Paleoclimate reconstruction during the Messinian evaporative drawdown of the Mediterranean Basin: Insights from microthermometry on halite fluid inclusions

Data constraining the paleoenvironmental conditions during the Messinian evaporative drawdown of the Mediterranean basin are still conflicting. Here we present a comprehensive paleoclimatic reconstruction during Messinian halite deposition from several Italian sites. We performed fluid inclusion analyses to define better both the composition of the Mediterranean water body and the paleotemperatures of the Messinian brine during halite crystallization. We measured homogenization temperatures on 218 primary all-liquid fluid inclusions in Messinian halite from the Volterra, Crotone, and Caltanissetta evaporite basins. These measurements provided mean homogenization temperatures of 17-18C, with a range between 10-11C and 28-29C, which should be close to the SST of the Mediterranean Sea during halite deposition. The occurrence of major elements such as Cl, Na, Mg, S, Ca, and K within the halite fluid inclusions, together with the presence of minerals such as pentahydrite, polyhalite, and Ca-, K-, and Mg-sulfates, indicates that these salt bodies originated from mainly marine water. Taking into account both the present-day annual SST of the Mediterranean Sea around the sampling sites, which ranges between 18 and 20C, and the lower latitude of the Mediterranean Basin during the Messinian Salinity Crisis, our homogenization temperatures point to a colder climate during the Messinian halite deposition compared to the present interglacial climate stage. This conclusion is consistent with halite deposition during a Late Miocene glacial interval (TG12).