Evidence for deep-water deposition of abyssal Mediterranean evaporites during the Messinian salinity crisis

Abstract

Keywords:Messinian salinity crisis ACE index TEX 86 Mediterranean sea deep sea drilling project Scientific drilling of the abyssal evaporites beneath the deepest parts of the Mediterranean basin gave rise to the idea that the Mediterranean sea completely evaporated at the end of the Messinian. Herein, we show, using new organic geochemical data, that those evaporites were deposited beneath a deepwater saline basin, not in a subaerial saltpan, as originally proposed. Abundant fossil organic lipids were extracted from evaporites in Mediterranean Deep Sea Drilling Project cores. The archaeal lipid distribution and new analyses, using the ACE salinity proxy and TEX 86 temperature proxy, indicate that surface waters at the time of evaporite deposition had normal marine salinity, ranging from ∼26 to 34 practical salinity units, and temperatures of 25-28 • C. These conditions require a deep-water setting, with a mixed layer with normal marine salinity and an underlying brine layer at gypsum and halite saturation. After correction for isostatic rebound, our results indicate maximum drawdown of ∼2000 m and ∼2900 m relative to modern sea level in the western and eastern Mediterranean basins, respectively. Our results are consistent with previously proposed scenarios for sea level drawdown based on both subaerial and submarine incision and backfilling of the Rhone and Nile rivers, which require Messinian sea level drops of ∼1300 m and ∼200 m, respectively. This study provides new evidence for an old debate and also demonstrates the importance of further scientific drilling and sampling of deeper part of the abyssal Messinian units.

The Messinian salinity crisis: open problems and possible implications for Mediterranean petroleum systems

“…In the scenario of Roveri et al (2014c), the amplitude of the base-level changes during the salinity crisis was much less pronounced than usually envisaged; we think that the Mediterranean Sea experienced only a moderate relative base-level fall (Christeleit et al 2015) and that desiccation, as well as a catastrophic refill (Hsü et al 1973), did 287 The Messinian salinity crisis: petroleum systems not occur. The lower slopes and the deep-water settings did not undergo subaerial exposure and erosion.…”

Calcium sulfate precipitation pathways in natural and engineered environments

“…This amount exceeds by a factor of 50 the expected amount of salt contained in the Mediterranean Sea, and the precise origin/genesis of this, and other, salt giant(s), is still a matter of intense research and debate (e.g. Gargani and Rigollet, 2007;Govers, 2009;García-Castellanos and Villaseñor, 2011;Roveri et al, 2014;Christeleit et al, 2015, Scribano et al, 2017Hovland et al, 2018;Madof et al, 2019). Present day examples of gypsum precipitation in evaporitic environments are found in sabkhas of the Mediterranean coast of Egypt, salt lakes in South Australia (Warren, 1982) and India (Sinha and Raymahashay, 2004), salars of the Atacama desert ( Fig.…”

Tracking the Serpentinite Feet of the Mediterranean Salt Giant

“…More interestingly, the mechanical stress for piercing the country rocks likely breaches the gypsum accumulated on top of the diapir, giving rise to clastic deposits at seabed, as Perthuisot [147], evidenced in salt diapirs outcropping in northern Tunisia (see later). On the other hand, soluble salts extruded at seafloor may produce the brine layer at the basin bottom (Figure 2b) as invoked by Christeleit et al [60] to explain salt deposits in Mediterranean deep basins.…”

“…On the other hand, those hypotheses suggesting the evaporite deposition under persistent deep-water conditions must take into account that halite starts to precipitate when the remaining solution is reduced to 10% of the original seawater volume, implying a dramatic drop of the basin sea level. On the above bases, it is opportune to mention that fossil archaeal lipids in cores of subseafloor salts drilled in the Sardino-Balearic and Ionian abyssal basins, strongly suggest the existence of surface waters with normal salinity (26-34 psus) and temperature of 25-28 °C, at the time of salt deposition [60]. Therefore, these authors inferred that such conditions point to a deep-water basin with normal salinity seawater floating on a higher-density, saturated in gypsum and halite, brine layer.…”