Changes in planktic and benthic foraminifer assemblages in the Gulf of Lions, off south France: Response to climate and sea level change from MIS 6 to MIS 11

Abstract

AbstractA multidisciplinary study involving micropaleontological and geochemical tools was carried out in borehole PRGL1 (Promess 1), with the aim of reconstructing the impact of climate change and sea level variation between 133 ka and 406 ka in the upper slope of the Gulf of Lions. We used factor analysis to obtain three main benthic assemblages related to eutrophic, mesotrophic, and oxygenated environments; planktic foraminifers were grouped as warm‐water and cold‐turbulent species. These results were compared with records of CaCO3 and major and trace elements (Al, Ca, K, Sr) as well as the C/N ratio of organic matter. Power and cross‐spectral analysis showed a straightforward relationship between precession minima and thermal stratification of the water column as well as the occurrence of eutrophic bottom conditions during lowstand periods and mesotrophic environments at times of highstand. These eutrophic‐mesotrophic oscillations, usually driven by global eustatic change, also involved regional variations in CaCO3 source to this environment. During periods of precession maxima, enhancement of northwesterly winds increased primary productivity by mixing, enhancing the percentage of cold‐turbulent species in the water column and the proportion of oxygenated benthic species on the bottom. During interglacial stages, these events were recorded by lower biogenic carbonate at the expense of higher silicate‐related components most likely due to a higher supply from Pyrenees rivers. The record of oxygenated benthic species can be a good proxy to monitor past changes in Winter Intermediate Water dynamics driven by northwesterly winds.