Assessment of selective preservation is of prime importance for the interpretation of proxies. Zonneveld et al. (1997) demonstrated strong selective changes in dinocyst assemblages as a result of aerobic degradation in the MAP F-turbidite. Based on two sets of 3 samples only, this did not allow much further differentiation. The present study relates palynological with geochemical changes at the transition from anoxic to oxic conditions in MAP turbidites with a high, 0.5-1 cm resolution. We now can understand why the geochemical processes already modify the peridinioid component of the dinoflagellate assemblage in the anoxic zone below the oxidation front, and why they lead to increasing cyst concentrations for some species close to the front. We demonstrate how taxon-specific differences in cyst degradation lead to successive dominance of Brigantedinium, Spiniferites and Impagidinium when degradation proceeds. We show the importance of knowledge of selective preservation by interpreting the assemblages with and without taking this process into account.