Representaciones de Heliocosphaera en sedimentos del Neógeno en el Atlántico oriental

Abstract

The present paper is centred on the study of helicoliths which can be recognized in different sections of the Guadalquivir and South-Riff basins (Spain and Morocco), as well as in Deep Sea Drilling Project sites of the Western-Atlantic. Of said morphotype a systematic study is carried out, similarly another quantative character is shown with wich we will try to prove its variability depending on environmental changes which could have taken place. By comparison with the distribution of the other index taxa, it is observed that the morphotype in general (whose dominant specie is Helicosphaera carteri [WALLICH]) suffers a quantative reduction linked to a lowering of the temperature of the water masses. The most important quantative change takes place in the Upper Tortonian. Towards the Upper Messinian a certain recuperation seems to start, probably related to a relatively warmer waters. Aspects of preservation are also dealt with. The relatively easy dissolution of the Helicosphaera taxa determines that, based on its absence, presence and the particular state of the nannoliths, they can be used to evaluate the degree of alteration of an association in a determined sample.