USE OF ENVIRONMENTAL ISOTOPES TO EVALUATE THE SOURCES OF SUBMARINE FRESHWATER IN THE SOUTHERN SHORELINE IN LEBANON

摘要

Geochemical and isotopic techniques are applied to evaluate the origin ofsubmarine springs in the southern and northern shoreline in Lebanon. Submarinesprings have different geochemistry reflecting a difference in the specific geology ofsouthern and northern shoreline. Environmental isotopes including 2 H, 18 O, 34 S and18 O in sulfate have proved the different geological features. A more enriched isotopiccomposition of submarine groundwater is investigated in the south where submarinesprings are primarily artesian flows. The deep circulation of groundwater is affectedby a high geothermal gradient. Also a high sulfate content is related to a fractionationin 34 S isotopic composition. This is due to the dissolution of gypsum minerals and itsreduction of marlylimestones of the Upper Cretaceous and Lower Eocene in theconfined aquifers. In the northern part, a slightly depleted isotopic composition is foundfor submarine and groundwater. The highly karstified northern region induces a fastinfiltration of groundwater till its discharge as submarine springs.