Revista Chilena de Historia Natural 76 (3): 347-362, 2003
RESEARCH ARTICLE
Variations of Punta Angamos upwelling system (23º S) and the Oxygen Minimum Zone during
the recent past. An approximation from sedimentary record of Mejillones del Sur Bay
Geochemical (organic carbon, biogenic silica and cadmium) and petrographic (organic
matter) parameters analyzed in a sediment core of Mejillones del Sur Bay, have been used to reconstruct past variations in superficial
biological productivity and subsuperficial oxygenation, during the last 2,000 years. This study tends to demonstrate that into the bay, the
productivity has diminished up to the present, while the Oxygen Minimum Zone has intensified. Productivity variations can be attributed
to changes in the upwelling intensity associated to changes in local wind system, and/or to displacement of the Punta Angamos
upwelling center closer or far away of the bay. The variations of the subsuperficial oxygenation can be attributed to deep position
changes of de Oxygen Minimum Zone. The geochemical and petrographic analysis of this study show a good correlation with
bioindicator studies carried out in other sediment core of the bay, and reinforce the hypothesis that climatic events like the Little Ice Age
and the Medieval Warm Period are recorded in this bay of northern Chile. The present study shows that the firstclimatic event was
characterized by a high superficial productivity and a low subsuperficial oxygen disponibility, while the latter climatic event was
characterized by a low productivity and a better subsuperficial oxygenation.
Key words:
geochemistry,
petrography, organic matter, paleoceanography, Chile
