An attempt to date saline groundwater in the multi aquifers system of the Dead Sea area, using carbon isotopes

Dating of brines is a great challenge due to their complex chemical characteristic. This work presents an attempt to date hypersaline groundwater in the Dead Sea (DS) area, using carbon species and isotopes of groundwater. While most ions exhibit conservative behavior, the carbon system parameters indicate additional processes. The depletion in the delta C-13(DIC) in saline groundwater, compared to the DS, is probably due to anaerobic oxidation of organic matter by sulfate reduction and methane oxidation. Methane was indeed found, in low concentrations, in many groundwater samples. The very low C-14(DIC) value of some of the saline groundwater samples (similar to 14 pMC, > 10000 years), much lower than both fresh and saline end-members of the system, suggests the presence of ancient brine source in the lower sub-aquifer. Other samples of saline groundwater, from the upper sub-aquifer, have 14CDIC values closer to that of the DS (similar to 80 pMC, < 150 years).