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| Titel |
Was Mediterranean region that dry during the Messinian Salinity Crisis? |
| VerfasserIn |
Iuliana Vasiliev, Eveline Mezger, Stefano Lugli, Gert-Jan Reichart, Vinicio Manzi, Marco Roveri |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131520
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| Publikation (Nr.) |
 EGU/EGU2016-11940.pdf |
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| Zusammenfassung |
| Between 5.97-5.33 Ma kilometres-thick evaporite units were deposited in the Mediterranean
basin during an event known as the Messinian salinity crisis (MSC). It is generally
accepted that the MSC was a dry period, with higher evaporation than precipitation and
runoff. However, how dry climate was during the MSC is difficult to assess because
a modern analogue is missing. Here we reconstruct hydrological changes in the
Mediterranean basin during the MSC using excellently preserved biomarkers extracted
from three reference sections for the Messinian evaporites: Monte Tondo, in the
northern Apennines, Realmonte salt mine and Eraclea Minoa, in Sicily that cover
the main stages of the MSC: the ‘Primary Lower Gypsum’ (stage 1 of the MSC),
halite unit (stage 2) and ‘Upper Gypsum’ (stage 3) respectively. We used long chain
n-alkanes with a strong odd over even predominance as terrestrial biomarkers, and their
hydrogen isotopic values (δD) to reconstruct the large scale hydrological changes on
the land adjacent to the Mediterranean covering ∼640 kyrs of the MSC interval.
Additionally, the δD record of long-chain alkenones produced by haptophyte algae is
used to observe changes in the source for the Mediterranean Sea water. The δDof
thelong-chain n-alkanes recorded during the deposition of Lower Evaporites in
Monte Tondo (MSC stage 1) indicate a δD of the precipitation largely similar to
the present-day Mediterranean. This implies that the overall hydrologic regime
was similar to today, with only some levels being more δD enriched (i.e. more
arid/warmer). Enriched δD values of the alkenones from halite unit of the Realmonte
mine (MSC stage 2) are associated with kainite (mineral forming under extreme
evaporation) and giant polygons (evidence of an exposure surface), in line with the high
evaporative conditions during halite deposition. The δDof thelong-chain n-alkanes
recorded during the deposition of Upper Evaporites in Eraclea Minoa (MSC stage 3)
indicate a δD of precipitation much different from the present-day Mediterranean Sea
hydrologic regime. The values are typical for much drier settings, similar to the Red Sea
– Gulf of Aden, region known for extreme evaporation taking place today. The
relative contribution of the different alkenones from Eraclea Minoa is similar to that
observed in present-day marine settings. This implies that a connection to the open
Ocean is likely, even though a connection with the Parathetys might have existed as
well. However, the δDalkenones values recorded during deposition of the Upper
Evaporites in Eraclea Minoa are similar to those recorded synchronously in the
Black Sea area, DSDP 42B Hole 380. The source for the surface water from the
Upper Evaporites was similar to the one from the coeval Black Sea suggesting a
similar hydrologic regime characterized by extended drought over large areas of
the southeastern Europe. Because of the δDalkenones similarity and the alleged
Paratethys type of fauna defining the ´Lago Mare´ of the Mediterranean we further
speculate that the surface water from the Upper Evaporites could, at times, be derived
from the Black Sea, consistent with Paratethys water inflow into the Mediterranean. |
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