Some geochemical aspects of the Dead Sea and the question of its age

Abstract

A comparison between the chemical composition of the water of the Dead Sea and its tributaries and that of other lakes and the ocean shows the average salinity of the Dead Sea water (31.50%) to be exceptionally high, concentration of the SO 4″-ion to be very low and that of Br (5920mg/1) to be probably the highest on record for any surface water. Most of the cationic calcium in the Dead Sea and its tributaries is balanced by chloride. A short summary of the geological history of the area shows that the Dead Sea is not a relict body of sea water; its salt assemblage is the result of accumulation in a closed inland basin under arid conditions. The salts originate from two main sources, about one third from the Jordan River and about two thirds from highly saline springs discharging into the Dead Sea. On this fact a method can be based for calculating the age of the Dead Sea leading to a maximum figure of about 70,000 and a minimum of 12,000 years, the latter being more probable. The annual amount of chemical precipitation in the Southern Dead Sea basin is calculated to 0.306 gr/cm 2 and it is shown that NaCl and CaSO 4 are the major and that CaCO 3 is a minor component. This result is in good agreement with observations on the present rate of chemical sedimentation in the Dead Sea. Volcanic and organic origins for the vast bromine reserve in the Dead Sea are rejected and the derivation of the bromine from fossil residual brines, formed during the Tertiary, is tentatively accepted.