Variaciones de rango orbital en la dinámica de la Nutriclina/Termoclina en el Pacifíco Ecuatorial durante los últimos 500 Ka indicado por cocolitofóridos (Site 1240, Leg 202)

Abstract

The ODP Site 1240 is located in the equatorial cold tongue in the Eastern Equatorial Pacific. The analysis of the calcareous nannofossil assemblages allow us to monitor fluctuations in the Nutricline/Thermocline over the last 500 Ka, using the relationship between the upper photic zone taxa (small placoliths) and the lower photic zone taxa (Florisphaera profunda), by means of the N ratio function. The variations in this N ratio pointed out two intervals with dominant higher relative abundances of small placoliths over Florisphaera profunda, and other interval with an abrupt increasing in the relative abundance of Florisphaera profunda over the small placoliths, controlled esentially by a precessional force, and during the last 177 Ka by a markedly excentricity component