Temperature calibration along the Iberian-NW Africa margin, using modern planktonic foraminifera trace element and stable isotope ratios

Regional calibration data are necessary for interpretation of high-resolution studies of past environments. However, there are few studies of foraminiferal trace and minor element calibration data for upwelling regions, mainly reflecting the challenges presented by these environments, such as high carbonate dissolution in many sediments underlying these regions and the possible living planktonic foraminifera response to several environmental variables at the same time. Here, we investigate trace element and stable isotopes from a large set of core-top sediment samples from the Iberian-NW upwelling system. Shell data are compared with present-day water column data and to “global” calibration data sets of the proxies with sea surface temperature (Mg/Ca and δ18O). We explore reconstructing upper water column structure using four species with different depth habitats, different seasonal abundances, and linked to specific hydrographic conditions in this region. Preliminary results show that Mg/Ca and δ18O of all four species are consistent with seasonal temperatures as well as different depth habitats in the Iberian margin and NW Africa margin. Nutrient proxies (including Cd/Ca and Ba/Ca) provide additional constraints. G. ruber (white) reflects surface conditions of the warm waters, the Portugal Coastal Countercurrent (PCCC) at Iberian margin and open ocean waters at NW Africa; G. inflata indicates the winter mixed layer but is also present in the PCCC; G. bulloides and N. pachyderma dextral appears related with upwelling. The insights gained from this study are being applied to reconstruct the upper water column structure of MD03-2699 core (recovered off Lisbon: 39 deg N; 10.7 deg W) during the Holocene.