Sea Surface Temperature and Salinity Changes in the Easternmost Mediterranean During the Pre-Evaporitic Messinian Controlled by the Restriction at Gibraltar

Abstract

During the latest Miocene, the Mediterranean Basin was affected by extreme paleoceanographic and paleoenvironmental changes culminating with evaporite (gypsum and halite) formation during the Messinian Salinity Crisis (MSC: 5.97–5.33 Ma). This event was driven by gradual disruptions in Mediterranean–Atlantic connectivity, which may have already led to increased salinity in the pre-evaporitic deposits of the Eastern Mediterranean. Here, we reconstruct sea surface temperature (SST) and sea surface salinity of the 7.70–5.98 Ma pre-evaporitic Pissouri section (Cyprus), using a multiproxy approach that combines biomarker-based TEX86 and (Formula presented.) proxies with oxygen isotope analyses of the planktic foraminifera Orbulina universa. Our results identify four distinct phases in sea surface paleoenvironmental conditions. In the late Tortonian–earliest Messinian (7.657–7.020 Ma), SST and salinity exhibited periodical, large amplitude fluctuations. An early Messinian cooler phase (7.020–6.701 Ma) accompanied eutrophic and hypersaline conditions. Progressive decline of SST and increase in salinity (6.701–6.254 Ma) led to the disappearance of planktic foraminifera, indicating environmental stress prior to the MSC. The interval up to the first evaporite bed (6.254–5.970 Ma) reflects hydrographic instability; the SST initially stayed rather constant before transitioning to cooler conditions, while salinity dropped to normal marine conditions. These results indicate strong climate variability before the MSC onset in the Eastern Mediterranean, with highly fluctuating SSTs and increasing salinity driving pre-evaporitic paleoceanographic transformations. The results highlight how progressive restriction of oceanic gateways influenced basin-wide hydrodynamics prior to the MSC, ultimately setting the stage for the development of a unique salt giant.