Cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre-evaporitic Messinian
in a marginal basin of the western Mediterranean. The fluctuations coincide with a dominantly precession-controlled
sedimentary cyclicity (sapropels). During sapropel deposition, high planktic foraminiferal diversities are indicative of
relatively stable marine conditions, while during homogeneous marl deposition low diversities seem to indicate the presence
of unfavourable, more saline surface water conditions. The dominance of a precession-related signal indicates that regional
climate oscillations rather than (obliquity-related) glacio-eustatically controlled influxes of Atlantic and/or Mediterranean
waters are responsible for the faunal fluctuations and sedimentary cyclicity. Our scenario links the persistence of normal
marine conditions during sapropel formation with increased rainfall and run-off along the western Mediterranean at times
that perihelion occurred in Northern Hemisphere summer. Less favourable, highly saline surface water conditions prevailed
during periods of drier climate induced by opposite processional extremes. The cyclical oceanographic fluctuations could
also have governed periodic reef growth along the margins