Calcareous microfossils as tracers of major palaeoceanographic perturbations: the case of the onset of the Messinian salinity crisis in the Tertiary Piedmont Basin (NW Italy)

Different kind of sedimentary rocks (primary gypsum, laminated shale) record the onset of the Messinian Salinity Crisis in the Mediterranean successions; this event occurred synchronously at 5.96 Ma. The disappearance of calcareous microfossils is one of the proxies used to identify this timeline. In the Tertiary Piedmont Basin calcareous microfossils disappear before, at or after the onset but, when present, they show a very distinctive stratigraphic sequence of bioevents. This allows placing the onset of the MSC in distal, intermediate, and marginal settings independently from gypsum deposition.