Mediterranean outflow pump; an alternative mechanism for the Lago-mare and the end of the Messinian salinity crisis

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doi: 10.1130/G37646.1
Author(s): Marzocchi, Alice; Flecker, Rachel; van Baak, Christiaan G. C.; Lunt, Daniel J.; Krijgsman, Wout
Author Affiliation(s): Primary:
University of Bristol, School of Geographical Sciences, Bristol, United Kingdom
Other:
Utrecht University, Netherlands
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 44(7), p.523-526. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 33 refs.; illus., incl. sketch map
Summary: The final stage of the Messinian salinity crisis (MSC) was characterized by brackish-water "Lago-mare" conditions in the intermediate and marginal basins of the Mediterranean Sea. The presence of Paratethyan (former Black Sea) fauna in these deposits has fueled long-lasting controversies over the connectivity between the Mediterranean and Paratethys and contemporary sea-level drops in both basins. Here, we use the results of sub-precessional climate simulations to calculate the freshwater budget of the Mediterranean and Paratethys in the Messinian. We show that, during the MSC, the freshwater budget of Paratethys was positive, while the Mediterranean was negative. Using these numerical constraints, we propose a Mediterranean outflow pump as an alternative scenario for the two most dramatic hydrological changes in the MSC: (1) the Halite-Lago-mare transition and (2) the Pliocene reestablishment of marine conditions. Following the maximum MSC lowstand during halite formation, progressive Mediterranean sea-level rise resulting from African river runoff and overspill from both the Atlantic and Paratethys eventually reached the level of the Paratethys sill. A density contrast at this gateway caused dense Mediterranean waters to flow into the Paratethys, driving a compensatory return flow. This "pump" mechanism significantly enhanced Paratethyan inflow to the Mediterranean, creating suitable conditions for the Lago-mare fauna to migrate and thrive. When the Mediterranean sea level finally reached the height of the Gibraltar sill, Mediterranean outflow restarted there and enhanced exchange with the Atlantic Ocean. During this reorganization of the circulation, brackish and hypersaline waters were pumped out of the Mediterranean, and open-marine conditions were reestablished without major flooding of the basin at the Miocene-Pliocene boundary.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Black Sea; Brackish-water environment; Cenozoic; DSDP Site 380; Deep Sea Drilling Project; Digital simulation; East Mediterranean; Expedition 339; General circulation models; Integrated Ocean Drilling Program; Lacustrine environment; Leg 42B; Marine environment; Mediterranean Sea; Messinian; Messinian salinity crisis; Miocene; Neogene; North Atlantic; Numerical models; Paleo-oceanography; Paleocirculation; Paleoecology; Paleoenvironment; Paleogeography; Paleosalinity; Paratethys; Pliocene; Sea-level changes; Tertiary; Upper Miocene
Coordinates: N420559 N420559 E0293654 E0293654
Record ID: 2016070838
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