PhD: Hydrology of Mediterranean Marginal basins during the formation of the Mediterranean Salt Giant (MSG)

Institut de Physique du Globe de Paris

Paris, , FR

To reconstruct the hydrology of selected marginal basins of the Mediterranean Sea
during the formation of the MSG using stable isotope tracers. Gypsum and
carbonate minerals precipitated form the water column of Mediterranean marginal
basins during the formation of the MSG record the isotope composition of basin
water (δ18OH2O and δDH2O) and of the dissolved sulfate (δ34SSO4 and δ18OSO4) and
strontium (87/86Sr) ions. These isotopes are sensitive to the hydrological exchanges
between the ocean and continental runoff, as well as evaporation and precipitation
processes (limited to δ18OH2O and δDH2O). Ongoing geochemical investigations of
Mediterranean marginal basins suggest that some of the gypsum deposits might
have formed at salinity lower than modern seawater, under the influence of SO4-
and/or Ca2+- rich river runoff and with little exchange with the Mediterranean Sea.
This scenario is radically different from the classical view interpreting the evaporites
of the Mediterranean marginal basins as formed by evaporation of seawater. ESR 6
will work in tight collaboration with field-based ESRs (ESRs 1, 4, 5, 8), and mining
sector partner KNAUF, to carry out a detailed sampling of primary gypsum deposits
outcropping on land. The isotope composition of gypsum will be measured at the
geochemical facilities of IPGP. In collaboration with ESR 7, ESR 6 will apply simple
numerical box models that simulate the isotopic composition of H2O and dissolved
SO4 and Sr in marginal basins. In conjunction with the isotope composition of
gypsum, these models will be used to deduce the hydrological cycle that dominated
at the time of gypsum deposition in the marginal basins of the Mediterranean Sea,
tackling the apparent contradiction of a marine-type evaporitic sequence bearing a
continental isotope signal.