Abstract
The supratidal, saline pans and surrounding wet sabkha area, south Jeddah, Saudi Arabia, have seawater seepages with a salinity of 40 ppm that increases to 80-140 and 220-375 ppm during deposition of gypsum and halite, respectively. The concentration order of the dominant cations and anions in the saline pans is sodium (Na (super +) ) > magnesium (Mg (super 2+) ) > potassium (K (super +) ) > calcium (Ca (super 2+) ) and chloride (Cl (super -) ) > sulfate ions (SO (sub 4) (super 2-) ) > bicarbonate ions (HCO (sub 3) (super -) ), respectively. The dominant brine type is Mg and sodium chloride. Correlations of the various ions in the saline pans indicate positive relations between Na (super +) and Cl (super -) , Na (super +) and total dissolved solids (TDS), and Cl (super -) and TDS due to halite precipitation at a high salinity value. Negative correlations between Ca (super 2+) and SO (sub 4) (super 2-) and between Ca (super 2+) and HCO (sub 3) (super -) are related to the reduction of SO (sub 4) (super 2-) and oxidation of organic matter by sulfate-reducing bacteria, which is confirmed also by the positive correlation of HCO (sub 3) (super -) and alkalinity. The high Mg/Ca ratio is related to the enrichment of the brine with bittern salts such as MgCl (sub 2) and KCl. The chemical data of the brines indicate their source from recent and old marine waters of MgCl (sub 2) and CaCl (sub 2) characters. The contribution of meteoric water has a minor effect on the composition of the brine in the saline pans. Copyright 2015 Saudi Society for Geosciences