Carina Klein examines the quality of the existing modern ammonoid zonation based on three methods, being Unitary Associations (UA), Constrained Optimization (CONOP) as well as Ranking and Scaling (RASC). The author sets out which of these three methods is best suitable to refine these zones. The results obtained are compared to each other with regard to ammonoid succession and resolution as well as with empirical data from selected reference sections. The analysis reveals that the UA and RASC methods are the most suitable since the results best mirror the empirical data from the single...