Straits to Extinction. Integrated Magneto-Bio-Stratigraphy and Cyclostratigraphy Studies Reveal the Destructive Power of Marine Gateways

The marine gateways are an important element in the geographic and paleogeographic architecture of oceans and seas. They influence the heat and chemical exchange between neighbouring water bodies, mixing or segregating them and influencing the climate and the ecosystems. In extreme configurations, they play a role in the onset of Salinity Crises and the formation of evaporites. However, detailed information on the sensitivity and functioning of gateways remains scarce as their geological records are poorly preserved. To counter the lack of reliable records our research focuses on the impact of the gateways on the adjacent seas. We studied marine sediments from basins that belonged to the Neogene system of seas and lakes of Eurasia (Paratethys). Integrated magneto-bio-stratigraphy and cyclostratigraphy studies in these basins have provided high-resolution correlations between the neighbouring seas within Paratethys, which, in turn, led to the identification of problematic gateway configurations. Here we focus on two such configurations: the setting that allows evaporite formation and the configuration that leads to extinction events. The gateway setting responsible for salinity crises not only leads to extinctions but also to the formation evaporites. We focus on the Badenian Salinity Crisis (BSC), an event that occurred between 13.8-13.3Ma, which is particularly interesting because it is a selective salinity crisis, happening only in some of the sub-basins of Paratethys. In this case, our initial evidence shows that the configuration requires multiple gateways that can produce water stratification and brine formation. The gateway configuration that triggers extinctions has been linked with the Badenian-Sarmatian Extinction Event (BSEE), placed at 12.65Ma. The event. that has completely destroyed the marine ecosystems of Central and Eastern Europe (with an extinction rate of 94%), has occurred in less than 10kyr and according to our numerical modelling results it only required a sea-level variation of 5m.