Temporal stability and origin of chemoclines in the deep hypersaline anoxic Urania basin

Abstract

Submarine brine lakes feature sharp and persistent concentration gradients between seawater and brine, though these should be smoothed out by free diffusion in open ocean settings. The anoxic Urania basin of the eastern Mediterranean contains an ultrasulfidic, hypersaline brine of Messinian origin above a thick layer of suspended sediments. With a dual modeling approach we reconstruct its contemporary stratification by geochemical solute transport fundamentals and show that thermal convection is required to maintain mixing in the brine and mud layer. The origin of the Urania basin stratification was dated to 1650 years B.P., which may be linked to a major earthquake in the region. The persistence of the chemoclines may be key to the development of diverse and specialized microbial communities. Ongoing thermal convection in the fluid mud layer may have important yet unresolved consequences for sedimentological and geochemical processes, also in similar environments.

A Serravallian (Middle Miocene) shark fauna from Southeastern Spain and its palaeoenvironment significance

“…One of the most important events that largely determined the current biodiversity of the Mediterranean was its almost complete desiccation during the so-called Messinian salinity crisis 5.59 Ma ago (Krijgsman et al 1999;Gibert et al 2013). The drastic changes in climate, salinity, anoxia and sea level fluctuation (Flores et al 2005, Cita 2006, García-Castellanos et al 2009, García-Castellanos and Villasen 2011, Goldhammer et al 2015 entirely eliminated deep-water environments, reducing available ecosystems and driving most species to extinction (Coll et al 2010). As a consequence, the actual diversity of the Mediterranean Sea comes directly from the repopulation of the Atlantic Ocean faunas through the Gibraltar Strait since its opening at the Zanclean flood (Gibert et al 2013).…”