The use of single foraminiferal shells for recording seasonal temperatures and water column stratification and its applicability to the fossil record

Mg/Ca- and oxygen isotope ratios in the shells of planktic foraminifera are widely used in paleoceanographic studies for the reconstruction of water temperatures. Standard investigations analyze multiple shells of a species at once. However, when single shells are analyzed substantial differences of the Mg/Ca- and oxygen isotope ratios are found. These are explained by seasonality and natural variability, and are increasingly used for the reconstruction of past environmental conditions. The present thesis analyzes the differences of the Mg/Ca- and oxygen isotope ratios between individual shells in the upwelling region off Northwest-Africa. The aim of this thesis is to quantify natural variability, to improve the applicability of single shells for the reconstruction of temperature seasonality and to show the potential of single specimens for recording past ocean stratification.