity in other fossil groups (dinoflagellates, calcareous nannoplankton and ammonites). It is observed an extraordinary correlation between biotic changes and major paleoceanographic events (sea level changes, temperatures, O, C and Sr isotopes, phosphorus accumulation rates and anoxic episodes) and it reveals a predominantly external control in the evolution of the group. The rate of turnover and the diversity through time of radiolarians seem good monitoring global environmental changes and allow us to better understand the relationship of plankton evolution, climate and paleoceanographic processes. The extinction mechanism involves the succession of two major paleoceanographic control that are key factor in the evolution of the radiolarians during the Cretaceous: firstly is the sea level regression, induced probably by tectonic reorganization, which lead to a drastic drop in the diversity as response to significant changes in the oceanographic circulation (enhancing climatic deterioration); and secondly is the reduction in habitat caused by the widespread development of oceanic anoxic water masses during post-regressive periods that lead to reach diversity minima and represent a detonator for the faunal turnover.