Sr isotope records from marginal marine basins track the mixing between seawater and localcontinental runoff, potentially recording the effects of sea level, tectonic, and climate forcing in marine fossilsand sediments. Our 110 new 87Sr/86Sr analyses on oyster and foraminifera samples from six late Miocenestratigraphic sections in southern Turkey, Crete, and Sicily show that 87Sr/86Sr fell below global seawater valuesin the basins several million years before the Messinian Salinity Crisis, coinciding with tectonic upliftand basin shallowing. 87Sr/86Sr from more centrally located basins (away from the Mediterranean coast)drop below global seawater values only during the Messinian Salinity Crisis. In addition to this general trend,55 new 87Sr/86Sr analyses from the astronomically tuned Lower Evaporites in the central Apennines (Italy)allow us to explore the effect of glacio-eustatic sea level and precipitation changes on 87Sr/86Sr. Most variationin our data can be explained by changes in sea level, with greatest negative excursions from global seawatervalues occurring during relative sea level lowstands, which generally coincided with arid conditions inthe Mediterranean realm. We suggest that this greater sensitivity to lowered sea level compared with higherrunoff could relate to the inverse relationship between Sr concentration and river discharge. Variations inthe residence time of groundwater within the karst terrain of the circum-Mediterranean region during aridand wet phases may help to explain the single (robust) occurrence of a negative excursion during a sealevel highstand, but this explanation remains speculative without more detailed paleoclimatic data for theregion.
|Numero di pagine||20|
|Rivista||Geochemistry, Geophysics, Geosystems|
|Stato di pubblicazione||Published - 2014|
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