Sr/Ca, Ba/Ca and 87Sr/86Sr ratios in fossil freshwater aragonitic gastropods (Melanopsis praemorsum and Melanoides tuberculata) have been used to reconstruct the water sources of Quaternary lakes in the Jordan River Rift Valley. The reconstruction is based on the assumption that the same waurces which supply freshwater into the Rift Valley in the present (i.e. carbonate water, basaltic water and Rift brines), were active throughout the Quaternary. The distribution coefficients for Sr and Ba were obtained from live gastropods which were collected from modern water bodies in the region. By using these distribution coefficients, the composition of the ancient waters could be derived from the fossil shells' chemistry. Altogether, four ancient sites were sampled of which Mishmar ha'Yarden and Gesher Benot Ya'akov Formations are located in the Upper Jordan Valley and Erq el-Ahmar and Ubeidiya Formations are in its central part. Low salinity carbonate waters (≈300 mg/l) comprised the main H2O source into the Hula basin in the Upper Jordan Valley. These solutions display a 87Sr/86Sr ratio of 0.7082±0.0002, which is significantly higher than the corresponding modern ratio (0.7070), suggesting that the ancient drainage system was initially fed by Upper Eocene carbonate aquifers and shifted later to a Jurassic carbonate system. The Erq el-Ahmar lake in the Central Jordan Valley was supplied by approximately equal proportions of carbonate and basaltic waters, resulting in a water body of low salinity (≈300 mg/l). The water source of Lake Ubeidiya, also in the Central Jordan Valley, was predominantly basaltic, yet its chemistry bears a strong Rift brine signature resulting in a salinity of about 1000-1300 mg/l. The values obtained are in good accord with the biological evaluation of the fossil biota.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Earth-Surface Processes