Paper No. 29
Presentation Time: 8:00 AM-12:00 PM
A PALEOLIMNOLOGIC STUDY OF THE LATE HOLOCENE HYDROCLIMATIC AND HYDROCHEMICAL HISTORY OF THE SEA OF GALILEE, ISRAEL
Reconstruction of the hydroclimatic and hydrochemical history of a rift valley lake, the Sea of Galilee, during the Late Holocene was established through a 143-cm long core taken from 10m depth on the western shore in January, 2012. The chronology of the core was established with 9 AMS 14 C dates on terrestrial macrofossils and the basal age is ca. 3900 cal yr BP. The core was extracted 1 km from the shore near the mouth of an ephemeral stream, transporting winter storm runoff from the Galilee Mountains into the Sea. The geology at the head of the stream begins as Cretaceous carbonates, a travertine valley floor and Pliocene basalts at elevation closer to the Sea. Landslide deposits are located in two areas of the valley from periods of heavy rain. The core contains two discrete fining upward unconformities at 90 cm and 109 cm indicating possible flood events based on age reversals, angular Melanopsis debris, and silicate mineral grains. Ostracodes were separated from the core and their species assemblage and abundance were determined to trace the historic rerouting of saline springs and general shifts in hydrochemistry. Cyprideis torosa is the most abundant species with both smooth and noded shells present. The carbonate and non-carbonate fractions of sediment were processed, respectively, for 87Sr/86Sr revealing an isolated excursion between 90-109 cm. The near absence of ostracodes in this portion of the core suggests the sediment has a terrestrial source unlike the majority of the core. The groundwater to the west contains a saline lens that gets injected into the Sea through springs and underground flow during extended rain events. A known diversion of these saline springs in 1964 will assist to understand the shifts in ostracode species assemblage and distribution throughout the core. The species assemblage indicates high specific conductivity (SC) from 90-100cm, which coincides with high 87Sr/86Sr (0.711 cf. 0.707 to 0.709 for other depths) for the carbonate-free fraction of bulk sediment. Comparing recharging groundwater forcing the discharge of saline springs in the last ca. 400 yrs to modern times, high SC segments suggest an increased precipitation in the Galilee Mountains (e.g. Gvirtzmann et al. 1997).