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AnimationBasin-scale migration
of continental-rift brines: Paleohydrologic modeling of the Dead Sea basin
Eyal Stanislavsky and Haim Gvirtzman
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It
was suggested that brine of the Dead Sea rift has originated from a residual product
of intensively evaporated seawater that invaded the rift, precipitated halite,
and later interacted through dolomitization with the host rock during subsurface
migration. Detection of this brine in many deep wells located at distances as
far as 100 km away of the rift was attributed to long-distance migration of the
brine. The physical feasibility of such migration, which probably spanned the
past 3-6 m.y., is quantitatively tested and verified in this study by using paleohydrologic
modeling. The structural formation of the rift is described by a chronological
sequence of geologic cross sections, serving as the basis for hydrodynamic calculations,
which assess the effects of the structure on fluid migration, salinity redistribution
and heat transport across the sedimentary basin. Results indicate that two basin-scale
ground-water systems, one atop the other but with opposite flow directions, coexisted
in the Dead Sea rift valley. The first is a topography-driven flow of meteoric
water, from the surrounding highlands toward the rift through relatively shallow
aquifers (down to about 1 km).
The
second is a density-driven migration of the Dead Sea brine through deep aquifers
(down to 4-5 km) in the opposite direction. The configuration of these flow systems
has changed during the structural evolution of the Dead Sea rift, illustrating
the interrelationships among basin formation, paleohydrology, and paleogeochemistry.