Multiple crises before the big crisis: Early Messinian Eastern Mediterranean paleoclimate reconstruction inferred from biomarkers and stable isotopes (Crete, Greece)

Messinian Mediterranean (7.24‒5.33 Ma) was a highly dynamic environment governed by global climatic and regional tectonic activity. The impact of these two environmental factors is highly distinguishable especially during the latest Messinian (5.97–5.33 Ma), when the famous Messinian salinity crisis (MSC) affected the Mediterranean realm. However, the interplay between climate and tectonics is less studied for the earliest Messinian. Here we use biomarker analysis, coupled with compound-specific hydrogen (δ²H) and carbon isotopes (δ¹³C), to track changes in the hydrological budget, mean annual air temperature (MAAT), vegetation and reconstruct the sea-land climate conditions in Eastern Mediterranean between 7.2‒6.5 Ma. Our data from Agios Myron section on Crete (Greece) confirms a series of drastic environmental changes in the Eastern Mediterranean during the mentioned time interval. δ²H values of alkenones indicate highly evaporitic events accompanied by shifts in vegetation, from dominant >C₃ plants to marked increasing dominance of C₄, with recurrence of C₃ vegetation at ~6.99 and 6.78 Ma respectively. The MAAT data indicate average values of 14⁰C and the overall trend suggests an orbitally paced continental climate, with maximum temperatures registered during eccentricity maxima. The reconstructed paleo-soil pH record follows a stepwise increasing trend towards slightly-alkaline soils, supporting an enhanced open vegetation contribution resulting from the ongoing continentalisation. These results provide new insights into the Messinian environmental conditions of the Mediterranean Sea, suggesting an ongoing restriction after 7 Ma, with multiple restrictive phases marked by increasing intensity until the final MSC event.