INTOMESS: Quantification of salinity and temperature changes accompanying the way INTO the Mediterranean MESSinian Salinity Crisis

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Since its discovery, the Messinian Salinity Crisis (MSC; 5.97 – 5.33 Ma) became the archetype of dramatic hydrologic change on an intracontinental scale providing the most recent and least disturbed long-term record of abrupt and severe water budget change in Earth’s history. The MSC was the result of altering the connections between the Atlantic Ocean and the Mediterranean basin resulting in dramatic sea level fluctuations, total turnover of bio-ecosystems governed by the development of hypersaline water bodies and deposition of >1000 m evaporite units on the basin floor. Despite many years of research, we still face important knowledge gaps, in particular concerning the hydrological dynamics en route to the MSC climax. A key to the solution can be found in the salinity history of the mediterranean bansin: Biomarker analytics allow us today to obtain sea surface temperature estimates by using the UK’37 and TEX86 proxies. Combining these sea surface temperature estimates with δ18Oforam data from the same stratigraphic levels then permits to quantify sea surface salinity changes that in turn inform about basin water evolution leading into the MSC crisis. Detailed salinity reconstructions, ultimately, will help deciphering if Messinian salinity change occured suddenly or in a gradual fashion and if precessional cyclicity was important in modulating the salinity variations during the Messinian until the onset of the MSC. Guiding key questions of this proposal will be: Was Mediterranean sea surface salinity already very high at the onset of the MSC, leading to the deposition of salts starting at 5.97 Ma? Are the salinity changes quasi-concomitant in the entire Mediterranean during the Messinian? Are the lithological differences expressed in the outcrops determined by salinity changes or result from diffrent oxygenation of the Mediterranean Sea water column? Collectively, these questions will allow us to identify if the salinity changes in the Messinian Mediterranean occurred in reversible steps modulated by precession or if these changes were controlled by the proximity to and restrictedness of the Atlantic gateway hence separating climatic from tectonic effects.