Large and rapid climate variability during the Messinian salinity crisis: Evidence from deuterium concentrations of individual biomarkers

During the Messinian, similar to6 m.y. ago, massive sea-level fall and wide spread deposition of evaporites occurred in the Mediterranean Sea when it b ecame isolated from the world oceans. Here we present the first hydrogen is otope data from individual sedimentary biomarkers, n-alkanes and isoprenoid s, that tracked climatically driven hydrographic changes in response to ext reme evaporation during the Messinian salinity crisis. The stable hydrogen and carbon isotope compositions of these biomarkers show a range of 160 par ts per thousand in deltaD values and 14 parts per thousand in delta C-13 va lues, and roughly covary. This indicates that the source waters of the biom arkers were therefore in some cases extremely enriched in deuterium, having average deltaD as great as +66 parts per thousand VSMOW (Vienna standard m ean ocean water). Such values are only known from desert climates today. Be cause the offset between the deltaD values of n-alkanes and isoprenoids pre served in the Miocene sedimentary rocks is similar to the offset found in m odern biological samples, we conclude that diagenesis did not significantly affect the primary deuterium concentrations.