A division that can be drawn across a pollen diagram on the basis of fluctuations in pollen types. Each pollen zone is dominated by high frequencies of a particular pollen type or types. In recent years, many palynologists have abandoned general zonation schemes and instead have divided their pollen diagrams into 'pollen assemblage zones' (p.a.z.). These are based simply on the pollen fluctuations seen in each particular diagram and can therefore take account of local variation in the history of vegetation.