Radiolaria as indicators of upwelling processes: The Peruvian connection

Abstract

In the sediments along the coastal region of Peru, certain radiolarian species have preferences to waters associated with upwelling. Such is the case for Polysolenia murrayana in the upwelling areas “fed” by equatorial water and for Cenosphaera (?) sp. in the upwelling areas “fed” by temperate (Subantarctic) water. Cycladophora (?) davisiana appears to “frame” the upwelling centers, suggesting that it prefers regions near thermic fronts. The down-core records of these species, as well as records of quartz and organic carbon, are depicted in three 14C andδ 18O dated cores, located along the Pacific coast of South America, between 11° and 13°S. They suggest that both the eolian and oceanic circulation were more intense during the last glacial stage (approximately between 33,000 and 11,000 years ago) than during the present postglacial. At these latitudes, the intensification in circulation was not only accompanied by an increased coastal upwelling and in turn by an increased primary productivity, but also by a larger supply of Temperate waters to the area.