The paleosalinity of water from which the gypsum precipitated during the Messinian
salinity crisis is a controversial issue. Recent microthermometry studies on primary fluid
inclusions in gypsum provided very low salinity values not compatible with precipitation from
seawater, and suggested strong mixing between seawater and nonmarine waters enriched in
calcium sulfate. We applied a new microthermometric protocol on gypsum crystals from nine
Mediterranean sections that were experimentally stretched to measure a larger population
of fluid inclusions. The results show salinities ranging from 9 to 238 wt‰ NaCl equivalent,
largely falling within the evaporation path of normal seawater. The data from previous studies
were obtained mostly from those fluid inclusions capable of nucleating a stable bubble
after a weak stretching, which probably correspond to those having a lower salinity acquired
through post-depositional crack-and-seal processes. Our data suggest instead that the primary
gypsum precipitated from a marine brine, later modified by post-trapping processes
during tectonics and exhumation
