Evolution Of The Peru And Equatorial Upwellings Throughout The Last 800 Ka. The Coccolithophore Point Of View.

Here we present the paleoenvironmental study of ODP Sites 1237 and 1238 from the Southeast Pacific ocean. These Sites are located under the Peru and Equatorial upwelling respectively and are mainly affected by the Peru System Currents and Equatorial Countercurrent. In both Sites the coccolithophore assemblage is dominated by "small" Gephyrocapsa, Gephyrocapsa oceanica and Florisphaera profunda because both areas were under the influence of similar paleoenvironmental conditions. Nevertheless, the abundance of the different taxa shows significant and specific differences between both sites. The relative abundance of the coccolith species, coccolith accumulation rate (NAR) and productivity (N ratio) absolute values indicate that the Equatorial assemblage was more productive than that from Peru and allowed us to identify three intervals dated by the identification of calibrated biostratigraphic events and paleomagnetic data. Interval I (0.86-0.45 Ma) and interval III (0.22-0 Ma), which are characterized by high abundance of Florisphaera profunda in relation to the "small" Gephyrocapsa, were related to weak upwelling and weak Trade Winds. These environmental conditions fit with those prevailing today during "El Nino" events. Interval II (0.45-0.22 Ma), characterized by dominant Gephyrocapsa caribbeanica and very abundant "small" Gephyrocapsa and Gephyrocapsa oceanica, was related with well defined upwelling and enhanced Trade Winds, the same features developed during "La Nina" events today.