Sea Surface Temperatures variations during the Messinian in the Sorbas Basin

In the Mediterranean region, the end of the Miocene is marked by the Messinian Salinity Crisis (MSC; 5.97 - 5.33 Ma), a peculiar event that governed environmental modifications in the region, causing the deposition of large thicknesses of evaporitic rock units, dramatic hydrological and ecological crises that affected both water and land-based habitats. The onset of the MSC has been proven to be synchronous over the Mediterranean basin as demonstrated by astronomical tuning of the pre-evaporitic sedimentary successions. Among these, the Sorbas Basin plays a pivotal role for the understanding of the palaeoceanographic evolution of the Western Mediterranean Sea before the onset of the MSC. Its location within proximity of the Atlantic gateway renders the Sorbas Basin an exceptional recorder of palaeoceanographic changes just prior to the MSC. The pre-evaporitic sequence starts with Tortonian calcarenites (belonging to the Azagador Member) followed by early Messinian clays and diatomites (belonging to the Abad Member). The Lower Abad Member, consists of indurated whitish marls and softer grey marls which contrast sapropel and diatomite alterations of the Upper Abad Member. Here, we present biomarker-based sea surface temperatures (SST) using TEX₈₆ paleotemperatures recorded in the Sorbas basin for the time interval between 7.3 and 6.1 Ma. The TEX₈₆ SST estimates show a generally decreasing trend, with a 7.26 Ma to 7.11 Ma warm phase (averaging 27 °C). This warm phase is followed by ~5°C cooling (to values averaging 22 °C) after 7.11 Ma, with two distinct colder peaks, one centred around 7.09 Ma and one around 6.95 Ma. The cooling after 7.11 Ma follows shallowing and restriction in the Betic and Rifian marine gateways and is most likely controlled by global cooling characterizing the latest Miocene. In a second step, we couple the TEX₈₆ SST estimates with oxygen stable isotope ratios (δ¹⁸O) measured on the surface-dwelling planktonic foraminifera Orbulina universa to reconstruct sea surface salinity (SSS) variations at the corresponding stratigraphic levels for the study interval. The newly acquired SST and SSS data from the Sorbas Basin provide a previously unavailable record of changed environmental conditions recorded in the Western Mediterranean Basin that permit direct comparison across the Mediterranean Basin with the recently acquired Messinian Eastern Mediterranean SST and SSS changes.