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Neogene palaeoceanographic changes off northern-central Chile based on benthic foraminifera from the Bahía Inglesa Formation

The modern oceanographic setting off northern-central Chile is characterized by highly productive waters and an extensive Oxygen Minimum Zone (OMZ), both resultant from coastal upwelling induced by the Humboldt Current System. However, oscillations of upwelling and OMZ properties during the Neogene are still poorly understood. Here, we assess palaeoceanographic conditions based on benthic foraminifera assemblage data of marine sediments from the Bahía Inglesa Formation (Upper Miocene-Pliocene), recovered from the Quebrada Tiburón outcrop (27°42' S, 70°59' W). Quantitative paleoenvironmental analyses of benthic Foraminifera >250 µm from 6 samples are currently conducted. Preliminary results show shifts in both, the diversity and abundance of hyaline species over the studied interval. High abundances of planospiral (predominantly epifaunal) morphotypes in sandy, heavily bioturbated parts of the studied section alternate with diatom-rich sediments bearing predominantly serial (infaunal) taxa such as Bolivina aenariensis and Uvigerina peregrina/striata. The observed changes in assemblage composition imply significant changes in biological productivity, bottom-water oxygenation, and ultimately, coastal upwelling off Chile in the Neogene. Further refinements of the stratigraphic model for the studied section will clarify the timing of the here described preliminary observations of paleoenvironmental fluctuations. This study contributes to project A4 “Land‐ocean coupling between the Humboldt Current System and Atacama palaeoclimate in the Neogene” of CRC 1211 “Earth-evolution at the dry limit”.


Fatima Bouhdayad1, Laura Makowka2, Laura Schneider1, Tiago Freire1, Jassin Petersen1, Sven Nielsen3, Marcelo Rivadeneira4, Patrick Grunert1
1Institute of Geology and Mineralogy, University of Cologne, Germany; 2Institute of Geology and Mineralogy, University of Cologne, Germany;Universidad de Salamanca, Salamanca, Spain; 3Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile; 4El Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Coquimbo, Chile
GeoMinKöln 2022