Proxies for reconstruction of past redox-conditions in oxygen minimum zones

Within the collaborative research project SFB754 we try to develop and apply a new set of geochemical and micropaleontological proxies for the reconstruction of past redox-conditions in the Peruvian oxygen minimum zone (OMZ). Due to their high degree of adaptation to extreme habitats, benthic foraminifera like Planulina limbata and Bolivina spissa are excellent archives for proxy reconstruction of present and past redox conditions. Recent studies showed that the pore density (PD) in foraminiferal tests reflects the nitrate and oxygen availability, respectively, in the adjacent seawater. Furthermore, redox sensitive element/Calcium ratios  in foraminiferal calcite (for example Mn/Ca) may also indicate fluctuations in redox conditions given that diagenetic alteration can be neglected.

These novel approaches shall help to reconstruct fluctuations in the oxygen concentrations at one of the most oxygen depleted OMZs in today´s world oceans during the glacial. This will help within the SFB754 to understand why tropical OMZ´s tend to expand in during the last 50 years and to develop models for the prediction of changes in the future.