Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6428092 | Earth and Planetary Science Letters | 2015 | 10 Pages |
â¢Fossil archaeal lipids are abundant in upper Messinian abyssal evaporites.â¢Upper Messinian abyssal evaporites were deposited in deep water, >200 m.â¢Basin had marine salinity surface layer and hypersaline underlying brine.â¢Results are consistent with proposed scenarios of sea level drawdown between 200 and 1300 m.
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 deep-water 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 TEX86 temperature proxy, indicate that surface waters at the time of evaporite deposition had normal marine salinity, ranging from â¼26 to 34 practical salinity units, and temperatures of 25-28â°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 â¼2000 m and â¼2900 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 â¼1300 m and â¼200 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.